CN114429231A - Shale gas well yield prediction method and system, storage medium and electronic equipment - Google Patents

Abstract

The invention discloses a production prediction method, system, storage medium and electronic equipment of shale gas wells, and relates to the technical field of oil and gas exploration. The stage production prediction model and the late quasi-steady-state flow stage production decline model are used to predict the production of each stage of the fracture. The prediction method can well solve the problems that the existing shale gas well productivity evaluation methods are difficult to apply in the early stage of gas well production, difficult to consider complex fracture morphology and lack of pertinence. Starting from the law of early and late production decline of shale gas wells, shale gas seepage mechanism, production data characteristic line analysis technology, and high-pressure physical property analysis technology are combined to determine the early and late stage production decline patterns of gas wells. Then, the complex fracture morphology is considered to correct the late production decline pattern of gas wells. On this basis, the production decline analysis of gas wells can be carried out to quickly and accurately predict the production capacity of gas wells with complex fracture patterns.

Description

Production prediction method, system, storage medium and electronic device of shale gas well

technical field

The invention belongs to the technical field of oil and gas exploration, and in particular relates to a production prediction method, system, storage medium and electronic equipment for shale gas wells.

Background technique

my country is rich in shale gas resources and has huge potential for exploration and development. Accurately predicting the productivity of shale gas fracturing horizontal wells (especially in the early stage of gas field development) is the premise for evaluating the development potential of gas fields and determining reasonable development technology policies.

Shale reservoirs are dense porous media with ultra-low porosity and ultra-low permeability, with obvious multi-scale effects and various gas occurrence modes. Gas production is affected by multiple mechanisms. The fluid seepage law in the production process is complex, and the production capacity is predicted. High difficulty. In addition, the complexity of well types and completion methods also greatly exacerbates the difficulty of predicting the productivity of shale gas wells. Shale gas reservoirs need horizontal well staged fracturing technology to achieve economical and effective development. However, some current fracture monitoring technologies (microseismic monitoring, radiological or chemical monitoring agent monitoring) and post-fracturing evaluation results have confirmed the fracturing process of gas wells. Most of the generated fracture systems are non-uniform (such as unequal lengths, different spacings, and partially ineffective) fracture systems. Since the coverage of fracture systems in shale gas reservoirs plays a decisive role in gas well productivity, irregular fracture systems exacerbate shale formation. The difficulty of predicting the productivity of rock gas wells.

Therefore, the urgent problem to be solved in the prediction of shale gas well productivity is to develop a flow-based method to accurately analyze the variation law of gas well production, while taking into account the complexity of reservoir fluid flow characteristics and the heterogeneity of fracture morphology caused by well completion as much as possible .

SUMMARY OF THE INVENTION

Based on the above technical problems, the present invention proposes a production prediction method, system, storage medium and electronic device for shale gas wells.

In a first aspect, an embodiment of the present invention provides a method for predicting production of a shale gas well, including:

Determine the length of the interference section of each fracture in the fracture distribution pattern of the shale gas well and the interference distance between adjacent interference sections; wherein, the interference section is a fracture section between two fractures that is not blocked by other fractures;

Determine the average formation pressure when the shale gas well evolves from the early unsteady flow stage to the late quasi-steady flow stage under the condition of uniform fracturing;

According to the average formation pressure, determine the pseudo-time correction coefficient corresponding to the average formation pressure, and determine the interference time of the interference section corresponding to each interference distance according to the pseudo-time correction coefficient;

Based on the disturbance time, determine the decrement rate of the disturbance segment corresponding to each disturbance time at the beginning of the late quasi-steady-state flow phase;

Accumulate the lengths of the interference sections with the same interference distance to obtain the cumulative interference section length corresponding to each interference distance, and determine the ratio of the length of each cumulative interference section to the total length of the fractures of the shale gas well, based on the Ratio, to determine the initial production of the shale gas well at the beginning of the late quasi-steady-state flow stage corresponding to the length of each cumulative interference section;

According to the average formation pressure and the bottom-hole flow pressure set by the shale gas well, determine the decline index of each of the interference sections when the shale gas well is in a late quasi-steady-state flow stage;

Based on the disturbance time, decline rate, initial production and decline index corresponding to each disturbance segment, the hyperbolic decline model is used to construct the production decline model of the late quasi-steady-state flow stage corresponding to each disturbance segment;

The production decline model of the late quasi-steady-state flow stage corresponding to each disturbance section is used to predict the production of the shale gas well in the late quasi-steady-state flow stage of each interference section.

Optionally, the output decline model in the late quasi-steady-state flow stage is:

Among them, q _late (j) is the output of the jth disturbance segment in the late quasi-steady flow stage, b _psd is the decrement index, q _c (j) is the initial output corresponding to the length of the jth cumulative disturbance segment, D _c (j) is the decrement rate of the j-th interference segment, T _c (j) is the interference time corresponding to the j-th interference segment, and t is the time.

Optionally, the method further includes:

determining a production decline model for the early unsteady flow phase of the shale gas well;

Based on the ratio of the length of each cumulative disturbance section to the total length of the fractures in the shale gas well, and using the production decline model in the early unsteady flow stage, a production prediction model in the early unsteady flow stage corresponding to each disturbance section is constructed ; wherein, the output prediction model of the early unsteady flow stage corresponding to each disturbance section is used to predict the output of each disturbance section of the shale gas well when it is in the early unsteady flow stage.

Optionally, the output decline model in the early unsteady flow stage is:

的关系曲线进 行散点拟合得到的斜率和截距；其中，q为日产量。Among them, q _ear is the output of the shale gas well in the early unsteady flow stage, t is the time, and a and b are constants; wherein, a and b are the 1/q and

The slope and intercept of the relationship curve obtained by scatter fitting; where q is the daily output.

Optionally, the output prediction model of the early unsteady flow stage corresponding to each disturbance segment is:

Among them, q _ear (j) is the production of the j-th disturbance section in the early unsteady flow stage, and R _a (j) is the ratio of the length of the j-th cumulative disturbance section to the total fracture length of the shale gas well.

Optionally, the method further includes:

Based on the late quasi-steady-state flow stage production decline model and the early unsteady flow stage production prediction model corresponding to each disturbance segment, combined with the disturbance time corresponding to each disturbance segment, a full-stage production decline model corresponding to each disturbance segment was constructed;

The full-stage production decline models of each interference section are superimposed to obtain the total production prediction model of the shale gas well.

Optionally, the full-stage production decline model is:

Among them, q(j) is the full-stage output of the j-th disturbance segment;

The total output prediction model is:

Wherein, q _a is the daily output of the shale gas well, and n is the number of interference sections.

Optionally, determining the average formation pressure when the shale gas well evolves from an early unsteady flow stage to a late pseudo-steady flow stage under uniform fracturing conditions, including:

S10, based on the geological parameters and fluid physical property parameters of the shale gas well, construct an iterative equation of average formation pressure; wherein, the iterative equation of average formation pressure is:

(c_tλ)_i为所述页岩气井在原始状态下的综合压缩系数与气体黏度 的乘积，(c_tμ)_c为所述页岩气井由早期非稳态流动阶段向晚期拟稳态流动阶段演 变时的综合压缩系数与气体黏度的乘积的平均值；Among them, p is the average formation pressure, p _i is the original formation pressure, _zi is the gas compression factor in the original state, c _ti is the comprehensive compression coefficient under the original formation pressure, μ _i is the gas viscosity in the original state, m( p _i ) is the pseudo pressure corresponding to the original formation pressure, p _wf is the bottom hole flow pressure, m(p _wf ) is the pseudo pressure corresponding to the bottom hole flow pressure,

(c _t λ) _i is the product of the comprehensive compressibility and gas viscosity of the shale gas well in the original state, (c _t μ) _c is the shale gas well from the early unsteady flow stage to the late pseudo-steady state The average value of the product of the comprehensive compressibility factor and the gas viscosity during the evolution of the flow stage;

where c _f is the rock compressibility, c _w is the water compressibility, S _gi is the gas saturation in the original state, z is the gas compressibility factor, S _wi is the water saturation in the original state, and φ is the porosity , ρ is the rock density, p _L is the Rankine pressure, _VL is the Rankine volume, z _sc is the gas compression factor under standard conditions, p _sc is the atmospheric pressure under standard conditions, T _sc is the temperature under standard conditions, T is the temperature;

的值；S20, establish an interpolation table based on the geological parameters and fluid physical property parameters of the shale gas well; wherein, the elements in the interpolation table include different formation pressures p and their corresponding

the value of;

的值；S30, take the original formation pressure of the shale gas well as the initial value of the average formation pressure in the iterative equation of the average formation pressure, and look up the value corresponding to the initial value of the average formation pressure from the interpolation table

the value of;

S40, based on the initial value of the average formation pressure, calculate the value of the right side term of the iterative equation of the average formation pressure;

的值以及所述平均地层压力迭代 方程的右侧项的值，利用残差计算式计算所述平均迭代方程的残差；其中，残差 计算式为：S50, based on the initial value of the average formation pressure corresponding to

and the value of the right-hand side of the iterative equation of the average formation pressure, use the residual calculation formula to calculate the residual of the average iterative equation; wherein, the residual calculation formula is:

为所述平均地层压力初值对应的

的值，

为 所述平均地层压力迭代方程的右侧项的值；Among them, rsd(i) is the residual,

corresponds to the initial value of the average formation pressure

the value of ,

is the value of the right-hand term of the iterative equation of the average formation pressure;

S60, when the residual is greater than a preset threshold, use the formation pressure in the interpolation table corresponding to the value of the right-hand side term of the average formation pressure iterative equation as a new initial value of the average formation pressure, and return to step S30, Iterative calculation based on the new average formation pressure initial value;

S70, when the residual is less than or equal to the preset threshold, use the initial value of the average formation pressure as the average formation pressure of the shale gas well, and stop the iteration.

Optionally, according to the average formation pressure, determine the pseudo-time correction coefficient corresponding to the average formation pressure, including:

According to the average formation pressure, the pseudo-time correction coefficient corresponding to the average formation pressure is calculated by using the first preset calculation formula; wherein, the first preset calculation formula is:

Among them, f _{cp_c} is the pseudo-time correction coefficient, ct is the comprehensive compressibility coefficient corresponding to the average formation pressure, μ is the gas viscosity corresponding to the average formation pressure, ( _{c t μ} ) _i is the shale gas well in the original (c _t μ) _c is the product of comprehensive compressibility and gas viscosity when the shale gas well evolves from an early unsteady flow stage to a late quasi-steady flow stage.

Optionally, according to the described pseudo-time correction coefficient, determine the interference time of the corresponding interference section of each interference distance, including:

According to the described pseudo-time correction coefficient, the second preset calculation formula is utilized to calculate the interference time of the corresponding interference section of each interference distance; wherein, the second preset calculation formula is:

Among them, T _c (j) is the disturbance time corresponding to the j-th disturbance section, φ is the porosity, μ is the gas viscosity, c _t is the comprehensive compressibility coefficient, (c _t μ) _i is the original state of the shale gas well The product of the comprehensive compressibility coefficient and the gas viscosity under , k is the permeability, f _{cp_c} is the pseudo-time correction coefficient, and y(j) is the interference distance corresponding to the jth interference section.

Optionally, based on the disturbance time, determine the decrement rate of the disturbance segment corresponding to each disturbance time at the beginning of the late quasi-steady-state flow phase, including:

Based on the disturbance time, the third preset calculation formula is used to calculate the decrement rate of the disturbance segment corresponding to each disturbance time at the beginning of the late pseudo-steady-state flow stage; wherein, the third preset calculation formula is:

Among them, D _c (j) is the decrement rate corresponding to the j-th interference time, T _c (j) is the interference time corresponding to the j-th interference segment, and a and b are constants.

Optionally, the determining the ratio of the length of each cumulative interference section to the total fracture length of the shale gas well includes:

According to the length of the cumulative interference section, the fourth preset calculation formula is used to calculate the ratio of the length of each cumulative interference section to the total fracture length of the shale gas well; wherein, the fourth preset calculation formula is:

Among them, R _a (j) is the ratio of the length of the j-th cumulative interference section to the total length of the fracture, L _cum (j) is the length of the j-th cumulative interference section, n _f is the total number of fractures, and x _f (i) is the crack half-length corresponding to the i-th crack.

Optionally, determining the initial production of the shale gas well at the beginning of the late pseudo-steady-state flow stage corresponding to the length of each cumulative disturbance section based on the ratio, including:

Based on the ratio, the fifth preset calculation formula is used to calculate the initial production of the shale gas well at the beginning of the late quasi-steady-state flow stage corresponding to the length of each cumulative disturbance section; wherein, the fifth preset The calculation formula is:

Among them, q _c (j) is the initial production corresponding to the length of the j-th cumulative disturbance section, R _a (j) is the ratio of the length of the j-th cumulative disturbance section to the total fracture length, and T _c (j) is the j-th The interference time corresponding to the interference segment, a and b are constants.

Optionally, the determining, according to the average formation pressure and the bottom hole flow pressure set by the shale gas well, determines the decrement index of each interference section when the shale gas well is in a late pseudo-steady state flow stage, including: :

Dividing the pressure interval formed by the average formation pressure and the bottom hole flow pressure of the shale gas well into several segments according to a preset pressure segment length to obtain multiple pressure points;

Determine the viscosity and compressibility corresponding to each pressure point to obtain the product of the viscosity and compressibility corresponding to each pressure point;

For each pressure point, the pseudo pressure corresponding to the pressure point is obtained by using the sixth preset calculation formula; wherein, the sixth preset calculation formula is:

Among them, m(p _j ) is the pseudo pressure corresponding to the jth pressure point, p _j is the formation pressure of the jth pressure point, p is the average formation pressure, z is the gas compression factor, and μ is the corresponding average formation pressure gas viscosity, p _sc is the atmospheric pressure under standard conditions;

Taking the product of the viscosity corresponding to each pressure point and the compressibility coefficient as the ordinate, and taking the pseudo pressure corresponding to each pressure point as the abscissa, draw the relation curve in the double logarithmic coordinate system;

Use the three-point method to determine the slope of any pressure point on the relationship curve;

Based on the pseudo pressure corresponding to the pressure point and the pseudo pressure corresponding to the bottom hole flow pressure of the shale gas well, the seventh preset calculation formula is used to calculate the dimensionless pseudo pressure difference of the pressure point; The default calculation formula is:

Among them, γ _j is the dimensionless pseudo-pressure difference of the j-th pressure point, m(p _j ) is the pseudo-pressure corresponding to the j-th pressure point, and m(p _wf ) is the pseudo-pressure of the bottom-hole flow pressure;

内，对所述压力点的斜率与无因次拟压力差 的乘积进行梯形积分，得到该压力点的斜率以及无因次拟压力差的乘积的积分； 其中，梯形积分的计算式为：in the quasi-pressure range

, the trapezoidal integral is performed on the product of the slope of the pressure point and the dimensionless pseudo-pressure difference, and the integral of the product of the slope of the pressure point and the dimensionless pseudo-pressure difference is obtained; wherein, the calculation formula of the trapezoidal integral is:

where b _int is the integral of the product of the slope of the pressure point and the dimensionless pseudo-pressure difference, n _p is the number of segments in the pressure interval formed by the average formation pressure and the bottom hole flow pressure of the shale gas well, and β _j is the first The product of the slope corresponding to the j pressure points and the dimensionless quasi-pressure difference;

Based on the slope of the pressure point and the integral of the product of the dimensionless pseudo-pressure difference, the eighth preset calculation formula is used to calculate the corresponding decreasing index of each described interference section; wherein, the eighth preset calculation formula is:

where b _psd is a decreasing index.

In a second aspect, an embodiment of the present invention provides a shale gas well production prediction system, including:

The interference section determination module is used to determine the interference section length of each fracture and the interference distance between adjacent interference sections in the fracture distribution mode of the shale gas well; wherein, the interference section is between two fractures that are not affected by other fractures. The crack segment covered by the crack;

The average formation pressure determination module is used to determine the average formation pressure when the shale gas well evolves from an early unsteady flow stage to a late quasi-steady flow stage under uniform fracturing conditions;

The interference time calculation module is used to determine the pseudo-time correction coefficient corresponding to the average formation pressure according to the average formation pressure, and determine the interference time of the interference section corresponding to each interference distance according to the pseudo-time correction coefficient; the lapse rate a determining module, configured to determine, based on the disturbance time, the decrement rate of the disturbance segment corresponding to each disturbance time at the beginning of the late quasi-steady-state flow phase;

The accumulation module is used to accumulate the lengths of the interference sections with the same interference distance, to obtain the cumulative interference section length corresponding to each interference distance, and to determine the difference between the length of each cumulative interference section and the total fracture length of the shale gas well. a ratio, based on the ratio, to determine the initial production of the shale gas well at the beginning of the late quasi-steady-state flow stage corresponding to the length of each cumulative disturbance section;

A decrement index determination module, configured to determine, according to the average formation pressure and the bottom-hole flow pressure set by the shale gas well, the decrement index of each of the interference sections when the shale gas well is in a late quasi-steady-state flow stage;

The model building module is used to construct the production decrement model corresponding to the late quasi-steady-state flow stage corresponding to each disturbance segment by using the hyperbolic decrement model based on the disturbance time, decrement rate, initial production and decrement index corresponding to each disturbance segment;

The production prediction module is used for predicting the production of the late quasi-steady-state flow stage of each interference section of the shale gas well by using the production decline model of the late quasi-steady-state flow stage corresponding to each interference section.

In a third aspect, an embodiment of the present invention provides a storage medium, where program codes are stored on the storage medium, and when the program codes are executed by a processor, the shale gas well according to any one of the foregoing embodiments is implemented. Yield forecasting method.

In a fourth aspect, an embodiment of the present invention provides an electronic device, the electronic device includes a memory and a processor, the memory stores program codes that can run on the processor, and the program codes are When executed by the processor, the method for predicting the production of a shale gas well described in any one of the foregoing embodiments is implemented.

In the method, system, storage medium, and electronic device for predicting the production of shale gas wells provided in the embodiments of the present invention, by segmenting the fractures of the shale gas well, and constructing a production prediction model in the early unsteady flow stage of each segment, and The production decline model for the late quasi-steady-state flow stage is used to predict the production of each stage of the fracture. This prediction method can well solve the problems that the existing shale gas well productivity evaluation methods are difficult to apply in the early stage of gas well production, difficult to consider complex fracture morphology and lack of pertinence. Starting from the law of early and late production decline of shale gas wells, shale gas seepage mechanism, production data characteristic line analysis technology, and high-pressure physical property analysis technology were combined to determine the early and late stage production decline patterns of gas wells. Then, considering the complex fracture shape, the production decline pattern in the late stage of the gas well is corrected. On this basis, the production decline analysis of gas wells can be carried out to quickly and accurately predict the productivity of gas wells with complex fracture patterns.

Description of drawings

The scope of the present disclosure may be better understood by reading the following detailed description of exemplary embodiments in conjunction with the accompanying drawings. The drawings included are:

FIG. 1 shows a schematic flowchart of a method for predicting production of a shale gas well proposed in Embodiment 1 of the present invention;

Figure 2 shows a schematic diagram of the crack distribution pattern;

3 shows a schematic diagram of an interference sequence diagram;

Figure 4 shows a schematic diagram of a relationship curve;

Figure 5 shows a schematic diagram of production dynamic data;

的散点图；Figure 6 shows

scatter plot;

Figure 7 shows a schematic diagram of the value of the product of viscosity and compressibility and the pseudo pressure at each pressure point;

Fig. 8 shows the schematic diagram that the three-point method obtains the slope;

Figure 9 shows a schematic diagram of the slope, the thus-free pseudo-pressure difference, and the slope and the dimensionless pseudo-pressure difference;

Figure 10 shows a schematic diagram of trapezoidal integration;

Figure 11 shows the comparison of the output value predicted by the total output forecasting model and the actual scatter;

Figure 12 shows the change curves of daily output and cumulative output with time.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the implementation method of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, thereby how to apply technical means to the present invention to solve technical problems and achieve the realization of technical effects The process can be fully understood and implemented accordingly.

Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific details disclosed below. Example limitations.

Example 1

According to an embodiment of the present invention, a method for predicting production of shale gas wells is provided. FIG. 1 shows a schematic flowchart of a method for predicting production of shale gas wells proposed in Embodiment 1 of the present invention. As shown in FIG. 1 , the page Rock and gas well production prediction methods can include:

In step 11, the length of the interference section of each fracture in the fracture distribution pattern of the shale gas well and the interference distance between adjacent interference sections are determined; wherein the interference section is not blocked by other fractures between two fractures crack section.

Here, the fracture distribution pattern of shale gas wells, that is, the fracture length distribution map, is drawn through the on-site microseismic monitoring data. Among them, the microseismic monitoring data can be interpreted to obtain the length of each fracture; if there is no microseismic monitoring data, the length of each fracture can be obtained by interpretation according to the fracturing construction parameters; if the length value of the fracture segment cannot be obtained, only the length of each fracture can be determined ratio between.

Fig. 2 shows a schematic diagram of the fracture distribution pattern. As shown in Fig. 2, the fracture distribution pattern of the shale gas well is drawn through the on-site microseismic monitoring data.

After drawing the fracture length distribution diagram of the shale gas well, the fracture interference sequence diagram is drawn in combination with the graphical method. The fracture interference sequence diagram contains two parts of information: fracture interference distance and interference segment length. The steps for drawing the crack interference sequence diagram are:

S111: Determine the length of the interference segment between the jth (j=1: _nf ) crack and the rth (r=1: _nf ) crack, where the interference segment is a crack between the two cracks that is not shielded by other cracks part.

S112, if the length of the interference segment is greater than 0, calculate the distance between the two cracks, which is the crack interference distance.

S113, delineate a rectangular outer boundary for the entire fracturing horizontal well, the center of the rectangle is located at the center of the horizontal wellbore, wherein the length of the rectangular side along the direction of the fracture is the maximum fracture length, and the length of the rectangular side along the direction of the horizontal wellbore is the length of the horizontal well .

S114: Determine the interference length between the jth (j=1:n _f ) crack and the two rectangular outer boundaries (outer boundaries parallel to the crack direction).

S115, calculate the interference distance between the jth (j=1:nf) crack and the two rectangular outer boundaries (outer boundaries parallel to the crack direction), but need to multiply by 2 on the basis of the solution result in step S121.

S116: Classify the interference distances according to different values to obtain a plurality of different interference distances.

S117, each interference distance corresponds to one or more interference lengths greater than 0, and the two are used as side lengths to draw a rectangular frame, and the rectangular frame represents the effective leakage area of the interference length section.

S118, classify the rectangular frames formed by drawing, and display rectangular frames with the same interference distance with the same background color. The background color of the rectangular boxes is the same, indicating that the corresponding fracture segments have the same interference time, and finally the fracture interference sequence diagram is formed.

Fig. 3 shows a schematic diagram of the interference sequence diagram, as shown in Fig. 3, in which 9 kinds of interference distances and corresponding interference segments are shown.

In step 12, the average formation pressure when the shale gas well evolves from an early unsteady flow stage to a late quasi-steady flow stage under uniform fracturing conditions is determined.

In an optional embodiment, in step 12, determining the average formation pressure when the shale gas well evolves from an early unsteady flow stage to a late quasi-steady flow stage under uniform fracturing conditions, including:

S10, based on the geological parameters and fluid physical property parameters of the shale gas well, construct an iterative equation of average formation pressure; wherein, the iterative equation of average formation pressure is:

(c_tμ)_i为所述页岩气井在原始状态下的综合压缩系数与气体黏度 的乘积，(c_tμ)_c为所述页岩气井由早期非稳态流动阶段向晚期拟稳态流动阶段演 变时的综合压缩系数与气体黏度的乘积的平均值；Among them, p is the average formation pressure, p _i is the original formation pressure, _zi is the gas compression factor in the original state, ct _i is the comprehensive compression coefficient under the original formation pressure, μ _i is the gas viscosity in the original state, m( p _i ) is the pseudo pressure corresponding to the original formation pressure, p _wf is the bottom hole flow pressure, m(p _wf ) is the pseudo pressure corresponding to the bottom hole flow pressure,

(c _t μ) _i is the product of the comprehensive compressibility and gas viscosity of the shale gas well in the original state, (c _t μ) _c is the shale gas well from the early unsteady flow stage to the late pseudo-steady state The average value of the product of the comprehensive compressibility factor and the gas viscosity during the evolution of the flow stage;

where c _f is the rock compressibility, c _w is the water compressibility, S _gi is the gas saturation in the original state, z is the gas compressibility factor, S _wi is the water saturation in the original state, and φ is the porosity , p is the rock density, p _L is the Rankine pressure, _VL is the Rankine volume, z _sc is the gas compression factor under the standard condition, p _sc is the atmospheric pressure under the standard condition, T _sc is the temperature under the standard condition, T is the temperature;

的值；S20, establish an interpolation table based on the geological parameters and fluid physical property parameters of the shale gas well; wherein, the elements in the interpolation table include different formation pressures p and their corresponding

the value of;

的值；S30, take the original formation pressure of the shale gas well as the initial value of the average formation pressure in the iterative equation of the average formation pressure, and look up the value corresponding to the initial value of the average formation pressure from the interpolation table

the value of;

S40, based on the initial value of the average formation pressure, calculate the value of the right side term of the iterative equation of the average formation pressure;

的值以及所述平均地层压力迭代 方程的右侧项的值，利用残差计算式计算所述平均迭代方程的残差；其中，残差 计算式为：S50, based on the initial value of the average formation pressure corresponding to

and the value of the right-hand side of the iterative equation of the average formation pressure, use the residual calculation formula to calculate the residual of the average iterative equation; wherein, the residual calculation formula is:

为所述平均地层压力初值对应的

的值，

为 所述平均地层压力迭代方程的右侧项的值；Among them, rsd(i) is the residual,

corresponds to the initial value of the average formation pressure

the value of ,

is the value of the right-hand term of the iterative equation of the average formation pressure;

S60, when the residual is greater than a preset threshold, use the formation pressure in the interpolation table corresponding to the value of the right-hand side term of the average formation pressure iterative equation as a new initial value of the average formation pressure, and return to step S30, Iterative calculation based on the new average formation pressure initial value;

S70, when the residual is less than or equal to the preset threshold, use the initial value of the average formation pressure as the average formation pressure of the shale gas well, and stop the iteration.

In step 13, a pseudo-time correction coefficient corresponding to the average formation pressure is determined according to the average formation pressure, and the interference time of the interference section corresponding to each interference distance is determined according to the pseudo-time correction coefficient.

In an optional embodiment, in step 13, according to the average formation pressure, determine a pseudo-time correction coefficient corresponding to the average formation pressure, including:

According to the average formation pressure, the pseudo-time correction coefficient corresponding to the average formation pressure is calculated by using the first preset calculation formula; wherein, the first preset calculation formula is:

Among them, f _{cp_c} is the pseudo-time correction coefficient, ct is the comprehensive compressibility coefficient corresponding to the average formation pressure, μ is the gas viscosity corresponding to the average formation pressure, ( _{c t μ} ) _i is the shale gas well in the original (c _t μ) _c is the product of comprehensive compressibility and gas viscosity when the shale gas well evolves from an early unsteady flow stage to a late quasi-steady flow stage.

In an optional embodiment, in step 13, according to the described pseudo-time correction coefficient, determine the interference time of the corresponding interference section of each interference distance, including:

According to the described pseudo-time correction coefficient, the second preset calculation formula is utilized to calculate the interference time of the corresponding interference section of each interference distance; wherein, the second preset calculation formula is:

Among them, T _c (j) is the disturbance time corresponding to the j-th disturbance section, φ is the porosity, μ is the gas viscosity, c _t is the comprehensive compressibility coefficient, (c _t μ) _i is the original state of the shale gas well The product of the comprehensive compressibility coefficient and the gas viscosity under , k is the permeability, f _{cp_} c is the pseudo-time correction coefficient, and y(j) is the interference distance corresponding to the jth interference section.

In step 14, based on the disturbance time, the decrement rate of the disturbance segment corresponding to each disturbance time at the beginning of the late quasi-steady-state flow phase is determined.

In an optional embodiment, in step 14, based on the disturbance time, determine the decrement rate of the disturbance segment corresponding to each disturbance time at the beginning of the late quasi-steady-state flow phase, including:

Based on the disturbance time, the third preset calculation formula is used to calculate the decrement rate of the disturbance segment corresponding to each disturbance time at the beginning of the late pseudo-steady-state flow stage; wherein, the third preset calculation formula is:

Among them, D _c (j) is the decrement rate corresponding to the j-th interference time, T _c (j) is the interference time corresponding to the j-th interference segment, and a and b are constants.

In step 15, the lengths of the interference sections with the same interference distance are accumulated to obtain the cumulative interference section length corresponding to each interference distance, and the difference between the length of each cumulative interference section and the total length of the fractures of the shale gas well is determined. A ratio, based on the ratio, to determine the initial production of the shale gas well at the beginning of the late quasi-steady-state flow phase corresponding to each of the cumulative disturbance section lengths.

Here, the lengths of the interference segments with the same interference distance are accumulated to obtain multiple interference segment lengths, and each interference segment length corresponds to an interference distance.

In an optional embodiment, in step 15, determining the ratio of the length of each cumulative interference section to the total length of the fractures of the shale gas well, including:

According to the length of the cumulative interference section, a fourth preset calculation formula is used to calculate the ratio of the length of each cumulative interference section to the total fracture length of the shale gas well; wherein, the fourth preset calculation formula is:

Among them, R _a (j) is the ratio of the length of the j-th cumulative interference section to the total length of the fracture, L _cum (j) is the length of the j-th cumulative interference section, n _f is the total number of fractures, and x _f (i) is the crack half-length corresponding to the i-th crack.

In an optional embodiment, in step 19, based on the ratio, determining the initial production of the shale gas well at the beginning of the late quasi-steady-state flow stage corresponding to the length of each cumulative disturbance section, including:

Based on the ratio, the fifth preset calculation formula is used to calculate the initial production of the shale gas well at the beginning of the late quasi-steady-state flow stage corresponding to the length of each cumulative disturbance section; wherein, the fifth preset The calculation formula is:

Among them, q _c (j) is the initial production corresponding to the length of the j-th cumulative disturbance section, R _a (j) is the ratio of the length of the j-th cumulative disturbance section to the total fracture length, and T _c (j) is the j-th The interference time corresponding to the interference segment, a and b are constants.

In step 16, according to the average formation pressure and the bottom-hole flow pressure set by the shale gas well, a decreasing index of each of the interference sections when the shale gas well is in a late quasi-steady-state flow stage is determined.

In an optional embodiment, in step 16, according to the average formation pressure and the bottom-hole flow pressure set by the shale gas well, it is determined that each of the interference sections is in a late pseudo-steady state in the shale gas well Decreasing indices during the flow phase, including:

Dividing the pressure interval formed by the average formation pressure and the bottom hole flow pressure of the shale gas well into several segments according to a preset pressure segment length to obtain multiple pressure points;

Determine the viscosity and compressibility corresponding to each pressure point to obtain the product of the viscosity and compressibility corresponding to each pressure point;

For each pressure point, the pseudo pressure corresponding to the pressure point is obtained by using the sixth preset calculation formula; wherein, the sixth preset calculation formula is:

Among them, m(p _j ) is the pseudo pressure corresponding to the jth pressure point, p _j is the formation pressure of the jth pressure point, p is the average formation pressure, z is the gas compression factor, and μ is the corresponding average formation pressure The gas viscosity of , p _sc is the atmospheric pressure under standard conditions; among them, the value of p _sc is 0.1.

Taking the product of the viscosity corresponding to each pressure point and the compressibility coefficient as the ordinate, and taking the pseudo pressure corresponding to each pressure point as the abscissa, draw the relation curve in the double logarithmic coordinate system;

Use the three-point method to determine the slope of any pressure point on the relationship curve;

Based on the pseudo pressure corresponding to the pressure point and the pseudo pressure corresponding to the bottom hole flow pressure of the shale gas well, the seventh preset calculation formula is used to calculate the dimensionless pseudo pressure difference of the pressure point; The default calculation formula is:

Among them, γ _j is the dimensionless pseudo-pressure difference of the j-th pressure point, m(p _j ) is the pseudo-pressure corresponding to the j-th pressure point, and m(p _wf ) is the pseudo-pressure of the bottom-hole flow pressure;

内，对所述压力点的斜率与无因次拟压力差 的乘积进行梯形积分，得到该压力点的斜率以及无因次拟压力差的乘积的积分； 其中，梯形积分的计算式为：in the quasi-pressure range

, the trapezoidal integral is performed on the product of the slope of the pressure point and the dimensionless pseudo-pressure difference, and the integral of the product of the slope of the pressure point and the dimensionless pseudo-pressure difference is obtained; wherein, the calculation formula of the trapezoidal integral is:

where b _int is the integral of the product of the slope of the pressure point and the dimensionless pseudo-pressure difference, n _p is the number of segments in the pressure interval formed by the average formation pressure and the bottom hole flow pressure of the shale gas well, and β _j is the first The product of the slope corresponding to the j pressure points and the dimensionless quasi-pressure difference;

Based on the slope of the pressure point and the integral of the product of the dimensionless pseudo-pressure difference, the eighth preset calculation formula is used to calculate the corresponding decreasing index of each described interference section; wherein, the eighth preset calculation formula is:

where b _psd is a decreasing index.

Here, the specific process of obtaining the decreasing index is as follows:

S161, determining the bottom hole flow pressure p _wf set by the gas well based on the collected gas well working system of the shale gas well;

S162 , based on the average formation pressure p _c , a pressure interval is defined.

Among them, the pressure interval is: (p _c , p _wf ).

S163: Divide the pressure interval formed by the average formation pressure and the bottom hole flow pressure of the shale gas well into several segments according to a preset pressure segment length to obtain multiple pressure points.

For example, the pressure interval is divided into n _p sections with the pressure section length Δp=0.1MPa, then n _p pressure points are obtained, n _p =(p _c -p _wf )/Δp+1, where the jth pressure point is : p _j =P _wf +(j-1)×Δp j = 1, 2, 3...n _p

S164 , for each pressure point, calculate the corresponding viscosity and compressibility coefficient to obtain the product (uc _t ) _j of the viscosity u _j corresponding to each pressure point and the compressibility coefficient c _tj .

S165, for each pressure point, use the sixth preset calculation formula to obtain the pseudo pressure corresponding to the pressure point; wherein, the sixth preset calculation formula is:

S166, take the product of the viscosity corresponding to each pressure point and the compressibility coefficient as the abscissa, and take the pseudo pressure corresponding to each pressure point as the ordinate, and draw a relationship curve.

Among them, if the relationship curve is drawn in the double logarithmic coordinate, the ordinate is the pseudo pressure corresponding to each pressure point, and the abscissa is the product of the viscosity corresponding to each pressure point and the compressibility coefficient. Figure 4 shows a schematic diagram of the relationship curve shown in Figure 4 .

S167, using the three-point method to determine the slope of any pressure point on the relationship curve.

Here, take the logarithm of m(p _j ) and (uc _t ) _j corresponding to each pressure point, respectively, to obtain log[m(p _j )] and log[(uc _t ) _j ]. To simplify the calculation, define two variables:

x _j =log[m(p _j )]

f(x _j )=log[(uc _t ) _j ]

If j=1, the derivation formula is:

If j=n _p , the derivation formula is:

For other pressure points, the derivation formula is:

Get the slope at any pressure point and take the absolute value. Then the slope α _j =|f'(x _j )|.

S168 , based on the pseudo pressure corresponding to the pressure point and the pseudo pressure corresponding to the bottom hole flow pressure of the shale gas well, use a seventh preset calculation formula to obtain a dimensionless pseudo pressure difference at the pressure point; wherein the The seventh preset calculation formula is:

Among them, γ _j is the dimensionless pseudo-pressure difference of the j-th pressure point, m(p _j ) is the pseudo-pressure corresponding to the j-th pressure point, and m(p _wf ) is the pseudo-pressure of the bottom-hole flow pressure;

内，对所述压力点的斜率与无因次拟 压力差的乘积进行梯形积分，得到该压力点的斜率以及无因次拟压力差的乘积的 积分；其中，梯形积分的计算式为：S169, in the pseudo-pressure range

, the trapezoidal integral is performed on the product of the slope of the pressure point and the dimensionless pseudo-pressure difference, and the integral of the product of the slope of the pressure point and the dimensionless pseudo-pressure difference is obtained; wherein, the calculation formula of the trapezoidal integral is:

where b _int is the integral of the product of the slope of the pressure point and the dimensionless pseudo-pressure difference, n _p is the number of segments in the pressure interval formed by the average formation pressure and the bottom hole flow pressure of the shale gas well, and β _j is the first The product of the slope corresponding to the j pressure points and the dimensionless quasi-pressure difference;

S1691, based on the slope of the pressure point and the integral of the product of the dimensionless pseudo-pressure difference, utilize the eighth preset formula to calculate and obtain the decreasing index; wherein, the eighth preset formula is:

where b _psd is a decreasing index.

Here, the decreasing exponent is the decreasing exponent in the hyperbolic decreasing model. The hyperbolic decline model is a commonly used decline model in the late quasi-steady flow stage of shale gas wells.

In step 17, based on the disturbance time, the decline rate, the initial production and the decline index, combined with a hyperbolic decline model, a production decline model in the late pseudo-steady-state flow stage corresponding to each disturbance section is constructed.

Among them, the output decline model of the late pseudo-steady-state flow stage is:

Among them, q _late (j) is the output of the jth disturbance segment in the late quasi-steady flow stage, b _psd is the decrement index, q _c (j) is the initial output corresponding to the length of the jth cumulative disturbance segment, D _c (j) is the decrement rate of the j-th interference segment, T _c (j) is the interference time corresponding to the j-th interference segment, and t is the time.

Here, time t is the cumulative gas production time of shale gas wells, in days, and T _c (j) refers to the time when the disturbance segment evolves to the late quasi-steady-state flow stage, such as T _c (j)=7 , then on the 7th day, the disturbance segment entered the late quasi-steady-state flow stage.

In step 18, the production of the shale gas well in the late pseudo-steady-state flow stage is predicted using the late pseudo-steady-state flow stage production decline model.

Here, each fracture section of the shale gas well includes one or more interference sections, and by determining the production decline model in the late quasi-steady flow stage of each interference section, that is, the late quasi-steady flow stage of the shale gas well can be determined. production forecast.

In an optional embodiment, the method further includes:

determining a production decline model for the early unsteady flow phase of the shale gas well;

Based on the ratio of the length of each cumulative interference section to the total length of fractures in the shale gas well, combined with the production decline model in the early unsteady flow stage, the production prediction of the early unsteady flow stage corresponding to each interference section is constructed The model; wherein, the early unsteady flow stage production prediction model corresponding to each disturbance section is used to predict the production of each disturbance section of the shale gas well in the early unsteady flow stage.

Here, the production decline model in the late quasi-steady-state flow stage predicts the production of the shale gas well in the late quasi-steady-state flow stage, while the production prediction of the shale gas well in the early unsteady flow stage can be calculated by constructing each The production forecasting model of the early unsteady flow stage corresponding to the disturbance section is used to forecast the production.

Among them, the output decline model in the early unsteady flow stage is:

的关系曲线进 行散点拟合得到的斜率和截距；其中，q为日产量。Among them, q _ear is the output of the shale gas well in the early unsteady flow stage, t is the time, and a and b are constants; wherein, a and b are the 1/q and

The slope and intercept of the relationship curve obtained by scatter fitting; where q is the daily output.

Here, in the early production of the horizontal well with multiple fractures, there is no interference between the fractures. At this time, the change law of productivity of the whole gas well is consistent with the change law of the production of the gas well under the condition of a single fracture; the early prediction model is established considering the production process of the shale gas well. There is desorption of adsorbed gas in the formation. Combined with the Langmuir adsorption isotherm model, the effect of desorption of adsorbed gas on gas well production is described by correcting the gas compressibility. Then the output decreasing model in the early unsteady flow stage is:

q为气井产量，10⁴m³/d，t：时间，d；T：温度，K；h： 气藏厚度，m；μ：气体粘度，cp；m(p)：压力p对应的拟压力，

MPa²/cp；x_f：裂缝半长，m；k：渗透率，mD；z：气体压缩因子，无因次。in,

q is gas well production, 10 ⁴ m ³ /d, t: time, d; T: temperature, K; h: gas reservoir thickness, m; μ: gas viscosity, cp; m(p): pseudo pressure corresponding to pressure p ,

MPa ² /cp; x _f : fracture half-length, m; k: permeability, mD; z: gas compressibility factor, dimensionless.

c_t：修正后气体压 缩系数，MPa^-1；c_g：气体压缩系数，MPa^-1；c_ads：吸附气解吸所产生的附加气体 压缩系数，MPa^-1；ρ：岩石密度，g/cm³；φ：孔隙度，小数；p_L：兰氏压力， MPa；V_L兰氏体积，m³/m³；p：压力，MPa。The modified compression factor is: c _t =c _g +c _ads ; where:

c _t : modified gas compressibility, MPa ^-1 ; c _g : gas compressibility, MPa ^-1 ; _cads : additional gas compressibility generated by desorption of adsorbed gas, MPa ^-1 ; ρ: rock density, g/cm ³ ; φ: porosity, decimal; p _L : Rankine pressure, MPa; _VL Rankine volume, m ³ /m ³ ; p: pressure, MPa.

关系曲线在直角坐标系中为一过原点的直线段。对于多 裂缝水平井，缝间干扰出现之前，该线性关系仍然成立。考虑井筒、裂缝污染等 原因，

直线段可能偏离原点，据此将早期非稳态线性流动阶段整个压裂水 平井产量递减模式定为：According to this model,

The relationship curve is a straight line segment through the origin in the Cartesian coordinate system. For multi-fractured horizontal wells, this linear relationship still holds before interfracture interference occurs. Considering the wellbore, fracture pollution and other reasons,

The straight line section may deviate from the origin, so the production decline mode of the whole fracturing horizontal well in the early unsteady linear flow stage is defined as:

散点图，寻 找早期直线段，散点拟合求得直线段斜率a、截距b，得到早期非稳态流动阶段 产量递减模型：Then, calculate the reciprocal 1/q of the collected yield, plotted in Cartesian coordinates

Scatter plot, looking for the early straight line segment, scatter point fitting to obtain the slope a and intercept b of the straight line segment, and obtain the output decline model in the early unsteady flow stage:

Wherein, the output prediction model of the early unsteady flow stage corresponding to each disturbance segment is:

Wherein, q _ear (j) is the production of the j-th disturbance section in the early unsteady flow stage, and R _a (j) is the ratio of the cumulative length of the disturbance section to the total fracture length of the shale gas well.

In an optional embodiment, the method further includes:

Based on the late quasi-steady-state flow stage production decline model and the early unsteady flow stage production prediction model corresponding to each interference section, combined with the interference time of the interference section, construct the full-stage production decline model of each interference section;

The full-stage production decline models of each interference section are superimposed to obtain the total production prediction model of the shale gas well.

Wherein, the full-stage production decline model is:

Among them, q(j) is the full-stage output of the j-th disturbance segment;

The total output prediction model is:

Wherein, q _a is the daily output of the shale gas well, and n is the number of interference sections.

In this embodiment, the prediction method can well solve the problems that the existing shale gas well productivity evaluation methods are difficult to apply in the early stage of gas well production, difficult to consider complex fracture shapes and lack of pertinence. Starting from the law of early and late production decline of shale gas wells, comprehensive shale gas seepage mechanism, production data characteristic line analysis technology, and high-pressure physical property analysis technology, the production decline pattern of gas wells in the early and late stages is determined. Then, considering the complex fracture shape, the production decline pattern in the late stage of the gas well is corrected. On this basis, the production decline analysis of gas wells can be carried out to quickly and accurately predict the productivity of gas wells with complex fracture patterns.

Embodiment 2

In this embodiment, an actual shale gas production well is taken as an example to describe the shale gas well production prediction method proposed by the present invention in detail.

S210, establishing a production decline model in the early unsteady flow stage of the shale gas well.

Here, the established production decline model for the entire fracturing horizontal well in the early unsteady flow stage is:

散点图， 图6示出了

的散点图，如图6所示，寻找早期直线段，利用散点拟合方法 求得直线段斜率为0.0115。直线近似通过坐标轴远点，截距近似为0，据此得到 早期非稳态流动阶段产量预测模型为：Then, the production performance data of the gas well is obtained, which includes the daily production of the gas well. Figure 5 shows a schematic diagram of the production performance data. As shown in Figure 5, the production performance data includes the data of daily gas production and bottom hole pressure. According to the production performance data of the gas well, it is drawn in the Cartesian coordinate system

scatter plot, Figure 6 shows

The scatter diagram of , as shown in Figure 6, finds the early straight line segment, and uses the scatter fitting method to obtain the slope of the straight line segment to be 0.0115. The straight line approximately passes through the far point of the coordinate axis, and the intercept is approximately 0. According to this, the output prediction model in the early unsteady flow stage is obtained as:

S220, determining the average formation pressure when the shale gas well evolves from an early unsteady flow stage to a late quasi-steady flow stage under the condition of uniform fracturing.

Here, the solution process of the average formation pressure is as follows:

Based on the geological parameters and fluid physical property parameters of the shale gas well, an iterative equation of average formation pressure is constructed; wherein, the iterative equation of average formation pressure is:

The iterative calculation of the average formation pressure iteration equation is performed using an iterative algorithm to obtain the average formation pressure.

Among them, the geological parameters and fluid physical parameters of the shale gas well are shown in Table 1, and the set bottom hole flow pressure is 7.5MPa.

Table 1

的插值表。Based on the geological parameters and fluid physical parameters of the shale gas well, p and

interpolation table.

The interpolation table is shown in Table 2:

Table 2

Set the residual of the mean formation pressure iteration equation to 0.1 MPa and proceed to the next iteration.

为 48.959MPa；基于目前平均地层压力、原始地层压力、井底流压，计算得到平均 地层压力迭代方程右侧项

为43.449MPa；计算平均地层压力迭代方程残差为 5.510MPa，远远大于给定的误差限，因此不满足条件。The first iteration: take the original formation pressure of 66MPa as the initial value of the average formation pressure; based on the given basic parameters and the calculation formula of z ^** , the corresponding initial value of the average formation pressure is calculated.

is 48.959MPa; based on the current average formation pressure, original formation pressure, and bottom-hole flow pressure, the right-hand term of the iterative equation for average formation pressure is calculated.

is 43.449MPa; the residual error of the iterative equation for calculating the average formation pressure is 5.510MPa, which is much larger than the given error limit, so it does not meet the conditions.

取值为43.449MPa时对应的压 力p为51.25MPa，以此值作为新的平均地层压力初值；同样计算对应的z**，计 算得到平均地层压力初值对应的

为43.453MPa；基于目前平均地层压力、原 始地层压力、井底流压，计算得到平均地层压力迭代方程右侧项

为 42.735MPa；计算平均地层压力迭代方程残差为0.718MPa，该值仍大于给定的误 差限，因此不满足条件。Second iteration: lookup in p and p/z** difference table

When the value is 43.449MPa, the corresponding pressure p is 51.25MPa, and this value is used as the initial value of the new average formation pressure; the corresponding z** is also calculated, and the corresponding initial value of the average formation pressure is calculated.

is 43.453MPa; based on the current average formation pressure, original formation pressure, and bottom-hole flow pressure, the right-hand term of the iterative equation for average formation pressure is calculated.

is 42.735MPa; the residual error of the iterative equation for calculating the average formation pressure is 0.718MPa, which is still larger than the given error limit, so the condition is not satisfied.

取值为42.735MPa时对应的压 力p为49.550MPa，以此值作为新的平均地层压力初值，则计算得到z**的值， 计算得到平均地层压力初值对应的

为42.737MPa；基于目前平均地层压力、 原始地层压力、井底流压，计算得到平均地层压力迭代方程右侧项

为 42.625MPa；计算平均地层压力迭代方程残差为0.112MPa，该值仍稍大于给定的 误差限，因此不满足条件。Third iteration: look up in the p and p/z** difference table

When the value is 42.735MPa, the corresponding pressure p is 49.550MPa, and this value is used as the initial value of the new average formation pressure, then the value of z** is calculated, and the corresponding initial value of the average formation pressure is calculated.

is 42.737MPa; based on the current average formation pressure, original formation pressure, and bottom-hole flow pressure, the right-hand term of the iterative equation for average formation pressure is calculated

is 42.625MPa; the residual error of the iterative equation for calculating the average formation pressure is 0.112MPa, which is still slightly larger than the given error limit, so it does not meet the conditions.

取值为42.625MPa时对应的压 力p为49.250MPa，以此值作为新的平均地层压力初值；同样计算对应的z**， 计算得到平均地层压力初值对应的

为42.609MPa；基于目前平均地层压力、 原始地层压力、井底流压，计算得到平均地层压力迭代方程右侧项

为42.605MPa；计算平均地层压力迭代方程残差为0.004MPa，该值小于给定的误差 限，因此满足条件，迭代结束。Fourth iteration: look up in the p and p/z** difference table

When the value is 42.625MPa, the corresponding pressure p is 49.250MPa, and this value is used as the initial value of the new average formation pressure; the corresponding z** is also calculated, and the corresponding initial value of the average formation pressure is calculated.

is 42.609MPa; based on the current average formation pressure, original formation pressure, and bottom-hole flow pressure, the right-hand term of the iterative equation for average formation pressure is calculated

is 42.605MPa; the residual error of the iterative equation for calculating the average formation pressure is 0.004MPa, which is less than the given error limit, so the condition is satisfied, and the iteration ends.

Then the average formation pressure is: 49.250MPa, and the pseudo-time correction coefficient is: 0.8743.

S230, determining a production decline model of a shale gas well in a late pseudo-steady-state flow stage under the condition of uniform fracturing.

Here, the bottom hole flow pressure during production of the shale gas well is set to be 7.5MPa, then the specific steps of S230 are as follows:

According to the obtained average formation pressure, the pressure interval is determined as (7.5, 49.3);

Set the pressure section length Δp=0.1MPa, divide the pressure interval into 419 sections, and the jth pressure point is: p _j =7.5+(j-1)×0.1

For each pressure point p(j), calculate the corresponding viscosity u _j and compressibility c _tj , obtain the product (uc _t ) _j , and calculate the pseudo pressure m(p _j ) corresponding to p _j for each pressure point. Figure 7 shows a schematic diagram of the value of the product of viscosity and compressibility and the pseudo-pressure at each pressure point. As shown in Figure 7, the dotted line in Figure 7 represents the value of the product of viscosity and compressibility at each pressure point. The solid line in 7 represents the corresponding relationship between pressure and pseudo-pressure.

As a result of the calculation, 419 data pairs corresponding to one-to-one are obtained, namely [m(p _j ), (uc _t ) _j ].

Then, based on the data pairs, plot the m(p _j )～(uc _t ) _j relationship curve in logarithmic coordinates to obtain the slope corresponding to each pressure point.

FIG. 8 shows a schematic diagram of the slope obtained by the three-point method, and the relationship curve is shown as the solid line in FIG. 8 .

On the m(p _j )～(uc _t ) _j relationship curve, select three typical points as shown in Figure 8 to illustrate the solution process of the slope:

For the first point, three data pairs, [x ₁ , f(x ₁ )], [x ₂ , f(x ₂ )], [x ₃ , f(x ₃ )], are needed to solve the slope. The three data pairs obtained by solving are: (3.569, -2.658), (3.624, -2.684), (3.676, -2.709), then the slope of the first point is -0.468.

For the 210th point, when solving the slope at this point, the data pairs that need to be used are (4.644, -3.212), (4.657, -3.220) and (4.670, -3.229), and the slope of the 210th point is obtained by solving is -0.646.

For the 419th point, when solving the slope here, the data pairs that need to be used are (5.013, -3.477), (5.019, -3.483) and (5.026, -3.488), and the slope of the 419th point is - 0.807. The slope of the remaining points can be solved in a similar way,

Based on the pseudo pressure corresponding to the pressure point and the pseudo pressure corresponding to the bottom hole flow pressure of the shale gas well, the seventh preset calculation formula is used to calculate the dimensionless pseudo pressure difference of the pressure point; The default calculation formula is:

Among them, γ _j is the dimensionless pseudo-pressure difference of the j-th pressure point, m(p _j ) is the pseudo-pressure corresponding to the j-th pressure point, and m(p _wf ) is the pseudo-pressure of the bottom-hole flow pressure;

Fig. 9 shows a schematic diagram of the slope, the pseudo-pressure difference without a factor, and the slope and the pseudo-pressure difference without a dimension. As shown in Fig. 9, α is the slope, γ is the slope, and β is the pseudo-pressure difference without the dimension, and the slope and the dimensionless pseudo-pressure difference The product of the secondary quasi-pressure differences.

内，对所述压力点的斜率与无因次拟 压力差的乘积进行梯形积分，得到多边形的面积，图10示出了梯形积分的示意 图，如图10所示，曲线圈定的面积即为b_int，最终结果为b_int＝60702.18。Then, in the quasi-pressure interval

Inside, the trapezoidal integral is performed on the product of the slope of the pressure point and the dimensionless quasi-pressure difference to obtain the area of the polygon. Figure 10 shows a schematic diagram of the trapezoidal integral. As shown in Figure 10, the area enclosed by the curve is b _int , the final result is b _int =60702.18.

Finally, based on the eighth preset calculation formula, the decrement index b _psd of the late quasi-steady-state flow stage production decline model is 0.593. The calculation of other parameters in the model has been described in detail in the above embodiments, and will not be repeated here.

S240, revising the production decline model in the late quasi-steady-state flow stage.

Here, due to the non-uniform fracture system in the fracturing process, its influence on the production decline law of gas wells needs to be considered, and the production decline model in the late quasi-steady-state flow stage needs to be corrected. The amount of sand is added to the fracturing construction parameters to determine the length ratio of each fracture, and the fracture shape distribution diagram is drawn according to the ratio, as shown in Figure 2. Among them, the length ratio of each crack is shown in Table 3.

table 3

crack number 1 2 3 4 5 6 length ratio 57 43 51 58 58 58 crack number 7 8 9 10 11 12 length ratio 58 53 44 35 16 16 crack number 13 14 15 16 17 18 length ratio 40 40 40 40 40 25 crack number 19 20 twenty one twenty two twenty three length ratio 40 48 39 44 32

The purpose of drawing the disturbance sequence diagram is to determine the fracture disturbance distance and the disturbance segment. Among them, there are 23 fractures in this shale gas well. Taking the 8th fracture as an example, the method for obtaining the interference distance and the length of the interference section in the process of drawing the interference sequence diagram is explained.

1) It is determined that the interference length of the 8th crack and the 1st to 6th, 10th to 19th, and 21st to 23rd cracks are all 0; the interference length of the 7th crack is 53m, and the corresponding interference distance is 66.1m; The interference length of the crack is 44m, and the interference distance is 66.1m; the interference length with the 20th crack is 4m, and the interference distance is 793.2m.

2) Delineate a rectangular outer boundary for the entire fracturing horizontal well. The center of the rectangle is located at the center of the horizontal well. The rectangle is 1520m long and 58m wide. The dotted line in Fig. 3 shows the delineated rectangular outer boundary.

3) Using the method in step 1), determine the interference distance between the eighth crack and the two rectangular outer boundaries (parallel to the crack direction). The interference length between the eighth crack and the left rectangular outer boundary is 0, and the interference length between the eighth crack and the right rectangular outer boundary is 5 m. When solving the interference distance, it is necessary to multiply the solution result in step 1) by 2, which is 2049.1 m.

4) Similar to step 3), the interference length and interference distance of the remaining cracks can be determined.

5) Classify the interference distances according to the different values, obtain num=9 different interference distances, and label them in order from small to large, as shown in Table 4:

Table 4

6) Draw a rectangular frame with the interference distance and the interference length as the side lengths, and the rectangular frame represents the effective leakage area of the interference length section.

7) Classify the rectangular frames formed by drawing, and the rectangular frames with the same interference distance are displayed with the same background color and finally form the interference sequence diagram. As shown in Figure 3, there are 9 kinds of interference distances, so the rectangular frames have 9 different backgrounds. color.

8) Based on the interference sequence diagram, calculate the cumulative interference section length, the ratio of the cumulative interference section length to the total fracture length of the shale gas well, and the interference time, decline rate, and initial production of the interference section corresponding to each interference distance.

Then the interference time and decrement rate of the interference segment corresponding to each interference distance are shown in Table 5.

table 5

The interference lengths corresponding to the same interference distance are accumulated to obtain 9 accumulated interference lengths Lcum, and the ratio of each accumulated interference length to the total crack length is calculated. The calculation results are shown in Table 6.

Table 6

The output at the beginning of the late quasi-steady-state flow phase corresponding to each cumulative disturbance length is calculated, as shown in Table 7.

Table 7

Taking the first cumulative disturbance length as an example, the established production decline model in the late quasi-steady-state flow stage is:

Taking the first cumulative disturbance length as an example, the whole-stage production decline model is constructed as:

The production decreasing models corresponding to the other accumulated disturbance length segments can be established with reference to the first accumulated disturbance length.

9) The production of each fractured section is superimposed to obtain the production of the entire horizontal well:

Figure 11 shows the comparison between the output value predicted by the total output forecasting model and the actual scatter. As shown in Figure 11, the output predicted by the total output forecasting model is in line with the actual demand.

Figure 12 shows the change curves of daily production and cumulative production with time. As shown in Figure 12, the prediction result shows that the cumulative gas production of this shale gas well is 118 million cubic meters.

Embodiment 3

According to an embodiment of the present invention, a production prediction system for shale gas wells is also provided, including:

The interference section determination module is used to determine the length of the interference section of each fracture in the fracture distribution mode of the shale gas well and the interference distance between adjacent interference sections; wherein, the interference section is the distance between two fractures that is not affected by other fractures. The crack segment covered by the crack;

The average formation pressure determination module is used to determine the average formation pressure when the shale gas well evolves from an early unsteady flow stage to a late quasi-steady flow stage under uniform fracturing conditions;

The interference time calculation module is used to determine the pseudo-time correction coefficient corresponding to the average formation pressure according to the average formation pressure, and determine the interference time of the interference section corresponding to each interference distance according to the pseudo-time correction coefficient; the lapse rate a determining module, configured to determine, based on the disturbance time, the decrement rate of the disturbance segment corresponding to each disturbance time at the beginning of the late quasi-steady-state flow phase;

The accumulation module is used to accumulate the lengths of the interference sections with the same interference distance, to obtain the cumulative interference section length corresponding to each interference distance, and to determine the difference between the length of each cumulative interference section and the total fracture length of the shale gas well. a ratio, based on the ratio, to determine the initial production of the shale gas well at the beginning of the late quasi-steady-state flow stage corresponding to the length of each cumulative disturbance section;

A decrement index determination module, configured to determine, according to the average formation pressure and the bottom-hole flow pressure set by the shale gas well, the decrement index of each of the interference sections when the shale gas well is in a late quasi-steady-state flow stage;

The model building module is used to construct the production decrement model corresponding to the late quasi-steady-state flow stage corresponding to each disturbance segment by using the hyperbolic decrement model based on the disturbance time, decrement rate, initial production and decrement index corresponding to each disturbance segment;

The production prediction module is used for predicting the production of the late quasi-steady-state flow stage of each interference section of the shale gas well by using the production decline model of the late quasi-steady-state flow stage corresponding to each interference section.

Embodiment 4

According to an embodiment of the present invention, a storage medium is also provided, and a program code is stored on the storage medium, and when the program code is executed by a processor, the shale gas well production rate according to any one of the foregoing embodiments is realized. method of prediction.

Embodiment 5

According to an embodiment of the present invention, there is also provided an electronic device, the electronic device includes a memory and a processor, the memory stores program codes that can be executed on the processor, and the program codes are stored by the When executed by the processor, the method for predicting the production of a shale gas well according to any one of the foregoing embodiments is implemented.

The technical solutions of the present invention are described in detail above with reference to the accompanying drawings. Considering the related art, the production decline prediction method of shale gas fracturing horizontal wells has the problems of being difficult to apply in the early stage of gas well production, difficult to consider complex fracture shapes and lack of pertinence. The present invention provides a production prediction method, system, storage medium and electronic equipment for shale gas wells. In order to solve the problem that the production decline prediction method for shale gas fracturing horizontal wells is difficult to apply in the early stage of gas well production, it is difficult to consider complex fracture shapes and does not target Therefore, a set of productivity prediction process for shale gas horizontal wells with uneven fracturing has been established. When predicting the productivity of a horizontal well with non-uniform fracturing, the present invention first determines the production decline mode of the gas well in the early flow stage, and uses the production data characteristic line analysis technology under the guidance of the mode to determine the production prediction model in the early unsteady flow stage; By introducing the high-pressure physical property analysis technology, the production decline mode of the gas well in the late quasi-steady stage stage under the condition of uniform fracturing was determined. Then, a graphic method was introduced to describe the influence of non-uniform fracturing on the production change law of the gas well in the late stage. The complex fractures are segmented, and the production decline model of each fracture segment is established and then superimposed to obtain the productivity prediction model of the entire fracturing horizontal well, which solves the problem that the conventional decline analysis method is difficult to consider the complex fracture shape. Finally, a set of feasible shale gas non-uniform fracturing horizontal well productivity prediction methods have been formed.

In the several embodiments provided in this application, it should be understood that the disclosed apparatus and method may be implemented in other manners. For example, the apparatus embodiments described above are only illustrative. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated. To another system, or some features can be ignored, or not implemented.

Units described as separate components may or may not be physically separated, and components shown as units may or may not be physical units, that is, may be located in one place, or may be distributed over multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solutions of the embodiments of the present invention.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically alone, or two or more units may be integrated into one unit. The above-mentioned integrated units may be implemented in the form of hardware, or may be implemented in the form of software functional units.

The integrated unit, if implemented as a software functional unit and sold or used as a stand-alone product, may be stored on a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or a part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium , including several instructions for causing an electronic device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of the various embodiments of the present invention. The aforementioned storage medium includes: U disk, removable hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program codes. .

Although the disclosed embodiments of the present invention are as above, the content described is only an embodiment adopted to facilitate understanding of the present invention, and is not intended to limit the present invention. Any person skilled in the art to which the present invention belongs, without departing from the spirit and scope disclosed by the present invention, can make any modifications and changes in the form and details of the implementation, but the protection scope of the present invention is still The scope as defined by the appended claims shall prevail.

Claims (17)

1. a shale gas well production prediction method, is characterized in that, comprises: determining the length of the interference section of each fracture in the fracture distribution pattern of the shale gas well and the interference distance between adjacent interference sections; wherein the interference section is a fracture section between two fractures that is not blocked by other fractures; determining the average formation pressure when the shale gas well evolves from an early unsteady flow stage to a late quasi-steady flow stage under the condition of uniform fracturing; According to the average formation pressure, determine the pseudo-time correction coefficient corresponding to the average formation pressure, and determine the interference time of the interference section corresponding to each interference distance according to the pseudo-time correction coefficient; Based on the disturbance time, determining the decrement rate of the disturbance segment corresponding to each disturbance time at the beginning of the late quasi-steady-state flow phase; Accumulate the lengths of the interference sections with the same interference distance to obtain the cumulative interference section length corresponding to each interference distance, and determine the ratio of the length of each cumulative interference section to the total length of the fractures of the shale gas well, based on the Ratio, to determine the initial production of the shale gas well at the beginning of the late quasi-steady-state flow stage corresponding to the length of each cumulative interference section; According to the average formation pressure and the bottom-hole flow pressure set by the shale gas well, determining a decline index of each of the interference sections when the shale gas well is in a late quasi-steady-state flow stage; Based on the disturbance time, decrement rate, initial production and decrement index corresponding to each disturbance segment, using the hyperbolic decrement model, the production decline model of the late quasi-steady-state flow stage corresponding to each disturbance segment is constructed; The output of the shale gas well in the late quasi-steady-state flow stage of each interference section of the shale gas well is predicted by using the production decline model of the late quasi-steady-state flow stage corresponding to each interference section. 2. shale gas well production forecasting method according to claim 1, is characterized in that, described late pseudo-steady-state flow stage production decline model is:

Among them, q _late (j) is the output of the jth disturbance segment in the late quasi-steady flow stage, b _psd is the decrement index, q _c (j) is the initial output corresponding to the length of the jth cumulative disturbance segment, D _c (j) is the decrement rate of the j-th interference segment, T _c (j) is the interference time corresponding to the j-th interference segment, and t is the time. 3. The method for predicting shale gas well production according to claim 2, wherein the method further comprises: determining a production decline model for the early unsteady flow phase of the shale gas well; Based on the ratio of the length of each cumulative disturbance section to the total length of the fractures in the shale gas well, and using the production decline model in the early unsteady flow stage, a production prediction model in the early unsteady flow stage corresponding to each disturbance section is constructed ; wherein, the output prediction model of the early unsteady flow stage corresponding to each disturbance section is used to predict the output of each disturbance section of the shale gas well when it is in the early unsteady flow stage. 4. shale gas well production prediction method according to claim 3, is characterized in that, described early unsteady flow stage production decline model is:

Among them, q _ear is the output of the shale gas well in the early unsteady flow stage, t is the time, and a and b are constants; wherein, a and b are the 1/q and

The slope and intercept of the relationship curve obtained by scatter fitting; where q is the daily output. 5. The method for predicting production of shale gas wells according to claim 4, wherein the production prediction model in the early stage of unsteady flow corresponding to each interference section is:

Among them, q _ear (j) is the production of the j-th disturbance section in the early unsteady flow stage, and R _a (j) is the ratio of the length of the j-th cumulative disturbance section to the total fracture length of the shale gas well. 6. The method for predicting shale gas well production according to claim 5, wherein the method further comprises: Based on the late quasi-steady-state flow stage production decline model and the early unsteady flow stage production prediction model corresponding to each disturbance segment, combined with the disturbance time corresponding to each disturbance segment, construct the full-stage production decline model corresponding to each disturbance segment; The full-stage production decline models of each interference section are superimposed to obtain the total production prediction model of the shale gas well. 7. The shale gas well production prediction method according to claim 6, wherein the full-stage production decline model is:

Among them, q(j) is the full-stage output of the j-th disturbance segment; The total output prediction model is:

Wherein, q _a is the daily output of the shale gas well, and n is the number of interference sections. 8. The method for predicting the production of shale gas wells according to claim 1, characterized in that, when the shale gas wells evolve from an early unsteady flow stage to a late quasi-steady flow stage under the determined uniform fracturing condition. Average formation pressure, including: S10, constructing an iterative equation of average formation pressure based on the geological parameters and fluid physical property parameters of the shale gas well; wherein, the iterative equation of average formation pressure is:

Among them, p is the average formation pressure, p _i is the original formation pressure, _zi is the gas compression factor in the original state, c _ti is the comprehensive compression coefficient under the original formation pressure, μ _i is the gas viscosity in the original state, m( p _i ) is the pseudo pressure corresponding to the original formation pressure, p _wf is the bottom hole flow pressure, m(p _wf ) is the pseudo pressure corresponding to the bottom hole flow pressure,

(c _t μ) _i is the product of the comprehensive compressibility and gas viscosity of the shale gas well in the original state, (c _t μ) _c is the shale gas well from the early unsteady flow stage to the late pseudo-steady state The average value of the product of the comprehensive compressibility factor and the gas viscosity during the evolution of the flow stage;

where c _f is the rock compressibility, c _w is the water compressibility, S _gi is the gas saturation in the original state, z is the gas compressibility factor, S _wi is the water saturation in the original state, and φ is the porosity , ρ is the rock density, p _L is the Rankine pressure, _VL is the Rankine volume, z _sc is the gas compression factor under standard conditions, p _sc is the atmospheric pressure under standard conditions, T _sc is the temperature under standard conditions, T is the temperature; S20, establish an interpolation table based on the geological parameters and fluid physical property parameters of the shale gas well; wherein, the elements in the interpolation table include different formation pressures p and their corresponding

the value of; S30, take the original formation pressure of the shale gas well as the initial value of the average formation pressure in the iterative equation of the average formation pressure, and look up the value corresponding to the initial value of the average formation pressure from the interpolation table

the value of; S40, based on the initial value of the average formation pressure, calculate and obtain the value of the right side term of the iterative equation of the average formation pressure; S50, based on the initial value of the average formation pressure corresponding to

and the value of the right-hand side of the iterative equation of the average formation pressure, use the residual calculation formula to calculate the residual of the average iterative equation; wherein, the residual calculation formula is:

Among them, rsd(i) is the residual,

corresponds to the initial value of the average formation pressure

the value of ,

is the value of the right-hand term of the iterative equation of the average formation pressure; S60, when the residual is greater than a preset threshold, use the formation pressure in the interpolation table corresponding to the value of the right-hand side term of the average formation pressure iterative equation as a new initial value of the average formation pressure, and return to step S30, Iterative calculation based on the new average formation pressure initial value; S70, when the residual is less than or equal to the preset threshold, use the initial value of the average formation pressure as the average formation pressure of the shale gas well, and stop the iteration. 9 . The method for predicting the production of shale gas wells according to claim 1 , wherein, determining the pseudo-time correction coefficient corresponding to the average formation pressure according to the average formation pressure, comprising: 10 . According to the average formation pressure, the pseudo-time correction coefficient corresponding to the average formation pressure is calculated by using the first preset calculation formula; wherein, the first preset calculation formula is:

Among them, f _cp-c is the pseudo-time correction coefficient, ct is the comprehensive compression coefficient corresponding to the average formation pressure, μ is the gas viscosity corresponding to the average formation pressure, ( _{c t μ} ) _i is the shale gas well The product of the comprehensive compressibility and the gas viscosity in the original state, (c _t μ) _c is the difference between the comprehensive compressibility and the gas viscosity when the shale gas well evolves from the early unsteady flow stage to the late quasi-steady flow stage product. 10. The shale gas well production prediction method according to claim 1, wherein, according to the pseudo-time correction coefficient, determining the interference time of the interference section corresponding to each interference distance, comprising: According to the pseudo-time correction coefficient, the second preset calculation formula is used to calculate the interference time of the interference segment corresponding to each interference distance; wherein, the second preset calculation formula is:

Among them, T _c (j) is the disturbance time corresponding to the j-th disturbance section, φ is the porosity, μ is the gas viscosity, c _t is the comprehensive compressibility coefficient, (c _t μ) _i is the original state of the shale gas well The product of the comprehensive compressibility coefficient and the gas viscosity under , k is the permeability, f _{cp_c} is the pseudo-time correction coefficient, and y(j) is the interference distance corresponding to the jth interference section. 11. The method for predicting production of shale gas wells according to claim 1, characterized in that, based on the disturbance time, determining the decline rate of the disturbance section corresponding to each disturbance time at the beginning of the late quasi-steady-state flow phase, include: Based on the disturbance time, a third preset calculation formula is used to calculate the decrement rate of the disturbance segment corresponding to each disturbance time at the beginning of the late quasi-steady-state flow stage; wherein, the third preset calculation formula is:

Among them, D _c (j) is the decrement rate corresponding to the j-th interference time, T _c (j) is the interference time corresponding to the j-th interference segment, and a and b are constants. 12. The method for predicting production of a shale gas well according to claim 1, wherein the determining the ratio of the length of each of the cumulative interference sections to the total length of fractures in the shale gas well comprises: According to the length of the accumulated interference section, a fourth preset calculation formula is used to calculate the ratio of the length of each accumulated interference section to the total length of the fractures of the shale gas well; wherein, the fourth preset calculation formula is:

Among them, R _a (j) is the ratio of the length of the j-th cumulative interference section to the total length of the fracture, l _cum (j) is the length of the j-th cumulative interference section, n _f is the total number of fractures, and x _f (i) is the crack half-length corresponding to the i-th crack. 13. The method for predicting the production of a shale gas well according to claim 1, wherein, based on the ratio, it is determined that the shale gas well corresponding to the length of each cumulative interference section is in a late pseudo-steady-state flow stage Initial output at start, including: Based on the ratio, the fifth preset calculation formula is used to calculate the initial production of the shale gas well at the beginning of the late quasi-steady-state flow stage corresponding to the length of each cumulative disturbance section; wherein, the fifth preset The calculation formula is:

Among them, q _c (j) is the initial production corresponding to the length of the j-th cumulative disturbance section, R _a (j) is the ratio of the length of the j-th cumulative disturbance section to the total fracture length, and T _c (j) is the j-th The interference time corresponding to the interference segment, a and b are constants. 14. The method for predicting the production of a shale gas well according to claim 1, wherein, according to the average formation pressure and the bottom hole flow pressure set by the shale gas well, it is The decline index of the shale gas wells in the late quasi-steady-state flow stage, including: Divide the pressure interval formed by the average formation pressure and the bottom hole flow pressure of the shale gas well into several segments according to a preset pressure segment length to obtain multiple pressure points; Determine the viscosity and compressibility corresponding to each pressure point to obtain the product of the viscosity and compressibility corresponding to each pressure point; For each pressure point, the pseudo pressure corresponding to the pressure point is obtained by using the sixth preset calculation formula; wherein, the sixth preset calculation formula is:

Among them, m(p _j ) is the pseudo pressure corresponding to the jth pressure point, p _j is the formation pressure of the jth pressure point, p is the average formation pressure, z is the gas compression factor, and μ is the corresponding average formation pressure gas viscosity, p _sc is the atmospheric pressure under standard conditions; Taking the product of the viscosity and the compression coefficient corresponding to each pressure point as the ordinate, and the pseudo pressure corresponding to each pressure point as the abscissa, draw the relationship curve in the double logarithmic coordinate system; Use the three-point method to determine the slope of any pressure point on the relationship curve; Based on the pseudo pressure corresponding to the pressure point and the pseudo pressure corresponding to the bottom hole flow pressure of the shale gas well, the seventh preset calculation formula is used to calculate the dimensionless pseudo pressure difference of the pressure point; The default calculation formula is:

Among them, γ _j is the dimensionless pseudo-pressure difference of the j-th pressure point, m(p _j ) is the pseudo-pressure corresponding to the j-th pressure point, and m(p _wf ) is the pseudo-pressure of the bottom-hole flow pressure; in the quasi-pressure range

, the trapezoidal integral is performed on the product of the slope of the pressure point and the dimensionless pseudo-pressure difference, and the integral of the product of the slope of the pressure point and the dimensionless pseudo-pressure difference is obtained; wherein, the calculation formula of the trapezoidal integral is:

where b _int is the integral of the product of the slope of the pressure point and the dimensionless pseudo-pressure difference, n _p is the number of segments in the pressure interval formed by the average formation pressure and the bottom hole flow pressure of the shale gas well, and β _j is the first The product of the slope corresponding to the j pressure points and the dimensionless quasi-pressure difference; Based on the slope of the pressure point and the integral of the product of the dimensionless quasi-pressure difference, the eighth preset calculation formula is used to calculate the decrement index corresponding to each of the interference segments; wherein, the eighth preset calculation formula is:

where b _psd is a decreasing index. 15. A shale gas well production prediction system, characterized in that it comprises: The interference section determination module is used to determine the interference section length of each fracture and the interference distance between adjacent interference sections in the fracture distribution mode of the shale gas well; wherein, the interference section is between two fractures that are not affected by other fractures. The crack segment covered by the crack; The average formation pressure determination module is used to determine the average formation pressure when the shale gas well evolves from an early unsteady flow stage to a late quasi-steady flow stage under the condition of uniform fracturing; The interference time calculation module is used to determine the pseudo-time correction coefficient corresponding to the average formation pressure according to the average formation pressure, and determine the interference time of the interference section corresponding to each interference distance according to the pseudo-time correction coefficient; the lapse rate a determining module, configured to determine, based on the disturbance time, the decrement rate of the disturbance segment corresponding to each disturbance time at the beginning of the late quasi-steady-state flow phase; The accumulation module is used to accumulate the lengths of the interference sections with the same interference distance, to obtain the cumulative interference section length corresponding to each interference distance, and to determine the difference between the length of each cumulative interference section and the total fracture length of the shale gas well. a ratio, based on the ratio, to determine the initial production of the shale gas well at the beginning of the late quasi-steady-state flow stage corresponding to the length of each cumulative disturbance section; a decrement index determination module, configured to determine, according to the average formation pressure and the bottom-hole flow pressure set by the shale gas well, the decrement index of each of the interference sections when the shale gas well is in a late quasi-steady-state flow stage; The model building module is used to construct the production decline model of the late pseudo-steady-state flow stage corresponding to each disturbance segment by using the hyperbolic decline model based on the disturbance time, decline rate, initial production and decline index corresponding to each disturbance segment; The production prediction module is used to predict the production of the late quasi-steady-state flow stage of each interference section of the shale gas well by using the production decline model of the late quasi-steady-state flow stage corresponding to each interference section. 16. A storage medium on which program codes are stored, characterized in that, when the program codes are executed by a processor, the shale gas well production prediction according to any one of claims 1 to 14 is realized method. 17. An electronic device, characterized in that the electronic device comprises a memory and a processor, and the memory stores program codes that can run on the processor, and when the program code is executed by the processor , realizing the production prediction method of a shale gas well as claimed in any one of claims 1 to 14.

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