CN108133086A - Water Fractured Gas Wells fracture half-length's inversion method is produced in a kind of stress sensitive reservoir - Google Patents

Abstract

The present invention relates to a method for half-length inversion of fractures in water-producing fracturing gas wells in stress-sensitive reservoirs. Calculation of gas-water equivalent relative permeability under different pressure conditions; (3) Calculation of improved quasi-parameters considering the complex seepage characteristics of gas-water two-phase in stress-sensitive reservoirs; (4) Drawing and using the improved time curve under the root sign Identify the linear flow of the formation; (5) Carry out linear regression on the data points in the linear flow stage of the formation, and use the inversion model to calculate based on the obtained straight line slope, so as to realize the inversion of the half length of the fracture. The present invention can comprehensively consider complex seepage characteristics such as phase permeability curve stress sensitivity, absolute permeability stress sensitivity, and slippage effect during gas-water two-phase seepage in stress-sensitive reservoirs, eliminates errors caused by traditional calculation methods, and can be widely used Post-fracture evaluation of water-producing fractured gas wells in stress-sensitive reservoirs.

Description

A fracture half-length inversion method for water-producing fractured gas wells in stress-sensitive reservoirs

technical field

The invention relates to the technical field of post-fracturing evaluation of hydraulic fracturing, in particular to a method for half-length inversion of fractures in water-producing fracturing gas wells in stress-sensitive reservoirs.

Background technique

During the production process of stress-sensitive reservoirs, due to the continuous change of formation stress conditions, the reservoir pore-throat structure will change accordingly. For water-producing gas wells in stress-sensitive reservoirs, the change of pore-throat structure with stress will lead to complex phenomena such as absolute permeability stress sensitivity, phase permeability curve stress sensitivity, and dynamic slippage effect in the gas-water two-phase seepage process. seepage characteristics. On the other hand, stress-sensitive reservoirs usually have low permeability and require fracturing to obtain industrial gas flow. The half-length of fractures formed by fracturing is an important indicator for evaluating fracturing effects, and is of great significance for subsequent productivity prediction and development plan formulation. The presence of complex gas-water two-phase seepage characteristics in stress-sensitive reservoirs makes the half-length inversion of water-producing fractured wells quite different from that of conventional gas wells.

However, some existing fracture half-length inversion methods do not comprehensively consider the complex seepage characteristics of gas-water two-phase in stress-sensitive reservoirs, especially ignore the stress sensitivity of the gas-water phase permeability curve, and the obtained fracture half-length There is usually a certain difference between the value and the true value, so it is not suitable for fracture half-length inversion of water-producing fractured gas wells in stress-sensitive reservoirs.

Contents of the invention

The technical problem to be solved by the present invention is: in order to overcome the deficiencies in the prior art, the present invention provides a half-length inversion method for water-producing fracturing gas well fractures in stress-sensitive reservoirs, which comprehensively considers the relative permeability curve stress sensitivity, etc. Gas-water two-phase seepage characteristics, thus improving the accuracy of fracture inversion results.

The technical solution adopted by the present invention to solve the technical problem is: a half-length inversion method for water-producing fracturing gas well fractures in stress-sensitive reservoirs, which has the following steps:

(1) Collection and arrangement of daily production data of gas wells, reservoir physical properties, fluid physical properties, gas-water phase permeability data, and stress-sensitive data;

(2) Considering the stress sensitivity of phase permeability curve, absolute permeability stress sensitivity and dynamic slippage effect, calculate the equivalent gas-water relative permeability of gas-water two-phase complex seepage characteristics under different pressure conditions;

(3), using the equivalent gas-water phase permeability curve, combined with the production data of the gas well, according to the following formula, calculate the improved pseudo-pressure and pseudo-time considering the complex seepage characteristics of the gas-water two-phase in the stress-sensitive reservoir;

Among them, ψ _two is the improved pseudo-pressure MPa/cp considering the complex seepage characteristics of gas-water two-phase in stress-sensitive reservoirs; t _two is the improved pseudo-time d considering the complex seepage characteristics of gas-water two-phase in stress-sensitive reservoirs; ^p is the pressure in MPa; p _a is the reference pressure in MPa; t is _the real time _d ; t _a is the reference time d; ρ _g is the gas phase subsurface density kg/m ³ ; is the ground standard density of water kg/m ³ ; is the underground gas density kg/m ³ corresponding to the average pressure; k _rgE is the gas phase equivalent relative permeability; ^k _rwE is the water phase equivalent relative permeability; is the gas-phase equivalent relative permeability corresponding to the average pressure; is the water equivalent relative permeability corresponding to the average pressure; μ _g is the gas viscosity cp; μ _w is the water viscosity cp; μ _gi is the gas viscosity cp under the original formation pressure; is the gas viscosity corresponding to the average pressure, cp; is the viscosity cp of water corresponding to the average pressure; C _t-twoi is the gas-water two-phase comprehensive compressibility MPa ^-1 under the original formation pressure; is the gas-water two-phase comprehensive compressibility MPa ^-1 corresponding to the average pressure;

(4), based on the improved pseudo-pressure and pseudo-time obtained by calculation, draw and use the improved square root time curve to identify the formation linear flow;

(5) Carry out linear regression on the scattered points on the curve, and use the inversion model to calculate according to the slope of the straight line obtained by the regression, so as to realize the inversion of the half-length of the fracture.

In the above step (1), the necessary data to be collected and sorted include: on-site production data of the gas well including water production q _w , gas production q _g , water-gas ratio f _w , casing pressure p _c or bottom hole flow pressure p _wf ; Reservoir thickness h and reservoir physical parameters such as porosity φ _i , absolute permeability ki _, gas slippage factor b _i under original formation pressure conditions; fluid viscosity μ _g , μ _w and compressibility coefficient C _g under different pressure conditions , C _w and other fluid physical parameters; relative permeability curve endpoint values corresponding to original formation pressure (S _wci , S _gri , k _rgendi , k _rwendi ), reservoir pore-throat anisodiametric coefficient λ and bending coefficient η and other relative permeability curves Parameters; reservoir absolute permeability, porosity, and stress sensitivity coefficients (α, γ, C, D, E, F) of the endpoints of relative permeability curves, etc.;

In step (2), the calculation model of equivalent gas-water relative permeability is:

in, and The calculation formulas are respectively:

Among them, k _rgE-p1 <S _w > is the gas phase equivalent relative permeability at a certain pressure (p ₁ ) and saturation (S _w ); k _rwE-p1 <S _w > is a certain pressure (p ₁ ) and water phase equivalent relative permeability at saturation (S _w ); k _rg-p1 <S _w > is gas phase relative permeability at a certain pressure (p ₁ ) and saturation (S _w ); k _rw-p1 <S _w > is the relative permeability of the water phase at a certain pressure (p ₁ ) and saturation (S _w ); b _i is the slippage factor corresponding to the original formation pressure; B is the slippage factor regression coefficient; α is the permeability Stress sensitivity coefficient MPa ^-1 ; k _rgendi is gas phase permeability endpoint value under original formation pressure; S _w is water saturation; S _wci is irreducible water saturation under original formation pressure; S _gri is residual under original formation pressure gas saturation; λ is the capillary distribution index; η is the capillary bending coefficient; k _rwendi is the water phase permeability endpoint value under the original formation pressure; C is the gas phase permeability endpoint value stress sensitivity coefficient, the unit is MPa ^-1 ; Stress sensitivity coefficient of water phase permeability endpoint value, unit is MPa ^-1 ; E is irreducible water saturation stress sensitivity coefficient, unit is MPa ^-1 ; F is residual gas saturation stress sensitivity coefficient, unit is MPa ^-1 ; p is Specified formation pressure, unit is MPa; p _i is original formation pressure, unit is MPa;

In step (3), the calculation method of pseudo pressure is:

(a) Using the gas production q _g and water production q _w corresponding to each time point t, calculate the ratio q _w /q _g of water production and gas production corresponding to each time point;

(b) Taking time t ₁ as an example, select the first pressure point p ₁ within the integration range, and calculate the relevant physical property parameter value (μ _g , B _g , μ _w , B _w );

(c), use the following formula to calculate the ratio k _rwE /k _rgE of the water phase and gas phase equivalent relative permeability under the condition of the pressure _p1 ;

(d) Using the equivalent phase permeability curves established in step (2) under different pressure conditions, further determine the ratio of water phase equivalent relative permeability to gas phase equivalent relative permeability (k _rwE /k _rgE ) under each pressure condition Variation characteristics with water saturation;

(e), in combination with the results of step (c) and step (d), determine the water saturation value corresponding to the pressure point, and use the saturation to calculate the gas-phase equivalent relative permeability k _rgE corresponding to the pressure point _p1 and Water equivalent relative permeability k _rwE ;

(f) Select the next pressure point p ₂ within the integration range, and use a similar method for analysis to obtain the gas-phase equivalent relative permeability and water-phase equivalent relative permeability corresponding to the pressure point p ₂ ...and so on, if in the integration If the number of pressure points selected within the range is sufficient, the relationship between the pressure value and the equivalent relative permeability k _rgE or k _rwE of the gas phase and water phase can be established, and then substituted into the following formula to realize the numerical integration of the relevant parameters, and obtain the applicable Improved pseudo-pressure for gas-water two-phase seepage in stress-sensitive reservoirs;

Among them, q _g is the surface gas production, m ³ /d; q _w is the surface water production, m ³ /d; B _g is the gas volume coefficient; B _w is the water volume coefficient.

In step (3), the calculation method of pseudo time is:

(a) Select the time point t ₁ within the integration range, and determine the pressure influence range or the average formation pressure in the reservoir by the pressure propagation distance formula or the flow material balance method Then determine the relevant gas-water physical property parameter values (μ _g , B _g , μ _w , B _w ) corresponding to the average pressure;

(c), based on the equivalent phase permeability curve in step (2), obtain the equivalent relative permeability ratio of the water phase and the gas phase under the average pressure condition Variation characteristics with water saturation;

(d), combining the results of steps (b) and (c), determine the average saturation value corresponding to the average pressure, and then calculate the average pressure The corresponding average gas-phase equivalent relative permeability and the average horizontal equivalent relative permeability

(e) Select the next time point t ₂ within the integration range, and use a similar method for analysis to obtain the average equivalent relative permeability of the gas phase and the average equivalent relative permeability of the water phase corresponding to the time t ₂ ... and so on, if The number of time points selected in the integration range is sufficient, and the time and average gas and water phase equivalent relative permeability can be established , so as to substitute into the following formula to realize the numerical integration of relevant parameters, and obtain the improved pseudo time suitable for gas-water two-phase seepage in stress-sensitive reservoirs;

Among them, t is the real time, d; is the average formation pressure, MPa; is the gas-phase equivalent relative permeability corresponding to the average pressure; is the gas-phase equivalent relative permeability corresponding to the average pressure.

In step (3), the calculation method of the comprehensive compressibility coefficient of gas-water two-phase seepage in the reservoir in the pseudo-time calculation formula is:

Among them, C _t-two is the comprehensive compressibility coefficient of gas-water two-phase, MPa ^-1 ; S _g is the saturation of gas phase; C _g is the compressibility coefficient of gas, MPa ^-1 ; C _w is the compressibility coefficient of water, MPa ^-1 ; _p is the rock pore compressibility coefficient, MPa ^-1 .

In step (4), when drawing the time curve under the root sign, when the gas well is producing at a constant gas content, the abscissa is And when the gas production rate of the gas well is not constant, the abscissa is while the ordinate is The abscissa in the case of variable gas production It can be calculated using the following formula.

Among them, ψ _twoi is the improved pseudo-pressure corresponding to the original formation pressure; ψ _twowf is the improved pseudo-pressure corresponding to the bottomhole flowing pressure; q _two is the total gas-water production; t _sl-two is the improvement corresponding to the formation linear flow stage The material balance quasi-time of is used to transform the variable yield condition into the constant yield condition, the unit is day (d); n is the total number of data points.

Among them, m _two-s is the slope of the straight line obtained by regression of the data points of the formation linear flow stage on the improved time curve under the root sign; x _f is the half-length of the fracture in m; φ is the porosity; h is the effective thickness of the gas layer in m; k _i is the original permeability mD under the original formation pressure.

Through the above steps, the half-length inversion of fractures in water-producing fractured gas wells in stress-sensitive reservoirs can be realized.

The beneficial effects of the present invention are: the present invention has the following advantages and beneficial effects compared with the current inversion method due to the adoption of the above technical method:

1. This method comprehensively considers complex seepage characteristics such as relative permeability curve stress sensitivity, so compared with the current mainstream fracture half-length inversion method, it is closer to the actual seepage situation of the reservoir, and the obtained fracture half-length is more accurate;

2. This method adopts a semi-analytic method, which is simpler and faster than the numerical analysis method;

3. This method is based on the analysis of daily production data, which solves the disadvantages of the traditional well test inversion method relying too much on field well test tests, without the need for shut-in tests, and significantly reduces the cost of fracture half-length inversion.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is the flow chart of the present invention.

Fig. 2 is the water-gas ratio and bottom hole flow pressure data in the embodiment of the present invention.

Fig. 3 is the equivalent phase permeability curve in the embodiment of the present invention.

Fig. 4 is the improved time curve under the root sign in the embodiment of the present invention.

Detailed ways

The present invention is described in further detail now in conjunction with accompanying drawing. These drawings are all simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, so they only show the configurations related to the present invention.

As shown in Figure 1, it is a flow chart of the half-length inversion method for water-producing fracturing gas well fractures in a stress-sensitive reservoir of the present invention, and its steps are as follows:

In step (1), the necessary data to be collected and sorted out include: field production data of gas wells including water production q _w , gas production q _g , water-gas ratio f _w , bottomhole flow pressure p _wf , etc.; reservoir thickness h and original Reservoir physical parameters such as porosity φ _i , absolute permeability ki _, gas slippage factor b _i under formation pressure conditions; fluid physical properties such as fluid viscosity μ _g , μ _w and compressibility coefficient C _g , C _w under different pressure conditions Parameters; relative permeability curve parameters corresponding to original formation pressure (S _wci , S _gri , k _rgendi , k _rwendi ), relative permeability curve parameters such as reservoir pore throat anisotropy coefficient λ and bending coefficient η; absolute reservoir permeability Ratio, porosity, and stress sensitivity coefficients (α, γ, C, D, E, F) of the endpoint values of the relative permeability curve, etc. Among them, the water-gas ratio and bottomhole flow pressure data in this embodiment are shown in Figure 2, and some other basic parameters collected are shown in Table 1.

Table 1

In step (2), the equivalent relative permeability is calculated based on the following formula, and the corresponding equivalent relative permeability curve is drawn. The result is shown in Figure 3:

in, and The calculation formulas are respectively:

Among them, k _rgE-p1 <S _w > is the gas phase equivalent relative permeability at a certain pressure (p ₁ ) and saturation (S _w ); k _rwE-p1 <S _w > is a certain pressure (p ₁ ) and water phase equivalent relative permeability at saturation (S _w ); k _rg-p1 <S _w > is gas phase relative permeability at a certain pressure (p ₁ ) and saturation (S _w ); k _rw-p1 <S _w > is the relative permeability of the water phase at a certain pressure (p ₁ ) and saturation (S _w ); b _i is the slippage factor corresponding to the original formation pressure, MPa; B is the slippage factor regression coefficient; α is Stress sensitivity coefficient of permeability, MPa ^-1 ; k _rgendi is gas phase permeability endpoint value under original formation pressure; S _w is water saturation; S _wci is irreducible water saturation under original formation pressure; S _gri is original formation pressure λ is the capillary distribution index; η is the capillary bending coefficient; k _rwendi is the water phase permeability endpoint value under the original formation pressure; C is the gas phase permeability endpoint value stress sensitivity coefficient; E is the stress sensitivity coefficient of irreducible water saturation; F is the stress sensitivity coefficient of residual gas saturation; p is the specified formation pressure, in MPa; p _i is the original formation pressure, in MPa;

In step (3), the improved pseudo-pressure considering the complex seepage characteristics of gas-water two-phase is calculated according to the following procedure:

(a) Using the gas production q _g and water production q _w corresponding to each time point t, calculate the ratio q _w /q _g of water production and gas production corresponding to each time point;

(b) Taking time t ₁ as an example, select the first pressure point p ₁ within the integration range, and calculate the relevant physical property parameter value (μ _g , B _g , μ _w , B _w );

(c), use the following formula to calculate the ratio k _rwE /k _rgE of the water phase and gas phase equivalent relative permeability under the condition of the pressure _p1 ;

(d) Using the equivalent phase permeability curves established in step (2) under different pressure conditions, further determine the ratio of water phase equivalent relative permeability to gas phase equivalent relative permeability (k _rwE /k _rgE ) under each pressure condition Variation characteristics with water saturation;

(e), in combination with the results of step (c) and step (d), determine the water saturation value corresponding to the pressure point, and use the saturation to calculate the gas-phase equivalent relative permeability k _rgE corresponding to the pressure point _p1 and Water equivalent relative permeability k _rwE ;

(f) Select the next pressure point p ₂ within the integration range, and use a similar method for analysis to obtain the gas-phase equivalent relative permeability and water-phase equivalent relative permeability corresponding to the pressure point p ₂ ...and so on, if in the integration If the number of pressure points selected within the range is sufficient, the relationship between the pressure value and the equivalent relative permeability k _rgE or k _rwE of the gas phase and water phase can be established, and then substituted into the following formula to realize the numerical integration of the relevant parameters, and obtain the applicable Improved pseudopressure for gas-water two-phase seepage in stress-sensitive reservoirs,

Among them, ψ _two is the improved pseudo-pressure MPa/cp considering the complex seepage characteristics of gas-water two-phase in the stress-sensitive reservoir; p is the pressure in MPa; p _a is the reference pressure in MPa; ρ _g is the underground density of the gas phase in kg/m ³ ; ρ _w is the underground density of water, kg/m ³ ; ρ _wsc is the surface standard density of water, kg/m ³ ; k _rgE is the gas phase equivalent relative permeability; k _rwE is the water phase equivalent relative permeability; μ _g is the gas viscosity cp; μ _w is the viscosity cp of water; q _g is the surface gas production m ³ /d; q _w is the surface water production m ³ /d; B _g is the gas volume coefficient; B _w is the water volume coefficient.

In step (3), the calculation method of pseudo time is:

(a) Select the time point t ₁ within the integration range, and determine the pressure influence range or the average formation pressure in the reservoir by the pressure propagation distance formula or the flow material balance method Then determine the relevant gas-water physical property parameter values (μ _g , B _g , μ _w , B _w ) corresponding to the average pressure;

(c), based on the equivalent phase permeability curve in step (2), obtain the equivalent relative permeability ratio of the water phase and the gas phase under the average pressure condition Variation characteristics with water saturation;

(d), combining the results of steps (b) and (c), determine the average saturation value corresponding to the average pressure, and then calculate the average pressure The corresponding average gas-phase equivalent relative permeability and the average horizontal equivalent relative permeability

(e) Select the next time point t ₂ within the integration range, and use a similar method for analysis to obtain the average equivalent relative permeability of the gas phase and the average equivalent relative permeability of the water phase corresponding to the time t ₂ ... and so on, if The number of time points selected in the integration range is sufficient, and the time and average gas and water phase equivalent relative permeability can be established In order to realize the numerical integration of relevant parameters and obtain the improved pseudo-time suitable for gas-water two-phase seepage in stress-sensitive reservoirs,

in, t is the real time d; is the average formation pressure MPa; is the gas-phase equivalent relative permeability corresponding to the average pressure; is the gas phase equivalent relative permeability corresponding to the average pressure; C _{t-two is} the gas-water two-phase comprehensive compressibility coefficient MPa ^-1 ; S _g is the gas phase saturation; C _g is the gas compressibility coefficient MPa ^-1 ; C _p is the rock pore compressibility coefficient MPa ^-1 , t _two is the improved quasi-time d considering the complex seepage characteristics ^of gas-water two-phase in the stress-sensitive reservoir; t _a is the reference time d; is the underground gas density kg/m ³ corresponding to the average pressure; is the water phase ground standard density kg/m ³ corresponding to the average pressure; is the gas-phase equivalent relative permeability corresponding to the average pressure; is the water phase equivalent relative permeability corresponding to the average pressure; μ _g is the gas viscosity cp; μ _w is the water viscosity cp; is the gas viscosity cp corresponding to the average pressure; is the viscosity cp of water corresponding to the average pressure; C _t-twoi is the gas-water two-phase comprehensive compressibility MPa ^-1 under the original formation pressure; is the gas-water two-phase comprehensive compressibility MPa ^-1 corresponding to the average pressure.

In step (4), since the present embodiment is the production of fixed gas production, the abscissa is while the ordinate is Draw the improved time curve under the root sign, as shown in Figure 4.

Among them, ψ _twoi is the improved pseudo-pressure corresponding to the original formation pressure; ψ _twowf is the improved pseudo-pressure corresponding to the bottomhole flowing pressure; q _two is the total gas-water production.

In step (5), based on the linear slope m _two-s obtained by regression, the calculation model of the half-length of the fracture is used It is calculated that the fracture half-length of the water-producing fracturing gas well in the stress-sensitive reservoir is 101.02m.

Among them, m _two-s is the slope of the straight line obtained by regression of the data points of the formation linear flow stage on the improved time curve under the root sign; x _f is the half-length of the fracture in m; φ is the porosity; h is the effective thickness of the gas layer in m; k _i is the original permeability mD under the original formation pressure.

Inspired by the above-mentioned ideal embodiment according to the present invention, through the above-mentioned description content, relevant workers can make various changes and modifications within the scope of not departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, but must be determined according to the scope of the claims.

Claims (8)

1. A half-length inversion method for a fracture of a water-producing fractured gas well in a stress-sensitive reservoir is characterized by comprising the following steps:

(1) collecting and sorting daily production data, reservoir physical properties, fluid physical properties, gas-water phase permeability data and stress sensitive data of a gas well;

(2) comprehensively considering stress sensitivity of a phase permeation curve, stress sensitivity of absolute permeability and dynamic slippage effect, and calculating equivalent gas-water relative permeability of gas-water two-phase complex seepage characteristics under different pressure conditions;

(3) calculating improved pseudo-pressure and pseudo-time considering the gas-water two-phase complex seepage characteristics of the stress sensitive reservoir according to the following formula by using the equivalent gas-water phase seepage curve and combining with the gas well production data;

wherein psi_twoThe improved pseudo pressure MPa/cp for considering the gas-water two-phase complex seepage characteristic of the stress sensitive reservoir; t is t_twoThe simulation time d for considering the improvement of the gas-water two-phase complex seepage characteristic of the stress sensitive reservoir; p is pressure MPa; p is a radical of_aIs a reference pressure MPa; rho_gIs gas phase underground density kg/m³(ii) a t is the real time d; t is t_aIs a reference time d; rho_wUnderground density of water kg/m³；ρ_wscGround standard density of water kg/m³；Gas phase underground density kg/m corresponding to average pressure³；The standard density of the water phase ground corresponding to the average pressure is kg/m³；k_rgEIs the gas phase equivalent relative permeability; k is a radical of_rwEIs the water phase equivalent relative permeability;the gas phase equivalent relative permeability corresponding to the average pressure;the equivalent relative permeability of the water phase corresponding to the average pressure; mu.s_gIs the gas viscosity cp; mu.s_wIs the viscosity of water cp; mu.s_giAt the pressure of the original formationGas viscosity cp of (a);the gas viscosity cp is the average pressure;the viscosity cp of water corresponding to the average pressure; c_t-twoiIs the gas-water two-phase comprehensive compression coefficient MPa under the original formation pressure^-1；Gas-water two-phase comprehensive compression coefficient MPa corresponding to average pressure^-1；

(4) Based on the improved pseudo-pressure and pseudo-time obtained by calculation, drawing and utilizing an improved time curve under the root to identify formation linear flow;

(5) and performing linear regression on data points of the formation linear flow stage, and calculating by using an inversion model according to the linear slope obtained by regression so as to realize the inversion of the half length of the fracture.

2. The method for inverting the half-length of a fracture of a water-producing fractured gas well in a stress-sensitive reservoir as claimed in claim 1, wherein the method comprises the following steps: the necessary data to be collected and collated in step (1) includes: comprising the water yield q_wGas production q_gWater-gas ratio f_wSleeve pressure p_cOr bottom hole flow pressure p_wfProduction data in situ for the gas well; reservoir thickness h and porosity phi under original formation pressure conditions_iAbsolute permeability k_iGas slip factor b_iReservoir physical property parameters; fluid viscosity μ under different pressure conditions_g、μ_wAnd compression factor C_g、C_wA fluid physical property parameter; end point value (S) of permeability curve corresponding to original formation pressure_wci、S_gri、k_rgendi、k_rwendi) Reservoir pore throat non-isodiametric coefficient lambda and bending coefficient η facies permeability curve parameter, reservoir absolute permeability, porosity and facies permeability curve endPoint values stress sensitivity coefficients (α, γ, C, D, E, F).

3. The method for inverting the half-length of a fracture of a water-producing fractured gas well in a stress-sensitive reservoir as claimed in claim 1, wherein the method comprises the following steps: the calculation model of the equivalent gas-water relative permeability in the step (2) is as follows:

wherein,andthe calculation formulas of (A) and (B) are respectively as follows:

wherein k is_rgE-p1<S_w>At a certain pressure (p)₁) And saturation (S)_w) Gas phase equivalent relative permeability; k is a radical of_rwE-p1<S_w>At a certain pressure (p)₁) And saturation (S)_w) The equivalent relative permeability of the water phase; k is a radical of_rg-p1<S_w>At a certain pressure (p)₁) And saturation (S)_w) Relative permeability of the gas phase; k is a radical of_rw-p1<S_w>At a certain pressure (p)₁) And saturation (S)_w) Relative permeability of the aqueous phase; b_iSlip factor MPa corresponding to original formation pressure, slip factor regression coefficient, and permeability stress sensitivity coefficient MPa α^-1；k_rgendiIs the gas phase permeability endpoint value at the original formation pressure; s_wThe water saturation; s_wciIs original toIrreducible water saturation at incipient formation pressure; s_griThe residual gas saturation under the original formation pressure, lambda is the capillary distribution index, η is the capillary bending coefficient, k_rwendiIs the water phase permeability endpoint value under the original formation pressure; c is the stress sensitivity coefficient of the gas phase infiltration endpoint value with the unit of MPa^-1(ii) a D is the stress sensitivity coefficient of the water phase seepage endpoint value with the unit of MPa^-1(ii) a E is the stress sensitivity coefficient of the saturation of the irreducible water in MPa^-1(ii) a F is the residual gas saturation stress sensitivity coefficient with the unit of MPa^-1(ii) a p is the specified formation pressure in MPa; p is a radical of_iIs the original formation pressure in MPa.

4. The method for inverting the half-length of a fracture of a water-producing fractured gas well in a stress-sensitive reservoir as claimed in claim 1, wherein the method comprises the following steps: the calculation method of the pseudo pressure in the step (3) comprises the following steps:

(a) utilizing the gas production q corresponding to each time point t_gAnd water yield q_wCalculating the ratio q of water yield to gas yield corresponding to each time point_w/q_g；

(b) At time t₁For example, a first pressure point p is selected within the integration range₁Based on the relation between the physical parameters of gas phase and water phase and pressure, the related physical parameter value (mu) corresponding to the pressure value is calculated_g、B_g、μ_w、B_w)；

(c) Calculating the pressure p by using the following formula₁Ratio k of equivalent relative permeability of water phase and gas phase under the condition_rwE/k_rgE

(d) And (3) further determining the ratio (k) of the equivalent relative permeability of the water phase to the equivalent relative permeability of the gas phase under each pressure condition by using the equivalent relative permeability curves under different pressure conditions established in the step (2)_rwE/k_rgE) A characteristic of change with water saturation;

(e) combining the steps (c) anddetermining the water saturation value corresponding to the pressure point as a result of the step (d), and calculating the pressure point p by using the saturation value₁Corresponding gas phase equivalent relative permeability k_rgEAnd water phase equivalent relative permeability k_rwE；

(f) Selecting the next pressure point p in the integral range₂And analyzing by similar method to obtain pressure point p₂Corresponding gas phase equivalent relative permeability and water phase equivalent relative permeability … … are analogized in turn, if the number of the pressure points selected in the integral range is enough, the pressure value and the gas phase and water phase equivalent relative permeability k can be established_rgEOr k_rwESubstituting the relation into the following formula to realize the numerical integration of the relevant parameters and obtain the improved simulated pressure suitable for the gas-water two-phase seepage of the stress sensitive reservoir;

wherein q is_gFor ground gas production, m³/d；q_wWater yield on the ground, m³/d；B_gIs the gas volume coefficient; b is_wIs the volume factor of water.

5. The method for inverting the half-length of a fracture of a water-producing fractured gas well in a stress-sensitive reservoir as claimed in claim 1, wherein the method comprises the following steps: the calculation method of the pseudo-time in the step (3) comprises the following steps:

(a) selecting a time point t within the integration range₁Determining the pressure influence range or the average formation pressure in the reservoir by a pressure propagation distance formula or a flowing material balance methodFurther determining the corresponding gas-water physical parameter value (mu) of the average pressure_g、B_g、μ_w、B_w)；

(b) Calculating the equivalent relative permeability ratio of the water phase and the gas phase under the average pressure condition by using the following formula

(c) Obtaining the equivalent relative permeability ratio value of the water phase and the gas phase under the average pressure condition based on the equivalent phase permeability curve in the step (2)A characteristic of change with water saturation;

(d) combining the results of the steps (b) and (c), determining an average saturation value corresponding to the average pressure, and further calculating the average pressureCorresponding average gas phase equivalent relative permeabilityAnd average water phase equivalent relative permeability

(e) Selecting the next time point t in the integral range₂Analysis was carried out by a similar method to obtain t₂The gas phase average equivalent relative permeability and the water phase average equivalent relative permeability corresponding to the moment are analogized in turn by … …, if the number of the selected time points in the integral range is enough, the time and the average gas phase and water phase equivalent relative permeability can be establishedThe equation (b) is substituted into the following equation to realize the numerical integration of the relevant parameters and obtain the improved simulation time suitable for the gas-water two-phase seepage of the stress sensitive reservoir.

Wherein t is real time and d;mean formation pressure, MPa;the gas phase equivalent relative permeability corresponding to the average pressure;the gas phase equivalent relative permeability is the average pressure.

6. The method for inverting the half-length of a fracture of a water-producing fractured gas well in a stress-sensitive reservoir as claimed in claim 5, wherein the method comprises the following steps: the method for calculating the gas-water two-phase seepage comprehensive compression coefficient in the reservoir in the simulated time calculation formula in the step (3) comprises the following steps:

wherein, C_t-twoIs gas-water two-phase comprehensive compression coefficient MPa^-1；S_gThe gas phase saturation; c_gIs a gas compression coefficient MPa^-1；C_wCompression factor MPa of water^-1；C_pIs the rock pore compression coefficient MPa^-1。

7. The method for inverting the half-length of a fracture of a water-producing fractured gas well in a stress-sensitive reservoir as claimed in claim 1, wherein the method comprises the following steps: when the improved time curve under the root is drawn in the step (4), when the gas well is produced with a fixed gas content, the abscissa isAnd when the gas well gas production is not constant, the abscissaIs composed ofAnd the ordinate isAbscissa under variable gas productionThe calculation can be carried out using the following formula,

wherein psi_twoiSimulating pressure for the improvement corresponding to the original formation pressure; psi_twowfThe improved pseudo pressure corresponding to the bottom hole flowing pressure; q. q.s_twoIs the total gas-water yield; t is t_sl-twoSimulating time for improved material balance corresponding to the formation linear flow stage, wherein the time is used for converting the variable yield condition into the constant yield condition, and the unit is day; n is the total number of data points.

8. The method for inverting the half-length of a fracture of a water-producing fractured gas well in a stress-sensitive reservoir as claimed in claim 1, wherein the method comprises the following steps: in the step (5), the slope m of the straight line obtained based on the regression_two-sThe calculation model of the half-length of the crack is

Wherein m is_two-sThe slope of a straight line obtained by regression of data points at the formation linear flow stage on the improved time curve under the root is obtained; x is the number of_fIs the half-length m of the crack; phi is porosity; h is the effective thickness m of the gas layer; k is a radical of_iIs the original permeability mD at the original formation pressure conditions.