CN108133087A - A kind of Gas-water phases seepage stress sensitivity reservoir original permeability inversion method - Google Patents

Abstract

The invention relates to a gas-water two-phase seepage stress-sensitive reservoir original permeability inversion method, comprising the following steps: (1) collecting and sorting out the daily production data of the gas well, the physical properties of the reservoir, the physical properties of the fluid, and the stress-sensitive data; (2) ) Calculation of gas-water equivalent phase permeability curves 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 semi-logarithmic curve Identify quasi-radial flow; (5) Perform linear regression on the scattered points on the curve, and use the reservoir original permeability calculation model to realize the inversion of the original permeability according to the linear slope obtained from the regression. The present invention can fully 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 Reservoir parameter evaluation for stress-sensitive reservoirs.

Description

A method for original permeability inversion of gas-water two-phase seepage stress-sensitive reservoir

technical field

The invention relates to the technical field of gas reservoir development, in particular to an original permeability inversion method for a gas-water two-phase seepage stress-sensitive reservoir.

Background technique

The permeability of stress-sensitive reservoirs is usually low and changes continuously with the change of formation pressure. Before the development of stress-sensitive gas reservoirs, the formation pressure remains at the original formation pressure, and the permeability at this time is called the original permeability. For stress-sensitive reservoirs with gas-water two-phase seepage, accurate acquisition of original permeability is very important for predicting the change law of reservoir permeability during development, predicting gas well productivity, and formulating a reasonable development plan.

However, some existing original permeability 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 phase permeability curves. There is usually a certain difference between the real values, so it is not suitable for the inversion of the original permeability of the gas-water two-phase seepage stress-sensitive reservoir.

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 an original gas-water two-phase seepage stress-sensitive reservoir that comprehensively considers the characteristics of gas-water two-phase seepage such as the stress sensitivity of the phase permeability curve. Permeability inversion method, thereby improving the accuracy of the original permeability inversion results.

The technical scheme adopted by the present invention to solve the technical problem is: a method for inversion of the original permeability of a gas-water two-phase seepage stress-sensitive reservoir, comprising 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) Calculating the equivalent gas-water phase permeability curve under different pressure conditions considering the stress sensitivity of the phase permeability curve, the stress sensitivity of the absolute permeability and the dynamic slippage effect, etc.

(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 considering the complex gas-water two-phase seepage characteristics of the stress-sensitive reservoir, MPa/cp; t _two is the improved pseudo-time considering the gas-water two-phase complex seepage characteristics of the stress-sensitive reservoir, d; p is the pressure, MPa; p _a is the reference pressure, MPa; t is the real time, d; t _a is the reference time, d; ρ _g is the underground density of gas phase, kg/m ³ ; ρ _w is the underground density of water , kg/m ³ ; ρ _wsc is the ground standard density of water, kg/m ³ ; is the underground density of gas phase corresponding to the average pressure, kg/m ³ ; is the water phase surface standard density corresponding to the average pressure, kg/m ³ ; 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; μ _g is the gas viscosity, cp; μ _w is the water viscosity, cp; μ _gi is the gas viscosity under the original formation pressure, cp; is the gas viscosity corresponding to the average pressure, cp; is the viscosity of water corresponding to the average pressure, cp; C _t-twoi is the comprehensive compressibility coefficient of gas-water two-phase under the original formation pressure, MPa ^-1 ; is the comprehensive compressibility coefficient of gas-water two-phase corresponding to the average pressure, MPa ^-1 ;

(4), based on the improved pseudo-pressure and pseudo-time obtained by calculation, draw and use the improved semi-logarithmic curve to identify pseudo-radial flow;

(5) Carry out linear regression on the scattered points on the curve, and use the calculation model of the original permeability of the reservoir to realize the inversion of the original permeability according to the slope of the straight line obtained by the regression.

In the above step (4), when drawing the improved time curve under the root sign, when the gas well is producing with constant gas content, the abscissa is lg(t _two ), and when the gas production of the gas well is not constant, the abscissa is lg(t _sr-two ), while the ordinate is The abscissa lg(t _sr-two ) in the case of variable gas production 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 flow pressure; q _two is the total gas-water production; t _sr-two is the corresponding pseudo-radial flow stage The improved material balance pseudo time is used to convert the variable yield condition into the constant yield condition, the unit is day (d); n is the total number of data points.

In the above step (5), based on the linear slope m _two-r obtained by regression, the calculation model of the original permeability is Among them, m _two-r is the slope of the straight line obtained by regression of the data points in the formation linear flow stage on the improved square root time curve; h is the effective thickness of the gas layer m; _ki is the original permeability mD under the original formation pressure condition.

Through the above steps, the inversion of the original permeability of the gas-water two-phase seepage stress-sensitive reservoir can be realized.

The beneficial effects of the present invention are:

1. Compared with the existing original permeability determination method, this method comprehensively considers the complex seepage characteristics such as relative permeability curve stress sensitivity, so compared with the current mainstream original permeability inversion method, it is closer to the actual stress-sensitive reservoir In case of seepage, the obtained original permeability is more accurate.

2. Compared with the current common numerical solution methods, this method adopts a semi-analytic method, and the calculation speed is faster.

3. Compared with the current common well test interpretation method, 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 the field test test, without the need for shut-in test, which significantly reduces the The cost of original absolute permeability inversion is reduced.

4. Compared with the current core test method, because the core volume in the test method is usually small, the original permeability of the core obtained cannot represent the permeability characteristics of the entire well control range in heterogeneous formations, and this paper What the inversion method obtains is the original permeability of the reservoir within the entire well control range, which has greater practical significance for oil and gas development.

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 an improved semi-logarithmic curve in an 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, a gas-water two-phase seepage stress-sensitive reservoir original permeability inversion method has the following steps:

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 and gas slippage factor b _i under formation pressure; fluid physical parameters such as fluid viscosity μ _g , μ _w and compressibility coefficient C _g , C _w under different pressure conditions; Corresponding relative permeability curve endpoint values (S _wci , S _gri , k _rgendi , k _rwendi ), reservoir pore-throat anisotropy coefficient λ and bending coefficient η and other relative permeability curve parameters; absolute permeability, porosity and facies of reservoir The stress sensitivity coefficient (α, γ, C, D, E, F) of the end point value of the seepage curve, etc. Among them, the water-gas ratio and bottom hole 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), calculate and draw equivalent relative permeability curve based on the following formula, as shown in accompanying drawing 3:

in, and They are:

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) Using the following formula, calculate the ratio k _rwE /k _rgE of the effective relative permeability of the water phase and the gas phase under the condition of the pressure p ₁ .

(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 phase 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 considering the complex seepage characteristics of gas-water two-phase in stress-sensitive reservoirs, MPa/cp; p is the pressure, MPa; p _a is the reference pressure, MPa; ρ _g is the gas-phase subsurface density, 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 gas viscosity, cp; μ _w is water viscosity, cp; q _g is surface gas production, m ³ /d; q _w is surface water production, m ³ /d; B _g is gas volume coefficient; B _w is the volume factor of water.

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

(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 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 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 _w is the compressibility coefficient of water, MPa ^-1 ; C _p is the compressibility coefficient of rock pores, MPa ^-1 , t _two is the improved pseudo time considering the complex seepage characteristics of gas-water two-phase in stress-sensitive reservoirs, d; t _a is the reference time, d; is the underground density of gas phase corresponding to the average pressure, kg/m ³ ; is the standard density of water phase ground corresponding to the average pressure, kg/m ³ ; 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; is the gas viscosity corresponding to the average pressure, cp; is the viscosity of water corresponding to the average pressure, cp; C _t-twoi is the comprehensive compressibility coefficient of gas-water two-phase under the original formation pressure, MPa ^-1 ; is the comprehensive compressibility coefficient of gas-water two-phase corresponding to the average pressure, MPa ^-1 .

In step (4), since the present embodiment is the production of fixed gas production, the abscissa is lg(t _two ), and 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-r obtained by regression of data points in the quasi-radial flow stage on the improved semi-logarithmic curve, the original permeability calculation formula is used The calculated original permeability of the stress-sensitive reservoir is 0.098mD.

Among them, m _two-r is the slope of the straight line obtained by regression of the data points in the formation linear flow stage on the improved square root time curve; h is the effective thickness of the gas layer m; _ki is the original permeability mD under the original formation pressure condition.

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 (3)

1. A gas-water two-phase seepage stress sensitive reservoir original permeability inversion method 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) calculating equivalent gas-water phase seepage curves comprehensively considering gas-water phase complex seepage characteristics such as phase seepage curve stress sensitivity, absolute permeability stress sensitivity, dynamic slippage effect and the like 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_twoD, simulating time for considering improvement of the gas-water two-phase complex seepage characteristic of the stress-sensitive reservoir; p is pressure, MPa; p is a radical of_aReference pressure, MPa; t is the real time, d; t is t_aIs a reference time, d; rho_gIs gas phase underground density, kg/m³；ρ_wIs the underground density of water, kg/m³；ρ_wscIs the ground standard density of water, kg/m³；Is the gas phase underground density corresponding to the average pressure, kg/m³；Is the standard density of the water phase ground corresponding to the average pressure, 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_wViscosity of water, cp; mu.s_giGas viscosity at virgin formation pressure, cp;gas viscosity, cp, corresponding to the average pressure;viscosity of water, cp, corresponding to the average pressure; c_t-twoiIs the gas-water two-phase comprehensive compression coefficient under the original formation pressure, MPa^-1；Is the gas-water two-phase comprehensive compression coefficient corresponding to the average pressure, MPa^-1；

(4) Based on the improved quasi-pressure and quasi-time obtained by calculation, drawing and utilizing the improved semilogarithmic curve to identify quasi-radial flow;

(5) and performing linear regression on scattered points on the curve, and realizing inversion of the original permeability by using a reservoir original permeability calculation model according to the linear slope obtained by the regression.

2. The gas-water two-phase seepage stress sensitive reservoir original permeability inversion method according to claim 1, characterized in that: when the improved time under root curve is plotted in step (4), the abscissa is lg (t) when the gas well is produced for a fixed gas content_two) And lg (t) on the abscissa when gas well gas production is not constant_sr-two) And the ordinate isAbscissa lg (t) in the case of variable gas production_sr-two) The calculation can be carried out using the following formula,

wherein psi_twoiFor improved pseudo-pressure corresponding to original formation pressureForce; psi_twowfThe improved pseudo pressure corresponding to the bottom hole flowing pressure; q. q.s_twoIs the total gas-water yield; t is t_sr-twoSimulating time for improved material balance corresponding to the simulated radial flow stage for converting variable yield conditions to constant yield conditions in days (d); n is the total number of data points.

3. The gas-water two-phase seepage stress sensitive reservoir original permeability inversion method according to claim 1, characterized in that: in the step (5), the slope m of the straight line obtained based on the regression_two-rThe calculation model of the original permeability is

Wherein m is_two-rThe 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; 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.