Method for determining reasonable displacement pressure difference in heavy oil reservoir viscosity reduction and pressure drive development

Abstract

The application provides a method for determining reasonable displacement pressure difference in thickened oil reservoir viscosity reduction and pressure drive development, comprising the following steps: fitting a relationship between thickened oil mobility and threshold pressure gradient on the basis of experimental results; calculating the mobility value of thickened oil in the reservoir, and calculating the corresponding threshold pressure gradient value according to the relationship; determining the threshold pressure value between injection and production wells according to pressure drive injection-production well spacing, which is taken as the minimum displacement pressure difference; determining the maximum displacement pressure difference through the maximum liquid production capacity of the oil well; calculating the cumulative net present value corresponding to different production pressure differences within the displacement pressure difference limit range; and taking the displacement pressure difference corresponding to the maximum cumulative net present value as the reasonable displacement pressure difference in thickened oil reservoir viscosity reduction and pressure drive development. The method for determining the reasonable displacement pressure difference in thickened oil reservoir viscosity reduction and pressure drive development determines the reasonable displacement pressure difference in thickened oil reservoir viscosity reduction and pressure drive development by using the optimization theory and taking the financial net present value as the optimization target through reservoir numerical simulation and dynamic economic evaluation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield development, and particularly relates to a method for determining a reasonable displacement pressure difference in thickened oil reservoir viscosity reduction and pressure drive development. BACKGROUND

[0002] The thickened oil reservoirs in Shengli Oilfield are rich in resources, with geological reserves of 320 million tons. However, in the development process, the contradiction of "small swept volume, rapid water cut rise, and low liquid volume of oil well" has existed, which seriously restricts the improvement of the development effect of thickened oil reservoirs.

[0003] In the process of viscosity reduction and drive development of thickened oil reservoirs, affected by the viscosity ratio of the displacement phase and the displaced phase, the displacement phase is prone to channeling along the high and deep strips in the reservoir, resulting in small effective swept volume of the displacement phase, rapid water cut rise of the oil well, and poor displacement effect. In addition, the thickened oil reservoir itself has a high starting pressure, and part of the pressure difference between the injection well and the production well needs to be consumed to overcome the starting pressure of the thickened oil reservoir, thereby resulting in small effective displacement pressure difference and low liquid volume of the oil well, and further affecting the oil well productivity. Therefore, it is necessary to conduct in-depth research and explore means to greatly improve the producing degree of thickened oil reservoirs, so as to realize the economic and efficient development of thickened oil reservoirs.

[0004] Viscosity reduction and pressure drive is to inject a large amount of water-soluble viscosity reducer solution into the thickened oil reservoir at a very high injection rate in a short time, so as to reduce the viscosity of the thickened oil, rapidly increase the formation pressure coefficient, form a man-made high pressure in the reservoir, overcome the starting pressure between the injection well and the production well, thereby improve the effective displacement pressure difference of the reservoir and increase the liquid volume of the oil well. Since the injection pressure of viscosity reduction and pressure drive is close to the formation fracture pressure, during the injection process of viscosity reduction and pressure drive, a large number of network micro-fractures will be formed near the injection well and continuously and uniformly expand into the formation, and the viscosity reducer solution will enter the deep part of the reservoir along with the expansion of the micro-fractures, thereby expanding the swept volume of the viscosity reduction system. In addition, the micro-fractures formed by viscosity reduction and pressure drive can effectively reduce the adverse effects of the heterogeneity of the reservoir, which is beneficial to the balanced advancement of the viscosity reduction system.

[0005] In the process of viscosity reduction and pressure drive development, the determination of the reasonable displacement pressure difference is a very key factor. If the displacement pressure difference is too low, the effective production pressure difference of the oil well is small, which is not conducive to the improvement of the liquid volume and productivity of the single well; if the displacement pressure difference is too large, the injected water-soluble viscosity reduction system will rapidly channel to the production well under the action of the pressure difference, causing the water breakthrough time of the oil well to be greatly advanced, and affecting the overall development effect of the block.

[0006] In the Chinese patent application with the application number CN201810122003.0, a method and device for determining the recovery degree of oil in a core are involved. The method comprises: determining a target capillary radius of a single capillary in a capillary bundle based on initial capillary radius distribution data, wherein the target capillary radius is used to represent the radius of the effective flow channel when the fluid is imbibed in the single capillary under a specified displacement pressure difference; determining the recovery degree of oil in the single capillary under the specified displacement pressure difference based on the target capillary radius; and determining the recovery degree of oil in the capillary bundle under the specified displacement pressure difference according to the recovery degrees of oil in each single capillary in the capillary bundle under the specified displacement pressure difference, and taking the recovery degree of oil in the capillary bundle as the recovery degree of oil in the core.

[0007] In the Chinese patent application with the application number CN201710166925.7, an automatic displacement test method for measuring and calculating core physical property parameters is involved. The displacement test method comprises the following implementation steps: S1, test data acquisition: first, detect the mass data change of the mass measuring instrument, and when it is detected that the mass change of the mass measuring instrument changes linearly with time, it indicates that the displacement reaches stability, at which time the test data acquisition is started. The test data includes the flow rate of the constant-speed constant-pressure pump, the pressure difference between the two ends of the core holder, and the mass change of the mass measuring instrument with time. After a period of t, the constant-speed constant-pressure pump is controlled to stop working, and the test data acquisition is ended. S2, test data analysis and processing: according to the type of the liquid in the liquid container, it is determined whether the displacement type is single-phase displacement or two-phase displacement, and then the core permeability under single-phase displacement and two-phase displacement is calculated respectively.

[0008] In the Chinese patent application with the application number CN201410823131.X, an oil well treatment method for improving the displacement pressure difference of an oil reservoir is involved. The method comprises: closing an injection well corresponding to a high water cut layer of a production well, and injecting an oil reservoir crude oil cleaning agent and an oilfield injection water spacer into the oil reservoir from the production well; injecting a rock surface electrical property modifier into the oil reservoir from the production well; injecting a high-strength polymer delayed crosslinking gel system into the oil reservoir from the production well; injecting a self-degradable polymer gel system into the oil reservoir from the production well; and injecting a gel cleaning system into the oil reservoir from the production well, closing the production well and waiting for a preset time.

[0009] The above prior arts are quite different from the present application, and cannot solve the technical problems we want to solve. Therefore, we have invented a new method for determining the reasonable displacement pressure difference for viscous oil reservoir viscosity reduction and pressure drive development. SUMMARY

[0010] The purpose of the present application is to provide a method for determining the reasonable displacement pressure difference for viscous oil reservoir viscosity reduction and pressure drive development, which provides a way for determining the reasonable injection parameters for viscous oil reservoir viscosity reduction and pressure drive development.

[0011] The object of the present application can be achieved by the following technical measures: a method for determining a reasonable displacement pressure difference in thickened oil reservoir viscosity reduction and pressure drive development, comprising:

[0012] Step 1: based on experimental results, fitting a relationship between thickened oil mobility and starting pressure gradient;

[0013] Step 2, calculate the mobility value of thickened oil in the reservoir, and calculate the corresponding starting pressure gradient value according to the relationship;

[0014] Step 3: determine the starting pressure value between injection and production wells according to the pressure drive injection-production well spacing, as the minimum displacement pressure difference;

[0015] Step 4: determine the maximum displacement pressure difference through the maximum liquid production capacity of the oil well;

[0016] Step 5: calculate the cumulative net present value corresponding to different production pressure differences within the displacement pressure difference limit range;

[0017] Step 6: take the displacement pressure difference corresponding to the maximum cumulative net present value as the reasonable displacement pressure difference in thickened oil reservoir viscosity reduction and pressure drive development.

[0018] The object of the present application can also be achieved by the following technical measures:

[0019] In step 1, the relationship between crude oil viscosity, reservoir permeability and starting pressure gradient is determined by experiment, and the experimental results are plotted on a chart, and the relationship between thickened oil mobility and starting pressure gradient is fitted by multiple regression.

[0020] In step 1, there is a function relationship between crude oil viscosity, reservoir permeability and thickened oil mobility as follows:

[0021] λ=K / μ

[0022] In the formula, λ is the thickened oil mobility; K is the reservoir permeability; μ is the crude oil viscosity.

[0023] In step 1, the relationship between thickened oil mobility and starting pressure gradient is expressed as:

[0024] log G p =-a×logλ+b

[0025] In the formula, Gp is the starting pressure gradient of the thickened oil reservoir; λ is the thickened oil mobility; a, b are the coefficients of the linear equation obtained by regression;

[0026] In step 2, the mobility value of thickened oil in the reservoir is calculated according to the permeability and crude oil viscosity of the actual reservoir, and the starting pressure gradient value corresponding to the mobility value of thickened oil in the reservoir is calculated through the relationship obtained in step 1.

[0027] In step 3, according to the injection-production well spacing of the pressure drop and viscosity reduction drive pattern, and the reservoir threshold pressure gradient value obtained in step 2, the threshold pressure value between the injection well and the production well is calculated, and the value is taken as the minimum displacement pressure difference between the injection well and the production well in the development process of the pressure drop and viscosity reduction drive.

[0028] In step 3, there is a function relationship between the injection-production well spacing, the threshold pressure gradient, and the threshold pressure between the injection well and the production well as follows:

[0029] P SH =G p ×L WO

[0030] In the formula, P SH is the threshold pressure between the injection well and the production well; Gp is the threshold pressure gradient of the heavy oil reservoir; L wo is the injection-production well spacing.

[0031] In step 4, according to the working condition of the oil well, the maximum liquid production capacity of the oil well is determined, and the displacement pressure difference required to reach the maximum liquid production capacity is determined through the displacement capacity calculation formula, and the displacement pressure difference is taken as the maximum displacement pressure difference between the injection well and the production well in the development process of the pressure drop and viscosity reduction drive.

[0032] In step 4, there is a function relationship between the displacement pressure difference and the liquid production capacity of the oil well as follows:

[0033]

[0034] In the formula, P d is the displacement pressure difference; Q is the liquid production capacity of the oil well; μ is the viscosity of the crude oil; r is the pressure drive control radius; r w is the wellbore radius of the oil well; h is the reservoir thickness; K is the reservoir permeability; Gp is the reservoir threshold pressure gradient.

[0035] In step 4, the maximum liquid production capacity of the oil well is determined through the working condition of the oil well, and the displacement pressure difference corresponding to the maximum liquid production capacity is the maximum displacement pressure difference between the injection well and the production well.

[0036] In step 5, the minimum displacement pressure difference between the injection well and the production well in step 3 is taken as the lower limit of the displacement pressure difference, and the maximum displacement pressure difference between the injection well and the production well in step 4 is taken as the upper limit of the displacement pressure difference, the cumulative oil production corresponding to different displacement pressure differences in the displacement pressure difference range is calculated, and the cumulative net present value corresponding to different cumulative oil productions is calculated by using the dynamic economic evaluation method.

[0037] In step 6, the displacement pressure difference corresponding to the maximum cumulative net present value is taken as the reasonable displacement pressure difference of the heavy oil reservoir development by the pressure drop and viscosity reduction drive by using the mathematical optimization method.

[0038] There is a function relationship between the cumulative net present value NPV and the displacement pressure difference P d as follows:

[0039] NPV = aP d 2 +bP d +c

[0040] wherein NPV is the cumulative net present value, P d is the displacement pressure difference, a, b, c are the coefficients of the quadratic equation obtained by regression.

[0041] The method for determining the reasonable displacement pressure difference in the heavy oil reservoir viscosity-reducing pressure flooding development in the application establishes the relationship between the heavy oil mobility and the threshold pressure gradient in the heavy oil reservoir viscosity-reducing pressure flooding development process through experiments, and then the minimum and maximum displacement pressure differences are obtained according to the viscosity-reducing pressure flooding injection-production well spacing and the maximum liquid production capacity of the oil well. Through reservoir numerical simulation and dynamic economic evaluation, the reasonable displacement pressure difference in the heavy oil reservoir viscosity-reducing pressure flooding development is determined by using the optimization theory and taking the financial net present value as the optimization target, thereby providing a way for determining the reasonable injection parameters in the heavy oil reservoir viscosity-reducing pressure flooding development. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The flow chart of a specific embodiment of the method for determining the reasonable displacement pressure difference in the heavy oil reservoir viscosity-reducing pressure flooding development in the application;

[0043] Figure 2 The heavy oil mobility and threshold pressure gradient change relationship chart in a specific embodiment 1 of the application;

[0044] Figure 3 The relationship curve between the different displacement pressure differences and the cumulative net present value when the reasonable displacement pressure difference is obtained in a specific embodiment 1 of the application;

[0045] Figure 4 The heavy oil mobility and threshold pressure gradient change relationship chart in a specific embodiment 2 of the application;

[0046] Figure 5 The relationship curve between the different displacement pressure differences and the cumulative net present value when the reasonable displacement pressure difference is obtained in a specific embodiment 2 of the application;

[0047] Figure 6 The heavy oil mobility and threshold pressure gradient change relationship chart in a specific embodiment 3 of the application;

[0048] Figure 7 The relationship curve between the different displacement pressure differences and the cumulative net present value when the reasonable displacement pressure difference is obtained in a specific embodiment 3 of the application. DETAILED DESCRIPTION

[0049] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0050] It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0051] The method for determining a reasonable displacement pressure difference in the development of a heavy oil reservoir by viscosity reduction and pressure drive of the present application comprises the following steps:

[0052] Step 1, experimentally determine the relationship between the viscosity of crude oil, the permeability of the reservoir and the threshold pressure gradient, plot the experimental results on a chart, and fit the relationship between the heavy oil mobility (the ratio of the permeability of the reservoir to the viscosity of the crude oil) and the threshold pressure gradient by multiple regression;

[0053] The following functional relationship exists between the viscosity of crude oil, the permeability of the reservoir and the heavy oil mobility:

[0054] λ = K / μ

[0055] In the formula, λ is the heavy oil mobility; K is the permeability of the reservoir; and μ is the viscosity of the crude oil.

[0056] In Step 1, the relationship between the heavy oil mobility and the threshold pressure gradient can be expressed as:

[0057] log G p = -a x log λ + b

[0058] In the formula, Gp is the threshold pressure gradient of the heavy oil reservoir; λ is the heavy oil mobility; and a and b are the coefficients of the linear equation obtained by regression;

[0059] Step 2, calculate the mobility value of the heavy oil in the reservoir according to the permeability and the viscosity of the crude oil of the actual reservoir, and calculate the threshold pressure gradient value corresponding to the mobility value of the heavy oil in the reservoir by the relationship obtained in Step 1;

[0060] Step 3, calculate the threshold pressure value between the injection well and the production well according to the injection-production well spacing of the well pattern for viscosity reduction and pressure drive, and in combination with the threshold pressure gradient value obtained in Step 2, and take the value as the minimum displacement pressure difference between the injection well and the production well in the development process of viscosity reduction and pressure drive;

[0061] The following functional relationship exists between the injection-production well spacing, the threshold pressure gradient and the threshold pressure between the injection well and the production well:

[0062] P SH =G p ×L WO

[0063] wherein P SH is the displacement pressure difference between injection well and production well; Gp is the threshold pressure gradient of the heavy oil reservoir; L wo is the distance between injection well and production well.

[0064] Step 4, according to the working condition of the oil well, the maximum liquid production capacity of the oil well is determined, and the displacement pressure difference required to reach the maximum liquid production capacity is determined through the pressure drive productivity calculation formula, and the displacement pressure difference is taken as the maximum displacement pressure difference between injection well and production well in the viscosity reduction pressure drive development process;

[0065] The displacement pressure difference and the liquid production capacity of the oil well have the following functional relationship:

[0066]

[0067] wherein P d is the displacement pressure difference; Q is the liquid production capacity of the oil well; μ is the viscosity of the crude oil; r is the pressure drive control radius; r w is the wellbore radius of the oil well; h is the reservoir thickness; K is the reservoir permeability; Gp is the threshold pressure gradient of the reservoir;

[0068] The maximum liquid production capacity of the oil well is determined through the working condition of the oil well, and the displacement pressure difference corresponding to the maximum liquid production capacity is the maximum displacement pressure difference between injection well and production well.

[0069] Step 5, taking the minimum displacement pressure difference between injection well and production well in step 3 as the lower limit of the displacement pressure difference, and taking the maximum displacement pressure difference between injection well and production well in step 4 as the upper limit of the displacement pressure difference, the cumulative oil production corresponding to different displacement pressure differences within the displacement pressure difference range is calculated through the reservoir numerical simulation software, and the cumulative net present value corresponding to different cumulative oil production is calculated by using the dynamic economic evaluation method;

[0070] The cumulative net present value corresponding to different displacement pressure differences is scattered in the table, and step 6 is entered;

[0071] Step 6, using mathematical optimization method, the displacement pressure difference corresponding to the maximum cumulative net present value is taken as the reasonable displacement pressure difference of the heavy oil reservoir in the viscosity reduction pressure drive development.

[0072] The cumulative net present value NPV and the displacement pressure difference P d have the following functional relationship:

[0073] NPV = aP d 2 +bP d +c

[0074] wherein NPV is the cumulative net present value, P da, b, c are coefficients of the quadratic equation obtained by regression.

[0075] The method for determining the reasonable displacement pressure difference in the development of heavy oil reservoirs by viscosity reduction and pressure displacement of the application establishes the relationship between the heavy oil mobility and the threshold pressure gradient in the development process of heavy oil reservoirs by viscosity reduction and pressure displacement through experiments, and then determines the minimum and maximum displacement pressure differences according to the injection-production well spacing and the maximum liquid production capacity of the oil well in the development of heavy oil reservoirs by viscosity reduction and pressure displacement. Through numerical simulation and dynamic economic evaluation of the reservoir, the reasonable displacement pressure difference in the development of heavy oil reservoirs by viscosity reduction and pressure displacement is determined by using the optimization theory and taking the financial net present value as the optimization target, thereby providing a way for determining the reasonable injection parameters in the development of heavy oil reservoirs by viscosity reduction and pressure displacement.

[0076] The following are several specific embodiments of the application.

[0077] Embodiment 1

[0078] In the specific embodiment 1 of the application, as shown in Figure 1 , Figure 1 is a flow chart of the method for determining the reasonable displacement pressure difference in the development of heavy oil reservoirs by viscosity reduction and pressure displacement.

[0079] In step 101, the relationship between the crude oil viscosity, the reservoir permeability and the threshold pressure gradient is determined by experiments, and the relationship between the heavy oil mobility (the ratio of the reservoir permeability to the crude oil viscosity) and the threshold pressure gradient is calculated and plotted according to the experimental results, and the established chart is as shown in Figure 2 .

[0080] Based on the relationship chart between the heavy oil mobility and the threshold pressure gradient obtained by experiments, the relationship between the heavy oil mobility and the threshold pressure gradient is fitted by multiple regression, and the function relationship obtained by fitting is:

[0081] l0g G p =-0.92logλ-1.73

[0082] In the formula, Gp is the threshold pressure gradient of the heavy oil reservoir; and λ is the heavy oil mobility.

[0083] The flow proceeds to step 102.

[0084] In step 102, the mobility value of the heavy oil in the reservoir is calculated according to the permeability and the crude oil viscosity of the actual reservoir, and the threshold pressure gradient value corresponding to the mobility value of the heavy oil in the reservoir is calculated by the relationship obtained in step 1.

[0085] For example, the crude oil viscosity under the reservoir conditions is 1100 mPa.s, the reservoir permeability is 760×10 -3 μm 2 , and the heavy oil mobility under the reservoir conditions is calculated to be 0.69×10 -3 μm 2 / mPa.s. Using the relationship between heavy oil mobility and starting pressure gradient obtained in step 101, the heavy oil mobility can be calculated to be 0.69 × 10⁻⁶ mPa·s. -3 μm 2 The corresponding startup pressure gradient at / mPa.s is 0.018MPa / m. The process proceeds to step 103.

[0086] In step 103, based on the injection-production well spacing of the viscosity-reducing pressure-driven well network and the reservoir initiation pressure gradient value obtained in step 102, the initiation pressure value between injection and production wells is calculated. The following functional relationship exists between the injection-production well spacing, the initiation pressure gradient, and the initiation pressure between injection and production wells:

[0087] P SH =G p ×L WO

[0088] In the formula, P SH Gp represents the initiation pressure between injection and production wells; Gp represents the initiation pressure gradient of the heavy oil reservoir; L wo This refers to the distance between injection and production wells.

[0089] For example, in the viscosity-reducing pressure drive development of a heavy oil reservoir, the well spacing between injection and production wells is 280m. The starting pressure gradient calculated in step 102 is 0.018MP / m, and the calculated starting pressure between injection and production wells is 5.1MPa. This value is the minimum displacement pressure difference between injection and production wells during the viscosity-reducing pressure drive development process. The process then proceeds to step 104.

[0090] In step 104: Based on the well operating conditions, the maximum production capacity of the well is determined, and the displacement pressure difference required to achieve the maximum production capacity is determined using the pressure-driven production capacity calculation formula. The displacement pressure difference and the well production capacity have the following functional relationship:

[0091]

[0092] In the formula, P d The displacement pressure differential; Q is the well production capacity; μ is the crude oil viscosity; r is the pressure drive control radius; r w Where is the wellbore radius; h is the reservoir thickness; K is the reservoir permeability; Gp is ​​the reservoir initiation pressure gradient;

[0093] For example, based on the operating conditions of the oil well, the maximum fluid production capacity of the oil well is determined to be 40m³. 3 / d, crude oil viscosity is 1100 mPa·s, pressure drive control radius is 260 m, reservoir thickness is 12 m, reservoir permeability is 760 × 10⁻⁶. -3 μm 2, the reservoir threshold pressure gradient is 0.018 MPa / m, and according to the above formula, the displacement pressure difference required for the oil well to reach the maximum liquid production capacity is 13.2 MPa, which is the maximum displacement pressure difference between the injection well and the production well in the viscosity reduction pressure drive development process. The process enters step 105.

[0094] In step 105, the minimum displacement pressure difference of 5.1 MPa between the injection well and the production well determined in step 103 is taken as the lower limit of the displacement pressure difference, and the maximum displacement pressure difference of 13.2 MPa between the injection well and the production well determined in step 104 is taken as the upper limit of the displacement pressure difference. The displacement pressure difference between the injection well and the production well is changed within the displacement pressure difference value range, and the cumulative oil production corresponding to different displacement pressure differences between the injection well and the production well is calculated by using the reservoir numerical simulation software. Using the dynamic economic evaluation method, the cumulative net present value corresponding to different cumulative oil production is calculated, and the cumulative net present value corresponding to different displacement pressure differences between the injection well and the production well is obtained. The process enters step 106.

[0095] In step 106, the cumulative net present value scatter point data under different displacement pressure differences between the injection well and the production well is plotted into a data table, the one-dimensional quadratic regression of the scatter point data is performed, and the maximum value of the one-dimensional quadratic equation obtained by regression is calculated. The displacement pressure difference corresponding to the maximum value is the reasonable displacement pressure difference for the heavy oil reservoir viscosity reduction pressure drive development.

[0096] The cumulative net present value NPV and the displacement pressure difference P d between the injection well and the production well satisfy the following function relationship:

[0097] NPV=aP d 2 +bP d +c

[0098] In the formula, NPV is the cumulative net present value, P d is the displacement pressure difference, a, b, and c are the coefficients of the one-dimensional quadratic equation obtained by regression.

[0099] Figure 3 The relationship curve between different displacement pressure differences and the cumulative net present value is shown in FIG. 1. The quadratic function of regression is:

[0100] y=-4327.7x 2 +94079x+158834

[0101] Using the extreme value formula of the quadratic function, the maximum net present value is 672441.2 yuan, and the corresponding displacement pressure difference is 10.4 MPa, which is the reasonable displacement pressure difference for the heavy oil reservoir viscosity reduction pressure drive development.

[0102] The method establishes the relationship between the heavy oil mobility and the threshold pressure gradient in the process of viscosity-reducing pressure flooding development of the heavy oil reservoir through experiments, and according to the injection-production well spacing and the maximum liquid production capacity of the oil well, the minimum and maximum displacement pressure differentials are obtained, and through numerical simulation and dynamic economic evaluation of the reservoir, the reasonable displacement pressure differential of the viscosity-reducing pressure flooding development of the heavy oil reservoir is determined by using the optimization theory and taking the financial net present value as the optimization target. The present application provides a method for determining the reasonable displacement pressure differential of the viscosity-reducing pressure flooding development of the heavy oil reservoir, and provides technical support and theoretical support for the viscosity-reducing pressure flooding development.

[0103] Embodiment 2

[0104] In the specific embodiment 2 of the present application, as shown in Figure 1 , Figure 1 a flow chart of the method for determining the reasonable displacement pressure differential of the viscosity-reducing pressure flooding development of the heavy oil reservoir.

[0105] In step 101, the relationship between the crude oil viscosity, the reservoir permeability and the threshold pressure gradient is determined through experiments, and the relationship chart between the heavy oil mobility (the ratio of the reservoir permeability to the crude oil viscosity) and the threshold pressure gradient is calculated and plotted according to the experimental results, and the established chart is as shown in Figure 4 ;

[0106] Based on the relationship chart between the heavy oil mobility and the threshold pressure gradient obtained through experiments, the relationship formula between the heavy oil mobility and the threshold pressure gradient is fitted through multiple regression, and the function relationship formula obtained through fitting is:

[0107] log G p =-0.51logλ-1.89

[0108] In the formula, Gp is the threshold pressure gradient of the heavy oil reservoir; and λ is the heavy oil mobility.

[0109] The flow proceeds to step 102.

[0110] In step 102, the mobility value of the heavy oil in the reservoir is calculated according to the permeability and the crude oil viscosity of the actual reservoir, and the threshold pressure gradient value corresponding to the mobility value of the heavy oil in the reservoir is calculated through the relationship formula obtained in step 1.

[0111] For example, the crude oil viscosity under the reservoir condition is 2000 mPa.s, the reservoir permeability is 350x10 -3 μm 2 , and the calculated heavy oil mobility under the reservoir condition is 0.175x10 -3 μm 2 / mPa.s. Through the relationship formula between the heavy oil mobility and the threshold pressure gradient obtained in step 101, the heavy oil mobility of 0.175x10 -3 μm 2The corresponding starting pressure gradient at / mPa.s is 0.037MPa / m. The process proceeds to step 103.

[0112] In step 103, based on the injection-production well spacing of the viscosity-reducing pressure-driven well network and the reservoir initiation pressure gradient value obtained in step 102, the initiation pressure value between injection and production wells is calculated. The following functional relationship exists between the injection-production well spacing, the initiation pressure gradient, and the initiation pressure between injection and production wells:

[0113] P SH =G p ×L WO

[0114] In the formula, P SH Gp represents the initiation pressure between injection and production wells; Gp represents the initiation pressure gradient of the heavy oil reservoir; L wo This refers to the distance between injection and production wells.

[0115] For example, in the viscosity-reducing pressure drive development of a heavy oil reservoir, the well spacing between injection and production wells is 220m. The starting pressure gradient calculated in step 102 is 0.037MP / m, and the calculated starting pressure between injection and production wells is 8.14MPa. This value is the minimum displacement pressure difference between injection and production wells during the viscosity-reducing pressure drive development process. The process then proceeds to step 104.

[0116] In step 104: Based on the well operating conditions, the maximum production capacity of the well is determined, and the displacement pressure difference required to achieve the maximum production capacity is determined using the pressure-driven production capacity calculation formula. The displacement pressure difference and the well production capacity have the following functional relationship:

[0117]

[0118] In the formula, P d The displacement pressure differential; Q is the well production capacity; μ is the crude oil viscosity; r is the pressure drive control radius; r w Where is the wellbore radius; h is the reservoir thickness; K is the reservoir permeability; Gp is ​​the reservoir initiation pressure gradient;

[0119] For example, based on the operating conditions of the oil well, the maximum fluid production capacity of the oil well is determined to be 32m³. 3 / d, crude oil viscosity 2000 mPa·s, pressure drive control radius 200 m, reservoir thickness 9 m, reservoir permeability 350 × 10⁻⁶. -3 μm 2 The reservoir initiation pressure gradient is 0.037 MPa / m. According to the above formula, the displacement pressure difference required for the oil well to reach its maximum production capacity is 22.1 MPa. This value is the maximum displacement pressure difference between injection and production wells during viscosity-reducing pressure drive development. The process proceeds to step 105.

[0120] In step 105, the minimum displacement pressure difference between injection and production wells (8.14 MPa) determined in step 103 is taken as the lower limit of the displacement pressure difference value, and the maximum displacement pressure difference between injection and production wells (22.1 MPa) determined in step 104 is taken as the upper limit of the displacement pressure difference value. The displacement pressure difference between injection and production wells is adjusted within this range, and the cumulative oil production corresponding to different displacement pressure differences between injection and production wells is calculated using reservoir numerical simulation software. Using a dynamic economic evaluation method, the cumulative net present value corresponding to different cumulative oil production is calculated, thus obtaining the cumulative net present value corresponding to different displacement pressure differences between injection and production wells. The process then proceeds to step 106.

[0121] In step 106, the cumulative net present value scatter plots under different injection-production well displacement pressure differences are plotted in a data table. A quadratic regression is performed on the scatter plots, and the maximum value of the quadratic equation obtained from the regression is obtained. The displacement pressure difference corresponding to the maximum value is the reasonable displacement pressure difference for viscosity-reducing pressure drive development of heavy oil reservoirs.

[0122] Cumulative Net Present Value (NPV) and Displacement Pressure Difference (P) between Injection and Production Wells d The following functional relationship exists between them:

[0123] NPV = aP d 2 +bP d +c

[0124] In the formula, NPV is the cumulative net present value, and P... d Let be the displacement pressure difference, and a, b, and c be the coefficients of the quadratic equation obtained from the regression.

[0125] Figure 5 This is a curve showing the relationship between different displacement pressure differentials and cumulative net present value. The quadratic regression function is:

[0126] y = -3576.8x 2 +111310x-197552

[0127] Using the quadratic function extremum formula, the maximum net present value can be calculated to be 647,992.2 yuan, corresponding to a displacement pressure difference of 14.8 MPa. This value is the reasonable displacement pressure difference for viscosity-reducing pressure flooding development of heavy oil reservoirs.

[0128] This method experimentally establishes the relationship between heavy oil mobility and starting pressure gradient during viscosity-reducing pressure-driven development of heavy oil reservoirs. Based on the injection-production well spacing and the maximum production capacity of the oil wells, it calculates the minimum and maximum displacement pressure differentials. Then, through reservoir numerical simulation and dynamic economic evaluation, and applying optimization theory, it determines the reasonable displacement pressure differential for viscosity-reducing pressure-driven development of heavy oil reservoirs with net present value as the optimization objective. This invention provides a method for determining the reasonable displacement pressure differential for viscosity-reducing pressure-driven development of heavy oil reservoirs, offering technical and theoretical support for this development.

[0129] Embodiment 3:

[0130] In the specific embodiment 3 of the present application, as shown in Figure 1 , Figure 1 is a flow chart of a method for determining a reasonable displacement pressure difference for a heavy oil reservoir viscosity reduction and pressure drive development.

[0131] In step 101, the relationship between the viscosity of crude oil, the permeability of the reservoir and the threshold pressure gradient is determined by experiment, and a graph between the heavy oil mobility (the ratio of the permeability of the reservoir to the viscosity of crude oil) and the threshold pressure gradient is calculated and plotted according to the experimental results, and the established graph is as shown in Figure 6 ;

[0132] Based on the graph between the heavy oil mobility and the threshold pressure gradient obtained by experiment, the relationship between the heavy oil mobility and the threshold pressure gradient is fitted by multiple regression, and the function relationship fitted is:

[0133] logG p =-1.44logλ-1.59

[0134] In the formula, Gp is the threshold pressure gradient of the heavy oil reservoir; λ is the heavy oil mobility;

[0135] The flow enters step 102.

[0136] In step 102, the mobility value of the heavy oil in the reservoir is calculated according to the permeability and the viscosity of the crude oil of the actual reservoir, and the threshold pressure gradient value corresponding to the mobility value of the heavy oil in the reservoir is calculated through the relationship obtained in step 1.

[0137] For example, under the reservoir conditions, the viscosity of the crude oil is 1500 mPa.s, the permeability of the reservoir is 900x10 -3 μm 2 , and the heavy oil mobility under the reservoir conditions is calculated to be 0.6x10 -3 μm 2 / mPa.s. Through the relationship between the heavy oil mobility and the threshold pressure gradient obtained in step 101, the threshold pressure gradient corresponding to the heavy oil mobility of 0.6x10 -3 μm 2 / mPa.s is calculated to be 0.024 MPa / m. The flow enters step 103.

[0138] In step 103, the threshold pressure value between the injection well and the production well is calculated according to the injection-production well spacing of the viscosity reduction and pressure drive well pattern, and in combination with the threshold pressure gradient value of the reservoir obtained in step 102. There is a function relationship between the injection-production well spacing, the threshold pressure gradient and the threshold pressure between the injection well and the production well as follows:

[0139] P SH =G p xLWO

[0140] In the formula, P SH Gp represents the initiation pressure between injection and production wells; Gp represents the initiation pressure gradient of the heavy oil reservoir; L wo This refers to the distance between injection and production wells.

[0141] For example, in the viscosity-reducing pressure drive development of a heavy oil reservoir, the well spacing between injection and production wells is 330m. The starting pressure gradient calculated in step 102 is 0.024MP / m, and the calculated starting pressure between injection and production wells is 7.92MPa. This value is the minimum displacement pressure difference between injection and production wells during the viscosity-reducing pressure drive development process. The process then proceeds to step 104.

[0142] In step 104: Based on the well operating conditions, the maximum production capacity of the well is determined, and the displacement pressure difference required to achieve the maximum production capacity is determined using the pressure-driven production capacity calculation formula. The displacement pressure difference and the well production capacity have the following functional relationship:

[0143]

[0144] In the formula, P d The displacement pressure differential; Q is the well production capacity; μ is the crude oil viscosity; r is the pressure drive control radius; r w Where is the wellbore radius; h is the reservoir thickness; K is the reservoir permeability; Gp is ​​the reservoir initiation pressure gradient;

[0145] For example, based on the operating conditions of the oil well, the maximum fluid production capacity of the oil well is determined to be 38m³. 3 / d, crude oil viscosity 900 mPa·s, pressure drive control radius 300 m, reservoir thickness 10 m, reservoir permeability 900 × 10⁻⁶ -3 μm 2 The reservoir initiation pressure gradient is 0.024 MPa / m. According to the above formula, the displacement pressure difference required for the oil well to reach its maximum production capacity is 19.4 MPa. This value is the maximum displacement pressure difference between injection and production wells during viscosity-reducing pressure drive development. The process proceeds to step 105.

[0146] In step 105, the minimum displacement pressure difference between injection and production wells (7.92 MPa) determined in step 103 is taken as the lower limit of the displacement pressure difference value, and the maximum displacement pressure difference between injection and production wells (19.4 MPa) determined in step 104 is taken as the upper limit of the displacement pressure difference value. The displacement pressure difference between injection and production wells is adjusted within this range, and the cumulative oil production corresponding to different displacement pressure differences between injection and production wells is calculated using reservoir numerical simulation software. Using a dynamic economic evaluation method, the cumulative net present value corresponding to different cumulative oil production is calculated, thus obtaining the cumulative net present value corresponding to different displacement pressure differences between injection and production wells. The process then proceeds to step 106.

[0147] In step 106, the cumulative net present value scatter plots under different injection-production well displacement pressure differences are plotted in a data table. A quadratic regression is performed on the scatter plots, and the maximum value of the quadratic equation obtained from the regression is obtained. The displacement pressure difference corresponding to the maximum value is the reasonable displacement pressure difference for viscosity-reducing pressure drive development of heavy oil reservoirs.

[0148] Cumulative Net Present Value (NPV) and Displacement Pressure Difference (P) between Injection and Production Wells d The following functional relationship exists between them:

[0149] NPV = aP d 2 +bP d +c

[0150] In the formula, NPV is the cumulative net present value, and P... d Let be the displacement pressure difference, and a, b, and c be the coefficients of the quadratic equation obtained from the regression.

[0151] Figure 7 This is a curve showing the relationship between different displacement pressure differentials and cumulative net present value. The quadratic regression function is:

[0152] y = -9564x 2 +265022x-147228

[0153] Using the quadratic function extremum formula, the maximum net present value can be calculated to be 792,551.5 yuan, corresponding to a displacement pressure difference of 13.8 MPa. This value is the reasonable displacement pressure difference for viscosity-reducing pressure flooding development of heavy oil reservoirs.

[0154] This method experimentally establishes the relationship between heavy oil mobility and starting pressure gradient during viscosity-reducing pressure-driven development of heavy oil reservoirs. Based on the injection-production well spacing and the maximum production capacity of the oil wells, it calculates the minimum and maximum displacement pressure differentials. Then, through reservoir numerical simulation and dynamic economic evaluation, and applying optimization theory, it determines the reasonable displacement pressure differential for viscosity-reducing pressure-driven development of heavy oil reservoirs with net present value as the optimization objective. This invention provides a method for determining the reasonable displacement pressure differential for viscosity-reducing pressure-driven development of heavy oil reservoirs, offering technical and theoretical support for this development.

[0155] This invention establishes the relationship between heavy oil mobility and starting pressure gradient during the development of heavy oil reservoirs by viscosity reduction and pressure drive through experiments. After determining the minimum and maximum displacement pressure difference based on the injection-production well spacing and the maximum production capacity of the oil wells, the invention uses reservoir numerical simulation and dynamic economic evaluation, and applies optimization theory to determine the reasonable displacement pressure difference for the development of heavy oil reservoirs by viscosity reduction and pressure drive with the net present value as the optimization objective.

[0156] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that modifications can be made to the technical solutions described in the foregoing embodiments, or some of the technical features thereof can be replaced equivalently, without departing from the spirit and principle of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

[0157] All that is not described in the specification is known to those skilled in the art.

Claims

1. A method for determining a reasonable displacement pressure differential in viscosity-reducing pressure flooding development of heavy oil reservoirs, characterized in that, The methods for determining the reasonable displacement pressure differential for viscosity-reducing pressure flooding development of this heavy oil reservoir include: Step 1: Based on the experimental results, fit the relationship between heavy oil mobility and starting pressure gradient; Step 2: Calculate the mobility of heavy oil in the reservoir and calculate the corresponding starting pressure gradient value according to the formula; Step 3: Determine the starting pressure value between injection and production wells based on the pressure-driven injection-production well spacing, which will serve as the minimum displacement pressure difference; Step 4: Determine the maximum displacement pressure differential based on the maximum fluid production capacity of the oil well; Step 5: Calculate the cumulative net present value corresponding to different displacement pressure differentials within the displacement pressure differential limit range; Step 6: Use the displacement pressure difference corresponding to the maximum cumulative net present value as the reasonable displacement pressure difference for viscosity reduction pressure flooding development of heavy oil reservoirs, including: using mathematical optimization methods to use the displacement pressure difference corresponding to the maximum cumulative net present value as the reasonable displacement pressure difference for viscosity reduction pressure flooding development of heavy oil reservoirs. Cumulative Net Present Value (NPV) and Displacement Pressure Difference (P) d The following functional relationship exists between them: ； In the formula, NPV is the cumulative net present value, and P... d Let be the displacement pressure difference, and a, b, and c be the coefficients of the quadratic equation obtained from the regression.

2. The method for determining a reasonable displacement pressure differential in viscosity-reducing pressure flooding development of heavy oil reservoirs according to claim 1, characterized in that, In step 1, the relationship between crude oil viscosity, reservoir permeability and starting pressure gradient is experimentally determined, and the experimental results are plotted on a graph. The relationship between heavy oil mobility and starting pressure gradient is fitted by multiple regression.

3. The method for determining a reasonable displacement pressure differential in viscosity-reducing pressure flooding development of heavy oil reservoirs according to claim 2, characterized in that, In step 1, the following functional relationship exists between crude oil viscosity, reservoir permeability, and heavy oil mobility: ； In the formula, λ is the heavy oil mobility; K is the reservoir permeability; and μ is the crude oil viscosity.

4. The method for determining a reasonable displacement pressure differential in viscosity-reducing pressure flooding development of heavy oil reservoirs according to claim 3, characterized in that, In step 1, the relationship between heavy oil mobility and starting pressure gradient is expressed as follows: ； In the formula, Gp is ​​the starting pressure gradient of the heavy oil reservoir; λ is the heavy oil mobility; and a and b are the coefficients of the linear equation obtained from the regression.

5. The method for determining a reasonable displacement pressure differential in viscosity-reducing pressure flooding development of heavy oil reservoirs according to claim 1, characterized in that, In step 2, the mobility value of heavy oil in the reservoir is calculated based on the actual reservoir permeability and crude oil viscosity. Using the relationship obtained in step 1, the starting pressure gradient value corresponding to the mobility value of heavy oil in the reservoir is calculated.

6. The method for determining a reasonable displacement pressure differential in viscosity-reducing pressure flooding development of heavy oil reservoirs according to claim 1, characterized in that, In step 3, based on the injection-production well spacing of the viscosity-reducing pressure drive well network and the reservoir start-up pressure gradient value obtained in step 2, the start-up pressure value between injection and production wells is calculated, and this value is used as the minimum displacement pressure difference between injection and production wells during the viscosity-reducing pressure drive development process.

7. The method for determining a reasonable displacement pressure differential in viscosity-reducing pressure flooding development of heavy oil reservoirs according to claim 6, characterized in that, In step 3, the injection-production well spacing, the initiation pressure gradient, and the initiation pressure between injection and production wells have the following functional relationship: ； In the formula, P SH Gp represents the initiation pressure between injection and production wells; Gp represents the initiation pressure gradient of the heavy oil reservoir; L wo This refers to the distance between injection and production wells.

8. The method for determining a reasonable displacement pressure differential in viscosity-reducing pressure flooding development of heavy oil reservoirs according to claim 1, characterized in that, In step 4, the maximum production capacity of the oil well is determined based on the oil well operating conditions, and the displacement pressure difference required to achieve the maximum production capacity is determined by the pressure drive production capacity calculation formula. This displacement pressure difference is used as the maximum displacement pressure difference between injection and production wells during the viscosity reduction pressure drive development process.

9. The method for determining a reasonable displacement pressure differential in viscosity-reducing pressure flooding development of heavy oil reservoirs according to claim 8, characterized in that, In step 4, the displacement pressure differential and the well's production capacity have the following functional relationship: ； In the formula, P d The displacement pressure differential; Q is the well production capacity; μ is the crude oil viscosity; r is the pressure drive control radius; r w denoted as wellbore radius; h as reservoir thickness; K as reservoir permeability; and Gp as reservoir initiation pressure gradient.

10. The method for determining a reasonable displacement pressure differential in viscosity-reducing pressure flooding development of heavy oil reservoirs according to claim 8, characterized in that, In step 4, the maximum production capacity of the oil well is determined by the oil well operating conditions. The displacement pressure difference corresponding to the maximum production capacity is the maximum displacement pressure difference between the injection and production wells.

11. The method for determining a reasonable displacement pressure differential in viscosity-reducing pressure flooding development of heavy oil reservoirs according to claim 1, characterized in that, In step 5, the minimum displacement pressure difference between injection and production wells in step 3 is taken as the lower limit of the displacement pressure difference value, and the maximum displacement pressure difference between injection and production wells in step 4 is taken as the upper limit of the displacement pressure difference value. The cumulative oil production corresponding to different displacement pressure differences within the displacement pressure difference limit range is calculated, and the cumulative net present value corresponding to different cumulative oil production is calculated using the dynamic economic evaluation method.

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