A method for improving oil recovery in high water-cut stage of heavy oil reservoir with active edge and bottom water

Abstract

The present invention relates to the technical field of oilfield development, and specifically to a method for improving the recovery rate of active bottom water heavy oil reservoirs at the high water-cut stage. The method comprises: selecting a foaming viscosity reducer that has both foaming and viscosity reducing effects, and characterizing its performance parameters; determining the relative position between the injection well and the production well, and deploying the well network; injecting the foaming viscosity reducer for displacement development; calculating the amount of nitrogen used in the displacement process, and injecting the nitrogen into the reservoir through the injection well; calculating the cumulative net present value under different displacement pressure differences between the injection and production wells; and determining the injection pressure of the injection well and the bottom hole flow pressure of the production well during the displacement process. The method of the present invention is based on the numerical simulation characterization of the reservoir performance of the foaming viscosity reducer, combined with dynamic economic evaluation, and uses optimization theory to achieve balanced displacement and effective utilization of the residual oil between wells in active bottom water heavy oil reservoirs, and provides a way for the effective utilization of the residual oil between wells in the high water-cut stage of active bottom water heavy oil reservoirs.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield development, and in particular to a method for improving the recovery rate of an active edge and bottom water heavy oil reservoir at a high water content stage. Background Art

[0002] Shengli Oilfield has rich active marginal and bottom water heavy oil reservoir resources, which are mainly distributed in 86 unit blocks such as Changdi, Linpan and Dalujia, with geological reserves of 296 million tons.

[0003] Affected by active edge and bottom water, the water-free production period of heavy oil reservoirs is short and the water content rises rapidly. After the reservoir is put into development, it will rise to the ultra-high water content period in a short time. In addition, after the bottom water cone of the active edge and bottom water heavy oil reservoir, affected by the oil-water mobility ratio, the edge and bottom water will enter the oil well along the water channel in large quantities, and the residual oil between the wells is difficult to mobilize, resulting in the problem of high liquid volume and low oil volume in oil well production, and the cost of surface water treatment is also high. For the active edge and bottom water heavy oil reservoirs in Shengli Oilfield, the calibrated recovery rate is only 22.1%, and the overall utilization degree is low. Under the current oil price conditions, it is necessary to deepen research to reduce the development cost of active edge and bottom water heavy oil reservoirs, further improve the utilization degree, and realize the efficient development of active edge and bottom water heavy oil reservoirs.

[0004] Chinese patent application CN106285584A discloses a diversified utilization and development method for active bottom water heavy oil reservoir conversion drive, which method includes the following steps: the step of reducing reservoir pressure in the selected active bottom water heavy oil reservoir block; the step of determining the development method and parameter optimization for the target well group of the above-mentioned reservoir block; the step of treating and comprehensively utilizing the formation water of the above-mentioned reservoir block. The reservoir pressure reduction refers to drilling a water well at the bottom of the bottom water, taking water to the ground through the water well, and using it for existing water use measures on the ground after water quality treatment until the water layer pressure is reduced to below 4.5MPa, reaching the reservoir conditions suitable for steam drive. The invention combines reservoir pressure reduction, development method and parameter optimization, formation water treatment and comprehensive utilization, effectively mobilizes active bottom water heavy oil reservoirs and realizes smooth steam drive, and ultimately improves the recovery rate and reserve utilization rate of heavy oil reservoirs.

[0005] However, in the current situation of low oil prices and rising development costs, in order to reduce development costs while improving development benefits and reservoir utilization, it is necessary to develop a new method that can improve the recovery rate of active edge and bottom water heavy oil reservoirs. Summary of the invention

[0006] The main purpose of the present invention is to provide a method for improving the recovery rate of an active bottom water heavy oil reservoir in the high water content stage. The method of the present invention is based on the reservoir numerical simulation characterization of the performance of a foaming viscosity reducer, combined with dynamic economic evaluation, and uses optimization theory to achieve balanced displacement and effective utilization of the remaining oil between wells in the active bottom water heavy oil reservoir, providing a new way for the effective utilization of the remaining oil between wells in the high water content stage of the active bottom water heavy oil reservoir.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for improving the recovery rate of an active edge and bottom water heavy oil reservoir in a high water content stage, which comprises the following steps:

[0009] Select a foaming viscosity reducing agent that has both foaming and viscosity reducing effects, and characterize its performance parameters;

[0010] Determine the relative position between injection wells and production wells and deploy the well pattern;

[0011] Inject foaming viscosity reducer for displacement development;

[0012] Calculate the amount of nitrogen used in the displacement process and inject nitrogen into the reservoir through the injection well;

[0013] Calculate the cumulative net present value under different displacement pressure differences between injection and production wells;

[0014] Determine the injection pressure of the injection well and the bottom hole flowing pressure of the production well during the displacement process.

[0015] Furthermore, the performance parameters for characterizing the foaming viscosity reducer include: the relationship between the interfacial tension reduction performance and the foaming viscosity reducer concentration, the relationship between the viscosity reduction performance and the foaming viscosity reducer concentration, the relationship between the foam resistance factor and the foaming viscosity reducer concentration, and the relationship between the foam half-life and the foaming viscosity reducer concentration.

[0016] Furthermore, the relative positions of the injection well and the production well in the horizontal and vertical directions are determined.

[0017] Furthermore, the relative position of the injection well in the vertical direction can simultaneously meet the requirements of longitudinal balanced displacement of residual oil between wells, such as the foaming viscosity reducer in the lower oil layer foaming when encountering water to block water channeling, the foaming viscosity reducer in the middle oil layer encountering residual oil between wells to reduce viscosity and then displace and advance, and nitrogen over-covering oil displacement at the top of the oil layer.

[0018] Furthermore, the relative positions of the production wells on the plane can ensure that the production wells in the injection and production well group can achieve uniform effects under the nitrogen foam viscosity reduction drive development method.

[0019] Furthermore, the foaming viscosity reducer is injected from the injection well into the oil reservoir to displace the remaining oil between the wells.

[0020] Furthermore, the nitrogen consumption is equal to the sum of the nitrogen consumption for forming nitrogen foam plugging in the water channel at the bottom of the reservoir and the nitrogen consumption for nitrogen overburden flooding at the top of the reservoir.

[0021] Furthermore, the oil production under different displacement pressure differences was predicted by numerical simulation, and the cumulative net present value under different displacement pressure differences was calculated using dynamic economic evaluation method.

[0022] Furthermore, by using mathematical optimization methods, the displacement pressure difference corresponding to the maximum cumulative net present value is taken as the reasonable displacement pressure difference to determine the injection pressure of the injection well and the bottom hole flow pressure of the production well during the displacement process.

[0023] Furthermore, there is the following functional relationship between the cumulative net present value NPV and the displacement pressure difference Pd:

[0024] NPV=aP d 2 +bP d +c

[0025] Where NPV is the cumulative net present value, Pd is the displacement pressure difference, and a, b, and c are the coefficients of the quadratic equation obtained by regression.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The method of the present invention characterizes the performance parameters of the foaming viscosity reducer through a numerical model, and based on this, optimizes the relative positions of the injection well and the production well, and deploys the well network; calculates the nitrogen consumption for foaming and oil displacement, and optimizes with the maximum financial net present value as the mathematical goal, determines the reasonable displacement pressure difference between the injection well and the production well in the production process, thereby providing technical guidance and theoretical support for improving the recovery rate in the high water-cut stage of active edge bottom water reservoirs. The present invention is a method for improving the recovery rate in the high water-cut stage of active edge bottom water heavy oil reservoirs that comprehensively considers technical and economic factors. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0029] Figure 1 It is a flow chart of a method for improving oil recovery in a high water-cut stage of an active edge-bottom water heavy oil reservoir according to a specific embodiment of the present invention;

[0030] Figure 2 A schematic diagram of fluid distribution in an oil reservoir during the implementation of a method for improving oil recovery in a high water-cut stage of an active edge-bottom water heavy oil reservoir according to a specific embodiment of the present invention;

[0031] Figure 3The figure is a curve diagram showing the relationship between displacement pressure difference and cumulative net present value when obtaining a reasonable displacement pressure difference for a specific example of the present invention. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0034] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0035] Example 1

[0036] like Figure 1 As shown, the method for improving the recovery factor in the high water-cut stage of an active edge-bottom water heavy oil reservoir comprises the following steps:

[0037] In step 101, a foaming viscosity reducer having both foaming and viscosity reducing effects is selected, and the performance experimental data of the foaming viscosity reducer is fitted using reservoir numerical simulation software, and the relationship between the interfacial tension reduction performance, viscosity reduction performance, foam resistance factor, and half-life of the foaming viscosity reducer and the concentration of the foaming viscosity reducer is characterized in the numerical simulation software to provide the necessary data basis for subsequent optimization. The process enters step 102.

[0038] In step 102, the displacement state of the inter-well residual oil is calculated by using reservoir numerical simulation when the injection well and the production well are in different positions. The positions of the injection well and the production well corresponding to the balanced displacement of the inter-well residual oil in the vertical and horizontal directions are deployed as the optimal injection and production well positions. The relative position of the injection well in the vertical direction can simultaneously meet the requirements of balanced displacement of the inter-well residual oil such as the foaming viscosity reducer in the lower part of the oil layer blocking the water channel when it meets water, the foaming viscosity reducer in the middle of the oil layer meeting the inter-well residual oil and then displacing and advancing, and the nitrogen overburdening oil displacement at the top of the oil layer. The relative position of the production well in the plane can meet the requirements that the production wells in the injection and production well group can achieve uniform effect under the nitrogen foam viscosity reduction drive development mode. Figure 2 It is a schematic diagram of fluid distribution in the reservoir during the implementation of step 102. The process enters step 103.

[0039] In step 103 , a foaming viscosity reducer is injected from the injection well into the oil reservoir to displace the remaining oil between the wells. The flow proceeds to step 104 .

[0040] In step 104, the amount of nitrogen is calculated using numerical simulation software. The amount of nitrogen can satisfy the requirement of forming a stable foam to plug the water channeling channel at the bottom of the oil layer with the foam-type viscosity reducer, realizing nitrogen overburden displacement at the top of the oil layer, and the displacement front can be advanced evenly. The amount of nitrogen is equal to the sum of the amount of nitrogen used to form nitrogen foam plugging of the water channeling channel at the bottom of the reservoir and the amount of nitrogen used to overburden displacement of the nitrogen at the top of the reservoir. The process enters step 105.

[0041] In step 105, the displacement pressure difference is changed, and the daily oil production under different displacement pressure differences is predicted by numerical simulation. After the daily net present value is calculated, the daily net present value is accumulated to obtain the cumulative net present value in the entire production cycle, and the cumulative net present value corresponding to the different displacement pressure differences is obtained. The process proceeds to step 106.

[0042] In step 106, a mathematical optimization method is used to determine the injection pressure of the injection well and the bottom hole flow pressure of the production well during the displacement process by taking the displacement pressure difference corresponding to the maximum cumulative net present value as the reasonable displacement pressure difference.

[0043] The scatter data of the cumulative net present value under different displacement pressure differences are plotted into the data table, and a quadratic regression is performed on the scatter data. The maximum value of the quadratic equation obtained by regression is obtained, and the displacement pressure difference corresponding to the maximum value is the reasonable displacement pressure difference in the displacement process.

[0044] There is the following functional relationship between the cumulative net present value NPV and the displacement pressure difference Pd:

[0045] NPV=aP d 2 +bP d +c

[0046] Where NPV is the cumulative net present value, Pd is the displacement pressure difference, and a, b, and c are the coefficients of the quadratic equation obtained by regression.

[0047] Figure 3 This is the relationship curve between different displacement pressure differences and cumulative net present value. The quadratic function of regression is:

[0048] y=-1113.4x 2 +22531x+672533

[0049] Using the quadratic function extreme value formula, the maximum net present value can be calculated as: 786,518.5 yuan, and the corresponding displacement pressure difference oil is 10.1 MPa. This value is a reasonable production pressure difference, which means that when the difference between the injection pressure of the injection well and the bottom hole flow pressure of the production well is maintained at 10.1 MPa, the late development of active edge and bottom water heavy oil reservoirs with high water content can achieve the best input-output ratio and realize the economical and efficient development of the reservoir.

[0050] The invention has been tested in a field in a certain block of Shengli Oilfield. The test results show that the technology can reduce the water content of production wells by 14% and increase the recovery rate of the test block by about 6%.

[0051] The method for improving the recovery rate of active bottom water heavy oil reservoirs at a high water content stage of the present invention is based on numerical simulation and combines economic evaluation, mathematical optimization and other methods to optimize the relative positions of injection and production wells, clarify the nitrogen dosage and the reasonable displacement pressure difference, thereby realizing the economical and efficient development of active bottom water heavy oil reservoirs at a high water content stage, and providing technical and theoretical support for oilfield production.

[0052] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for improving oil recovery in a high water-cut stage of an active edge-bottom water heavy oil reservoir, characterized in that: It includes the following steps: Step 1, selecting a foaming viscosity reducing agent having both foaming and viscosity reducing effects, and characterizing its performance parameters; Step 2, determine the relative position between the injection well and the production well, and deploy the well pattern; Step 3, injecting a foaming viscosity reducer for displacement development; Step 4, calculating the amount of nitrogen used in the displacement process, and injecting the nitrogen into the reservoir through the injection well; Step 5, calculating the cumulative net present value under different displacement pressure differences between injection and production wells; Step 6, determining the injection pressure of the injection well and the bottom hole flow pressure of the production well during the displacement process; In step 1, the performance parameters for characterizing the foaming viscosity reducer include: the relationship between the interfacial tension reduction performance and the foaming viscosity reducer concentration, the relationship between the viscosity reduction performance and the foaming viscosity reducer concentration, the relationship between the foam resistance factor and the foaming viscosity reducer concentration, and the relationship between the foam half-life and the foaming viscosity reducer concentration; In step 2, the relative positions of the injection well and the production well in the horizontal direction and in the vertical direction are determined; In step 3, the relative position of the injection well in the vertical direction can simultaneously meet the requirements that the foaming viscosity reducer in the lower part of the oil layer bubbles up when it meets water to block the water channeling channel, the foaming viscosity reducer in the middle part of the oil layer meets the residual oil between the wells to reduce the viscosity and then drive forward, and the residual oil between the wells is vertically balanced. In step 4, the relative position of the production wells on the plane can satisfy the requirement that the production wells in the injection and production well group can achieve uniform effect under the nitrogen foam viscosity reduction drive development mode; the nitrogen consumption is equal to the sum of the nitrogen consumption for nitrogen foam plugging of the water channel at the bottom of the reservoir and the nitrogen consumption for nitrogen overburden flooding at the top of the reservoir; In step 5, the oil production under different displacement pressure differences is predicted by numerical simulation, and the cumulative net present value under different displacement pressure differences is calculated by using dynamic economic evaluation method; In step 6, the injection pressure of the injection well and the bottom hole flow pressure of the production well are determined during the displacement process by using a mathematical optimization method and taking the displacement pressure difference corresponding to the maximum cumulative net present value as a reasonable displacement pressure difference; There is the following functional relationship between the cumulative net present value NPV and the displacement pressure difference Pd: NPV=αP d 2 +bP d +c Where NPV is the cumulative net present value, Pd is the displacement pressure difference, and a, b, and c are the coefficients of the quadratic equation obtained by regression.

2. The method according to claim 1, characterized in that: The foaming viscosity reducer is injected into the reservoir from the injection well to displace the remaining oil between wells.

Images