A method for calculating the injection volume of large displacement water replenishment

Abstract

The present invention relates to the technical field of oil production engineering, and in particular to a method for calculating the injection amount of large-displacement water replenishment, the method comprising determining a basic fluid replenishment radius according to the distance between the injection and production wells; determining a basic fluid replenishment amount according to the basic fluid replenishment radius, the effective thickness and porosity of the oil layer; determining a maximum action distance of the injected liquid according to the current oil layer pressure, the depth of the middle part of the oil layer, the oil layer pressure gradient, and the maximum allowable construction pressure; determining a directional additional fluid amount in the connection direction according to the maximum action distance, the basic fluid replenishment radius, the effective thickness and the porosity; determining a supplement coefficient of the directional additional fluid amount according to the soaking time and the formation water injection effect time; and determining a final fluid replenishment amount of a target well according to the basic fluid replenishment amount, the directional additional fluid amount and the supplement coefficient. The present invention improves the accuracy of the large-displacement fluid replenishment injection amount.

Description

Technical Field

[0001] The invention relates to the technical field of oil production engineering, and in particular to a method for calculating the injection amount of large-displacement water replenishment. Background Art

[0002] Water flooding technology is the main means of oilfield development, and the effect of water flooding is a key factor in determining production and benefits. However, due to factors such as oil layer pollution, poor oil layer development, and imperfect injection and production, the injection pressure of some water wells continues to rise, the water absorption capacity of the formation continues to decline, the proportion of non-absorbent wells increases, and the number of under-injected wells gradually increases.

[0003] Chinese patent application publication number: CN112627792A discloses a method for increasing production by fluid replenishment after fracturing oil recovery at isolated well points. This method introduces a single sand body fluid volume optimization method with sand body thickness conversion, sand body control area calculation value, injection PV number, and porosity as the main design parameters by optimizing the fluid replenishment timing, changing the defects of the traditional single-card segment multi-layer general scale design of fracturing, and improving the reasonable matching of the single sand body construction scale and sand body development. The flexible fluid replenishment method of transferring fluid replenishment to adjacent wells of fracturing oil recovery wells and adopting differentiated injection of skid-mounted equipment in stratified sections is effectively applicable to secondary energy and efficiency enhancement of fracturing oil recovery wells. The cumulative oil increase of the test well group has reached 2,452 tons during the effective period. Calculated based on the geological reserves of 22,000 tons per well, the recovery rate of a single well after fluid replenishment can be further increased by more than 5%. However, there are the following problems in the prior art: the prior art has great limitations and is not suitable for the accurate determination of the fluid replenishment amount of large-volume fluid replenishment technology, resulting in the problem of low accuracy of large-volume fluid replenishment injection. Summary of the invention

[0004] To this end, the present invention provides a method for calculating the injection amount of a large-displacement fluid replacement, so as to overcome the problem of low accuracy of the injection amount of a large-displacement fluid replacement in the prior art.

[0005] To achieve the above object, the present invention provides a method for calculating the injection amount of large displacement water replenishment, comprising:

[0006] Step S1, obtaining the injection-production well spacing of the target well, and determining a basic fluid replenishment radius according to the injection-production well spacing, wherein the basic fluid replenishment radius is a multiple of the injection-production well spacing;

[0007] Step S2, obtaining the effective thickness and porosity of the oil layer of the target well, and determining the basic fluid replenishment amount according to the basic fluid replenishment radius, the effective thickness of the oil layer and the porosity, wherein the basic fluid replenishment amount is the product of the basic fluid replenishment area determined by the basic fluid replenishment radius and the effective thickness of the oil layer multiplied by the porosity;

[0008] Step S3, obtaining the current reservoir pressure, the middle depth of the reservoir, the reservoir pressure gradient and the maximum allowable construction pressure of the target well, and determining the maximum effective distance of the injected liquid according to the current reservoir pressure, the middle depth of the reservoir, the reservoir pressure gradient and the maximum allowable construction pressure of the target well, wherein the maximum effective distance is the ratio of the sum of the reservoir pressure converted from the maximum allowable construction pressure and the middle depth of the reservoir minus the current reservoir pressure to the reservoir pressure gradient;

[0009] Step S4, obtaining the number of connection directions of the target well, and determining the amount of directional replenishment fluid in the connection direction according to the maximum action distance, the basic replenishment radius, the effective thickness and the porosity;

[0010] Step S5, obtaining the shut-in time of the target well and the effective time of formation water injection, and determining the supplement coefficient of the amount of supplementary fluid in the direction according to the shut-in time of the target well and the effective time of formation water injection;

[0011] Step S6, determining the final fluid replenishment volume of the target well according to the basic fluid replenishment volume, the directional fluid replenishment volume and the replenishment coefficient, wherein the final fluid replenishment volume is the replenishment coefficient multiplied by the sum of the basic fluid replenishment volume and the directional fluid replenishment volume.

[0012] Furthermore, in step S1, the basic fluid replenishment radius is calculated according to the following formula:

[0013] ;

[0014] In the formula, R represents the basic fluid replenishment radius, and L represents the injection-production well spacing.

[0015] Furthermore, in step S2, the basic fluid replacement amount is calculated according to the following formula:

[0016] ;

[0017] In the formula, V 基础 represents the basic fluid replenishment volume, R represents the basic fluid replenishment radius, H represents the effective thickness of the oil layer, Indicates porosity.

[0018] Furthermore, in step S3, the maximum action distance is calculated according to the following formula:

[0019] ;

[0020] In the formula, D represents the maximum range, P max Indicates the maximum allowable construction pressure, H 中深 It represents the depth of the middle part of the oil layer, P0 represents the current oil layer pressure, and ΔP represents the oil layer pressure gradient.

[0021] Furthermore, in step S4, the direction supplementation liquid amount is calculated according to the following formula:

[0022] ;

[0023] In the formula, V 方向 Indicates the amount of fluid replenishment in a certain direction, n indicates the number of connected directions, R indicates the basic fluid replenishment radius, D indicates the maximum effective distance, H indicates the effective thickness of the oil layer, Indicates porosity.

[0024] Furthermore, in step S5, the supplementation coefficient is calculated according to the following formula:

[0025] ;

[0026] In the formula, γ represents the supplement coefficient, t represents the soaking time, and T represents the time it takes for formation water injection to take effect.

[0027] Furthermore, in step S6, the final injection amount is calculated according to the following formula:

[0028] ;

[0029] In the formula, V 最终 represents the final volume of fluid replenishment, γ represents the replenishment coefficient, V 基础 Indicates the basic fluid replacement volume, V 方向 Indicates the direction of replenishing fluid volume.

[0030] Furthermore, it also includes:

[0031] Step S11, obtaining the number of pores, pore distribution density and pore area ratio of the target well that are lower than a preset porosity, and determining a well condition evaluation value according to the number of pores, pore distribution density and pore area ratio of the target well;

[0032] Step S22, determining a fluid replenishment method of the target well according to the well condition evaluation value of the target well, wherein the fluid replenishment method includes a conventional fluid replenishment method and a fluid replenishment method after determining a compensation supplement coefficient according to a pressure drop rate;

[0033] Step S33, obtaining the water content at the same oil production rate of several wells after fluid replenishment, the water content in the original oil layer, and the water content at the oil production rate of several wells before fluid replenishment, and determining the displacement effect evaluation value after fluid replenishment of several wells according to the water content at the same oil production rate after fluid replenishment of several wells, the water content in the original oil layer, and the water content at the oil production rate of several wells before fluid replenishment;

[0034] Step S44, determining to reduce the basic fluid replenishment radius according to the displacement effect evaluation values ​​of the determined wells after fluid replenishment.

[0035] Furthermore, in step S11, the well condition evaluation value is the arithmetic square root of the ratio of the pore number multiplied by the pore distribution density to the square of the pore area ratio.

[0036] Further, based on the comparison result that the well condition evaluation value is greater than the preset well condition evaluation value, it is determined to perform fluid replenishment according to the conventional fluid replenishment method of steps S1-S6.

[0037] Furthermore, based on the comparison result that the well condition evaluation value is less than or equal to the preset well condition evaluation value, the fluid replenishment method after compensating the supplementary coefficient in the step S5 is determined to perform fluid replenishment, and based on the comparison result that the pressure drop rate of the target well is less than or equal to the preset pressure drop rate, it is determined to increase the supplementary coefficient with the first preset compensation adjustment coefficient.

[0038] Furthermore, based on the comparison result that the well condition evaluation value is less than or equal to the preset well condition evaluation value, the fluid replenishment method after compensating the supplementary coefficient in the step S5 is determined to perform fluid replenishment, and based on the comparison result that the pressure drop rate is greater than the preset pressure drop rate, it is determined to increase the supplementary coefficient with a second preset compensation adjustment coefficient.

[0039] Furthermore, in step S33, the displacement effect evaluation value is the difference between the water content in the original oil layer and the water content of the several wells at the same oil production after fluid replenishment divided by the difference between the water content in the original oil layer and the water content of the several wells at the oil production before fluid replenishment.

[0040] Further, based on the comparison result that the displacement effect evaluation value is less than or equal to the preset displacement effect evaluation value, it is determined that the basic liquid replenishment radius is reduced by the first preset supplementary radius adjustment coefficient.

[0041] Further, based on the comparison result that the displacement effect evaluation value is greater than the preset displacement effect evaluation value, it is determined that the basic liquid replenishment radius is reduced by the second preset supplementary radius adjustment coefficient.

[0042] Compared with the prior art, the beneficial effect of the present invention lies in that the present invention accurately calculates the final fluid replenishment volume required for the target well by comprehensively considering geological parameters (such as injection and production well spacing, effective thickness, porosity), reservoir conditions (such as reservoir pressure, mid-reservoir depth, pressure gradient, maximum allowable construction pressure), well connectivity, and time factors in water injection operations (well soaking time and water injection effectiveness time). By accurately calculating the final fluid replenishment volume, the efficiency of the water injection operation is improved, the maximization of the water drive effect is ensured, and the accuracy of the large-volume fluid replenishment injection volume is improved.

[0043] Furthermore, the present invention evaluates the well conditions and determines the fluid replenishment method through pore parameters, and then determines to adjust the basic supplementary radius according to the evaluation value of the displacement effect after fluid replenishment to optimize the water injection strategy. This operation can accurately guide the fluid replenishment operation and ensure the maximization of the water injection effect. At the same time, the water injection strategy is adjusted in time through effect evaluation, thereby improving the accuracy of large-volume fluid replenishment injection.

[0044] Furthermore, the present invention selects a fluid replenishment method with a compensating supplement coefficient or a conventional fluid replenishment method through a comparison result between the well condition evaluation value and a preset well condition evaluation value. This operation ensures accurate response to different well conditions through personalized selection of fluid replenishment methods, thereby improving the pertinence and effectiveness of water injection operations.

[0045] Furthermore, the present invention adjusts the supplementary coefficient by monitoring the pressure drop rate of the target well and comparing it with the preset pressure drop rate, thereby improving the flexibility and adaptability of the water injection operation and achieving more accurate and effective water injection control under different formation conditions and water injection stages.

[0046] Furthermore, the present invention determines the adjustment of the basic supplement radius by comparing the displacement effect evaluation value with the preset displacement effect evaluation value, and appropriately reduces the basic supplement radius by introducing a preset supplement radius adjustment coefficient, thereby achieving more accurate and effective water injection control under different formation conditions and water injection stages, thereby improving the accuracy of large-volume fluid injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a flow chart of a method for calculating the large displacement water injection amount according to an embodiment of the present invention;

[0048] Figure 2 A flow chart of determining a target well fluid replenishment method according to an embodiment of the present invention;

[0049] Figure 3 A flow chart for determining an increase in supplementary coefficient according to an embodiment of the present invention;

[0050] Figure 4 A flow chart for determining a method for reducing a basic supplementing radius according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0052] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0053] Those skilled in the art will appreciate that the present invention may determine a single parameter by selecting the value with the highest proportion as the preset standard parameter based on data distribution, using weighted summation to take the obtained value as the preset standard parameter, substituting each historical data into a specific formula and taking the obtained value using the formula as the preset standard parameter, or other selection methods, as long as the present invention can clearly define different specific situations in a single determination process through the obtained values.

[0054] See also Figure 1-Figure 4 As shown, Figure 1 This is a flow chart of a method for calculating the large displacement water injection amount according to an embodiment of the present invention; Figure 2 A flow chart of determining a target well fluid replenishment method according to an embodiment of the present invention; Figure 3 A flow chart for determining an increase in supplementary coefficient according to an embodiment of the present invention; Figure 4 A flow chart for determining a method for reducing a basic supplementing radius according to an embodiment of the present invention.

[0055] The embodiment of the present invention is used for a method for calculating a large displacement water replenishment injection amount, comprising:

[0056] Step S1, obtaining the injection-production well spacing of the target well, and determining a basic fluid replenishment radius according to the injection-production well spacing, wherein the basic fluid replenishment radius is a multiple of the injection-production well spacing;

[0057] Step S2, obtaining the effective thickness and porosity of the oil layer of the target well, and determining the basic fluid replenishment amount according to the basic fluid replenishment radius, the effective thickness of the oil layer and the porosity, wherein the basic fluid replenishment amount is the product of the basic fluid replenishment area determined by the basic fluid replenishment radius and the effective thickness of the oil layer multiplied by the porosity;

[0058] Step S3, obtaining the current reservoir pressure, the middle depth of the reservoir, the reservoir pressure gradient and the maximum allowable construction pressure of the target well, and determining the maximum effective distance of the injected liquid according to the current reservoir pressure, the middle depth of the reservoir, the reservoir pressure gradient and the maximum allowable construction pressure of the target well, wherein the maximum effective distance is the ratio of the sum of the reservoir pressure converted from the maximum allowable construction pressure and the middle depth of the reservoir minus the current reservoir pressure to the reservoir pressure gradient;

[0059] Step S4, obtaining the number of connection directions of the target well, and determining the amount of directional replenishment fluid in the connection direction according to the maximum action distance, the basic replenishment radius, the effective thickness and the porosity;

[0060] Step S5, obtaining the shut-in time of the target well and the effective time of formation water injection, and determining the supplement coefficient of the amount of supplementary fluid in the direction according to the shut-in time of the target well and the effective time of formation water injection;

[0061] Step S6, determining the final fluid replenishment volume of the target well according to the basic fluid replenishment volume, the directional fluid replenishment volume and the replenishment coefficient, wherein the final fluid replenishment volume is the replenishment coefficient multiplied by the sum of the basic fluid replenishment volume and the directional fluid replenishment volume.

[0062] Specifically, the present invention accurately calculates the final fluid replenishment volume required for the target well by comprehensively considering geological parameters (such as injection-production well spacing, effective thickness, porosity), reservoir conditions (such as reservoir pressure, mid-reservoir depth, pressure gradient, maximum allowable construction pressure), well connectivity, and time factors in water injection operations (well soaking time and water injection effectiveness time). By accurately calculating the fluid replenishment volume, the efficiency of the water injection operation is improved, the maximization of the water-to-oil effect is ensured, and the accuracy of the large-volume fluid replenishment injection volume is improved.

[0063] Specifically, in step S1, the basic fluid replenishment radius is calculated according to formula (1):

[0064] (1);

[0065] In formula (1), R represents the basic fluid replenishment radius, and L represents the distance between injection and production wells.

[0066] Specifically, in step S2, the basic fluid replacement volume is calculated according to formula (2):

[0067] (2);

[0068] In formula (2), V 基础 represents the basic fluid replenishment volume, R represents the basic fluid replenishment radius, H represents the effective thickness of the oil layer, Indicates porosity.

[0069] In the embodiment of the present invention, the effective thickness of the oil layer is the thickness of the part of the oil layer that has oil production capacity; the porosity is the ratio of the pore volume in the rock to the total volume, which is obtained by measuring the ratio of the pore volume to the total volume in the rock sample.

[0070] Specifically, in step S3, the maximum action distance is calculated according to formula (3):

[0071] (3);

[0072] In formula (3), D represents the maximum action distance, P max Indicates the maximum allowable construction pressure, H 中深 It represents the depth of the middle part of the oil layer, P0 represents the current oil layer pressure, and ΔP represents the oil layer pressure gradient.

[0073] In the embodiment of the present invention, the maximum allowable construction pressure is the maximum pressure value that can ensure the water injection effect without causing damage to the formation and the wellbore, and is calculated based on the fracture pressure of the reservoir rock; the middle depth of the oil layer is the depth from the midpoint of the oil layer in the vertical direction underground to the ground; the current oil layer pressure is the oil layer pressure of the target well before fluid injection; the oil layer pressure gradient is the pressure change per unit depth along the vertical direction of the formation.

[0074] Specifically, in step S4, the amount of the direction supplementary fluid is calculated according to formula (4):

[0075] (4);

[0076] In formula (4), V 方向 Indicates the amount of fluid replenishment in a certain direction, n indicates the number of connected directions, R indicates the basic fluid replenishment radius, D indicates the maximum effective distance, H indicates the effective thickness of the oil layer, Indicates porosity.

[0077] In the embodiment of the present invention, the number of connection directions is the number or direction of channels that can effectively exchange fluids between the target well and the surrounding oil layers, and is calculated by measuring the change in the bottom pressure of the target well.

[0078] Specifically, in step S5, the supplementation coefficient is calculated according to formula (5):

[0079] (5);

[0080] In formula (5), γ represents the supplement coefficient, t represents the soaking time, and T represents the time for formation water injection to take effect.

[0081] In the embodiment of the present invention, the soaking time is the time period during which the water injection operation is stopped to allow the pressure and temperature inside the oil well to naturally balance and recover, which is calculated by real-time collection and recording of the pressure and temperature data inside the well; the formation water injection effective time is the time period from the start of water injection to the time when the oil well begins to be affected by the injected water and shows positive effects such as increased production or pressure recovery, which is calculated by real-time monitoring of the production and pressure changes of the oil well.

[0082] Specifically, in step S6, the final injection amount is calculated according to formula (6):

[0083] (6);

[0084] In formula (6), V 最终 represents the final volume of fluid replenishment, γ represents the replenishment coefficient, V 基础 Indicates the basic fluid replacement volume, V 方向 Indicates the direction of replenishing fluid volume.

[0085] Specifically, an embodiment of the present invention further provides a method for calculating the injection amount of large displacement water replenishment, comprising:

[0086] Step S11, obtaining the number of pores, pore distribution density and pore area ratio of the target well that are lower than a preset porosity, and determining a well condition evaluation value according to the number of pores, pore distribution density and pore area ratio of the target well;

[0087] Step S22, determining a fluid replenishment method of the target well according to the well condition evaluation value of the target well, wherein the fluid replenishment method includes a conventional fluid replenishment method of steps S1-S6 and a fluid replenishment method after compensating for the supplementation coefficient in step S5 according to the pressure drop rate;

[0088] Step S33, obtaining the water content at the same oil production rate of several wells after fluid replenishment, the water content in the original oil layer, and the water content at the oil production rate of several wells before fluid replenishment, and determining the displacement effect evaluation value after fluid replenishment of several wells according to the water content at the same oil production rate after fluid replenishment of several wells, the water content in the original oil layer, and the water content at the oil production rate of several wells before fluid replenishment;

[0089] Step S44, determining to reduce the basic fluid replenishment radius according to the displacement effect evaluation values ​​after fluid replenishment of the plurality of wells determined in step S33.

[0090] Specifically, the present invention evaluates the well conditions and determines the fluid replenishment method through pore parameters, and then adjusts the basic fluid replenishment radius according to the evaluation value of the displacement effect after fluid replenishment to optimize the water injection strategy. This operation can accurately guide the fluid replenishment operation and ensure the maximization of the water injection effect. At the same time, the water injection strategy is adjusted in time through effect evaluation, thereby improving the accuracy of large-volume fluid replenishment injection.

[0091] Specifically, in step S11, the well condition evaluation value is calculated according to formula (7):

[0092] (7);

[0093] In formula (7), Q represents the well condition evaluation value, N represents the number of pores in the target well, M represents the pore distribution density, and A represents the pore area ratio.

[0094] In the embodiment of the present invention, the pore distribution density is the ratio of the total volume of pores in the rock to the total volume of the rock, and the pore area ratio is the ratio of the total area of ​​pores in the rock to the total exposed area of ​​the rock.

[0095] Specifically, under the condition of determining the well condition evaluation value, the embodiment of the present invention determines the fluid replenishment method of the target well according to the comparison result between the well condition evaluation value and the preset well condition evaluation value 0.87;

[0096] When the well condition evaluation value is less than or equal to the preset well condition evaluation value, it is determined to perform fluid replenishment in a fluid replenishment manner after compensating for the supplementary coefficient in step S5;

[0097] When the well condition evaluation value is greater than the preset well condition evaluation value, it is determined to perform fluid replenishment in the conventional fluid replenishment manner of steps S1-S6.

[0098] In the embodiment of the present invention, the preset well condition evaluation value is 0.87, but the above value is not limited thereto, and those skilled in the art may also adjust the value according to actual needs.

[0099] Specifically, the present invention selects the fluid replenishment method with a compensating supplement coefficient or the conventional fluid replenishment method through the comparison result between the well condition evaluation value and the preset well condition evaluation value. This operation ensures accurate response to different well conditions through personalized selection of fluid replenishment methods, thereby improving the pertinence and effectiveness of water injection operations.

[0100] Specifically, under the condition of determining the corresponding fluid replenishment method, the embodiment of the present invention determines the increase in the replenishment coefficient according to the comparison result of the pressure drop rate of the target well and the preset pressure drop rate of 10%;

[0101] When the pressure drop rate is less than or equal to the preset pressure drop rate, it is determined to increase the supplementary coefficient to a corresponding value using the first preset compensation adjustment coefficient of 1.04;

[0102] When the pressure drop rate is greater than the preset pressure drop rate, it is determined to increase the supplementary coefficient to a corresponding value using a second preset compensation adjustment coefficient of 1.13.

[0103] In the embodiment of the present invention, the preset pressure drop rate is 10%, but the above value is not limited thereto, and those skilled in the art may also adjust the value according to actual needs.

[0104] In the embodiment of the present invention, the added supplement coefficient is set to γ z , set γ z =γ×E j , where γ represents the supplementary coefficient, E j represents the jth preset compensation adjustment coefficient, j is 1 or 2, E1 is the first preset compensation adjustment coefficient, and E2 is the second preset compensation adjustment coefficient.

[0105] Specifically, the present invention adjusts the supplementary coefficient by monitoring the pressure drop rate of the target well and comparing it with the preset pressure drop rate, thereby improving the flexibility and adaptability of the water injection operation, and can also achieve more accurate and effective water injection control under different formation conditions and water injection stages.

[0106] Specifically, the pressure drop rate is the difference between the well pressure before the target well is replenished and the well pressure after the target well is replenished, divided by the well pressure after the target well is replenished.

[0107] Specifically, in step S33, the displacement effect evaluation value is calculated according to formula (8):

[0108] (8);

[0109] In formula (8), λ represents the displacement effect evaluation value, S0 represents the water content in the original oil layer, It represents the water content of several wells at the same oil production after fluid replenishment, S b It indicates the water content of several wells at the oil production level before fluid injection.

[0110] Specifically, under the condition of determining the displacement effect evaluation value, the embodiment of the present invention determines to reduce the basic fluid replenishment radius according to the comparison result of the displacement effect evaluation values ​​after fluid replenishment of several wells and the preset displacement effect evaluation value of 0.83;

[0111] When the displacement effect evaluation value is less than or equal to the preset displacement effect evaluation value, it is determined to reduce the basic liquid replenishment radius to a corresponding value using a first preset supplementary radius adjustment coefficient of 0.98;

[0112] When the displacement effect evaluation value is greater than the preset displacement effect evaluation value, it is determined to reduce the basic liquid replenishment radius to a corresponding value using a second preset supplementary radius adjustment coefficient of 0.93.

[0113] In the embodiment of the present invention, the preset displacement effect evaluation value is 0.83, but the above value is not limited thereto, and those skilled in the art may also adjust the value according to actual needs.

[0114] In the embodiment of the present invention, the reduced basic fluid replenishment radius is set to R z , set R z =R×K i , where R represents the basic rehydration radius, K i represents the i-th preset supplementary radius adjustment coefficient, i is 1 or 2, K1 is the first preset supplementary radius adjustment coefficient, and K2 is the second preset supplementary radius adjustment coefficient.

[0115] Specifically, the present invention decides to adjust the basic fluid replenishment radius by comparing the displacement effect evaluation value with the preset displacement effect evaluation value, and appropriately reduces the basic fluid replenishment radius by introducing a preset supplementary radius adjustment coefficient. Under different formation conditions and water injection stages, more precise and effective water injection control is achieved, thereby improving the accuracy of large-volume fluid injection. Embodiment 1:

[0116] The method of fluid replenishment in Well M and Well N of a low permeability block in Daqing Oilfield. Well M and Well N are under-injected wells in a low permeability block in Daqing Oilfield. Their formation effective time, maximum allowable construction pressure and pressure gradient are all 720d, 22.0MPa and 0.15MPa / m. The specific data are as follows:

[0117] hashtag Effective thickness (m) Depth of middle oil layer (m) Current reservoir pressure (MPa) Injection-production well spacing (m) Number of connected directions Porosity (%) Well soaking time (d) M 1.1 1270.6 13.1 320 2 15 15 N 5.2 1284.6 12.5 270 1 15 7

[0118] The amount of fluid replenishment for each layer of the well is determined according to the following steps:

[0119] a. Obtain the injection-production distance L, the number of connected directions n and the porosity of well M , 320m, 2 and 15.0% respectively; obtain the injection-production well spacing L, the number of connected directions n and the porosity of well N , which are 270m, 1 and 15.0% respectively.

[0120] b. Record the effective thickness H, middle depth of oil layer and current oil layer pressure of Well M, which are 1.1m, 1270.6m and 13.1MPa respectively; record the effective thickness H, middle depth of oil layer and current oil layer pressure of Well N, which are 5.2m, 1284.6m and 12.5MPa respectively.

[0121] c. Through indoor core displacement experiments, the soaking time of Well M and Well N was obtained, which were 15 days and 7 days respectively.

[0122] By the following formula:

[0123] (1);

[0124] (2);

[0125] (3);

[0126] (4);

[0127] (5);

[0128] (6);

[0129] The basic fluid replenishment radius, basic fluid replenishment volume, maximum effective distance, directional fluid replenishment volume, replenishment coefficient and final fluid replenishment volume are calculated. The specific data are as follows:

[0130] hashtag Basic rehydration radius (m) Basic fluid replacement volume (m³) Maximum operating distance (m) Direction supplementary fluid volume (m³) Supplementary coefficient Final volume of fluid replacement (m³) M 53.3 1473.71 144.0 2506.41 1.021 4062.18 N 45.0 4959.63 149.0 5729.66 1.010 10792.71

[0131] d. According to the needs of the project, the design scale is corrected and rounded to obtain the construction fluid replenishment volume for the convenience of preparation and measurement on site. The construction fluid replenishment volumes of Well M and Well N are calculated to be 4062m³ and 10792m³ respectively.

[0132] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0133] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calculating the injection volume of large displacement water replenishment, characterized in that: include: Step S1, obtaining the injection-production well spacing of the target well, and determining a basic fluid replenishment radius according to the injection-production well spacing, wherein the basic fluid replenishment radius is a multiple of the injection-production well spacing; Step S2, obtaining the effective thickness and porosity of the oil layer of the target well, and determining the basic fluid replenishment amount according to the basic fluid replenishment radius, the effective thickness of the oil layer and the porosity, wherein the basic fluid replenishment amount is the product of the basic fluid replenishment area determined by the basic fluid replenishment radius and the effective thickness of the oil layer multiplied by the porosity; Step S3, obtaining the current reservoir pressure, the middle depth of the reservoir, the reservoir pressure gradient and the maximum allowable construction pressure of the target well, and determining the maximum effective distance of the injected liquid according to the current reservoir pressure, the middle depth of the reservoir, the reservoir pressure gradient and the maximum allowable construction pressure of the target well, wherein the maximum effective distance is the ratio of the sum of the reservoir pressure converted from the maximum allowable construction pressure and the middle depth of the reservoir minus the current reservoir pressure to the reservoir pressure gradient; Step S4, obtaining the number of connection directions of the target well, and determining the amount of directional replenishment fluid in the connection direction according to the maximum action distance, the basic replenishment radius, the effective thickness and the porosity; Calculate the amount of fluid supplement according to the following formula: In the formula, V 方向 Indicates the amount of fluid replenishment in a certain direction, n indicates the number of connected directions, R indicates the basic fluid replenishment radius, D indicates the maximum effective distance, H indicates the effective thickness of the oil layer, represents porosity; Step S5, obtaining the shut-in time of the target well and the effective time of formation water injection, and determining the supplement coefficient of the amount of supplementary fluid in the direction according to the shut-in time of the target well and the effective time of formation water injection; The supplementary coefficient is calculated according to the following formula: In the formula, γ represents the supplement coefficient, t represents the soaking time, and T represents the time for formation water injection to take effect; Step S6, determining the final fluid replenishment volume of the target well according to the basic fluid replenishment volume, the directional fluid replenishment volume and the replenishment coefficient, wherein the final fluid replenishment volume is the replenishment coefficient multiplied by the sum of the basic fluid replenishment volume and the directional fluid replenishment volume.

2. The method for calculating the large displacement water injection amount according to claim 1 is characterized in that: In step S1, the basic fluid replenishment radius is calculated according to the following formula: In the formula, R represents the basic fluid replenishment radius, and L represents the injection-production well spacing.

3. The method for calculating the large displacement water injection amount according to claim 1, characterized in that: In step S2, the basic fluid replacement amount is calculated according to the following formula: In 基础 =π×R 2 ×H× In the formula, V 基础 represents the basic fluid replenishment volume, R represents the basic fluid replenishment radius, H represents the effective thickness of the oil layer, Indicates porosity.

4. The method for calculating the large displacement water injection amount according to claim 1, characterized in that: In step S3, the maximum operating distance is calculated according to the following formula: In the formula, D represents the maximum range, P max Indicates the maximum allowable construction pressure, H 中深 It represents the depth of the middle part of the oil layer, P0 represents the current oil layer pressure, and ΔP represents the oil layer pressure gradient.

5. The method for calculating the large displacement water injection amount according to claim 1 is characterized in that: In step S6, the final injection amount is calculated according to the following formula: V 最终 =γ×(V 基础 +V 方向 ) In the formula, V 最终 represents the final volume of fluid replenishment, γ represents the replenishment coefficient, V 基础 Indicates the basic fluid replacement volume, V 方向 Indicates the direction of replenishing fluid volume.

6. The method for calculating the large displacement water injection amount according to claim 1, characterized in that: Also includes: Step S11, obtaining the number of pores, pore distribution density and pore area ratio of the target well that are lower than a preset porosity, and determining a well condition evaluation value according to the number of pores, pore distribution density and pore area ratio of the target well; Step S22, determining a fluid replenishment method of the target well according to the well condition evaluation value of the target well, wherein the fluid replenishment method includes a conventional fluid replenishment method and a fluid replenishment method after determining a compensation supplement coefficient according to a pressure drop rate; Step S33, obtaining the water content at the same oil production rate of several wells after fluid replenishment, the water content in the original oil layer, and the water content at the oil production rate of several wells before fluid replenishment, and determining the displacement effect evaluation value after fluid replenishment of several wells according to the water content at the same oil production rate after fluid replenishment of several wells, the water content in the original oil layer, and the water content at the oil production rate of several wells before fluid replenishment; Step S44, determining to reduce the basic fluid replenishment radius according to the displacement effect evaluation values ​​of the determined wells after fluid replenishment.

7. The method for calculating the large displacement water injection amount according to claim 6 is characterized in that: In the step S11, the well condition evaluation value is the arithmetic square root of the ratio of the pore number multiplied by the pore distribution density to the square of the pore area ratio.

8. The method for calculating the large displacement water injection amount according to claim 7 is characterized in that: Based on the comparison result that the well condition evaluation value is greater than the preset well condition evaluation value, it is determined to perform fluid replenishment according to the conventional fluid replenishment method of steps S1-S6.

9. The method for calculating the large displacement water injection amount according to claim 7, characterized in that: Based on the comparison result that the well condition evaluation value is less than or equal to the preset well condition evaluation value, determine the fluid replenishment method after compensating the supplementary coefficient in the step S5, and determine to increase the supplementary coefficient with the first preset compensation adjustment coefficient according to the comparison result that the pressure drop rate of the target well is less than or equal to the preset pressure drop rate.

10. The method for calculating the large displacement water injection amount according to claim 7, characterized in that: Based on the comparison result that the well condition evaluation value is less than or equal to the preset well condition evaluation value, determine the fluid replenishment method after compensating the supplementary coefficient in the step S5, and determine to increase the supplementary coefficient with the second preset compensation adjustment coefficient according to the comparison result that the pressure drop rate is greater than the preset pressure drop rate.

11. The method for calculating the large displacement water injection amount according to claim 6, characterized in that: In step S33, the displacement effect evaluation value is the difference between the water content in the original oil layer and the water content of the wells at the same oil production after fluid replenishment divided by the difference between the water content in the original oil layer and the water content of the wells at the oil production before fluid replenishment.

12. The method for calculating the large displacement water injection amount according to claim 6, characterized in that: Based on the comparison result that the displacement effect evaluation value is less than or equal to the preset displacement effect evaluation value, it is determined to reduce the basic liquid replenishment radius by the first preset supplementary radius adjustment coefficient.

13. The method for calculating the large displacement water injection amount according to claim 6, characterized in that: Based on the comparison result that the displacement effect evaluation value is greater than the preset displacement effect evaluation value, it is determined to reduce the basic liquid replenishment radius by the second preset supplementary radius adjustment coefficient.

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