Method, device, medium and equipment for predicting oil reservoir recovery ratio function

Abstract

The invention provides a method, a device, a medium and equipment for predicting the recovery ratio of an oil reservoir, which can combine a corresponding target water drive characteristic curve with a Sierkhoff formula (the relationship between the well pattern density and the recovery ratio) according to oil reservoirs with different crude oil viscosities, so as to predict the recovery ratio of the oil reservoir. Establishing a relationship between the recovery ratio and the well pattern density under different oil reservoir conditions and water drive development rules, and under the relationship, reasonably determining the corresponding recovery ratio only by utilizing the reservoir thickness of the oil reservoir, the viscosity of crude oil, the permeability, the intercept of the target water drive characteristic curve and the densified well pattern density; the parameters are objective parameters, so that the accuracy of the recovery ratio can be ensured; and oil reservoirs with different crude oil viscosities are considered, so that the method also has universality.

Description

Technical Field

[0001] The present application relates to the technical field of oil extraction, and in particular to a method, device, medium and equipment for predicting oil reservoir recovery rate. Background Art

[0002] The recovery factor is the ratio of the amount of underground crude oil that can be recovered from an oil field or block under the current development technology and strategy to its total geological reserves. The recovery factor is an important basis for measuring the development potential of an oil field or block and adjusting future development strategies. The oil field recovery factor is determined by the oil displacement efficiency and volume sweep coefficient. For oil reservoirs developed by water drive, the recovery factor can be mainly improved by expanding the sweep coefficient. There is a close connection between the well network density and the recovery factor. As the exploration and development process of an oil field or block deepens, the injection and production well network will be densely adjusted to expand the sweep coefficient and improve the final recovery factor. The greater the well network density, the greater the recovery factor.

[0003] At present, secondary oil recovery technology, namely artificial water injection development, is still one of the most important oil and gas field development methods at home and abroad. After long-term water drive development, most oil fields have entered the medium-to-high water content period, and most of them are affected by the discontinuity and heterogeneity of the reservoir. Under the current injection and production well network conditions, the sweep coefficient is often low, resulting in a low final recovery rate. Since tertiary oil recovery technology is generally costly and has limited applicability, it is difficult to achieve industrial application in the entire oil field, so many oil fields can only continue to adopt the development strategy of artificial water injection in the future. This means that improving the water injection sweep coefficient by optimizing the density of the injection and production well network is still the most important method to improve the recovery rate in the future.

[0004] For the research on the prediction of the recovery rate of water-driven oil reservoirs, the existing technology has summarized a variety of methods. For example, the Sherkachev formula can be used to determine the relationship between the recovery rate and the well network density. However, the two parameters of the Sherkachev formula, the oil displacement efficiency and the well network index, are usually difficult to determine. After the well network density increases, the reservoir recovery rate cannot be accurately determined. In addition, there are studies that simplify the Sherkachev formula by establishing an empirical formula. However, the empirical formula obtained based on multi-sample statistics cannot be accurately applied to each oil reservoir, and its applicability is not strong. It is impossible to accurately predict the recovery rate of oil reservoirs with different characteristics after the well network is denser. Summary of the invention

[0005] In view of the problems existing in the prior art, the embodiments of the present invention provide a method, device, medium and equipment for predicting oil reservoir recovery rate, so as to solve or partially solve the technical problem that the recovery rate of medium and high water-cut oil reservoirs cannot be accurately predicted after the well network is densely densified.

[0006] A first aspect of the present invention provides a method for predicting oil reservoir recovery, characterized in that the method comprises:

[0007] Determine a corresponding target water drive characteristic curve according to the formation crude oil viscosity, and determine a basic recovery function and a sweep coefficient function according to the target water drive characteristic curve;

[0008] Establishing an oil recovery efficiency function according to the basic recovery rate function, the sweep coefficient function and the water drive development oil reservoir recovery degree function;

[0009] Establishing the slope function of the target water flooding characteristic curve according to the oil displacement efficiency function and the relationship function between the oil displacement efficiency and the flow coefficient;

[0010] Establishing a relationship function between the sweep coefficient and the well pattern density, establishing a new intercept function of the target water drive characteristic curve after the well pattern is densely packed according to the relationship function between the sweep coefficient and the well pattern density and the sweep coefficient function, and establishing a well pattern index function according to the old intercept function;

[0011] Establishing a target recovery function according to the basic recovery function, the slope function of the target water drive characteristic curve, the new intercept function of the target water drive characteristic curve after the well pattern is densely packed, and the well pattern index function;

[0012] When it is necessary to determine the oil reservoir recovery factor, the production data of the oil reservoir is obtained, and the oil reservoir recovery factor after the well pattern is densified is determined based on the production data and the target recovery factor function.

[0013] In the above scheme, the method of determining the corresponding target water drive characteristic curve according to the formation crude oil viscosity includes:

[0014] When the crude oil viscosity is 3-30 mPa·s, the target water drive characteristic curve is determined to be a type C water drive characteristic curve;

[0015] When the crude oil viscosity is less than 3 mPa·s, the target water drive characteristic curve is determined to be a D-type water drive characteristic curve;

[0016] When the crude oil viscosity is greater than 30 mPa·s, the target water drive characteristic curve is determined to be the Zhang Jinqing water drive characteristic curve.

[0017] In the above scheme, the oil recovery efficiency function is established according to the basic recovery rate function, the sweep coefficient function and the water drive development oil reservoir recovery degree function, including:

[0018] Substituting the basic recovery rate function and the sweep coefficient function into the water drive development reservoir recovery function, the oil recovery efficiency function is obtained; the oil recovery efficiency function is:

[0019] The E D is the oil displacement efficiency, B1 is the slope of the target water displacement characteristic curve, and N is the geological reserves.

[0020] In the above scheme, the slope function of the target water flooding characteristic curve is established according to the oil displacement efficiency function and the relationship function between the oil displacement efficiency and the flow coefficient, including:

[0021] The oil displacement efficiency function The relationship function between the oil displacement efficiency and the flow coefficient By combining the above, the slope function of the target water drive characteristic curve is obtained. in,

[0022] N is geological reserves, K is effective permeability of reservoir, μ is viscosity of crude oil, and h is thickness of reservoir.

[0023] In the above solution, the step of establishing a relationship function between the sweep coefficient and the well pattern density includes:

[0024] Get the recovery function of water flooding reservoir:

[0025] Get the Sherkachev function corresponding to the relationship between the basic recovery factor function and the well pattern density:

[0026] According to the Sherkachev function corresponding to the relationship between the water drive development reservoir recovery degree function and the basic recovery rate function and the well pattern density, a relationship function between the sweep coefficient and the well pattern density is established; the relationship function between the sweep coefficient and the well pattern density is: E V =e -aS ;

[0027] Among them, the E V is the sweep coefficient, a is the well network index, and S is the well network density.

[0028] In the above scheme, the new intercept function of the target water drive characteristic curve after well pattern density is established according to the relationship function between the sweep coefficient and the well pattern density and the sweep coefficient function, comprises:

[0029] The relationship function E between the sweep coefficient and the well pattern density is V =e -aS With the sweep coefficient function By combining the above, the intercept function of the target water drive characteristic curve under the well pattern density S is determined. The intercept function is: A is the current intercept of the target water drive characteristic curve at the well pattern density S;

[0030] Determine the intercept function when the reservoir water cut is the limit water cut:

[0031] When the well network density after the nth well network encryption is S n, the new intercept of the target water drive characteristic curve after the nth well pattern densification is A n When the target water drive characteristic curve is subjected to the well pattern density S at the time of the nth well pattern densification, the well pattern density S of the target water drive characteristic curve is determined based on the intercept function of the target water drive characteristic curve at the well pattern density S. n The new intercept function under The f WL is the limit moisture content, and the limit moisture content is 98%.

[0032] In the above scheme, the target recovery function is determined according to the basic recovery function, the slope function of the target water drive characteristic curve, the new intercept function of the target water drive characteristic curve after the well pattern is densely packed, and the well pattern index function, including:

[0033] Substitute the slope function of the target water drive characteristic curve, the new intercept function of the target water drive characteristic curve after the well pattern is densely packed, and the well pattern index function into the basic recovery function to obtain the target recovery function:

[0034]

[0035] K is the effective permeability of the reservoir, μ is the viscosity of crude oil, h is the reservoir thickness, S0 is the well network density before well network densification, and S n is the well pattern density after the nth well pattern densification, A0 is the old intercept of the target water drive characteristic curve before the well pattern densification, and f WL is the ultimate water content of the reservoir.

[0036] A second aspect of the present invention provides a device for predicting oil reservoir recovery, the device comprising:

[0037] A first determination unit determines a corresponding target water drive characteristic curve according to the formation crude oil viscosity, and determines a basic recovery function and a sweep coefficient function according to the target water drive characteristic curve;

[0038] A first establishing unit is used to establish an oil recovery efficiency function according to the basic recovery rate function, the sweep coefficient function and the water drive development oil reservoir recovery degree function;

[0039] The second establishing unit establishes the slope function of the target water drive characteristic curve according to the oil drive efficiency function and the relationship function between the oil drive efficiency and the flow coefficient; establishes the relationship function between the sweep coefficient and the well network density, establishes a new intercept function of the target water drive characteristic curve after the well network is densified according to the relationship function between the sweep coefficient and the well network density and the sweep coefficient function, and establishes a well network index function according to the old intercept function;

[0040] A third establishing unit is used to establish a target recovery function according to the basic recovery function, the slope function of the target water drive characteristic curve, the new intercept function of the target water drive characteristic curve after the well pattern is densely packed, and the well pattern index function;

[0041] The second determination unit is used to obtain the production data of the oil reservoir when it is necessary to determine the oil reservoir recovery rate, and determine the oil reservoir recovery rate after the well pattern is encrypted based on the production data and the target recovery rate function.

[0042] According to a third aspect of the present invention, a computer-readable storage medium is provided, on which a computer program is stored, and when the program is executed by a processor, the steps of any one of the methods described in the first aspect are implemented.

[0043] According to a fourth aspect of the present invention, a computer device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of any one of the methods described in the first aspect are implemented.

[0044] The present invention provides a method, device, medium and equipment for predicting oil reservoir recovery rate. The method comprises: determining a corresponding target water drive characteristic curve according to the viscosity of formation crude oil, determining a basic recovery rate function and a sweep coefficient function according to the target water drive characteristic curve; establishing an oil recovery efficiency function according to the basic recovery rate function, the sweep coefficient function and a water drive development oil reservoir recovery degree function; establishing a slope function of the target water drive characteristic curve according to the oil recovery efficiency function and a relationship function between the oil recovery efficiency and the flow coefficient; establishing a relationship function between the sweep coefficient and the well network density, establishing a new intercept function of the target water drive characteristic curve after the well network is densely packed according to the relationship function between the sweep coefficient and the well network density and the sweep coefficient function, and establishing a well network index function according to the old intercept function; establishing a well network index function according to the basic recovery rate function, the slope function of the target water drive characteristic curve, the well network density after the well network is densely packed ... The new intercept function of the target water drive characteristic curve and the well network index function establish a target recovery function; when it is necessary to determine the oil reservoir recovery rate, the production data of the oil reservoir is obtained, and the oil reservoir recovery rate after the well network is densely encrypted is determined based on the production data and the target recovery function; in this way, for oil reservoirs containing different crude oil viscosities, the corresponding target water drive characteristic curve is combined with the Shelkachev formula (the relationship between well network density and recovery rate) to establish a relationship between recovery rate and well network density applicable to different oil reservoir conditions and water drive development laws. Under this relationship, the corresponding recovery rate can be reasonably determined by using only the reservoir thickness, crude oil viscosity, permeability, intercept of the target water drive characteristic curve, and the dense well network density; since the above parameters are relatively objective parameters, the accuracy of the recovery rate can be ensured; and since oil reservoirs with different crude oil viscosities are taken into account, this method is also universal. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] By reading the detailed description of the preferred embodiment below, various other advantages and benefits will become clear to those of ordinary skill in the art. The accompanying drawings are only used for the purpose of illustrating the preferred embodiment and are not considered to be limitations of the present invention. In addition, the same reference symbols are used to represent the same components throughout the accompanying drawings.

[0046] In the attached picture:

[0047] Figure 1 A schematic diagram of a method for predicting oil reservoir recovery rate according to an embodiment of the present invention is shown;

[0048] Figure 2 A schematic diagram showing the relationship between recovery factor and well pattern density according to an embodiment of the present invention is shown;

[0049] Figure 3 A schematic diagram of the structure of a device for predicting oil reservoir recovery rate according to an embodiment of the present invention is shown;

[0050] Figure 4 A schematic diagram of injection-production well pattern densification according to an embodiment of the present invention is shown;

[0051] Figure 5 A schematic diagram of the production dynamics of a well group in an oil field according to an embodiment of the present invention is shown;

[0052] Figure 6 A schematic diagram of a type C water flooding characteristic curve corresponding to an oil field according to an embodiment of the present invention is shown;

[0053] Figure 7 A schematic diagram of a curve showing the relationship between the final recovery rate and the well spacing according to an embodiment of the present invention is shown;

[0054] Figure 8 The ultimate recovery factor and S according to one embodiment of the present invention are shown. n Schematic diagram of / S0 relationship curve. DETAILED DESCRIPTION

[0055] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0056] The present invention provides a method for predicting oil reservoir recovery rate. Figure 1 As shown, the method mainly includes the following steps:

[0057] S110, determining a corresponding target water drive characteristic curve according to the formation crude oil viscosity, determining a basic recovery factor function and a sweep coefficient function according to the target water drive characteristic curve; establishing an oil recovery efficiency function according to the basic recovery factor function, the sweep coefficient function and the water drive development oil reservoir recovery degree function.

[0058] The water drive characteristic curve is an empirical method for analyzing the dynamics of water drive development in oil reservoirs, which is established under the premise that the oil reservoirs are developed by water drive and there is produced water. The water drive characteristic curve describes the changing rules of oil production, water production and liquid production after the water-free oil production period, and reflects the development characteristics of water drive in oil reservoirs.

[0059] The water drive characteristic curve was first obtained by scientists using oil field and laboratory data through statistical laws to describe the law of water driving oil. It was then developed into various types of expressions, generally named after the researchers. Later, the water drive characteristic curves named after the researchers were changed to the order of A, B, C, and D. In recent years, with the continuous development, the types of water drive characteristic curves have reached hundreds, so the sequential naming is insufficient, so some water zone characteristic curves have returned to the naming method of the researchers.

[0060] In one embodiment, determining a corresponding target water drive characteristic curve according to formation crude oil viscosity includes:

[0061] When the crude oil viscosity is 3-30 mPa·s, the target water drive characteristic curve is determined to be the Type C water drive characteristic curve;

[0062] When the crude oil viscosity is less than 3 mPa·s, the target water drive characteristic curve is determined to be the D-type water drive characteristic curve;

[0063] When the crude oil viscosity is greater than 30 mPa·s, the target water drive characteristic curve is determined to be the Zhang Jinqing water drive characteristic curve.

[0064] Among them, when the target reservoir is in the middle and high water cut period, the water cut is greater than 50%; and the target reservoir is currently in stable water drive, the type C water drive characteristic curve is:

[0065]

[0066] The characteristic curve of type D water flooding is:

[0067]

[0068] Zhang Jinqing's water drive characteristic curve is:

[0069]

[0070] In the above three water drive characteristic curves, L P is the cumulative liquid production, NP is the cumulative oil production, W P is the cumulative water production, A is the intercept of the corresponding water drive characteristic curve, and B is the slope of the corresponding water drive characteristic curve.

[0071] Correspondingly, the basic recovery function and sweep coefficient function determined by different types of water drive characteristic curves are also different. In order to better illustrate the concept of the present invention, an oil reservoir with a crude oil viscosity of 3 to 30 mPa·s is first used as an example for explanation.

[0072] When the crude oil viscosity is 3-30 mPa·s, the basic recovery function and sweep coefficient function are determined according to the target water drive characteristic curve, as shown in formula (4) and formula (5):

[0073]

[0074]

[0075] In formulas (4) and (5), E R is the recovery factor, f w is the moisture content, E V is the sweep coefficient, A is the intercept of the corresponding water drive characteristic curve, and B is the slope of the corresponding water drive characteristic curve.

[0076] It should be noted that the method of deriving the basic recovery factor function and the sweep coefficient function using the water drive characteristic curve can be implemented using conventional methods, so it will not be described in detail here.

[0077] The recovery function of water flooding reservoir is shown in formula (6):

[0078] E R =E D ·E V (6)

[0079] Among them, E R is the recovery factor, E D is the oil recovery efficiency, E V is the sweep coefficient.

[0080] Then in one embodiment, an oil recovery efficiency function is established according to the basic recovery function, the sweep coefficient function and the water drive development reservoir recovery degree function, including:

[0081] Substituting the basic recovery function and sweep coefficient function into the recovery function of the water drive reservoir, the oil recovery efficiency function is obtained.

[0082] E D is the oil displacement efficiency, B is the slope of the target water displacement characteristic curve, and N is the geological reserves.

[0083] That is, the oil recovery efficiency function can be obtained from formulas (4), (5), and (6):

[0084]

[0085] It can be seen from formula (7) that in the process of well pattern densification, for any type of water drive characteristic curve, due to the oil recovery efficiency E D and geological reserves N are unchanged, so the slope B of the target water drive characteristic curve (type C water drive characteristic curve, type D water drive characteristic curve and Zhang Jinqing water drive characteristic curve) in the present invention is also unchanged.

[0086] S111, based on the reservoir thickness, crude oil viscosity and permeability of the oil reservoir, and according to the oil recovery efficiency function and the relationship function between the oil recovery efficiency and the flow coefficient, a slope function of the target water drive characteristic curve is established.

[0087] The oil recovery efficiency is also related to the flow coefficient of the reservoir, which is related to the well pattern density. The relationship between the five types of recovery factors and well pattern density divided by the flow coefficient is shown in Table 1 and Figure 2 shown.

[0088] Table 1

[0089]

[0090] The flow coefficient is Kh / μ, where K is the effective permeability of the reservoir, μm 2 ; h is the reservoir thickness, m; μ is the formation crude oil viscosity, mPa·s.

[0091] Furthermore, based on the above relationship, Sherkachev established a relationship function between oil recovery efficiency and flow coefficient:

[0092]

[0093] Then in one embodiment, the slope function of the target water flooding characteristic curve is established according to the oil displacement efficiency function and the relationship function between the oil displacement efficiency and the flow coefficient, including:

[0094] The oil displacement efficiency function The relationship function between the oil displacement efficiency and the flow coefficient Combined, the slope function of the target water drive characteristic curve is obtained in,

[0095] N is the geological reserve, K is the effective permeability of the reservoir, μ is the viscosity of crude oil, and h is the reservoir thickness.

[0096] That is, the slope function of the target water drive characteristic curve is:

[0097]

[0098] S112, establishing a relationship function between sweep coefficient and well pattern density, establishing a new intercept function of the target water drive characteristic curve after well pattern densification based on the relationship function between sweep coefficient and well pattern density and the sweep coefficient function, and establishing a well pattern index function based on the old intercept function.

[0099] In one embodiment, establishing a relationship function between the sweep coefficient and the well pattern density includes:

[0100] Get the recovery function of water flooding reservoir:

[0101] Get the Sherkachev function corresponding to the relationship between the basic recovery factor function and the well pattern density:

[0102] According to the Shelkachev function corresponding to the relationship between the recovery degree function of the water drive development reservoir and the basic recovery rate function and the well pattern density, the relationship function between the sweep coefficient and the well pattern density is established; the relationship function between the sweep coefficient and the well pattern density is: E V =e -aS ; Among them, E V is the sweep coefficient, a is the well pattern index, and S is the well pattern density.

[0103] Specifically, the relationship function between recovery factor and well pattern density can be obtained from the Shelkachev formula:

[0104] E R =E D ·e -aS (10)

[0105] Since formula (6) shows the recovery function E of water flooding reservoir R =E D ·E V , so combining formula (6) and formula (10) we can get the relationship function between the sweep coefficient and the well pattern density:

[0106] E V =e -aS (11)

[0107] In formulas (10) and (11), a is the well pattern index and S is the well pattern density.

[0108] In one embodiment, a new intercept function of the target water drive characteristic curve after the well pattern is densely packed is established based on the relationship function between the sweep coefficient and the well pattern density and the sweep coefficient function, including:

[0109] The relationship function E between the sweep coefficient and the well pattern density is V =e -aS And the sweep coefficient function By combining the above, the intercept function of the target water drive characteristic curve under the well pattern density S is determined. The intercept function is: A is the current intercept of the target water drive characteristic curve under the well pattern density S;

[0110] Determine the intercept function when the reservoir water cut is the limit water cut:

[0111] When the well network density after the nth well network encryption is S n , the new intercept of the target water drive characteristic curve after the nth well pattern densification is A n When the target water drive characteristic curve is subjected to the well pattern density S at the time of the nth well pattern densification, the well pattern density S of the target water drive characteristic curve is determined based on the intercept function of the target water drive characteristic curve at the well pattern density S. n The new intercept function is The f WL is the limit moisture content, and the limit moisture content is 98%.

[0112] Specifically, formula (11) and formula (5) can be combined to obtain formula (12):

[0113]

[0114] At this time, the moisture content f W is the limiting moisture content f WL , the limit moisture content is generally taken as 0.98, then formula (12) is:

[0115]

[0116] According to formula (13), the intercept function of the target water drive characteristic curve under the well pattern density S can be obtained. The intercept function is:

[0117]

[0118] At this time, if the well pattern density before well pattern densification is S0, and the old intercept of the target water drive characteristic curve before well pattern densification is A0, then the old intercept function of the target water drive characteristic curve before well pattern densification is:

[0119]

[0120] According to formula (15), the well pattern index function can be obtained as follows:

[0121]

[0122] Similarly, if the well network density after the nth well network encryption is S n , the new intercept of the target water drive characteristic curve after well pattern densification is A n, then the new intercept function of the target water drive characteristic curve after well pattern densification is:

[0123]

[0124] S113, establishing a target recovery function according to the basic recovery function, the slope function of the target water drive characteristic curve, the new intercept function of the target water drive characteristic curve after the well pattern is densely packed, and the well pattern index function.

[0125] After the new intercept function of the target water drive characteristic curve, the old intercept function, the slope function of the target water drive characteristic curve, the well network index function, the well network density before well network densification, and the well network density after well network densification are determined, substitute formulas (9), (16), (17) into formula (4) when the water cut is the limit water cut.

[0126] Here, when the water cut is the limit water cut, the intercept of the target water drive characteristic curve after the nth well pattern densification is A n When , formula (4) can be modified as follows: Similarly, when the water cut is the limit water cut and the intercept of the target water drive characteristic curve before well pattern densification is A0, formula (4) can be modified as follows:

[0127] Substituting formula (9), (16), (17) into formula (4) when the moisture content is the limit moisture content, we can obtain:

[0128]

[0129] After formula (18) is rearranged, we can get:

[0130]

[0131] It can be seen that according to formula (19), after determining the old intercept of the target water drive characteristic curve, the slope of the target water drive characteristic curve, the well density before well densification, and the well density after well densification, the recovery factor after well densification in the middle and high water cut stage can be determined when the crude oil viscosity is 3-30 mPa·s. It should be noted that the recovery factors determined in the present invention are the recovery factors when the oil field reaches the ultimate water cut.

[0132] Similarly, when the crude oil viscosity is less than 3 mPa·s, the basic recovery function and sweep coefficient function derived from the D-type water flooding characteristic curve are shown in formulas (20) and (21):

[0133]

[0134]

[0135] Then, referring to the above recovery factor determination process for crude oil viscosity of 3-30 mPa·s (the specific implementation process can be fully referred to the corresponding description above, and will not be repeated here), it is determined that when the well pattern density before well pattern densification is S0, the old intercept function of the target water drive characteristic curve is:

[0136]

[0137] The well pattern index function is:

[0138]

[0139] Similarly, if the well network density after the nth well network encryption is S n , the new intercept of the target water drive characteristic curve after well pattern densification is A n , then the new intercept function of the target water drive characteristic curve after well pattern densification is:

[0140]

[0141] Furthermore, when the moisture content is the limit moisture content, the intercept is A n When , formula (20) can be modified as follows:

[0142]

[0143] Substituting formula (22), (23) and (24) into formula (20) when the moisture content is the limit moisture content, we can obtain:

[0144]

[0145] That is, according to formula (25), after determining the old intercept of the target water drive characteristic curve, the slope of the target water drive characteristic curve, the well density before the well density and the well density after the well density, the recovery factor after the well density in the middle and high water cut stage when the crude oil viscosity is less than 3 mPa·s can be determined. It should be noted that the recovery factors determined in the present invention are the recovery factors when the oil field reaches the ultimate water cut.

[0146] Similarly, when the crude oil viscosity is greater than 30 mPa·s, the basic recovery function and sweep coefficient function derived from Zhang Jinqing's water flooding characteristic curve are shown in formulas (26) and (27):

[0147]

[0148]

[0149] Then, referring to the above recovery factor determination process for crude oil viscosity of 3-30 mPa·s (the specific implementation process can be fully referred to the corresponding description above, and will not be repeated here), it is determined that when the well network density before well network densification is S0, the old intercept function of the target water drive characteristic curve (Zhang Jinqing water drive characteristic curve) is:

[0150]

[0151] The well pattern index function is:

[0152]

[0153] Similarly, if the well network density after the nth well network encryption is S n , the new intercept of the target water drive characteristic curve after well pattern densification is A n , then the new intercept function of the target water drive characteristic curve after well pattern densification is:

[0154]

[0155] Furthermore, when the moisture content is the limit moisture content, the intercept is A n When , formula (26) can be modified as follows:

[0156]

[0157] Substituting formula (28), (29), (30) into formula (26) when the moisture content is the limit moisture content, we can obtain:

[0158]

[0159] That is, according to formula (31), after determining the old intercept of the target water drive characteristic curve, the slope of the target water drive characteristic curve, the well density before the well density and the well density after the well density, the recovery factor after the well density in the middle and high water cut stage when the crude oil viscosity is greater than 30 mPa·s can be determined. It should be noted that the recovery factors determined in the present invention are the recovery factors when the oil field reaches the limit water cut.

[0160] In summary, for reservoirs with different crude oil viscosities, the recovery factor determined after well pattern densification is as shown in formula (32):

[0161]

[0162] S114, when it is necessary to determine the oil reservoir recovery rate, obtain the production data of the oil reservoir, and determine the oil reservoir recovery rate after the well pattern is densified based on the production data and the target recovery rate function.

[0163] In practical applications, when it is necessary to determine the recovery rate of a certain reservoir after the well network is intensified in the high water content stage, the production data of the reservoir is obtained, and the recovery rate of the reservoir after the well network is intensified is determined based on the production data and the target recovery rate function. Among them, the production data includes: the well network density before the well network is intensified, the well network density after the well network is intensified, the reservoir thickness, the effective permeability of the reservoir, the crude oil viscosity, and the old intercept of the target water drive characteristic curve before the well network is intensified to predict the corresponding recovery rate.

[0164] In this embodiment, for oil reservoirs with different crude oil viscosities, the corresponding target water drive characteristic curve is combined with the Sherkachev formula (the relationship between well grid density and recovery factor), and the relationship between recovery factor and well grid density applicable to different oil reservoir conditions and water drive development rules is established. Under this relationship, the corresponding recovery factor can be reasonably determined by using the reservoir thickness, crude oil viscosity, permeability, intercept of the target water drive characteristic curve, and the densified well grid density of the oil reservoir; since the above parameters are relatively objective parameters, the accuracy of the recovery factor can be ensured; and since oil reservoirs with different crude oil viscosities are taken into account, the method is also universal.

[0165] Based on the same inventive concept as in the above-mentioned embodiment, this embodiment also provides a device for predicting oil reservoir recovery rate, such as Figure 3 As shown, the device comprises:

[0166] A first determination unit 31 determines a corresponding target water drive characteristic curve according to the formation crude oil viscosity, and determines a basic recovery function and a sweep coefficient function according to the target water drive characteristic curve;

[0167] A first establishing unit 32 is used to establish an oil recovery efficiency function according to the basic recovery rate function, the sweep coefficient function and the water drive development oil reservoir recovery degree function;

[0168] The second establishing unit 33 establishes the slope function of the target water drive characteristic curve according to the oil drive efficiency function and the relationship function between the oil drive efficiency and the flow coefficient; establishes the relationship function between the sweep coefficient and the well pattern density, establishes a new intercept function of the target water drive characteristic curve after the well pattern is densified according to the relationship function between the sweep coefficient and the well pattern density and the sweep coefficient function, and establishes a well pattern index function according to the old intercept function;

[0169] A third establishing unit 34 is used to establish a target recovery function according to the basic recovery function, the slope function of the target water drive characteristic curve, the new intercept function of the target water drive characteristic curve after the well pattern is densely packed, and the well pattern index function;

[0170] The second determination unit 35 is used to obtain the production data of the oil reservoir when it is necessary to determine the oil reservoir recovery factor, and determine the oil reservoir recovery factor after the well pattern is encrypted based on the production data and the target recovery factor function.

[0171] Since the device introduced in the embodiment of the present invention is a device used to implement the method for predicting oil reservoir recovery rate in the embodiment of the present invention, based on the method introduced in the embodiment of the present invention, the person skilled in the art can understand the specific structure and deformation of the device, so it is not repeated here. All devices used in the method of the embodiment of the present invention belong to the scope of protection of the present invention.

[0172] Based on the same inventive concept, this embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements any step of the method described above when executing the computer program.

[0173] Based on the same inventive concept, this embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of any of the methods described above are implemented.

[0174] In practical applications, when the recovery rate of a certain high water-cut sandstone oil field is predicted using the above-mentioned method and device for predicting oil reservoir recovery rate, the following is achieved:

[0175] First, the reservoir thickness of the oil field is determined to be 9.6m, the reservoir permeability is 393.3mD, and the crude oil viscosity is 23.3mPa·s. A regular five-point injection and production well pattern is selected in the oil field. It is known that the geological reserves in the area controlled by the well group are 208,600 tons. Figure 4 As shown in the figure, the well pattern density of the well group is designed to be encrypted successively until n times of encryption is reached, and the well pattern density gradually increases from S0 to S n .

[0176] Among them, Figure 4 In the figure, f0 is the well spacing in the well pattern when the well pattern density is S0; f1 is the well spacing in the well pattern when the well pattern density is S1; f3 is the well spacing in the well pattern when the well pattern density is S3; f n The well pattern density is S n , the well spacing in the well network.

[0177] The well group has been in production for nearly 40 years and has always maintained stable water drive development. It has now entered the high water cut stage with a comprehensive water cut of 95%. The production dynamic data of the well group are as follows: Figure 5 shown.

[0178] From the above, we can know that since the crude oil viscosity of this oil field is 23.3mPa·s, it belongs to medium viscosity oil reservoir, and the type C water drive characteristic curve is selected. According to the collected production dynamic data, the cumulative oil production N of the well group is calculated. P and the cumulative liquid production L P , establish L in the coordinate system P / N P With N P The relationship curve, such as Figure 6 As shown, the regression results show that the intercept A0=1.16878 and the slope B=1.38237E-06 of the type C water drive characteristic curve.

[0179] Then calculate the current well network density S0 (before well network density is increased), and then gradually increase the well network density from S0 to S n .

[0180] Specifically, the current five-point well spacing is 0.28km, the well spacing of the reverse nine-point well spacing after the first densification is designed to be 0.2km, and the well spacing of the second densification is 0.14km. Assuming that in the design stage of well densification, the well spacing will eventually be 0.1km. Then the calculated well density before densification S0 = 0.08km 2 / well, the well density after each encryption is: S1 = 0.04km 2 / well, S2 = 0.02 km 2 / well...S n =0.01km 2 / well.

[0181] Then the recovery factor under the well pattern density before densification can be determined according to the modified formula (4):

[0182]

[0183] Then the recovery rate corresponding to each infilling is determined by formula (19):

[0184] The corresponding recovery rate after the well pattern is dense is:

[0185]

[0186] The corresponding recovery rate after the secondary well pattern is intensified is:

[0187]

[0188] The corresponding recovery rate after three well pattern densifications is:

[0189]

[0190] The calculated final recovery factor and recoverable reserves are shown in Table 2.

[0191] Table 2

[0192]

[0193]

[0194] In summary, the method provided in this embodiment can not only accurately determine the recovery factor after the well pattern is intensified, but also establish a relationship curve between the final recovery factor and the well pattern spacing according to the designed multiple intensification calculation results in the well pattern density design stage, such as Figure 7 As shown; and the ultimate recovery factor and S n / S0 relationship curve, such as Figure 8 As shown; then combine relevant economic parameters to determine the reasonable well network density.

[0195] Through one or more embodiments of the present invention, the present invention has the following beneficial effects or advantages:

[0196] The present invention provides a method, device, medium and equipment for predicting oil reservoir recovery rate. The method comprises: determining a corresponding target water drive characteristic curve according to the viscosity of formation crude oil, determining a basic recovery rate function and a sweep coefficient function according to the target water drive characteristic curve; establishing an oil recovery efficiency function according to the basic recovery rate function, the sweep coefficient function and a water drive development oil reservoir recovery degree function; establishing a slope function of the target water drive characteristic curve according to the oil recovery efficiency function and a relationship function between the oil recovery efficiency and the flow coefficient; establishing a relationship function between the sweep coefficient and the well network density, establishing a new intercept function of the target water drive characteristic curve after the well network is densely packed according to the relationship function between the sweep coefficient and the well network density and the sweep coefficient function, and establishing a well network index function according to the old intercept function; establishing a well network index function according to the basic recovery rate function, the slope function of the target water drive characteristic curve, the well network density after the well network is densely packed ... The new intercept function of the target water drive characteristic curve and the well network index function establish a target recovery function; when it is necessary to determine the oil reservoir recovery rate, the production data of the oil reservoir is obtained, and the oil reservoir recovery rate after the well network is densely encrypted is determined based on the production data and the target recovery function; in this way, for oil reservoirs containing different crude oil viscosities, the corresponding target water drive characteristic curve is combined with the Shelkachev formula (the relationship between well network density and recovery rate) to establish a relationship between recovery rate and well network density applicable to different oil reservoir conditions and water drive development laws. Under this relationship, the corresponding recovery rate can be reasonably determined by using only the reservoir thickness, crude oil viscosity, permeability, intercept of the target water drive characteristic curve, and the dense well network density; since the above parameters are relatively objective parameters, the accuracy of the recovery rate can be ensured; and since reservoirs with different crude oil viscosities are taken into account, this method is also universal.

[0197] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for predicting oil reservoir recovery, characterized in that: The method comprises: Determine a corresponding target water drive characteristic curve according to the formation crude oil viscosity, and determine a basic recovery function and a sweep coefficient function according to the target water drive characteristic curve; Establishing an oil recovery efficiency function according to the basic recovery rate function, the sweep coefficient function and the water drive development oil reservoir recovery degree function; Establishing the slope function of the target water flooding characteristic curve according to the oil displacement efficiency function and the relationship function between the oil displacement efficiency and the flow coefficient; Establishing a relationship function between the sweep coefficient and the well pattern density, establishing a new intercept function of the target water drive characteristic curve after the well pattern is densely packed according to the relationship function between the sweep coefficient and the well pattern density and the sweep coefficient function, and establishing a well pattern index function according to the old intercept function; Establishing a target recovery function according to the basic recovery function, the slope function of the target water drive characteristic curve, the new intercept function of the target water drive characteristic curve after the well pattern is densely packed, and the well pattern index function; When it is necessary to determine the oil reservoir recovery factor, the production data of the oil reservoir is obtained, and the oil reservoir recovery factor after the well pattern is densified is determined based on the production data and the target recovery factor function.

2. The method according to claim 1, characterized in that Determining the corresponding target water drive characteristic curve according to the formation crude oil viscosity includes: When the crude oil viscosity is 3-30 mPa·s, the target water drive characteristic curve is determined to be a type C water drive characteristic curve; When the crude oil viscosity is less than 3 mPa·s, the target water drive characteristic curve is determined to be a D-type water drive characteristic curve; When the crude oil viscosity is greater than 30 mPa·s, the target water drive characteristic curve is determined to be the Zhang Jinqing water drive characteristic curve.

3. The method according to claim 1, characterized in that The step of establishing an oil recovery efficiency function according to the basic recovery rate function, the sweep coefficient function and the water drive development oil reservoir recovery degree function comprises: Substituting the basic recovery rate function and the sweep coefficient function into the water drive development reservoir recovery function, the oil recovery efficiency function is obtained; the oil recovery efficiency function is: The E D is the oil displacement efficiency, B1 is the slope of the target water displacement characteristic curve, and N is the geological reserves.

4. The method according to claim 1, characterized in that The slope function of the target water flooding characteristic curve is established according to the oil displacement efficiency function and the relationship function between the oil displacement efficiency and the flow coefficient, including: The oil displacement efficiency function The relationship function between the oil displacement efficiency and the flow coefficient By combining the above, the slope function of the target water drive characteristic curve is obtained. in, N is geological reserves, K is effective permeability of reservoir, μ is viscosity of crude oil, and h is thickness of reservoir.

5. The method according to claim 1, characterized in that The establishing of the relationship function between the sweep coefficient and the well pattern density comprises: Get the recovery function of water flooding reservoir: Get the Sherkachev function corresponding to the relationship between the basic recovery factor function and the well pattern density: According to the Sherkachev function corresponding to the relationship between the water drive development reservoir recovery degree function and the basic recovery rate function and the well pattern density, a relationship function between the sweep coefficient and the well pattern density is established; the relationship function between the sweep coefficient and the well pattern density is: E V =e -aS ; Among them, the E V is the sweep coefficient, a is the well network index, and S is the well network density.

6. The method according to claim 1, characterized in that The method of establishing a new intercept function of the target water drive characteristic curve after the well pattern is densely packed based on the relationship function between the sweep coefficient and the well pattern density and the sweep coefficient function comprises: The relationship function E between the sweep coefficient and the well pattern density is V =e -aS With the sweep coefficient function By combining the above, the intercept function of the target water drive characteristic curve under the well pattern density S is determined. The intercept function is: A is the current intercept of the target water drive characteristic curve at the well pattern density S; Determine the intercept function when the reservoir water cut is the limit water cut: When the well network density after the nth well network encryption is S n , the new intercept of the target water drive characteristic curve after the nth well pattern densification is A n When the target water drive characteristic curve is subjected to the well pattern density S at the time of the nth well pattern densification, the well pattern density S of the target water drive characteristic curve is determined based on the intercept function of the target water drive characteristic curve at the well pattern density S. n The new intercept function is The f WL is the limit moisture content, and the limit moisture content is 98%.

7. The method according to claim 1, characterized in that The determining of the target recovery function according to the basic recovery function, the slope function of the target water drive characteristic curve, the new intercept function of the target water drive characteristic curve after the well pattern is densely packed, and the well pattern index function comprises: Substitute the slope function of the target water drive characteristic curve, the new intercept function of the target water drive characteristic curve after the well pattern is densely packed, and the well pattern index function into the basic recovery function to obtain the target recovery function: K is the effective permeability of the reservoir, μ is the viscosity of crude oil, h is the reservoir thickness, S0 is the well network density before well network densification, and S n is the well pattern density after the nth well pattern densification, A0 is the old intercept of the target water drive characteristic curve before the well pattern densification, and f WL is the ultimate water content of the reservoir.

8. A device for predicting oil reservoir recovery, characterized in that: The device comprises: A first determination unit determines a corresponding target water drive characteristic curve according to the formation crude oil viscosity, and determines a basic recovery function and a sweep coefficient function according to the target water drive characteristic curve; A first establishing unit is used to establish an oil recovery efficiency function according to the basic recovery rate function, the sweep coefficient function and the water drive development oil reservoir recovery degree function; The second establishing unit establishes the slope function of the target water drive characteristic curve according to the oil drive efficiency function and the relationship function between the oil drive efficiency and the flow coefficient; establishes the relationship function between the sweep coefficient and the well network density, establishes a new intercept function of the target water drive characteristic curve after the well network is densified according to the relationship function between the sweep coefficient and the well network density and the sweep coefficient function, and establishes a well network index function according to the old intercept function; A third establishing unit is used to establish a target recovery function according to the basic recovery function, the slope function of the target water drive characteristic curve, the new intercept function of the target water drive characteristic curve after the well pattern is densely packed, and the well pattern index function; The second determination unit is used to obtain the production data of the oil reservoir when it is necessary to determine the oil reservoir recovery rate, and determine the oil reservoir recovery rate after the well pattern is encrypted based on the production data and the target recovery rate function.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the method according to any one of claims 1 to 7 are implemented.

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