A method for evaluating recoverable reserves in water-flooded oil reservoirs under reserve transfer conditions

Abstract

A method for evaluating recoverable reserves under the condition of reserve transfer in water-driven oil reservoirs. The method mainly solves the problem of inaccurate evaluation results of existing methods for evaluating recoverable reserves in water-driven oil reservoirs under the condition of continuous reserve transfer. The method includes the following steps: determining the type A water-driven curve of the entire oil reservoir composed of n identical homogeneous units; determining the technical recoverable reserves and remaining technical recoverable reserves of a certain unit, and determining the technical recoverable reserves and remaining technical recoverable reserves of the entire oil reservoir; calculating the total recoverable reserves and remaining recoverable reserves of the entire area through the technical recoverable reserves; assuming that m units are transferred to polymer drive development, the total recoverable reserves after the transfer of m units are obtained, thereby obtaining a revised formula for calculating recoverable reserves under the condition of reserve transfer in multi-structure oil fields. The method solves the problem of the high results of directly applying the type A water-driven curve to predict recoverable reserves after the reserve transfer, and the results are reliable, which provides a basis for scientifically and rationally evaluating the recoverable reserves under the condition of reserve transfer in water-driven oil reservoirs.

Description

Technical Field

[0001] The invention relates to the field of oil field production engineering, in particular to a method for evaluating recoverable reserves under water drive oil reservoir reserve transfer conditions. Background Art

[0002] Since the Daqing Oilfield began to fully promote polymer drive in 1995, a certain amount of geological reserves have been transferred from water drive development to tertiary development every year. After the reserves are transferred, the original development object of water drive has changed, which will affect the indicator change pattern of the remaining water drive reserves, and then affect the recoverable reserves of water drive.

[0003] At present, for water-driven oil reservoirs in the middle and late stages of development, the commonly used methods for evaluating recoverable reserves are the water-driven curve method and the decline curve method. These two methods generally require that the evaluation object should be relatively stable and have a good dynamic change law, and can form a stable prediction trend. At the same time, it is required that there is no large measure to adjust the workload in order to have a high prediction accuracy. After the reserve transfer, the water-driven development reserves continue to decrease, especially the controlled geological reserves of the basic well network and the primary infill well network continue to decrease, and the corresponding recoverable reserves should also decrease. However, from the calculation results of the water-driven curve for the basic well network and the primary infill well network, the recoverable reserves have not changed much, which is obviously inconsistent with the actual situation. Due to the special situation of the continuous transfer of reserves in Daqing Oilfield to tertiary oil recovery, there is no suitable method to directly evaluate the changes in recoverable reserves under the conditions of continuous transfer of water-driven reserves. Summary of the invention

[0004] In order to overcome the disadvantage of inaccurate evaluation results of existing methods for evaluating recoverable reserves of water-driven oil reservoirs under the condition of continuous reserve transfer, the present invention provides a method for evaluating recoverable reserves of water-driven oil reservoirs under the condition of reserve transfer. The method solves the problem of high results of recoverable reserves predicted by directly applying type-A water-driven curve after reserve transfer, and the result is reliable, providing a basis for scientifically and rationally evaluating recoverable reserves of water-driven oil reservoirs under the condition of reserve transfer.

[0005] The technical solution of the present invention is: a method for evaluating recoverable reserves under water drive oil reservoir reserve transfer conditions, characterized by comprising the following steps:

[0006] Step 1, based on a certain homogeneous unit type A water drive curve, determine the type A water drive curve of the entire reservoir composed of n identical homogeneous units, and establish the relationship between the intercept and slope of the specific homogeneous unit and the type A water drive curve of the entire reservoir;

[0007] Step 2: Determine the technically recoverable reserves N of a specific homogeneous unit based on the relationship between cumulative oil production and water content of the Type A water drive curve. R , and the remaining technically recoverable reserves N under a specific water content condition RRBased on the relationship between the slope and intercept of the type A water drive curve for a specific homogeneous unit and the entire reservoir established in step 1, determine the technically recoverable reserves N of the entire reservoir. R ' and remaining technically recoverable reserves N RR ';

[0008] Step 3: Assuming that under a certain water-bearing condition, m units are transferred to polymer flooding development, the remaining technically recoverable reserves N of the transferred m units can be obtained based on the relationship between the slope and intercept of the type A water flooding curve of a certain homogeneous unit and m units. RRm ', thus obtaining the revised formula for calculating recoverable reserves under the conditions of reserve transfer in multi-structure oil fields.

[0009] Furthermore, in step 1, the type A water drive curve of the reservoir composed of n identical homogeneous units is:

[0010] ln(nW P )=a'+b'(nN P ) (2)

[0011] Available

[0012] a'=a+ln n (5)

[0013]

[0014] Where: W p —Cumulative water production, 10,000 tons; N p —Cumulative oil production, 10,000 tons; a', b'—intercept and slope of the type A water drive curve of the entire reservoir after synthesis, constant; a, b—intercept and slope of the type A water drive curve of a small unit, constant.

[0015] Further, in step 2, assuming that the water content is w0 The cumulative production at the time of t is the technically recoverable reserves, and the recoverable reserves calculation formula is:

[0016]

[0017] Where: N R —Technically recoverable reserves of a unit, 10,000 tons; w0 —water content, decimal;

[0018] When the water cut is fw1, the remaining recoverable reserves of each unit are:

[0019]

[0020] Where: N RR —The remaining technically recoverable reserves of a unit, 10,000 tons;

[0021] Total recoverable reserves in the area NR ' and remaining recoverable reserves N RR 'Respectively:

[0022] Total recoverable reserves:

[0023]

[0024] So we have:

[0025]

[0026] Where: N R '—The technically recoverable reserves of the entire area are 10,000 tons.

[0027] Remaining recoverable reserves:

[0028]

[0029] Where: N RR '—The remaining technically recoverable reserves in the entire area are 10,000 tons.

[0030] Further, in step 3, assuming that the water content is f w1 When m units are transferred to polymer flooding development, where m is less than n, the remaining technically recoverable reserves of m units transferred are:

[0031]

[0032] Right now

[0033]

[0034] Where: a”, b” are the intercept and slope of the type A water drive curve for transferring m units, respectively, constant; N RR —The remaining technically recoverable reserves of a unit, 10,000 tons; N RRm '—remaining technically recoverable reserves of m units transferred to polymer flooding, 10,000 tons;

[0035] The total recoverable reserves at this time can be expressed as:

[0036]

[0037] Where: N R(n-m) —Technically recoverable reserves of the remaining units after transferring to m units of polymer flooding, 10,000 tons;

[0038] Formula (18) is the revised formula for calculating recoverable reserves under the condition of reserve transfer in multi-structure oil fields.

[0039] Further, in step 1, a certain homogeneous unit type A water drive curve is:

[0040] l W P=a+bN P (1)

[0041] Where:

[0042] W p —Cumulative water production, 10,000 tons;

[0043] N p —Cumulative oil production, 10,000 tons;

[0044] a, b—intercept and slope of a small unit type A water drive curve, constant;

[0045] Further, in step 3, the type A water drive curve for transferring m units is

[0046] ln(mW P )=a”+b”(mN P ) (14)

[0047] Right now:

[0048] l W P =(a”-ln m)+b” (m)N P (15)

[0049] Combining formula (1) and formula (15) we can get:

[0050] a”=a+ln m

[0051]

[0052] Where: a”, b” are the intercept and slope of the type A waterflooding curve for transferring m units, respectively, constant;

[0053] Further, the water-containing f in step 3 w0 It is 98%.

[0054] The present invention has the following beneficial effects: Due to the adoption of the above scheme, on the basis of assuming that the oil reservoir is a complex composed of multiple homogeneous units, based on the type A water drive characteristic curve, the idea of ​​decomposition and synthesis is used to derive and establish a correction formula for calculating recoverable reserves under the condition of reserve transfer in multi-structure oil fields, solving the problem of high results of recoverable reserves predicted by directly applying the type A water drive curve after reserve transfer. The reliability of the results has been verified by numerical simulation and actual oil field inspection, providing a basis for scientifically and rationally evaluating recoverable reserves under the condition of reserve transfer in water drive oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 is a flow chart of the present invention;

[0056] Figure 2 It is the change of type A water drive curve during single layer mining;

[0057] Figure 3 It is the change of type A water drive curve when the 4th layer is mined;

[0058] Figure 4 It is the change of Type A water drive curve when mining four layers first and then changing to single layer mining;

[0059] Figure 5 It is the change of recoverable reserves and slope ratio between scheme 2, which mines four layers at the same time, and scheme 2, which mines only one layer;

[0060] Figure 6 The changes in the recoverable reserves and slope ratios of Scheme 3 (first mining 4 layers and then changing to single-layer mining) and Scheme 3 (mining only a single layer) are as follows;

[0061] Figure 7 is the type A water drive characteristic curve in Example 1;

[0062] Figure 8 The straight line segment of the type A water drive curve in the first embodiment is selected;

[0063] Fig. 9 is the water drive characteristic curve of type A in block A in Example 2;

[0064] Fig.10 It is the straight line segment fitted by the type A water drive characteristic curve of block A in Example 2. DETAILED DESCRIPTION

[0065] The present invention will be further described below in conjunction with the accompanying drawings:

[0066] Depend on Figure 1 As shown in the figure, a method for evaluating recoverable reserves under the condition of reserve transfer of water-driven oil reservoirs is proposed. The principle of decomposition and synthesis is applied, and an oil reservoir is regarded as a uniform body, and this uniform body is composed of multiple uniform bodies with similar seepage characteristics. Each small uniform body is regarded as an independent development unit. By studying the changes in recoverable reserves of each small unit, a method for evaluating recoverable reserves after reserve transfer of the entire oil reservoir is established.

[0067] The following steps are involved:

[0068] Step 1: According to a certain homogeneous unit type A water drive curve, determine the type A water drive curve of the entire reservoir composed of n identical homogeneous units, and establish the relationship between the intercept and slope of the specific homogeneous unit and the type A water drive curve of the entire reservoir.

[0069] For a specific homogeneous unit, the type A water drive curve is:

[0070] 1 W P =a+bN P (1)

[0071] Where:

[0072] W p —Cumulative water production, 10,000 tons;

[0073] N p —Cumulative oil production, 10,000 tons;

[0074] a, b—intercept and slope of a small unit type A water drive curve, constant;

[0075] Assuming that the reservoir consists of n identical homogeneous units, and each unit has the same seepage characteristics, the water drive curve of the entire area is:

[0076] ln(nW P )=a'+b'(nN P ) (2)

[0077] Right now:

[0078] ln n+ln W P =a'+b'(nN P ) (3)

[0079] So we have:

[0080] 1 W P =(a'-ln n)+(b'n)N P (4)

[0081] Combining formula (1) and formula (4) we can get:

[0082] a'=a+ln n (5)

[0083]

[0084] Where: a', b' - intercept and slope of the type A water drive curve of the entire reservoir after synthesis, constant;

[0085] That is, the slope of the total water drive curve in the entire area becomes 1 / n of the original, and the change in the intercept is also related to n.

[0086] Step 2: Determine the technically recoverable reserves N of a specific homogeneous unit based on the relationship between cumulative oil production and water content of the Type A water drive curve. R , and the remaining technically recoverable reserves N under a specific water content condition RR Based on the relationship between the slope and intercept of the type A water drive curve for a specific homogeneous unit and the entire reservoir established in step 1, determine the technically recoverable reserves N of the entire reservoir. R ' and remaining technically recoverable reserves N RR '.

[0087] Cumulative oil production of type A water drive curve N p The relationship with water content is:

[0088]

[0089] Where: f w —Water content, decimal.

[0090] Assuming water content to f w0 The cumulative production at the time of t is the technically recoverable reserves, and the recoverable reserves calculation formula is:

[0091]

[0092] Where: N R —Technically recoverable reserves of a certain unit, 10,000 tons.

[0093] In water containing w1 The remaining recoverable reserves of each unit are:

[0094]

[0095] Where: N RR —The remaining technically recoverable reserves of a unit, 10,000 tons.

[0096] The total recoverable reserves and remaining recoverable reserves of the area are:

[0097] Total recoverable reserves:

[0098]

[0099] So we have:

[0100]

[0101] Where: N R '—The technically recoverable reserves of the entire area are 10,000 tons.

[0102] Remaining recoverable reserves:

[0103]

[0104]

[0105] Where: N RR '—The remaining technically recoverable reserves in the entire area are 10,000 tons.

[0106] That is, assuming that after the oil reservoir is expanded n times in production, the recoverable reserves and remaining recoverable reserves will both expand to n times the original.

[0107] Step 3, assuming that the water content is f w1When m units are transferred to polymer flooding due to planning arrangements, where m is less than n, the development object is different from the original development object due to the change in mining structure. Therefore, the water flooding curve cannot be directly used to calculate the recoverable reserves. Based on the relationship between the slope and intercept of a specific homogeneous unit and the type A water flooding curve of m units, the remaining technical recoverable reserves N after transferring m units can be obtained. RRm ', thus obtaining the revised formula for calculating recoverable reserves under the conditions of reserve transfer in multi-structure oil fields.

[0108] The type A water drive curve for transferring m units is

[0109] ln(mW P )=a”+b”(mN P ) (14)

[0110] Right now:

[0111] 1 W P =(a”-ln m)+b” (m)N P (15)

[0112] Combining formula (1) and formula (15) we can get:

[0113] a”=a+ln m

[0114]

[0115] Remaining recoverable reserves:

[0116]

[0117] Right now

[0118]

[0119] Where: a”, b” are the intercept and slope of the type A water drive curve for transferring m units, respectively, constant; N RRm '—Remaining technically recoverable reserves of m units transferred to polymer flooding, 10,000 tons.

[0120] It can be seen from formula (17) that the remaining recoverable reserves of the transferred unit are related to the proportion of reserves transferred.

[0121] The total recoverable reserves can be expressed as:

[0122]

[0123] Where: N R(n-m) —Technically recoverable reserves of the remaining units after transferring to m units of polymer flooding, 10,000 tons;

[0124] Formula (18) is the calculation correction method of recoverable reserves under the condition of reserve transfer in multi-structure oil fields. The application of this method avoids the problem of overestimation of recoverable reserves calculated by directly applying water drive curve due to reserve transfer, and improves the calculation accuracy.

[0125] Usually, the cumulative production when the water content reaches 98% is taken as the technically recoverable reserves, that is, f w0 The cumulative production at this time is the technically recoverable reserves. The formula for calculating recoverable reserves is:

[0126]

[0127] In water containing w1 The remaining recoverable reserves of each unit are:

[0128]

[0129] The total recoverable reserves and remaining recoverable reserves of the area are:

[0130] Total recoverable reserves:

[0131]

[0132] So we have:

[0133]

[0134] Remaining recoverable reserves:

[0135]

[0136] Remaining recoverable reserves:

[0137]

[0138] Right now

[0139]

[0140] Total recoverable reserves are:

[0141]

[0142] N R(n-m) —The technically recoverable reserves of the remaining units after transferring to m units for polymer flooding are 10,000 tons.

[0143] In order to verify the above method, four groups of five-point well network numerical simulation models were established using ECLIPSE numerical simulation software. The well spacing is 250 meters, the model grid is 25*25*3, and the grid size in the X and Y directions is 25 meters. The phase permeability curve of each layer is obtained from the porosity-permeability correspondence curve of the actual oil field statistics. The production mode is fixed liquid production. It is assumed that the model consists of 4 homogeneous development units, which are produced in three sets of plans.

[0144] Option 1: Mining only a single layer, type A water drive curve is shown in Figure 2 ;

[0145] Option 2: Exploit 4 layers simultaneously, type A water drive curve is shown in Figure 3 ;

[0146] Option 3: Initially, 4 layers are mined. From a certain point in time, the other 3 layers are stopped and a single layer is mined. The type A water drive curve is shown in Figure 4 .

[0147] Figure 5 is the change in recoverable reserves and slope ratio between Scheme 2 and Scheme 1;

[0148] Table 1 Comparison of calculation results between Scheme 2 and Scheme 1

[0149] project Cumulative oil (tons) Slope Mineable (tons) Remaining recoverable (tons) Solution 1 7265.06 0.000632 8398.07 1133.01 Solution 2 29060.23 0.000158 33592.28 4532.05 ratio 4.00 0.25 4.00 4.00

[0150] From the comparison of the calculation results of Scheme 2 and Scheme 1, it can be seen that ( Figure 5 , Table 1), after expanding production by 4 times, the slope is reduced to 1 / 4 of the original, the ratio of recoverable reserves is expanded by 4 times, and the remaining recoverable reserves are also expanded by 4 times, which is consistent with the theoretical derivation and the actual oil field development.

[0151] Figure 6 is the change in recoverable reserves and slope ratio between Scheme 3 and Scheme 1;

[0152] Table 2 Comparison of calculation results between Scheme 3 and Scheme 1

[0153] project Cumulative oil (tons) Slope Mineable (tons) Remaining recoverable (tons) Solution 1 7265.06 0.000632 8398.07 1133.01 Option 3 28318.62 0.000176 32428.71 4110.09 ratio 3.90 0.28 3.86 3.63

[0154] From the comparison of the calculation results of Scheme 3 and Scheme 1, it can be seen that ( Figure 6, Table 2), when the other three layers stop production and only one oil layer is mined, according to the actual and theoretical derivation of the oil field, the remaining recoverable reserves should be consistent with the original exploitation of the single oil layer, but from the actual data change results, the remaining recoverable reserves are still nearly 4 times the original, which is obviously inconsistent with the actual oil field. In fact, when the oil field is expanded by n times, the cumulative oil and water production of the oil field will change greatly, and the shape of the corresponding water drive curve will also change. Even if the production mode is changed back to the original mode after a certain period of production, the shape of the curve will still change according to the original mining mode, and the slope will decrease, but the trend will not change much. This is why the recoverable reserves and remaining recoverable reserves of the entire oil field will not change much after the other three layers are turned off, because the future is still predicted according to the change trend of the past cumulative amount. Therefore, under the conditions of reserve transfer in the ultra-high water cut period, the recoverable reserves calculated by directly applying the type A water drive curve are too high, and the results must be corrected according to the transfer reserve ratio.

[0155] According to the established reserve calculation correction formula (26), when changing to single-layer mining, the recoverable reserves should be the total recoverable reserves of the four layers minus the remaining technical recoverable reserves of the three transferred layers. The specific calculation formula is 33592.28-4532.05*(3 / 4)=30193.24 million tons.

[0156] Embodiment 1:

[0157] 1. First, according to the actual data of a certain reservoir, the cumulative water production and cumulative oil production are calculated (see Table 3), and the type A water drive curve is drawn. Figure 7 .

[0158] Table 3 Changes in the main indicators of a certain oil reservoir

[0159]

[0160] 2. According to the recoverable reserves calculation formula of Type A water drive curve, calculate the total recoverable reserves and remaining recoverable reserves.

[0161] According to the shape of the water drive curve, the stable straight line segment from January 1994 to December 2016 was selected for fitting regression, see Figure 8 , find the intercept b = 6.5182, the slope a = 0.6 × 10 -7 According to the recoverable reserves calculation formula (Formula 19), the total recoverable reserves are calculated to be 33,859,181.53 tons. The cumulative oil production of the oil reservoir is 25,152,361.99 tons, so the remaining recoverable reserves are 8,706,819.53 tons.

[0162] 3. Calculate the total recoverable reserves of water drive after transfer according to the transfer reserve calculation formula (Formula 26).

[0163] In January 2017, the block implemented the transfer of geological reserves of 12 million tons, and the total geological reserves of the block were 84.65 million tons. The proportion of the transferred reserves to the third production was 14.2% of the total reserves. According to Formula 26, the total recoverable reserves of the reservoir after the transfer of the third production were 32622813.16 tons. The specific calculation formula is 33859181.53-8706819.53*0.142=32622813.16 tons.

[0164] Embodiment 2:

[0165] Take Block A of Daqing Sartu Oilfield as an example. The block was put into development in 1964, with a geological reserve of 73.068 million tons. There are 395 oil and water wells, including 269 oil wells, with an annual oil production of 232,000 tons, a comprehensive water content of 95.8%, and a cumulative oil production of 25.1524 million tons. Its annual production data is shown in Table 4.

[0166] Table 4 Changes in main indicators of reservoir in Block A

[0167]

[0168]

[0169] Based on the actual dynamic data of the block, the type A water drive curve of the block was drawn ( Fig. 9 ), select 2000 to 2016 as the fitting straight line segment ( Fig.10 ), the intercept b = 2.4369, the slope a = 0.0007, according to the recoverable reserves calculation formula (Formula 19), the total recoverable reserves are calculated to be 29.2272 million tons, the cumulative oil production of the reservoir is 25.1524 million tons, so the remaining recoverable reserves are 4.0748 million tons.

[0170] The block plans to transfer 15.417 million tons of reserves to polymer flooding in 2017, accounting for 21.1% of the total reserves of the block. According to Formula 26, the total recoverable reserves of the reservoir after the transfer to the third recovery are 28.3674 million tons. The specific calculation formula is 2922.72-407.48*0.211=28.3674 million tons.

[0171] Considering the impact of water flooding reserve transfer on recoverable reserves can achieve reasonable matching of recoverable reserves under different displacement modes, which is helpful to objectively evaluate the effect of different displacement technologies on improving oil recovery.

Claims

1. A method for evaluating recoverable reserves under water drive reservoir reserve transfer conditions, characterized in that The following steps are involved: Step 1, based on a certain homogeneous unit type A water drive curve, determine the type A water drive curve of the entire reservoir composed of n identical homogeneous units, and establish the relationship between the intercept and slope of the specific homogeneous unit and the type A water drive curve of the entire reservoir; Step 2: Determine the technically recoverable reserves N of a specific homogeneous unit based on the relationship between cumulative oil production and water content of the Type A water drive curve. R , and the remaining technically recoverable reserves N under a specific water content condition RR Based on the relationship between the slope and intercept of the type A water drive curve for a specific homogeneous unit and the entire reservoir established in step 1, determine the technically recoverable reserves N of the entire reservoir. R ' and remaining technically recoverable reserves N RR '; Assuming water content to f w0 The cumulative production at the time of t is the technically recoverable reserves, and the recoverable reserves calculation formula is: Where: N R —Technically recoverable reserves of a unit, 10,000 tons; w0 —water content, decimal; When the water cut is fw1, the remaining recoverable reserves of each unit are: Where: N RR —The remaining technically recoverable reserves of a unit, 10,000 tons; Total recoverable reserves in the area N R ' and remaining recoverable reserves N RR 'Respectively: Total recoverable reserves: So we have: Where: N R '—Technically recoverable reserves of the whole area, 10,000 tons; Remaining recoverable reserves: Where: N RR '—The remaining technically recoverable reserves in the whole area, 10,000 tons; Step 3: Assuming that under a certain water-cut condition, m units are transferred to polymer flooding development, the remaining technically recoverable reserves N of the transferred m units can be obtained based on the relationship between the slope and intercept of the type A water flooding curve of a certain homogeneous unit and m units. RRm ', thus obtaining the revised formula for calculating recoverable reserves under the reserve transfer conditions of multi-structure oil fields; The type A water drive curve for transferring m units is ln(mW P )=a”+b”(mN P ) (14) Right now: lnW P =(a”-lnm)+b”(m)N P (15) Combining formula (1) and formula (15) we can get: a"=a+lnm Where: a”, b” are the intercept and slope of the type A waterflooding curve for transferring m units, respectively, constant; Assuming that the water content is f w1 When m units are transferred to polymer flooding development, where m is less than n, the remaining technically recoverable reserves of m units transferred are: Right now Where: N RR —The remaining technically recoverable reserves of a unit, 10,000 tons; N RRm '—remaining technically recoverable reserves of m units transferred to polymer flooding, 10,000 tons; The total recoverable reserves at this time can be expressed as: Where: N R(n-m) —Technically recoverable reserves of the remaining units after transferring to m units of polymer flooding, 10,000 tons; Formula (18) is the revised formula for calculating recoverable reserves under the condition of reserve transfer in multi-structure oil fields.

2. The method for evaluating recoverable reserves under reserve transfer conditions of a water-flooding oil reservoir according to claim 1, characterized in that: In step 1, the type A water drive curve of the reservoir composed of n identical homogeneous units is: ln(nW P )=a'+b'(nN P ) (2) Available a'=a+lnn (5) Where: W p —Cumulative water production, 10,000 tons; N p —Cumulative oil production, 10,000 tons; a', b' are the intercept and slope of the type A water drive curve of the entire reservoir after synthesis, respectively, constants; a, b are the intercept and slope of the type A water drive curve of a small unit, respectively, constants.

3. The method for evaluating recoverable reserves under reserve transfer conditions of a water-flooding oil reservoir according to claim 1, characterized in that: In step 1, a certain homogeneous unit type A water drive curve is: in W P =a+bN P (1) Where: W p —Cumulative water production, 10,000 tons; N p —Cumulative oil production, 10,000 tons; a, b are the intercept and slope of a small unit type A water drive curve, constant.

4. The method for evaluating recoverable reserves under reserve transfer conditions of a water-flooding oil reservoir according to claim 1, characterized in that: The water-containing f w0 It is 98%.

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