Systematic economic method for determining whether sealed reserves are deblocked by water drive well or not

Abstract

The invention relates to a systematic economic method for determining whether sealed reserves are unsealed by using a water drive well or not. The method mainly solves the problem that whether the existing oil field sealed reserves are economically feasible by utilizing a water-drive well pattern to unseal is mainly solved. The method comprises the following steps: S1, selecting two well pattern development modes; wherein the mode 1 is a current well pattern development mode, and the mode 2 is a mode of unblocking by using a water drive well after a three-production well pattern returns upwards (downwards); s2, taking each layer section developed by the water drive well pattern and the three-production well pattern in the mode 1 and the mode 2 as a system, and totally considering and calculating the benefit conditions in the two modes; and S3, comparing the benefits in the two modes, and judging which mode is more reasonable to select according to the improved recovery efficiency and geological reserves of the change interval in the two modes and the cost of the supplement and blockage measures. The economic method of the system can accurately and quickly judge the economic feasibility of utilizing the water-drive well pattern to deblock, and provides support for sealing reserve deblocking and comprehensive utilization of the water-drive well pattern.

Description

Technical field:

[0001] The invention relates to the technical field of oil production, and in particular to a systematic economic method for determining whether a sealed storage volume should be unsealed by using a water drive well. Background technology:

[0002] my country's oil resources are distributed in a sedimentary oil-generating environment dominated by terrestrial strata, most of which are sandstone reservoirs, accounting for more than 90%. The development method is mainly water injection development, which has the characteristics of severe heterogeneity and high oil density. Taking the Lasaxing Oilfield in Daqing as an example, the Lasaxing Oilfield in Daqing is a typical terrestrial multi-layer sandstone oil reservoir. Since the stratified injection and production development was determined in the 1960s, the three oil layers of Sartu, Putaohua and Gaotaizi have been clearly divided into more than a dozen oil layers for development. Since 2002, the second type of oil layers (river sand with permeability greater than 100md and effective thickness greater than 1m) have begun to gradually carry out tertiary oil recovery development. During the period from 2013 to 2022, the second type of oil layers began secondary up (down) return development. As the second type of oil layers' secondary up (down) return injection reserves increased year by year, the first set of up return layer systems were gradually sealed. As of the end of 2021, the first set of reserves of the second type of oil layers had been sealed at 96.03 million tons, and it is estimated that 80.58 million tons will be sealed from 2023 to 2025. In 2026 and future development, the sealed reserves of Daqing Oilfield will reach tens of billions of tons.

[0003] As the tertiary oil recovery well network of the second oil layer is used to develop other strata, the reserves of the original strata are sealed, which affects the oil field production. In order to maximize the potential of sealed reserves, we can use water drive wells to fill holes or remove plugs to release the layers blocked after chemical flooding of the second oil layer. However, there is currently no very effective method to judge whether it is economically feasible to use water drive wells to unblock. For this reason, the invention of this patent can more conveniently determine whether to use water drive wells for unblocking, and can provide technical support for the future unblocking of sealed reserves and the comprehensive utilization of water drive well networks, which plays a huge role in supporting the comprehensive utilization and adjustment of well networks in Daqing Oilfield and my country's continental oilfields. Summary of the invention:

[0004] The present invention aims to solve the problem of whether it is economically feasible to unseal the sealed reserves of existing oil fields by using water-drive well networks in the background technology, and provide a systematic economic method for determining whether the sealed reserves are unsealed by using water-drive wells. The systematic economic method for determining whether the sealed reserves are unsealed by using water-drive wells can accurately and quickly determine the economic feasibility of unsealing by using water-drive well networks, and provide support for unsealing the sealed reserves and comprehensive utilization of water-drive well networks.

[0005] The present invention solves the problem by the following technical solution: the system economic method for determining whether the sealed storage capacity is unsealed by using a water drive well comprises the following steps:

[0006] S1. Determine two well network development modes, namely Mode 1 and Mode 2; Mode 1 is the current well network development mode; Mode 2 is to convert Mode 1 into a mode that uses water drive wells to unblock after upper or lower return of the three-recovery wells;

[0007] S2. Treat each layer developed by the water drive well network and the three-recovery well network in Mode 1 and Mode 2 as a system, and consider and calculate the benefits of the two modes as a whole;

[0008] S3. Compare the benefits of Mode 1 and Mode 2, and determine which mode is more reasonable based on the increased recovery rate and geological reserves of the changed layers in the two modes, as well as the costs of supplementary and plugging measures.

[0009] Furthermore, the method for converting mode 1 to mode 2 is as follows: in mode 1, a certain layer section of the original three-production well is developed by upward return or downward return, and the water drive well cooperates to seal the corresponding layer section developed by upward return or downward return, and a certain layer section developed by the original three-production well is unsealed for water drive development.

[0010] Further, determine the benefits of step S2 mode 1:

[0011] Assuming that the current well pattern remains unchanged, the system benefits from development to abandonment can be expressed as:

[0012] E1=Ea+Eb—C1 (1)

[0013] Where: E1: benefit of mode 1;

[0014] Ea: the benefit of all perforated intervals in the water drive well;

[0015] Eb: the benefits of all perforated intervals in the three-production well;

[0016] C1: Total cost of developing water drive wells and tertiary recovery wells.

[0017] Furthermore, the benefits of step S2 mode 2 are determined as follows:

[0018] Assuming that the tertiary recovery well network uses upturn for tertiary oil recovery, the system benefits can be expressed as:

[0019] E2=Ea'+Eb'-C2-C3-C4-Cj; (2)

[0020] Where: E2 is the benefit of mode 2;

[0021] Ea' The benefits of all perforated intervals in water drive wells;

[0022] The benefits of all perforated intervals in the Eb' three-production well;

[0023] C2: The cost of developing water drive wells and three-recovery wells, 10,000 yuan;

[0024] C3: Cost of plugging and perforating water drive wells, 10,000 yuan;

[0025] C4: The cost of plugging and re-perforating the tertiary recovery well, 10,000 yuan;

[0026] Cj: Cost of the three used pharmaceutical agents, ten thousand yuan.

[0027] Furthermore, the expression comparing the benefits of Mode 1 and Mode 2 is:

[0028] Y=E2-E1 (3)

[0029] Substituting formula (1) and (2) into (3), formula (3) can be expressed as:

[0030] Y=Ea'+Eb'-C2-C3-C4-Cj-Ea–Eb+C1; (4)

[0031] In formula (4), since both the return and unblocking are the development of the original well network, except for the cost of re-perforation and plugging, the other costs of the two modes are the costs generated by the production of the original well network. Therefore, the normal production costs C1 and C2 of the two modes are basically equal, and formula (4) becomes:

[0032] Y=Ea'+Eb'-C3-C4-Cj-Ea–Eb;

[0033] Where: The benefit of a certain perforated layer section E i =Qi*hsl*hl*a;

[0034] Where: Q i : The remaining total oil production of layer i;

[0035] hsl: crude oil barrel to ton conversion rate, optional 7.425;

[0036] hl: RMB to USD exchange rate, 6.19 RMB / USD is available;

[0037] a: Crude oil commodity rate, 98.37%;

[0038] Y=(Q si -Q wi )*hsl*hl*a+[Q wi+1 -Q si+1 ]*hsl*hl*a-C3-C4-Cj (5)

[0039] Where: Q si : The remaining total oil production of the i-th layer of the third recovery well;

[0040] Q wi : The remaining total oil production of the i-th layer of the water-flooding well;

[0041] Q si+1 : The remaining total oil production of the i+1 layer of the third recovery well;

[0042] Q wi+1 : The remaining total oil production of the water drive well after unblocking the i+1 layer;

[0043] Furthermore, in the formula (5), Q si -Q wi = Q is the production of three-stage recovery minus the water drive production of layer i, which can be replaced by the product of the recovery factor of three-stage recovery over water drive and the geological reserves, Q wi+1 -Q si+1 Q is the product of the change in production rate of the i+1 layer segment using water drive well development compared to the original three-production well pattern development and geological reserves; that is: si -Q wi =N i *EOR i *hsl*hl*a;

[0044] Q wi+1 -Q si+1 =N i+1 *EOR i+1 *hsl*hl*a;

[0045] Then formula (5) can be replaced by:

[0046] Y=(N i *EOR i +N i+1 *EOR i+1 )*hsl*hl*a-C3-C4-Cj (6)

[0047] Where: N i : Geological reserves of layer i, 10,000 tons;

[0048] N i+1 : Geological reserves of i+1 layer, 10,000 tons;

[0049] EOR i : The recovery factor of the tertiary oil recovery in layer i compared with water flooding, %;

[0050] EOR i+1 : The production change rate of the i+1 layer developed by water drive well pattern compared with the original three production wells, %.

[0051] Further, the method to determine which mode is more reasonable is:

[0052] (1) When Y = (N i *EOR i +N i+1 *EOR i+1)*hsl*hl*a-C3-C4-Cj>0, select mode 2;

[0053] (2) When Y=(N i *EOR i +N i+1 *EOR i+1 )*hsl*hl*a-C3-C4-Cj﹤0, select mode 1.

[0054] Compared with the above background technology, the present invention has the following beneficial effects:

[0055] The present invention provides a system economic method for determining whether to use water drive wells to unseal sealed storage capacity. The benefits generated by the incremental production of the variable layer section and the cost of supplementary and plugging measures are used to determine whether to use water drive wells to unseal the reserves after chemical drive. It can more conveniently determine whether to use water drive wells for unsealing. At the same time, the production of the variable layer section is converted into the product of the recovery factor and geological reserves increased by three recovery than water drive. The production of the variable layer section is quickly judged and accurately predicted, making the system economic method more accurate. The method has a very broad application prospect and can provide technical support for the unsealing of sealed storage capacity and the comprehensive utilization of water drive well networks in the future. It plays a huge role in supporting the comprehensive utilization and adjustment technology of the well network of my country's continental oil fields. Description of the drawings:

[0056] Attached Figure 1 is a flow chart of the present invention;

[0057] Attached Figure 2 Schematic diagram of the three-layer water polymer flooding development mode (mode 1) of the present invention; Figure 3 1 is a schematic diagram of a mode of unsealing a water drive well by using an upward return in a third production well according to an embodiment of the present invention (mode 2);

[0058] Attached Figure 4 It is a system benefit chart when the production of the unsealed layer section of the S block in the two modes of the embodiment of the present invention is higher than the original three-production well network development;

[0059] Attached Figure 5 This is a system benefit chart of the two modes of the embodiment of the present invention when the production of the unsealed layer section of the S block is lower than the original three-production well network development. Specific implementation method:

[0060] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0061] like Figure 1 As shown, the present invention provides a system economic method for determining whether to unblock sealed storage using a water drive well, comprising the following steps:

[0062] Step 1: Determine two well network development modes, namely Mode 1 and Mode 2; Mode 1 is the current well network development mode; Mode 2 is to convert Mode 1 into a mode that uses water drive wells to unblock after upper or lower return of the three-recovery well network;

[0063] The method for converting mode 1 to mode 2 is as follows: in mode 1, a certain layer section of the original three-production well is developed by upward return or downward return, and the water drive well cooperates to seal the corresponding layer section developed by upward return or downward return, and a certain layer section developed by the original three-production well is unsealed for water drive development.

[0064] Step 2: Consider each layer section developed by the water drive well network and the three-recovery well network in Mode 1 and Mode 2 as a system, and consider and calculate the benefits of the two modes as a whole;

[0065] 1. Determine the benefits of step S2 mode 1:

[0066] Assuming that the current well pattern remains unchanged, the system benefits from development to abandonment can be expressed as:

[0067] E1=Ea+Eb—C1 (1)

[0068] Where: E1: benefit of mode 1; Ea: benefit of all perforated layers of water drive wells; Eb: benefit of all perforated layers of tertiary recovery wells; C1: total cost of developing water drive wells and tertiary recovery wells.

[0069] 2. Determine the benefits of step S2 mode 2:

[0070] Assuming that the tertiary recovery well network uses upturn for tertiary oil recovery, the system benefits can be expressed as:

[0071] E2=Ea'+Eb'-C2-C3-C4-Cj; (2)

[0072] Where: E2 is the benefit of mode 2, 10,000 yuan;

[0073] Ea' The benefits of all perforated layers in the water drive well, 10,000 yuan;

[0074] The benefits of all perforated layers in Eb' Sanyou Well, 10,000 yuan;

[0075] C2: The cost of developing water drive wells and three-recovery wells, 10,000 yuan;

[0076] C3: Cost of plugging and perforating water drive wells, 10,000 yuan;

[0077] C4: The cost of plugging and re-perforating the tertiary recovery well, 10,000 yuan;

[0078] Cj: Cost of the three used pharmaceutical agents, ten thousand yuan.

[0079] Step 3: Compare the benefits of Mode 1 and Mode 2, and determine which mode is more reasonable based on the increased recovery rate and geological reserves of the changed layers in the two modes, as well as the cost of supplementary and plugging measures.

[0080] The expression comparing the benefits of Mode 1 and Mode 2 is:

[0081] Y=E2-E1 (3)

[0082] Substituting formula (1) and (2) into (3), formula (3) can be expressed as:

[0083] Y=Ea'+Eb'-C2-C3-C4-Cj-Ea–Eb+C1; (4)

[0084] In formula (4), since both the return and unblocking are the development of the original well network, except for the cost of re-perforation and plugging, the other costs of the two modes are the costs generated by the production of the original well network. Therefore, the normal production costs C1 and C2 of the two modes are basically equal, and formula (4) becomes:

[0085] Y=Ea'+Eb'-C3-C4-Cj-Ea–Eb;

[0086] Wherein: the benefit of a certain perforated layer section among all the perforated layers of the Ea' water drive well and all the perforated layers of the Eb' three-production well is Ei;

[0087] Ei=Qi*hsl*hl*a;

[0088] Where: Q i : The remaining total oil production of layer i;

[0089] hsl: crude oil barrel to ton conversion rate, optional 7.425;

[0090] hl: RMB to USD exchange rate, 6.19 RMB / USD is available;

[0091] a: Crude oil commodity rate, 98.37%;

[0092] Then Y=(Q si -Q wi )*hsl*hl*a+(Q wi+1 -Q si+1 )*hsl*hl*a-C3-C4-Cj (5)

[0093] Where: Q si : The remaining total oil production of the i-th layer of the third recovery well;

[0094] Q wi : The remaining total oil production of the i-th layer of the water-flooding well;

[0095] Q si+1 : The remaining total oil production of the i+1 layer of the third recovery well;

[0096] Q wi+1 : The remaining total oil production of the water drive well after unblocking the i+1 layer;

[0097] In the above formula (5), Q si -Q wi = Q is the production of three-stage recovery minus the water drive production of layer i, which can be replaced by the product of the recovery factor of three-stage recovery over water drive and the geological reserves, Q wi+1 -Q si+1 It is the product of the change in production rate of the i+1 layer segment developed by water drive wells compared with the original three-production well pattern and the geological reserves;

[0098] Then formula (5) can be replaced by:

[0099] Y=(N i *EOR i +N i+1 *EOR i+1 )*hsl*hl*a-C3-C4-Cj (6)

[0100] Where: N i : Geological reserves of layer i, 10,000 tons;

[0101] N i+1 : Geological reserves of i+1 layer, 10,000 tons;

[0102] EOR i : The recovery factor of the tertiary oil recovery in layer i compared with water flooding, %;

[0103] EOR i+1 : The production change rate of the i+1 layer developed by water drive well pattern compared with the original three production wells, %.

[0104] When Y>0, select mode 2;

[0105] When Y﹤0, select mode 1.

[0106] Example 1

[0107] The method of the present invention is used to determine whether the sealed storage capacity of the S block of Daqing Oilfield can be economically unsealed by water drive wells. The method includes the following steps:

[0108] First step model assumptions

[0109] The various layers developed by the water-drive well network and the three-production well network are regarded as a system. The overall consideration is to maintain the current well network development and the three-production well network after the return of the water-drive wells to unseal the two modes. It is determined whether to use the water-drive well network to unseal the reserves sealed after the three-production. Two modes are determined. The first mode is the current water-drive well development of the 1st and 3rd layers, and the three-production well development of the 2nd layer until the oilfield is abandoned (such as Figure 2 ); Mode 2 is to plug the 2nd layer of the tertiary recovery well and use the 1st layer to carry out tertiary oil recovery. The water drive well cooperates with plugging the 1st layer and re-perforating the 2nd layer to unlock the reserves after the tertiary recovery (such as Figure 3 ).

[0110] Step 2: Model building

[0111] (1) Model 1 benefit: Assuming that the current well pattern remains unchanged, the system benefit from development to abandonment is expressed as:

[0112] E1=a1+b2+a3-C1 (1)

[0113] Where: a1 = Q w1 *hsl*hl*a;

[0114] b2=Q s2 *hsl*hl*a;

[0115] a3=Q w3 *hsl*hl*a;

[0116] Where:

[0117] Q w1 : The remaining total oil production of the first layer of the water drive well;

[0118] Q s2 : The remaining total oil production of the 2nd layer of the third production well;

[0119] Q w3 : The remaining total oil production of the three-layer section of the water drive well;

[0120] a1: benefit of water flooding production in layer 1, ten thousand yuan;

[0121] b2: The benefit of the third mining output of the 2nd layer, 10,000 yuan;

[0122] a3: benefit of water flooding production in the 3rd layer, 10,000 yuan;

[0123] hsl: crude oil barrel to ton conversion rate, 7.425;

[0124] hl: RMB to USD exchange rate, 6.19 yuan / USD;

[0125] a: Crude oil commodity rate, 98.37%;

[0126] C1: Total cost of developing water drive wells and three-recovery wells, 10,000 yuan;

[0127] (2) Model 2 benefits: Assuming that the tertiary recovery well network uses upflow for tertiary oil recovery, the system benefits are expressed as:

[0128] E2=b1+a2+a3-C2-C3-C4-Cj (2)

[0129] Where: b1 = Q s1 *hsl*hl*a;

[0130] a2=Q w2 *hsl*hl*a;

[0131] a3=Q w3 *hsl*hl*a;

[0132] Where:

[0133] Q s1 : The remaining total oil production of the first layer of the third production well;

[0134] Q w2 : The remaining total oil production of the water drive well after unblocking the 2nd layer;

[0135] b1: The benefit of the three-stage production of the 1st layer, 10,000 yuan;

[0136] a2: benefit of water flooding production in layer 2, ten thousand yuan;

[0137] a3: benefit of water flooding production in the 3rd layer, 10,000 yuan;

[0138] C2: The cost of developing water drive wells and three-recovery wells, 10,000 yuan;

[0139] C3: Cost of plugging and perforating water drive wells, 10,000 yuan;

[0140] C4: The cost of plugging and re-perforating the tertiary recovery well, 10,000 yuan;

[0141] Cj: cost of the three adopted drugs, ten thousand yuan;

[0142] The system benefits of the two models can be compared to determine whether to adopt Model 2, which is to use the water drive well network to unblock the chemical drive and then develop the sealed storage capacity.

[0143] Y=E2-E1 (3)

[0144] Substituting formula (1) and (2) into (3), formula (3) can be written as:

[0145] Y=b1+a2+a3-C2-C3-C4-Cj-a1-b2-a3+C1 (4)

[0146] In formula (4), since both the return and unblocking are the development of the original well network, except for the cost of re-perforation and plugging, the other costs of the two modes are the costs generated by the production of the original well network. Therefore, the normal production costs C1 and C2 of the two modes are basically equal, and the formula becomes:

[0147] Y=b1+a2-C3-C4-Cj-a1-b2

[0148] =(Q s1 -Q w1 )*hsl*hl*a+(Q w2 -Q s2 )*hsl*hl*a-C3-C4-Cj (5)

[0149] In the above formula (5), Q s1 -Q w1 = Q is the production of three-layer recovery minus the water drive production of layer 1, which can be replaced by the product of the recovery factor of three-layer recovery over water drive and the geological reserves, Q w2 -Q s2 It is the product of the change in production rate of the 2-layer section developed using water drive wells compared to the original three-production well network development and the geological reserves.

[0150] Then formula (5) can be replaced by:

[0151] Y=(N1*EOR1+N2*EOR2)*hsl*hl*a-C3-C4-Cj (6)

[0152] Where:

[0153] N1: geological reserves of layer 1, 10,000 tons;

[0154] N2: Geological reserves of the 2nd layer, 10,000 tons;

[0155] EOR1: EOR compared with water flooding in tertiary oil recovery in 1 layer, %;

[0156] EOR2: Production change rate of the 2nd layer developed by water drive well pattern compared with the original three production wells, %

[0157] In this way, it is possible to determine whether to use the water drive well network to develop the reserves after chemical flooding based on the enhanced recovery and geological reserves of the 1st and 2nd layer sections in the two models, as well as the costs of the remedial and plugging measures.

[0158] Before applying the model calculation using the S block as an example, the basic data of the block where the upper return three-mining development will be implemented was obtained first.

[0159] The development plan for the second-class oil reservoir in this block is divided into three layers, 1, 2, and 3, for development. At present, the first layer 2 is being developed, and the water content is 98%. It is planned to use this set of three-production wells to develop the 1st layer. The basic profile of each layer in the S block is shown in Table 1; the cost calculation of plugging and re-hole filling using the water drive well network on the three-production well network of the S block is shown in Table 2.

[0160] Table 1 Basic overview of each layer in Block S

[0161]

[0162] Through the reservoir engineering plan of layer 1, it can be seen that the dry powder of tertiary oil recovery injection agent in layer 1 is 2.2 tons (Table 1), and the cost of chemical agent is 330 million yuan; Table 2 shows that the cost of plugging and perforating the water drive well C3 = 52.182 million yuan, and the cost of plugging and perforating the tertiary production well C4 = 74.268 million yuan.

[0163] Formula (6) becomes:

[0164] Y=(N1*EOR1+N2*EOR2)*hsl*hl*a-5218.2-7426.8-33000=

[0165] (680.68*EOR1+1292.5*EOR2)*hsl*hl*a-45645;

[0166] That is, the enhanced oil recovery of the two intervals is used to determine whether to use a water drive well pattern to develop chemical flooding reserves.

[0167] Table 2 Calculation table of the cost of plugging and re-hole filling by using water drive well network in the return layer system of the three production wells in block S

[0168]

[0169] Below, the enhanced oil recovery assumptions for the two intervals are calculated:

[0170] When the barrel-ton conversion rate is 7.425, the exchange rate is 6.19 yuan / US dollar, and the crude oil commodity rate is 98.37%, the benefit chart of the two models under different recovery factors under the conditions of oil prices of 30, 40, 50, 60, 70, 80, and 90 $ is obtained ( Figure 4 , Figure 5 ).

[0171] Figure 4For the first case (the production of the 2nd layer developed by the water drive well network is higher than that of the subsequent water drive well network of the original three-production), it is assumed that the 2nd layer is optimized by the water drive well network, the well network is adjusted by the flow line, and the best layer is selected for the re-perforation. Therefore, the recovery rate is increased by 1 percentage point when the water drive well network is used for development compared with the subsequent water drive well network. When EOR2 = 1%, the production is increased by 1265 × 0.01 = 126,500 tons. At this time, the total benefit chart of the 1st layer recovery under different oil prices is as follows Figure 4 As shown in the figure, when the horizontal axis is zero, that is, the system benefit is zero, the corresponding recovery rate is the minimum recovery rate of the 1st layer. If the actual recovery rate of the 1st layer is higher than this value, then the water drive well network can be used to unlock it. For example, in the figure, if the oil price is 30 US dollars per barrel, EOR1 needs to reach more than 3% to develop the 2nd layer using the water drive well network. As the oil price increases, the recovery rate limit required for EOR1 becomes smaller.

[0172] Figure 5 For another situation (the production of the 2nd layer developed by the water drive well network is lower than that of the subsequent water drive well network of the original three-production), it is assumed that the number of production wells used for the 2nd layer unblocking by water drive wells is less than that of the original three-production well network, resulting in less production after unblocking than that of the original well network. Assuming that the production rate is EOR1 = -2%, that is, the production is 1265 × (-0.02) = -253,000 tons less. Figure 5 When the horizontal axis is zero, that is, when the system benefit is zero and the oil price is $30 per barrel, EOR1 needs to reach more than 10% before the water drive well network can be used to develop 2 layers.

[0173] According to the reservoir engineering plan, the tertiary recovery in Block S is expected to increase oil recovery by 14%, so a water drive well pattern should be used to unblock the 2nd layer for development.

Claims

1. A system economic method for determining whether sealed storage should be unsealed using water drive wells, Features: The following steps are involved: S1. Determine two well network development modes, namely Mode 1 and Mode 2; Mode 1 is the current well network development mode; Mode 2 is to convert Mode 1 into a mode that uses water drive wells to unblock after upper or lower return of the three-recovery wells; S2. Treat each layer developed by the water drive well network and the three-recovery well network in Mode 1 and Mode 2 as a system, and consider and calculate the benefits of the two modes as a whole; S3. Compare the benefits of Mode 1 and Mode 2, and determine which mode is more reasonable based on the increased recovery rate and geological reserves of the changed layers in the two modes, as well as the costs of supplementary and plugging measures.

2. The system economic method for determining whether sealed storage is to be unsealed using a water drive well according to claim 1, Features: The method of converting mode 1 to mode 2 is as follows: in mode 1, a certain layer section of the original three-production well is developed by upward return or downward return, and the water drive well cooperates to seal the corresponding layer section developed by upward return or downward return, and a certain layer section developed by the original three-production well is unsealed for water drive development.

3. The system economic method for determining whether sealed storage is to be unsealed using a water drive well according to claim 1, Features: Determine the benefits of step S2 mode 1: Assuming that the current well pattern remains unchanged, the system benefits from development to abandonment can be expressed as: E1=Ea+Eb—C1 (1) Where: E1: benefit of mode 1; Ea: the benefit of all perforated intervals in the water drive well; Eb: the benefits of all perforated intervals in the three-production well; C1: Total cost of developing water drive wells and tertiary recovery wells.

4. The system economic method for determining whether sealed storage is to be unsealed using a water drive well according to claim 1, Features: Determine the benefits of step S2 mode 2: Assuming that the tertiary recovery well network uses upturn for tertiary oil recovery, the system benefits can be expressed as: E2=Ea'+ Eb'-C2-C3-C4-Cj; (2) Where: E2 is the benefit of mode 2; Ea' The benefits of all perforated intervals in water drive wells; The benefits of all perforated intervals in the Eb' three-production well; C2: Cost of developing water drive wells and three-recovery wells; C3: Water drive well plugging and perforation repair costs; C4: cost of plugging and re-perforating the tertiary recovery wells; Cj: Cost of the three used medicines.

5. The system economic method for determining whether sealed storage is to be unsealed using a water drive well according to claim 3 or 4, Features: The expression comparing the benefits of Mode 1 and Mode 2 is: Y=E2-E1; (3) Substituting formula (1) and (2) into (3), formula (3) can be expressed as: Y= Ea'+ Eb'-C2-C3-C4-Cj-Ea – Eb+C1; (4) In formula (4), since both the return and unblocking are the development of the original well network, except for the cost of re-perforation and plugging, the other costs of the two modes are the costs generated by the production of the original well network. Therefore, the normal production costs C1 and C2 of the two modes are basically equal, and formula (4) becomes: Y=Ea'+Eb'-C3-C4-Cj-Ea-Eb; (4-1).

6. The system economic method for determining whether sealed storage is to be unsealed using a water drive well according to claim 5, Features: The benefits of a certain perforated layer section among all the perforated layers of the Ea' water drive well and all the perforated layers of the Eb' three-production well: E i =Q i *hsl*hl*a; Where: Q i : The remaining total oil production of layer i; hsl: crude oil barrel to ton conversion rate; hl: exchange rate of RMB to USD; a: crude oil commodity rate; Then Y = (Q si - Q wi ) * hsl * hl * a + [Q wi+1 - Q si+1 * hsl * hl * a - C3 - C4 - Cj(5) Where: Q si : The remaining total oil production of the i-th layer of the third-production well; Q wi : The remaining total oil production of the i-th layer of the water-flooding well; Q si+1 : The remaining total oil production of the i+1 layer of the third recovery well; Q wi+1 : The remaining total oil production of the water-drive well after unsealing the i+1 interval.

7. The system economic method for determining whether sealed storage is to be unsealed using a water drive well according to claim 6, Features: In the formula (5), Q si -Q wi It is the production of three-stage recovery in layer i minus the production of water flooding, which can be replaced by the product of the recovery factor of three-stage recovery over water flooding and geological reserves; Q wi+1 -Q si+1 It is the product of the change in production rate of the i+1 layer segment developed by water drive wells compared with the original three-production well pattern and the geological reserves; That is: Q si -Q wi = N i *EOR i *hsl*hl*a; Q wi+1 -Q si+1 =N i+1 *EOR i+1 *hsl*hl*a; Then formula (5) can be replaced by: Y=(N i *EOR i +N i+1 *EOR i+1 )*hsl*hl*a-C3-C4-Cj (6) Where: N i : Geological reserves of layer i, 10,000 tons; N i+1 : Geological reserves of i+1 layer, 10,000 tons; EOR i : The recovery factor of the tertiary oil recovery in layer i compared with water flooding, %; EOR i+1 : The production change rate of the i+1 layer developed by water drive well pattern compared with the original three production wells, %.

8. The system economic method for determining whether sealed storage is to be unsealed using a water drive well according to claim 1 or 7, Features: The method to determine which mode is more reasonable is: (1) When Y = (N i *EOR i +N i+1 *EOR i+1 )*hsl*hl*a-C3-C4-Cj>0, select mode 2; (2) When Y=(N i *EOR i +N i+1 *EOR i+1 )*hsl*hl*a-C3-C4-Cj﹤0, select mode 1.

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