Method for determining reasonable formation pressure level of pressure drive of ultra-low permeability reservoir

Abstract

The invention provides a method for determining the reasonable pressure-drive formation pressure level of an ultra-low permeability reservoir, which comprises the following steps of: 1, counting and screening oil field pressure-drive water injection rate measuring and calculating methods which mainly comprise a material balance method and an inter-well profile method; 2, according to adaptability comparison of a material balance method and an inter-well profile method, a measuring and calculating method suitable for the reasonable pressure-drive water injection rate of the ultra-low permeability reservoir is optimized; 3, calculating the reasonable pressure-driving water injection rate of the block well group according to the reservoir physical property and the injection-production well spacing parameter by utilizing an inter-well section method; and step 4, according to the calculated pressure-driven water injection rate, calculating the corresponding formation pressure recovery level by adopting a material balance method. The method for determining the pressure-driving reasonable formation pressure level of the ultra-low permeability reservoir is scientific, reliable and high in practicability, can be directly used for the pressure-driving reasonable formation pressure recovery level of the ultra-low permeability reservoir, and also has important guiding significance on implementation of adaptability evaluation of a pressure-driving water injection reservoir scheme.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield development, and particularly to a method for determining a reasonable formation pressure level for pressure drive in ultra-low permeability reservoirs. Background Art

[0002] The low-permeability reservoirs in Shengli Oilfield have a large reserve scale but a low recovery rate. The main reason is the low formation pressure maintenance level, which restricts the efficient development of the reservoirs. Since the implementation of the pressure drive technology, good results have been achieved in new and old low-permeability reservoirs as a whole. However, there are still problems such as inconsistent calculation methods for pressure drive water volume and unclear reasonable formation pressure recovery level.

[0003] In the Chinese patent application with the application number: CN202110397422.7, it involves a method for calculating the optimal injection water volume for pressure drive development of an oil reservoir, including: calculating and establishing a relationship chart between the pressure drive injection water volume and the change in formation pressure through the comprehensive compressibility coefficient of the oil reservoir; determining the minimum economic limit production capacity of the oil reservoir through the dynamic and static economic evaluation parameters of the oil reservoir; determining the minimum limit production pressure difference required to reach the minimum economic limit production capacity according to the oil well production capacity calculation formula; determining the maximum limit production pressure difference according to the formation fracture pressure and the current oil reservoir pressure; finding and determining the minimum and maximum injection water volumes corresponding to the minimum and maximum limit production pressure differences respectively through the relationship chart between the pressure drive injection water volume and the change in formation pressure; calculating the cumulative net present value corresponding to different injection water volumes within the injection water volume value range; and taking the injection water volume corresponding to the maximum cumulative net present value as the optimal injection water volume for pressure drive development of the oil reservoir. This method for calculating the optimal injection water volume for pressure drive development of an oil reservoir provides a way for determining reasonable injection parameters for pressure drive development of an oil reservoir.

[0004] In the Chinese patent application with the application number: CN202111105863.1, it involves a method for determining the pressure drive injection allocation volume of an injection well, including: Step 1, calculating the relationship between the injection water volume and the formation pressure recovery using the material balance equation; Step 2, drawing a chart of formation pressure drop changes under different injection-production ratios based on Step 1; Step 3, drawing a well-to-well pressure change profile before pressure drive; Step 4, determining the limit easy-flow radius of the water injection well and the limit drainage radius of the oil well during pressure drive; Step 5, drawing a schematic diagram of the water drive sweep range between the oil and water injection wells during pressure drive, and calculating and establishing the maximum water drive front sweep radius corresponding to the effective displacement relationship using the fluid connection method; Step 6, calculating the pore volume within the water drive sweep radius using the ellipsoid model to determine the pressure drive injection water volume; Step 7, comparing and optimizing the pressure drive water volume calculated in Step 6 with the material balance method to determine the appropriate displacement radius and pressure drive injection allocation volume. This method determines the pressure drive water injection front and thus the pressure drive injection water volume according to the seepage characteristics of low-permeability reservoirs and in combination with the pressure change characteristics between oil and water injection wells.

[0005] In the Chinese patent application with the application number CN202211549394.7, a method for designing the injection volume under the condition of pressure drive in injection wells and optimizing the fracture parameters of oil wells is involved. It includes determining the formation micro-fracture pressure according to the formation pore pressure and formation fracture pressure; calculating the wellhead injection pressure; calculating the ultimate injection volume of the injection well; then classifying and setting the daily injection volume according to the ultimate injection volume and the change of the formation pressure coefficient during the injection process; establishing a heterogeneous three-dimensional pressure drive injection reservoir black oil geological model for the target block; adding surfactant components to the injection water using reservoir numerical simulation software, simulating shutting in the injection well after the injection is completed; then opening the production well to simulate the production capacity; and optimizing the half-length of the fracture of the optimal production well through the comparison of the cumulative oil production in three years to obtain the final cumulative oil production. This invention uses numerical simulation software to simulate the formation of the pressure drive fracture network in injection wells, and optimizes the fracture parameters of oil well fracturing on the premise of considering the pressure drive in injection wells, providing a new idea for the application of pressure drive in well sites.

[0006] However, the existing evaluation methods mostly have the following problems: ① The comprehensive compressibility coefficient of the reservoir is a variable value that is positively correlated with the formation pressure, and it is difficult to accurately calculate the pressure drive injection volume using a fixed value; ② The maximum ultimate production pressure difference in the reservoir is generally not used during the reservoir development process. Therefore, we have invented a new method for determining the reasonable formation pressure recovery level of pressure drive in ultra-low permeability reservoirs based on reservoir engineering. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for determining the reasonable formation pressure level of pressure drive in ultra-low permeability reservoirs, which can be directly used for determining the reasonable formation pressure recovery level of pressure drive in ultra-low permeability reservoirs.

[0008] The purpose of the present invention can be achieved by the following technical measures: A method for determining the reasonable formation pressure level of pressure drive in ultra-low permeability reservoirs, which includes:

[0009] Step 1: Statistically screen the calculation methods for the pressure drive injection volume in the oilfield. The main methods are the material balance method and the inter-well profile method.

[0010] Step 2: According to the adaptability comparison between the material balance method and the inter-well profile method, select the calculation method suitable for the reasonable pressure drive injection volume in ultra-low permeability reservoirs.

[0011] Step 3: Use the inter-well profile method to calculate the reasonable pressure drive injection volume of the block well group according to the reservoir physical properties and injection-production well spacing parameters.

[0012] Step 4: According to the calculated pressure drive injection volume, use the material balance method to calculate the corresponding formation pressure recovery level.

[0013] The purpose of the present invention can also be achieved by the following technical measures:

[0014] In Step 1, the material balance method designs the water injection volume with the goal of increasing the overall reservoir pressure. The calculation formula of the material balance method is:

[0015]

[0016] In the formula, V is the pressure drive water injection volume, m 3 ; —porosity, decimal; S is the oil-bearing area, m 2 ; H is the sand body thickness, m; C t —comprehensive compressibility, Mpa -1 ; △P: the pressure difference before and after the pressure drive of the reservoir, MPa;

[0017] Among them, the calculation formula of the comprehensive compressibility is:

[0018] C t = C o ·S o + C w ·S w + C p (2)

[0019] In the formula, C o —crude oil compressibility, 10 4 m 3 ; C w —formation water compressibility, Mpa -1 ; C P —rock pore compressibility, MPa -1 ; S o —oil saturation of the reservoir, decimal; S w —water saturation of the reservoir, decimal.

[0020] In Step 1, the cross-well profile method designs the water injection volume with the goal of establishing displacement between oil and water wells. The calculation formula of the cross-well profile method is:

[0021]

[0022] In the formula, V is the pressure drive water injection volume, m 3 ; L is the injection-production well spacing, m; △p is the production pressure difference of the production well, MPa; G po —formation crude oil starting pressure gradient, MPa / m; G pw —formation water starting pressure gradient, MPa / m; △P w —bottom hole pressure increase value of water injection volume per 10,000 m³, 10,000 m³ / MPa.

[0023] In Step 2, for ultra-low permeability reservoirs, the goal is to establish displacement, and the cross-well profile method is used to measure the pressure drive water volume; for low permeability reservoirs, the goal is to increase the reservoir pressure, and the material balance method is used.

[0024] Step 3 includes:

[0025] Step 31, calculating the reservoir startup pressure;

[0026] Step 32, calculating the bottom hole pressure rise values under different permeabilities and different injection volumes.

[0027] In Step 31, when the fluid viscosity is 1 mp.s, the calculation formula for the startup pressure gradient of turbidite rock is:

[0028] G p = 0.20331·k a -1.222 (6)

[0029] When the fluid viscosity is 3 mp.s, the calculation formula for the startup pressure gradient of turbidite rock is:

[0030] G p = 0.55582·k a -1.122 (7)

[0031] When the fluid viscosity is 1 mp.s, the calculation formula for the startup pressure gradient of beach-bar sand is:

[0032] G p = 0.13721·k a -1.222 (8)

[0033] When the fluid viscosity is 3 mp.s, the calculation formula for the startup pressure gradient of beach-bar sand is:

[0034] G p = 0.31665·k a -1.222 (9)

[0035] In the formula, G p — startup pressure gradient, MPa / m; k a — effective permeability, 10 -3 μm².

[0036] In Step 32, the calculation formula for the bottom hole pressure rise value under different permeabilities and different injection volumes is:

[0037] △P w = 0.0299k 1.1874 (10)

[0038] In the formula, △P w — bottom hole pressure rise value per 10,000 m³ of injection volume, 10,000 m³ / MPa; k — air permeability, 10 -3 μm²;

[0039] According to the above parameters, substituting them into the calculation formula of the cross-well profile method, the pressure drive injection volume can be calculated.

[0040] In step 4, the calculation formula for the increase value of formation pressure after pressure drive is as follows:

[0041]

[0042] In the formula, V is the injection volume of pressure drive, in cubic meters; —porosity, in decimal; S is the sand body distribution area of the well group, in m 2 ; H is the average sand body thickness of the well group, in m; C t —comprehensive compressibility, in Mpa -1 .

[0043] In step 4, the calculation formula for the formation pressure recovery level is as follows:

[0044]

[0045] In the formula, P O —original formation pressure, in MPa; p i —formation pressure coefficient, in decimal;

[0046] The object of the present invention can also be achieved by the following technical measures: a system for determining the reasonable formation pressure level of pressure drive in ultra-low permeability reservoirs, and this system for determining the reasonable formation pressure level of pressure drive in ultra-low permeability reservoirs uses the method for determining the reasonable formation pressure level of pressure drive in ultra-low permeability reservoirs to evaluate the reasonable formation pressure recovery level of pressure drive in ultra-low permeability reservoirs.

[0047] In the method for determining the reasonable formation pressure recovery level of pressure drive in ultra-low permeability reservoirs based on reservoir engineering in the present invention, the main calculation methods for the injection volume of pressure drive in oilfields are statistically screened, and the main methods are the material balance method and the inter-well profile method; according to the adaptability comparison between the material balance method and the inter-well profile method, the inter-well profile method is selected as the suitable method for ultra-low permeability reservoirs; using the inter-well profile method, according to the reservoir physical properties and injection-production well spacing parameters, the reasonable injection volume of pressure drive for the block (well group) is calculated; finally, according to the calculated injection volume of pressure drive, the material balance method is used to calculate the corresponding formation pressure recovery level. The evaluation method of the present invention is scientific, reliable and highly practical, and can be directly used for the reasonable formation pressure recovery level of pressure drive in ultra-low permeability reservoirs.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows: for ultra-low permeability reservoirs, the injection volume of pressure drive required to establish displacement for the well group is calculated based on the inter-well profile method, and the formation pressure level under this injection volume is calculated through the material balance method, and this pressure level is the reasonable formation pressure maintenance level for this well group. The evaluation method of the present invention is reliable and effective, and can not only evaluate the reasonable formation pressure recovery level of pressure drive in ultra-low permeability reservoirs, but also be used to guide the design of development adjustment plans. The evaluation method described in the present invention can be directly used for the evaluation of the reasonable formation pressure recovery level of pressure drive in ultra-low permeability reservoirs, and also has important guiding significance for the evaluation of the adaptability of the pressure drive injection reservoir scheme. Description of the Drawings

[0049] Figure 1 It is a flowchart of a specific embodiment of the method for determining the reasonable formation pressure level of pressure drive in an extra-low permeability reservoir according to the present invention;

[0050] Figure 2 It is a graph showing the injection volume of pressure drive measured by the material balance method and the cross-well profile method varying with permeability in a specific embodiment of the present invention;

[0051] Figure 3 It is a graph of the starting pressure gradient of a turbidite reservoir in a specific embodiment of the present invention;

[0052] Figure 4 It is a graph of the starting pressure gradient of a beach-bar sand reservoir in a specific embodiment of the present invention;

[0053] Figure 5 It is a graph of the rising value of the bottom-hole pressure under different permeabilities and different injection volumes in a specific embodiment of the present invention;

[0054] Figure 6 It is a graph of the formation oil compressibility versus formation pressure in a specific embodiment of the present invention;

[0055] Figure 7 It is a graph of the formation water compressibility versus formation pressure in a specific embodiment of the present invention;

[0056] Figure 8 It is a graph of the rock pore compressibility versus formation pressure in a specific embodiment of the present invention. Detailed Description of the Embodiment

[0057] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0058] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, and / or combinations thereof.

[0059] As Figure 1 shown, Figure 1 It is a flowchart of the method for determining the reasonable formation pressure level of pressure drive in an extra-low permeability reservoir according to the present invention. The method for determining the reasonable formation pressure level of pressure drive in an extra-low permeability reservoir includes:

[0060] Step 1: Statistically screen the calculation methods for the injection volume of oilfield pressure drive. Currently, the main methods for calculating the injection volume of pressure drive are the material balance method and the inter-well profile method.

[0061] The material balance method designs the injection volume with the goal of increasing the overall reservoir pressure. The essence of the method is that the changes in the volumes of oil, gas, and water in the reservoir always follow the material balance equation. However, the defect of this method is that it cannot ensure the establishment of displacement between the oil wells and water wells in the well group after pressure drive. Therefore, it is difficult to guarantee the implementation effect after pressure drive.

[0062] The inter-well profile method calculates the water volume that needs to be injected into the water well based on the seepage resistance required to establish displacement between the oil well and water well. This method designs the injection volume with the goal of establishing displacement between the oil well and water well, but using this method cannot calculate the formation pressure level of the well group after pressure drive. In addition, the parameter values of this method have relatively large errors, so the operability and popularization in the oilfield are not strong.

[0063] Step 2: According to the adaptability comparison between the material balance method and the inter-well profile method, optimize the calculation method for the reasonable injection volume of pressure drive suitable for ultra-low permeability reservoirs.

[0064] Ultra-low permeability reservoirs have poor physical properties, and it is difficult to establish displacement between oil wells and water wells. According to the statistics of the laws of the well groups with pressure drive implemented, the formation pressure coefficient required to establish displacement between oil wells and water wells in ultra-low permeability reservoirs is above 1.5. The idea of determining the reasonable formation pressure level of pressure drive can be to calculate the injection volume of pressure drive required to establish displacement between the oil well and water well according to the inter-well profile method, and then use the material balance method to calculate the corresponding formation pressure coefficient of the well group under this injection volume. This formation pressure coefficient is the reasonable formation pressure level of the well group for pressure drive.

[0065] Step 3: Use the inter-well profile method to calculate the injection volume of pressure drive required to establish displacement between the oil wells and water wells in the well group according to the reservoir physical properties and injection-production well spacing parameters.

[0066] Step 4: According to the calculated injection volume of pressure drive, use the material balance method to calculate the corresponding formation pressure recovery level.

[0067] In Step 1, statistically screen the main calculation methods for the injection volume of pressure drive in Shengli Oilfield.

[0068] Statistically screen the main design methods for the injection volume of pressure drive in the branch company, mainly including the material balance method and the inter-well profile method. Establish the reservoir engineering calculation formulas for the two methods.

[0069] ① The material balance method

[0070] Method essence: The changes in the volumes of oil, gas, and water in the reservoir always follow the material balance equation.

[0071] Calculation formula:

[0072]

[0073] Wherein, V—the injection volume of pressure drive, m 3 ; —porosity, decimal; S—oil-bearing area, m 2 ; H—sand body thickness, m; C t —comprehensive compressibility, Mpa -1 ; △P—the pressure difference before and after pressure drive in the reservoir, MPa;

[0074] Among them, the calculation formula of the comprehensive compressibility is:

[0075] C t = C o ·S o + C w ·S w + C p (2)

[0076] Wherein, C o —compressibility of crude oil, 10 4 m 3 ; C w —compressibility of formation water, Mpa -1 ; C P —compressibility of rock pores, MPa -1 ; S o —oil saturation in the reservoir, decimal; S w —water saturation in the reservoir, decimal.

[0077] The compressibility of formation crude oil is a physical quantity that characterizes the volume change of formation crude oil with the change of pressure. The compressibility of formation crude oil mainly depends on the density of crude oil and the pressure and temperature conditions.

[0078] Such as Figure 6 shown, it is the curve of the compressibility of crude oil with different densities under formation pressure. As the formation pressure rises, the compressibility of crude oil gradually decreases.

[0079] The calculation formula is:

[0080] Co = 1.25·10 -6 ·ρ o ·T 1.0442 ·e -0.0276P (3)

[0081] Wherein, ρ0—density of surface crude oil, g / cm 3 ; T—formation temperature, °F; P—formation pressure, MPa. (See Figure 6 )

[0082] The compressibility of formation water is a physical quantity that characterizes the volume change of formation water with the change of formation pressure and formation temperature. The compressibility of formation water mainly depends on the formation pressure and temperature conditions. Moreover, the compressibility of formation water is very low and not sensitive to the change of formation pressure.

[0083] As Figure 7 shown, it is the compressibility curve of formation water at formation temperature.

[0084] Compressibility of formation water:

[0085] C w =(C1 + C2T + C3·T2)×10 -6 (4)

[0087] In the formula, C1 = 3.8546 - 0.000134P, decimal; C2 = -0.01052 + 4.77×10 -7 P, decimal; C3 = 3.9267×10 -5 -8.8×10 -10 P, decimal; T—Fahrenheit degree, °F; P—formation pressure, psi; C w —unit is psi -1 . (See Figure 7 )

[0088] The compressibility of rock pores is the change in pore volume per unit volume of rock when the reservoir pressure drops by 1 MPa. The compressibility of rock pores needs to query the experimental data of the block.

[0089] Figure 8 It is the curve of the compressibility of rock pores and the effective overburden pressure for Chengdao, Shengtuo, and Daluhu oilfields in the Shengli Oilfield. Among them, the effective overburden pressure is the difference between the overburden pressure of the reservoir and the formation pressure.

[0090] ② Inter-well profile method:

[0091] Method connotation: Calculate the water injection volume required for the water injection well according to the seepage resistance to be overcome for establishing displacement between the oil production well and the water injection well.

[0092] Calculation formula:

[0093]

[0094] In the formula, V—pressure-driven water injection volume, m 3 ; L—distance between injection and production wells, m; △p—production pressure difference of the oil production well, MPa; G po —starting pressure gradient of formation crude oil, MPa / m; G pw —starting pressure gradient of formation water, MPa / m; △P w —bottom hole pressure rise value of water injection volume per 10,000 m³, 10,000 m³ / MPa.

[0095] In step 2, a reasonable calculation method for the injection volume of pressure-driven flooding suitable for ultra-low permeability reservoirs is compared and optimized.

[0096] For ultra-low permeability reservoirs, the general reservoir burial depth is 3000 m, the original formation pressure is 30 MPa, and the pore-permeability relationship is: In the inverted five-spot well pattern, the row spacing is 150 m, and the production pressure difference is 12 - 18 MPa. The comprehensive compressibility coefficient is 3.412×10 -3 MPa -1 , and the formation pressure is increased by 15 MPa using the material balance method, and the formation pressure coefficient is restored to 1.5.

[0097] Calculated according to the above parameters, the curves of the injection volume of pressure-driven flooding measured by the material balance method and the inter-well profile method versus permeability are obtained. As Figure 2 shown, it can be seen that when the permeability is lower than 10×10 -3 μm², the water volume calculated by the material balance method is less than that by the inter-well profile method. The main reason is that the main development contradiction of ultra-low permeability reservoirs is poor physical properties, and it is difficult to establish displacement between oil and water wells. When the formation pressure level of the well group is restored to 1.5, displacement cannot be established between the oil and water wells.

[0098] Considering that the goal of ultra-low permeability reservoirs is to establish displacement, it is recommended to use the inter-well profile method to calculate the injection volume of pressure-driven flooding for ultra-low permeability reservoirs.

[0099] In step 3, according to the optimized calculation method of the injection volume of pressure-driven flooding in step 2, the reasonable injection volume of pressure-driven flooding is calculated.

[0100] By querying and calculating relevant key parameters:

[0101] ① Calculation of the starting pressure of the reservoir

[0102] The starting pressure gradient of the reservoir is a parameter characterizing the seepage resistance of the reservoir. It is related to the reservoir permeability and crude oil viscosity. The larger the reservoir permeability, the smaller the starting pressure gradient. In addition, the larger the crude oil viscosity, the greater the seepage resistance and the larger the starting pressure gradient.

[0103] As Figure 3 shown, it is the scatter plot of the starting pressure gradient measured by indoor experiments for different turbidite reservoirs. The relationship curve between the starting pressure gradient of turbidite reservoirs and permeability and crude oil viscosity is fitted based on the scatter points.

[0104] As Figure 4 shown, it is the scatter plot of the starting pressure gradient measured by indoor experiments for different beach-bar sand reservoirs. The relationship curve between the starting pressure gradient of beach-bar sand reservoirs and permeability and crude oil viscosity is fitted based on the scatter points.

[0105] The calculation formula for the starting pressure gradient of turbidite rocks (fluid viscosity 1 mp.s) is:

[0106] Gp = 0.20331·k a -1.222 (6)

[0107] The calculation formula for the starting pressure gradient of turbidite rock (fluid viscosity 3 mp.s) is:

[0108] G p = 0.55582·k a -1.122 (7)

[0109] The calculation formula for the starting pressure gradient of beach-bar sand (fluid viscosity 1 mp.s) is:

[0110] G p = 0.13721·k a -1.222 (8)

[0111] The calculation formula for the starting pressure gradient of beach-bar sand (fluid viscosity 3 mp.s) is:

[0112] G p = 0.31665·k a -1.222 (9)

[0113] In the formula, G p — Starting pressure gradient, MPa / m; k a — Effective permeability, 10 -3 μm²;

[0114] ② Calculation of the bottom-hole pressure rise value under different permeabilities and injection volumes

[0115] The higher the reservoir permeability, the better the permeability, and the injected water is easy to diffuse outward, resulting in a decrease in the bottom-hole pressure. As the reservoir permeability increases, the amount of injected water required to increase the bottom-hole pressure of the injection well by 1 MPa increases accordingly.

[0116] As Figure 5 shown, it is the curve of the amount of injected water required to increase the bottom-hole pressure of the injection well by 1 MPa under different permeability conditions.

[0117] The formula is:

[0118] △P w = 0.0299k 1.1874 (10)

[0119] In the formula, △P w — Bottom-hole pressure rise value per 10,000 m³ of injected water, 10,000 m³ / MPa; k — Air permeability, 10 -3 μm²;

[0120] According to the above parameters, substituting them into formula (5), the pressure-driven injection volume can be calculated.

[0121] In step 4, according to the reasonable pressure drive injection volume measured in step 3, the corresponding reasonable pressure recovery level is measured by the material balance method.

[0122] The rising value of the formation pressure after pressure drive, and its calculation formula is:

[0123]

[0124] In the formula, V—the pressure drive injection volume, m³; —porosity, decimal; S—the sand body distribution area of the well group, m 2 ²; H—the average sand body thickness of the well group, m; C t —comprehensive compressibility, Mpa -1 ;

[0125] Formation pressure recovery level:

[0126]

[0127] In the formula, P O —original formation pressure, MPa; p i —formation pressure coefficient, decimal.

[0128] The following are several specific embodiments of applying the present invention:

[0129] Embodiment 1

[0130] In a specific embodiment 1 of applying the present invention, the method for determining the reasonable formation pressure level of pressure drive in ultra-low permeability oil reservoirs includes the following steps:

[0131] Step 1, statistically screen the main methods for measuring the pressure drive injection volume in Shengli Oilfield. At present, there are mainly two methods for designing the pressure drive injection volume: the material balance method and the inter-well profile method. The material balance method designs the injection volume with the goal of increasing the overall pressure of the oil reservoir, and the inter-well profile method designs the injection volume with the goal of establishing displacement between oil wells and water wells.

[0132] ① The calculation formula for the pressure drive injection volume by the material balance method:

[0133]

[0134] ② The calculation formula for the pressure drive injection volume by the inter-well profile method:

[0135] Method connotation: Calculate the water volume that needs to be injected into the water well according to the seepage resistance required to establish displacement between the oil well and the water well.

[0136] Calculation formula:

[0137]

[0138] where, V—the injection volume of pressure drive, m 3 ; L—the distance between injection and production wells, m; △p—the production pressure difference of production well, MPa; G po —the starting pressure gradient of formation crude oil, MPa / m; G pw —the starting pressure gradient of formation water, MPa / m; △P w —the increase value of bottom hole pressure per 10,000 m³ injection volume, 10,000 m³ / MPa.

[0139] In step 2, compare and optimize the reasonable calculation method for the injection volume of pressure drive suitable for ultra-low permeability reservoirs.

[0140] For ultra-low permeability reservoirs with the goal of establishing displacement, it is recommended to use the well-to-well profile method to calculate the injection volume of pressure drive. For general low permeability reservoirs with the goal of increasing reservoir pressure, the material balance method is used. Well group A in Shinan Oilfield with a permeability of 6 mD uses the well-to-well profile method to calculate the injection volume of pressure drive.

[0141] Step 3, use the well-to-well profile method determined in step 2 to calculate the injection volume of pressure drive.

[0142] The middle depth of the reservoir in Well Group A of Shinan Oilfield is 3000 m, the sand body thickness is 10 m, the porosity is 18.1%, the permeability is 6 mD, the reverse five-spot well pattern, 1 injection well and 4 production wells, the well spacing is 400 m, the row spacing is 150 m, the current formation pressure is 30 MPa, and the production pressure difference of the production well is 12 MPa.

[0143] ① Calculate key parameters

[0144] Starting pressure gradient of production well

[0145] G po = 0.55582k a -1.122 = 0.223 MPa / m (15)

[0146] Starting pressure gradient of injection well

[0147] G pw = 0.55582k a -1.122 = 0.08 MPa / m (16)

[0148] Increase of bottom hole pressure per 10,000 m³ injection volume

[0149] △P w = 0.0299k 1.1874 = 0.247 MPa / 10,000 m³ (17)

[0150] ② Use the well-to-well profile method to calculate the injection volume of pressure drive

[0151] Injection volume of pressure drive

[0152]

[0153] According to the above parameters, the injection volume of pressure drive is 24,000 cubic meters.

[0154] Step 4: Calculate the injection volume of pressure drive according to Step 3, and use the material balance method to inversely calculate the corresponding pressure recovery level.

[0155] ① Calculate key parameters

[0156] Formation oil compressibility

[0157] Co = 1.25·10 -6 ·ρ o ·T 1.0442 ·e -0.0276P (19)

[0158] Formation water compressibility

[0159] C w =(C1 + C2T + C3·T 2 )10 -6 (20)

[0160] Formation pressure after pressure drive

[0161]

[0162] ② After iterative calculation, △P = 31.4 MPa

[0163] ③ Formation pressure coefficient

[0164]

[0165] After calculation, the formation pressure coefficient is 2.05, that is, the reasonable formation pressure recovery level of this well group is 2.05.

[0166] Example 2

[0167] In a specific Example 1 of applying the present invention, a method for determining the reasonable formation pressure recovery level of pressure drive in ultra-low permeability reservoirs based on reservoir engineering includes the following steps:

[0168] Step 1: Statistically screen the main methods for calculating the injection volume of pressure drive in Shengli Oilfield. Currently, there are mainly two methods for designing the injection volume of pressure drive: the material balance method and the inter-well profile method. The material balance method designs the injection volume with the goal of increasing the overall pressure of the reservoir, and the inter-well profile method designs the injection volume with the goal of establishing displacement between oil wells and water wells.

[0169] ① The calculation formula for the injection volume of pressure drive by the material balance method:

[0170]

[0171] ② Calculation formula for pressure drive injection volume by cross - well profile method:

[0172] Method connotation: Calculate the injection volume required for the water injection well according to the seepage resistance to be overcome for establishing displacement between the oil well and the water injection well.

[0173] Calculation formula:

[0174]

[0175] In the formula, V—the pressure drive injection volume, m 3 ; L—the injection - production well spacing, m; △p—the production pressure difference of the oil production well, MPa; G po —the starting pressure gradient of formation crude oil, MPa / m; G pw —the starting pressure gradient of formation water, MPa / m; △P w —the bottom - hole pressure increase value per 10,000 m³ of injection volume, 10,000 m³ / MPa.

[0176] In step 2, compare and optimize the reasonable calculation method for pressure drive injection volume suitable for ultra - low permeability oil reservoirs.

[0177] For ultra - low permeability oil reservoirs with the goal of establishing displacement, it is recommended to use the cross - well profile method to calculate the pressure drive water volume. For general low - permeability oil reservoirs with the goal of increasing reservoir pressure, the material balance method is used. Well group A in Shinan Oilfield with a permeability of 8 mD uses the cross - well profile method to calculate the pressure drive water volume.

[0178] Step 3, use the cross - well profile method determined in step 2 to calculate the pressure drive water volume.

[0179] The middle depth of the reservoir in Well Group A of Shinan Oilfield is 3000 m, the sand body thickness is 10 m, the porosity is 18.1%, the permeability is 8 mD, the reverse five - spot well pattern, 1 injector and 4 producers, the well spacing is 400 m, the row spacing is 200 m, the current formation pressure is 30 MPa, and the production pressure difference of the oil well is 12 MPa.

[0180] ① Calculate key parameters

[0181] Starting pressure gradient of the oil well

[0182] G po =0.55582k a -1.122 =0.162 MPa / m (25)

[0183] Starting pressure gradient of the water injection well

[0184] G pw =0.55582k a -1.122 =0.05 MPa / m (26)

[0185] Bottom - hole pressure increase per 10,000 m³ of injection volume

[0186] △P w = 0.0299k 1.1874 = 0.34 MPa / 10,000 m³ (27)

[0187] ② Calculate the injection volume for pressure drive using the cross - well profile method

[0188] Injection volume for pressure drive

[0189]

[0190] Step 4: According to the reasonable injection volume for pressure drive measured by the cross - well profile method, use the material balance method to inversely calculate the corresponding pressure build - up level.

[0191] ① Calculate key parameters

[0192] Formation oil compressibility

[0193] Co = 1.25·10 -6 ·ρ o ·T 1.0442 ·e -0.0276P (29)

[0194] Formation water compressibility

[0195] C w =(C1 + C2T + C3·T 2 )10 -6 (30)

[0196] Formation pressure after pressure drive

[0197]

[0198] ② After iterative calculation, △P = 27.6 MPa

[0199] ③ Formation pressure coefficient

[0200]

[0201] After calculation, the formation pressure coefficient is 1.91, that is, the reasonable formation pressure build - up level for this well group is 1.91.

[0202] Example 3

[0203] In a specific Example 1 of applying the present invention, a method for determining the reasonable formation pressure build - up level for pressure drive in an extra - low permeability reservoir based on reservoir engineering includes the following steps:

[0204] Step 1: Statistically screen the main calculation methods for the injection volume of pressure drive in Shengli Oilfield. Currently, there are mainly two methods for designing the injection volume of pressure drive: the material balance method and the inter-well profile method. The material balance method designs the injection volume with the goal of increasing the overall reservoir pressure, and the inter-well profile method designs the injection volume with the goal of establishing displacement between oil and water wells.

[0205] ① Calculation formula for the injection volume of pressure drive by the material balance method:

[0206]

[0207] ② Calculation formula for the injection volume of pressure drive by the inter-well profile method:

[0208] Method connotation: Calculate the water volume that needs to be injected into the water well according to the seepage resistance required to establish displacement between oil and water wells.

[0209] Calculation formula:

[0210]

[0211] In the formula, V—the injection volume of pressure drive, m 3 ; L—the injection-production well spacing, m; △p—the production pressure difference of the production well, MPa; G po —the starting pressure gradient of formation crude oil, MPa / m; G pw —the starting pressure gradient of formation water, MPa / m; △P w —the bottom-hole pressure rise value per 10,000 m³ of injection volume, 10,000 m³ / MPa.

[0212] In Step 2, compare and optimize the calculation method for the reasonable injection volume of pressure drive suitable for ultra-low permeability reservoirs.

[0213] For ultra-low permeability reservoirs with the goal of establishing displacement, it is recommended to use the inter-well profile method to calculate the pressure drive water volume. For general low permeability reservoirs with the goal of increasing reservoir pressure, the material balance method is used. Well group A in Shinan Oilfield has a permeability of 8 mD, and the inter-well profile method is used to calculate the pressure drive water volume.

[0214] Step 3: Use the inter-well profile method determined in Step 2 to calculate the pressure drive water volume.

[0215] The middle depth of the reservoir in Well Group A of Shinan Oilfield is 3300 m, the sand body thickness is 10 m, the porosity is 17.0%, the permeability is 10 mD, the reverse five-spot well pattern, 1 injector and 4 producers, the well spacing is 350 m, the row spacing is 180 m, the current formation pressure is 30 MPa, and the production pressure difference of the production well is 12 MPa.

[0216] ① Calculate key parameters

[0217] Starting pressure gradient of the production well

[0218] G po =0.55582k a-1.122 = 0.126 MPa / m (35)

[0219] Injection well startup pressure gradient

[0220] G pw = 0.55582 k a -1.122 = 0.04 MPa / m (36)

[0221] Bottom-hole pressure increase with water injection volume of 10,000 m³

[0222] △P w = 0.0299 k 1.1874 = 0.439 MPa / 10,000 m³ (37)

[0223] ② Calculate the pressure-driven water injection volume using the inter-well profile method

[0224] Pressure-driven water injection volume

[0225]

[0226] Step 4: Based on the reasonable pressure-driven water injection volume measured by the inter-well profile method, use the material balance method to back-calculate the corresponding pressure recovery level.

[0227] ① Calculate key parameters

[0228] Formation crude oil compressibility

[0229] Co = 1.25·10 -6 ·ρ o ·T 1.0442 ·e -0.0276P (39)

[0230] Formation water compressibility

[0231] C w = (C1 + C2T + C3·T 2 )10 -6 (40)

[0232] Formation pressure after pressure drive

[0233]

[0234] ② After iterative calculation, △P = 17.3 MPa

[0235] ③ Formation pressure coefficient

[0236]

[0237] After calculation, the formation pressure coefficient is 1.58, that is, the reasonable formation pressure recovery level of this well group is 1.58.

[0238] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0239] Except for the technical features described in the specification, the rest are well-known technologies to those skilled in the art.

Claims

1. A method for determining a reasonable formation pressure level for pressure drive in an extra-low permeability reservoir, characterized in that, The method for determining the reasonable formation pressure level of pressure drive in extra-low permeability reservoirs includes: Step 1: Statistically screen the calculation methods for the water injection volume of pressure drive in the oilfield. The main methods are the material balance method and the well-to-well profile method. Step 2: According to the adaptability comparison between the material balance method and the well-to-well profile method, optimize the calculation method suitable for the reasonable pressure drive water injection volume in extra-low permeability reservoirs. Step 3: Using the well-to-well profile method, calculate the reasonable pressure drive water injection volume of the block well group according to the reservoir physical properties and injection-production well spacing parameters. Step 4: According to the calculated pressure drive water injection volume, use the material balance method to calculate the corresponding formation pressure recovery level.

2. The method for determining a reasonable formation pressure level for pressure drive in an extra-low permeability reservoir according to claim 1, wherein In Step 1, the material balance method designs the water injection volume with the goal of increasing the overall pressure of the reservoir. The calculation formula of the material balance method is: Where, V - injection volume of pressure drive, m 3 ; porosity, decimal; S - oil-bearing area, m 2 ; H - thickness of sand body, m; C t - comprehensive compressibility, Mpa -1 ; ΔP: pressure difference before and after pressure drive of reservoir, MPa; Among them, the calculation formula of the comprehensive compressibility coefficient is: C t = C o ·S o + C w ·S w + C p (2) Where, C o - Crude oil compressibility, 10 4 m 3 ; C w - Formation water compressibility, Mpa -1 ; C P - Rock pore compressibility, MPa -1 ; S o - Oil saturation of the reservoir, fraction; S w - Water saturation of the reservoir, fraction.

3. The method for determining a reasonable formation pressure level for pressure drive in an extra-low permeability reservoir according to claim 1, characterized in that In Step 1, the well-to-well profile method designs the water injection volume with the goal of establishing displacement between oil and water wells. The calculation formula of the well-to-well profile method is: Wherein, V is the injection volume of pressure drive, m 3 ; L is the injection-production well spacing, m; Δp - Production pressure differential of oil production well, MPa; G po - Initial pressure gradient of formation crude oil, MPa / m; G pw - Initial pressure gradient of formation water, MPa / m; ΔP w - Increase value of bottom hole pressure for every 10,000 m³ of water injection volume, 10,000 m³ / MPa.

4. The method for determining a reasonable formation pressure level for pressure drive in an extra-low permeability reservoir according to claim 1, characterized in that In Step 2, for extra-low permeability reservoirs with the goal of establishing displacement, the well-to-well profile method is used to calculate the pressure drive water volume; for low permeability reservoirs with the goal of increasing the reservoir pressure, the material balance method is used.

5. The method for determining a reasonable formation pressure level for pressure drive in an extra-low permeability reservoir according to claim 1, characterized in that, Step 3 includes: Step 31: Calculate the starting pressure of the reservoir. Step 32: Calculate the bottom-hole pressure rise values under different permeabilities and different injection volumes.

6. The method for determining a reasonable formation pressure level for pressure drive in an extra-low permeability reservoir according to claim 5, characterized in that In Step 31, when the fluid viscosity is 1 mp.s, the calculation formula for the starting pressure gradient of turbidite rock is: G p = 0.20331·k a -1.222 (6) When the fluid viscosity is 3 mp.s, the calculation formula for the starting pressure gradient of turbidite rock is: G p = 0.55582·k a -1.122 (7) When the fluid viscosity is 1 mp.s, the calculation formula for the starting pressure gradient of beach-bar sand is: G p = 0.13721·k a -1.222 (8) When the fluid viscosity is 3 mp.s, the calculation formula for the starting pressure gradient of beach-bar sand is: G p = 0.31665·k a -1.222 (9) where G p — starting pressure gradient, MPa / m; k a — effective permeability, 10 -3 μm².

7. The method for determining a reasonable formation pressure level for pressure drive in an extra-low permeability reservoir according to claim 5, characterized in that, In Step 32, the calculation formula for the bottom-hole pressure rise value under different permeabilities and different injection volumes is: △P w = 0.0299k 1.1874 (10) where, △P w — the increase value of bottom-hole pressure for injection volume of 10,000 m³, 10,000 m³ / MPa; k — air permeability, 10 -3 μm²; According to the above parameters, substituting them into the calculation formula of the well-to-well profile method, the pressure drive water injection volume can be calculated.

8. The method for determining a reasonable formation pressure level for pressure drive in an extra-low permeability reservoir according to claim 1, characterized in that In Step 4, the calculation formula for the formation pressure rise value after pressure drive is: In the formula, V—the water injection volume for pressure drive, m³; —porosity, decimal; S—the sand body distribution area of the well group, m 2 ²; H—the average sand body thickness of the well group, m; C t —comprehensive compressibility, Mpa -1 .

9. The method for determining a reasonable formation pressure level for pressure drive in an extra-low permeability reservoir according to claim 8, characterized in that In Step 4, the calculation formula for the formation pressure recovery level is: where P O — original formation pressure, MPa; p i — formation pressure coefficient, decimal fraction.

10. A system for determining a reasonable formation pressure level for pressure drive in an extra-low permeability reservoir, characterized in that, The system for determining the reasonable formation pressure level of pressure drive in extra-low permeability reservoirs uses the method for determining the reasonable formation pressure level of pressure drive in extra-low permeability reservoirs described in any one of claims 1-9 to evaluate the reasonable formation pressure recovery level of pressure drive in extra-low permeability reservoirs.

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