Pressure drive development water injection speed optimization method

Abstract

The invention provides a pressure drive development water injection speed optimization method. The optimization method comprises the steps that S1, a pressure value P1 at the limit oil supply radius is calculated according to the oil well yield; s2, according to the given total injection amount, the given pressure-driving injection speed and the corresponding pressure-driving water injection time are calculated, and the half length of the fracture is calculated; s3, solving a pressure value P2 at the limit oil supply radius of the pressure flooding water injection pressure profile according to the fracture half length; s4, comparing the pressure value P1 at the limit oil supply radius with the pressure value P2 at the limit oil supply radius of the pressure flooding water injection pressure profile; and S5, when P2 is larger than P1, it is indicated that displacement is effective, and otherwise, the water injection state is adjusted to achieve effective displacement. The optimal water injection speed is determined to ensure effective displacement of the pressure driving operation and avoid water channeling between the injection well and the production well.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development, and in particular to a method for optimizing water injection rate in pressure-driven development. Background Technology

[0002] Shengli Oilfield has abundant low-permeability oil reservoirs with geological reserves of 1.15 billion tons. However, during development, due to the poor reservoir properties, conventional water injection methods are difficult to inject large amounts of water into the reservoirs, resulting in a large water drive pressure gradient and a serious imbalance between formation injection and production.

[0003] Water-driven hydraulic injection (WDI) technology has proven highly effective in oilfield development in recent years. Conventional water injection typically maintains bottom-hole pressure below formation fracturing pressure. WDI, however, differs by using high-pressure pumps to raise the bottom-hole pressure above formation fracturing pressure, injecting a large amount of water into the formation within a short period. This replenishes formation energy, increases well productivity, and improves oil displacement efficiency, thereby enhancing the water-drive development effect of well groups. Currently, WDI technology is widely used in the Shengli Oilfield. WDI technology holds the promise of fundamentally solving the development challenges of low-permeability reservoirs, such as difficulty in maintaining energy, slow recovery rates, and low recovery rates.

[0004] In pressure-driven hydraulic system development, determining the injection rate is a crucial factor. A low injection rate results in lower bottom-hole pressure, making it difficult to expand the fracturing range of the reservoir near the injection well, thus limiting the reach of the injected water. Conversely, a high injection rate leads to fracturing along the principal stress direction. Excessive fracturing can cause water channeling into the production well, leading to pressure-driven failure. Simultaneously, increased wellbore pressure loss necessitates a corresponding increase in the output pressure of the surface injection equipment. Therefore, determining the optimal injection rate is key to ensuring effective displacement during pressure-driven operations while preventing water channeling between injection and production wells. Summary of the Invention

[0005] In view of the above problems, the present invention is proposed to provide a method for optimizing water injection rate in pressure-driven development to overcome or at least partially solve the above problems.

[0006] According to one aspect of the present invention, a method for optimizing water injection rate in pressure-driven development is provided, the optimization method comprising:

[0007] Step S1: Calculate the pressure value P1 at the limit oil supply radius obtained from the oil well production calculation;

[0008] Step S2: Based on the given total injection volume, calculate the given pressure-driven injection rate and the corresponding pressure-driven water injection time, and calculate the fracture half-length;

[0009] Step S3: Calculate the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile based on the half-length of the crack;

[0010] Step S4: When P2 > P1, it indicates that the displacement is effective; otherwise, adjust the water injection state to achieve effective displacement.

[0011] Optionally, step S1: calculating the pressure value P1 at the limit oil supply radius obtained from the oil well production specifically includes:

[0012] Calculate the pressure profile distribution around the oil well based on the oil well production;

[0013] Calculate the oil well supply radius based on the designed oil well production rate and bottom hole flowing pressure;

[0014] The pressure value P1 at the limit oil supply radius is calculated based on the oil well production.

[0015] Optionally, step S2: calculating the given pressure-driven injection rate and corresponding pressure-driven water injection time based on the given total injection volume, and calculating the fracture half-length specifically includes:

[0016] Based on the given total injection volume, calculate the given pressure drive injection rate and the corresponding pressure drive water injection time. If the water well is not fractured, calculate the half length of the fracture caused by pressure drive using the pressure drive injection rate and injection time.

[0017] If the well has a history of fracturing operations, the half-length of the fracture should be taken as half the length of the fracturing fracture.

[0018] Optionally, step S3: calculating the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile based on the half-length of the crack specifically includes:

[0019] Based on the calculated fracture half-length, the formula for the pressure profile distribution of the injection well under a given pressure-driven injection rate is calculated.

[0020] Solve for the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile.

[0021] Optionally, adjusting the water injection state specifically includes increasing the water injection speed.

[0022] Optionally, step S1: calculating the pressure value P1 at the limit oil supply radius obtained from the oil well production specifically includes:

[0023] When both the radius and time are large, the pressure profile distribution around the oil well can be approximated using the following formula:

[0024]

[0025] Where P0 is the reservoir pressure after pressure drive calculated based on the cumulative injection volume and material balance; P(r,t) is the pressure at time t at a distance r (cm) from the bottom of the well; Qc is the production volume; K is the permeability; μ is the fluid viscosity; and η is the formation pressure conductivity coefficient.

[0026] When the pressure gradient equals the initiation pressure gradient, that is:

[0027]

[0028] Where λ is the reservoir's initiation pressure gradient, and r c Let h be the maximum oil drain radius (m) and h be the crack height; then:

[0029] Substituting the drain radius value back into the pressure calculation formula, we obtain the pressure value P1 at the limit supply radius calculated based on the oil well production:

[0030]

[0031] Optionally, if the well is not fractured, calculating the half-length of the fracture caused by pressure driving using the injection rate and time specifically includes:

[0032] If the well has no history of fracturing, the process of hydraulic injection is simplified to a conventional hydraulic fracturing fracture propagation model, and the fracture length is calculated using the relevant hydraulic fracturing model.

[0033] Assume the total injection volume is V. i The injection speed is Q i Then the total injection time T i (s) is:

[0034] T i =V i / Q (5)

[0035] Calculate the fracture half-length x based on the pressure-driven injection rate and injection time. f (m);

[0036] Using the KGD calculation model, the formula for calculating the crack half-length is approximately as follows:

[0037]

[0038] Where C is the overall filtration coefficient and h is the crack height.

[0039] Optionally, if the well has a history of fracturing operations, the half-length of the fracture is taken as the half-length of the fracturing fracture, specifically including:

[0040] If a water well has undergone fracturing, it is assumed that the role of the injected fluid during the fracturing process is to expand the old fractures without creating new ones, and the fracture half-length is directly taken as the fracture half-length during the fracturing process.

[0041] Optionally, the formula for calculating the pressure profile distribution of the injection well at a given pressure-driven injection rate by combining the calculated fracture half-length specifically includes:

[0042] Establishing a coordinate system with the pressure-driven well as the origin, and considering the fractures generated by pressure driving as fractures with infinite conductivity, the pressure distribution formula is as follows:

[0043]

[0044] in,

[0045]

[0046] x D =x / x f

[0047] y D =y / x f

[0048] Where, x f Let P0 be the fracture half-length, P0 be the original formation pressure before pressure-driven water injection, B be the formation crude oil volume factor, and c be the volume factor. t The comprehensive elastic compressibility coefficient is used in water injection wells as the volume factor of the injected water under formation conditions.

[0049] Assuming the fracture direction is along the well line, y D =0, the above formula simplifies to:

[0050]

[0051] The coordinates at the limit oil supply radius of the oil well are:

[0052] x = L w -L i -L c -r c (9)

[0053] Among them, L w L is the spacing between injection and production wells. i For pressure-driven wells with an injection rate of Q i The lower half-length crack, L c r is the radius of the fracturing zone of the oil well. c This is the calculated ultimate pressure relief radius.

[0054] Optionally, the calculation of the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile specifically includes:

[0055] Substitute the coordinates of the bottom of the water injection well and the ultimate oil supply radius into the formula to calculate P at the two coordinate positions. D value;

[0056] After converting the pressure change to P-P0, and combining it with the bottom hole pressure of the injection well, the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile is determined.

[0057] This invention provides a method for optimizing the water injection rate in pressure-driven development. The optimization method includes: Step S1: Calculating the pressure value P1 at the limit oil supply radius obtained from the well production; Step S2: Calculating the given pressure-driven injection rate and corresponding pressure-driven water injection time based on the given total injection volume, and calculating the fracture half-length; Step S3: Solving for the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile based on the fracture half-length; Step S4: Comparing the pressure value P1 at the limit oil supply radius with the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile; Step S5: When P2 > P1, it indicates that the displacement is effective; otherwise, adjust the water injection state to achieve effective displacement. Determining the optimal water injection rate is crucial to ensuring effective displacement during pressure-driven operations and preventing water channeling between injection and production wells.

[0058] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0059] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0060] Figure 1 A flowchart of a method for optimizing water injection rate in pressure-driven development, provided as an embodiment of the present invention;

[0061] Figure 2 This is a schematic diagram of the pressure profile between oil and water wells provided in an embodiment of the present invention. Detailed Implementation

[0062] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0063] The terms "comprising" and "having," and any variations thereof, in the specification, embodiments, claims, and drawings of this invention are intended to cover non-exclusive inclusion, such as including a series of steps or units.

[0064] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0065] The purpose of this invention is to provide a calculation method for determining the optimal injection rate of pressure-driven water injection by coordinating the pressure drop profile of oil wells with the sweep range of pressure-driven water injection wells.

[0066] like Figure 1 As shown, the objective of this invention can be achieved through the following technical measures: an optimized calculation method for water injection volume in reservoir pressure-driven development, the optimized calculation method for water injection volume in reservoir pressure-driven development including:

[0067] Step 1: Calculate the pressure profile distribution around the oil well based on the well production rate, and calculate the oil supply radius based on the designed well production rate and bottom hole flowing pressure. Calculate the pressure value P1 at the limit oil supply radius calculated based on the well production rate;

[0068] Step 2: Based on the given total injection volume, calculate the given pressure drive injection rate and the corresponding pressure drive water injection time. If the well is not fractured, calculate the fracture half-length caused by pressure drive using the pressure drive injection rate and injection time. If the well has a history of fracturing operations, the fracture half-length is taken as the half-length of the fractured well.

[0069] Step 3: Based on the calculated fracture half-length, calculate the pressure profile distribution formula for the injection well at a given pressure-driven injection rate. Solve for the pressure value P2 at the ultimate oil supply radius of the pressure-driven water injection pressure profile;

[0070] Step 4: Compare the pressure value P1 at the limit oil supply radius calculated based on the oil well production with the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile;

[0071] Step 5: When P2>P1, it means that the displacement is effective; otherwise, it means that the water injection speed needs to be increased to achieve effective displacement.

[0072] Example 1

[0073] For the selected oil reservoir, two oil and water wells in Well Group A were chosen for pressure drive testing. The reservoir has an average air permeability of 10 mD, an average porosity of 12%, and an initial pressure gradient of 0.2 MPa·m. -1 The reservoir oil layer thickness is 10m, the formation fluid viscosity is 10mPa·s, and the formation pressure conductivity is 0.4cm. 2 / s. The well spacing between oil and water is 300m. The oil well has been fractured, with a fracture half-length of 70m and a fracture height of 50m. The water well has not been fractured. The daily fluid production of the oil well is 5m³. 3 / d, total injection volume is 10000m 3 Injection speed 1.5m 3 The filtration rate is 0.01 m / min, resulting in a large filtration loss when injecting clean water. Therefore, the overall filtration loss coefficient is taken as 0.01 m / min. 0.5 The reservoir pressure after water injection is calculated to be 30 MPa based on the comprehensive reservoir compressibility coefficient, and the bottom hole pressure of the water well during pressure-driven water injection is 45 MPa.

[0074] Step 101: Calculate the pressure profile distribution around the oil well based on the oil well production, such as... Figure 2 As shown, the well supply radius is calculated based on the designed well production rate and bottom hole flowing pressure. The formation pressure at the limit supply radius is then calculated.

[0075] First, calculate the pressure profile around the oil well. According to formula (1), at time t, the pressure around the oil well at a distance r from the bottom of the well can be expressed by the following formula:

[0076]

[0077] The pressure unit is 10. -1 Considering the starting pressure gradient, the ultimate drain radius is:

[0078]

[0079] Substituting into the pressure funnel formula, at time t, the pressure value at the limiting radius is:

[0080]

[0081] Where t represents time, and the unit is seconds (s).

[0082] Based on the total injection volume and injection rate, the total injection time is calculated as follows:

[0083] T i =V i / Q i =4×10 5 s

[0084] Substituting the limiting oil supply radius and time into the pressure distribution formula, we get P1 = 28.13 MPa.

[0085] Step 102: Based on the given total injection volume, calculate the given pressure drive injection rate and the corresponding pressure drive water injection time, and use the pressure drive injection rate and injection time to calculate the crack half length caused by pressure drive.

[0086] The half-length of the crack caused by water injection is:

[0087]

[0088] Step 103: Establish a coordinate system with the pressure-driven well as the origin. Treat the fractures generated by pressure driving as fractures with infinite conductivity. Then, the formula for the force distribution of pressure change is:

[0089]

[0090] The coordinates of the oil well's limit supply radius (x = 300 - 46 - 70 - 39 = 145) and the bottom of the well (x) are respectively set. D= 0), and substituting the water injection time into the above formula, the pressure change amounts at the limit oil supply radius of the water well and at the bottom of the injection well are obtained as 11.22 MPa and 23.13 MPa respectively. Combining with the bottom hole pressure of 45 MPa of the water well during the pressure drive process, the reservoir pressure value before the pressure drive is obtained as 45 MPa - 23.13 MPa = 21.87 MPa. From this, the pressure value at the limit oil supply radius is: 21.87 MPa + 11.22 MPa = 33.09 MPa. That is P2.

[0091] Step 104, compare the magnitudes of the calculated P1 and P2.

[0092] According to the above calculations, P1 = 28.13 MPa and P2 = 33.09 MPa. P1 < P2.

[0093] Step 105, P1 represents the formation pressure at the limit pressure relief radius of the oil well calculated according to the oil well pressure drop formula, and P2 represents the formation pressure at the limit pressure relief radius of the oil well calculated according to the pressure drive injection well. If P2 is greater than P1, it indicates that the displacement is effective, but attention should be paid to the risk of pressure channeling; otherwise, it indicates that the displacement is ineffective, and the pressure drive injection rate needs to be readjusted to achieve effective displacement. [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Step 102: Based on the given total injection volume, calculate the given pressure drive injection rate and the corresponding pressure drive water injection time, and use the pressure drive injection rate and injection time to calculate the crack half length caused by pressure drive.

[0103] The half-length of the crack caused by water injection is:

[0104]

[0105] Step 103: Establish a coordinate system with the pressure-driven well as the origin. Treat the fractures generated by pressure driving as fractures with infinite conductivity. Then, the formula for the force distribution of pressure change is:

[0106]

[0107] The coordinates of the oil well's limit oil supply radius are respectively

[0108] (x = 300 - 28.5 - 70 - 46 = 155.5 m), and the bottom of the well (x D Substituting the values ​​of =0) and the water injection time into the above formula, the pressure changes at the oil well's limit supply radius and the bottom of the water injection well are 9.96 MPa and 17.08 MPa, respectively. Combining this with the water well bottom pressure of 38 MPa during pressure drive, the reservoir pressure before pressure drive is 35 MPa - 17.08 MPa = 17.92 MPa. Therefore, the pressure at the limit supply radius is 17.92 MPa + 9.96 MPa = 27.88 MPa, which is P2.

[0109] Step 104: Compare the calculated values ​​of P1 and P2.

[0110] Based on the above calculations, P1 = 28.41 MPa, P2 = 27.88 MPa. P1 > P2.

[0111] Step 105: P1 represents the formation pressure at the ultimate pressure relief radius of the oil well calculated according to the oil well pressure drop formula, and P2 represents the formation pressure at the ultimate pressure relief radius of the oil well calculated according to the pressure-driven water injection well. If P2 is greater than P1, it indicates that the displacement is effective, but attention should be paid to the risk of pressure channeling; otherwise, it indicates that the displacement is ineffective, and the pressure-driven injection rate needs to be readjusted to achieve effective displacement.

[0112] In this example, P1>P2 indicates that at the oil well's limit supply radius, the reservoir pressure generated by the injected water is less than the pressure at the limit supply radius when the oil well meets production conditions. Therefore, the displacement is deemed ineffective, and the injection pressure needs to be appropriately increased to achieve effective displacement.

[0113] Example 3

[0114] The selected reservoir is a beach-bar sand reservoir. Two oil and water wells in Well Group B were selected for pressure drive tests. The reservoir has an average air permeability of 5 mD, an average porosity of 10%, and an initial pressure gradient of 0.3 MPa·m. -1 The reservoir oil layer thickness is 10m, the formation fluid viscosity is 10mPa·s, and the formation pressure conductivity is 0.3cm. 2 / s. The well spacing between oil and water wells is 400m. All wells have undergone fracturing, with a fracture half-length of 60m and a fracture height of 50m. The daily fluid production of the oil wells is 4m³. 3 / d, total injection volume is 7000m 3 Injection speed 1m 3 / min. The reservoir pressure after water injection is calculated to be 25MPa based on the comprehensive reservoir compressibility coefficient, and the bottom hole pressure of the water well is 55MPa during the pressure-driven water injection process.

[0115] Step 101: Calculate the pressure profile distribution around the oil well based on the oil well production rate, and calculate the oil well supply radius based on the designed oil well production rate and bottom hole flowing pressure. Calculate the formation pressure at the ultimate supply radius.

[0116] First, calculate the pressure profile around the oil well. According to formula (1), at time t, the pressure around the oil well at a distance r from the bottom of the well can be expressed by the following formula:

[0117]

[0118] The pressure unit is MPa. -1 Considering the starting pressure gradient, the limiting drain radius is:

[0119]

[0120] Substituting into the pressure funnel formula, at time t, the pressure value at the limiting radius is:

[0121]

[0122] Where t represents time, and the unit is seconds (s).

[0123] Based on the total injection volume and injection rate, the total injection time is calculated as follows:

[0124] T i =V i / Q i =4.2×10 5 s

[0125] Substituting the limiting oil supply radius and time into the pressure distribution formula, we get P1 = 22.15 MPa.

[0126] Step 102: After the well is fracturing, the half-length of the fracturing fracture is directly taken as 60m.

[0127] Step 103: Establish a coordinate system with the pressure-driven well as the origin. Consider the fracture generated by pressure-driven as a fracture with infinite conductivity. Then the formula for the distribution of pressure change force is as follows:

[0128]

[0129] Substitute the coordinates at the limit oil supply radius of the oil well

[0130] (x = 400 - 60 - 60 - 36.86 = 243.14), the bottom hole of the well (x D = 0), and the water injection time into the above formula. The pressure changes at the limit oil supply radius of the oil well and the bottom hole of the water injection well are obtained as 19.77 MPa and 43.80 MPa respectively. Combining with the bottom hole pressure of 55 MPa of the water injection well during the pressure-driven process, the reservoir pressure value before pressure-driven is 55 MPa−43.80 MPa = 11.20 MPa. Thus, the pressure value at the limit oil supply radius is: 11.20 MPa + 19.77 MPa = 30.97 MPa. This is P2.

[0131] Step 104: Compare the magnitudes of the calculated P1 and P2.

[0132] According to the above calculations, P1 = 22.15 MPa and P2 = 30.97 MPa. P1 < P2.

[0133] Step 105: P1 represents the formation pressure at the limit pressure relief radius of the oil well calculated according to the oil well pressure drop formula, and P2 represents the formation pressure at the limit pressure relief radius of the oil well calculated according to the pressure-driven water injection well. If P2 is greater than P1, it indicates that the displacement is effective, but attention should be paid to the risk of pressure channeling; otherwise, it indicates that the displacement is ineffective, and the pressure-driven injection rate needs to be readjusted to achieve effective displacement.

[0134] In this example, P1 < P2, so it is determined that the displacement is effective. If there is no risk of pressure channeling, there is no need to increase the injection rate.

[0135] Beneficial effects: Determining the optimal water injection rate can ensure effective displacement of pressure-driven operations and avoid water channeling between injection and production wells.

[0136] The above specific implementation manners further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are only specific implementation manners of the present invention and are not used to limit the protection scope of the present invention. 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.

Claims

1. A method for optimizing water injection rate in pressure-driven development, characterized in that, The optimization method includes: Step S1: Calculate the pressure value P1 at the limit oil supply radius obtained from the oil well production calculation; Step S2: Based on the given total injection volume, calculate the given pressure-driven injection rate and the corresponding pressure-driven water injection time, and calculate the fracture half-length; Step S3: Calculate the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile based on the half-length of the crack; Step S4: When P2 > P1, it indicates that the displacement is effective; otherwise, adjust the water injection state to achieve effective displacement.

2. The method for optimizing water injection rate in pressure-driven development according to claim 1, characterized in that, Step S1, calculating the pressure value P1 at the limit oil supply radius obtained from the oil well production calculation, specifically includes: Calculate the pressure profile distribution around the oil well based on the oil well production; Calculate the oil well supply radius based on the designed oil well production rate and bottom hole flowing pressure; The pressure value P1 at the limit oil supply radius is calculated based on the oil well production.

3. The method for optimizing water injection rate in pressure-driven development according to claim 1, characterized in that, Step S2: Based on the given total injection volume, calculate the given pressure-driven injection rate and the corresponding pressure-driven water injection time, and calculate the fracture half-length, specifically including: Based on the given total injection volume, calculate the given pressure drive injection rate and the corresponding pressure drive water injection time. If the water well is not fractured, calculate the half length of the fracture caused by pressure drive using the pressure drive injection rate and injection time. If the well has a history of fracturing operations, the half-length of the fracture should be taken as half the length of the fracturing fracture.

4. The method for optimizing water injection rate in pressure-driven development according to claim 1, characterized in that, Step S3, which involves calculating the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile based on the half-length of the crack, specifically includes: Based on the calculated fracture half-length, the formula for the pressure profile distribution of the injection well under a given pressure-driven injection rate is calculated. Solve for the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile.

5. The method for optimizing water injection rate in pressure-driven development according to claim 1, characterized in that, The adjustment of the water injection state specifically includes: increasing the water injection speed.

6. The method for optimizing water injection rate in pressure-driven development according to claim 1, characterized in that, Step S1, calculating the pressure value P1 at the limit oil supply radius obtained from the oil well production calculation, specifically includes: When both the radius and time are large, the pressure profile distribution around the oil well can be approximated using the following formula: Where P0 is the reservoir pressure after pressure drive calculated based on the cumulative injection volume and material balance; P(r,t) is the pressure at time t at a distance r (cm) from the bottom of the well; Qc is the production volume; K is the permeability; μ is the fluid viscosity; and η is the formation pressure conductivity coefficient. When the pressure gradient equals the initiation pressure gradient, that is: Where λ is the reservoir's initiation pressure gradient, and r c Let h be the maximum oil drain radius (m) and h be the crack height; then: Substituting the drain radius value back into the pressure calculation formula, we obtain the pressure value P1 at the limit supply radius calculated based on the oil well production:

7. The method for optimizing water injection rate in pressure-driven development according to claim 1, characterized in that, If the well is not fractured, the calculation of the fracture half-length caused by pressure driving using the injection rate and time specifically includes: If the well has no history of fracturing, the process of hydraulic injection is simplified to a conventional hydraulic fracturing fracture propagation model, and the fracture length is calculated using the relevant hydraulic fracturing model. Assume the total injection volume is V. i The injection speed is Q i Then the total injection time T i (s) is: T i =V i / Q (5) Calculate the fracture half-length x based on the pressure-driven injection rate and injection time. f (m); Using the KGD calculation model, the formula for calculating the crack half-length is approximately as follows: Where C is the overall filtration coefficient and h is the crack height.

8. The method for optimizing water injection rate in pressure-driven development according to claim 1, characterized in that, If the well has a history of fracturing operations, the fracture half-length is taken as the half-length of the fracturing fracture, specifically including: If a water well has undergone fracturing, it is assumed that the role of the injected fluid during the fracturing process is to expand the old fractures without creating new ones, and the fracture half-length is directly taken as the fracture half-length during the fracturing process.

9. The method for optimizing water injection rate in pressure-driven development according to claim 4, characterized in that, The formula for calculating the pressure profile distribution of a water injection well at a given pressure-driven injection rate, based on the calculated fracture half-length, specifically includes: Establishing a coordinate system with the pressure-driven well as the origin, and considering the fractures generated by pressure driving as fractures with infinite conductivity, the pressure distribution formula is as follows: in, x D =x / x f and D =y / x f Where, x f Let P0 be the fracture half-length, P0 be the original formation pressure before pressure-driven water injection, B be the formation crude oil volume factor, and c be the volume factor. t The comprehensive elastic compressibility coefficient is used in water injection wells as the volume factor of the injected water under formation conditions. Assuming the fracture direction is along the well line, y D =0, the above formula simplifies to: The coordinates at the limit oil supply radius of the oil well are: x=L w -L i -L c -r c (9) Among them, L w L is the spacing between injection and production wells. i For pressure-driven wells with an injection rate of Q i The lower half-length crack, L c r is the radius of the fracturing zone of the oil well. c This is the calculated ultimate pressure relief radius.

10. The method for optimizing water injection rate in pressure-driven development according to claim 4, characterized in that, The specific steps for determining the pressure value P2 at the limit oil supply radius of the pressure injection pressure profile include: Substitute the coordinates of the bottom of the water injection well and the ultimate oil supply radius into the formula to calculate P at the two coordinate positions. D value; After converting the pressure change to P-P0, and combining it with the bottom hole pressure of the injection well, the pressure value P2 at the limit oil supply radius of the pressure-driven water injection pressure profile is determined.

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