A method for determining a thermal water flooding limit well spacing of a heavy oil reservoir

Abstract

The present application relates to oil and gas field development technology, disclose a kind of heavy oil reservoir hot water drive limit well spacing determination method. Including the following steps: S1, the starting pressure gradient corresponding to different temperature is obtained by percolation experiment test;S2, according to the starting pressure gradient corresponding to different temperature, determine the inflection point temperature of starting pressure gradient curve;S3, based on the inflection point temperature of pressure gradient curve, the percolation area between injection well and production well is divided;S4, based on the percolation area divided, the percolation resistance R of darcy percolation area between injection well and production well is calculated d ;S5, based on R d The pressure drop ΔP of darcy percolation area between injection well and production well is calculated d ;S6, based on ΔP d The length l of non-darcy percolation area between injection well and production well is calculated nd ;S7, based on l nd Determine the limit well spacing L of heavy oil reservoir hot water drive. The determination method can guide the formulation of heavy oil reservoir hot water drive development plan, improve development effect.

Description

Technical Field

[0001] This invention relates to oil and gas field development technology, specifically to a method for determining the ultimate well spacing in hot water flooding of heavy oil reservoirs. Background Technology

[0002] The conventional water injection method for developing heavy oil reservoirs suffers from low recovery rates and poor economic benefits. Hot water flooding, as one of the effective development methods for heavy oil reservoirs, reduces the viscosity and starting pressure gradient of heavy oil by injecting hot water into the formation, thereby improving the fluidity of heavy oil in porous media and displacing the heavy oil in the formation to flow to production wells. Hot water flooding technology has been applied in several oilfields, including Shengli Oilfield, Bohai Oilfield, and Liaohe Oilfield.

[0003] When the well spacing between injection and production wells is large, the production from hydrothermal flooding is relatively low. To ensure that the production from hydrothermal flooding meets the production allocation requirements, the well spacing needs to be reduced until the hydrothermal flooding production just reaches the target production level. This well spacing is the limiting well spacing for hydrothermal flooding. Determining the limiting well spacing for hydrothermal flooding is of great significance for guiding the formulation of development plans for heavy oil fields and ensuring development effectiveness. When the limiting well spacing for hydrothermal flooding is small, it leads to a waste of development energy and poor economic benefits for the oil field. When the limiting well spacing for hydrothermal flooding is large, effective communication cannot be formed between injection and production wells, resulting in phenomena such as "no injection, no production," and the production failing to meet the allocation requirements, leading to poor development results for the oil field.

[0004] Therefore, there is an urgent need to provide a method for determining the limiting well spacing for hot water flooding in heavy oil reservoirs. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for determining the limiting well spacing of hot water flooding in heavy oil reservoirs. This method can guide the formulation of hot water flooding development plans for heavy oil reservoirs and improve development results.

[0006] This invention provides a method for determining the limiting well spacing in hot water flooding of heavy oil reservoirs, characterized by the following steps:

[0007] S1. The starting pressure gradient corresponding to different temperatures was obtained by seepage test;

[0008] S2. Based on the starting pressure gradients corresponding to different temperatures obtained in step S1, determine the inflection point temperature of the starting pressure gradient curve.

[0009] S3. Based on the inflection point temperature of the pressure gradient curve, divide the seepage zone between injection and production wells;

[0010] S4. Based on the seepage zones defined in step S3, calculate the seepage resistance R of the Darcy seepage zone between injection and production wells. d ;

[0011] S5. Based on the seepage resistance R of the Darcy seepage zone between the injection and production wells d Calculate the pressure drop ΔP in the Darcy seepage zone between injection and production wells. d ;

[0012] S6. Based on the pressure drop ΔP in the Darcy seepage zone between the injection and production wells. d Calculate the length l of the non-Darcy flow zone between injection and production wells. nd ;

[0013] S7, based on the length l of the non-Darcy seepage zone nd Determine the limiting well spacing L for hot water flooding of the heavy oil reservoir.

[0014] Preferably, in step S1, the method for obtaining the starting pressure gradient corresponding to different temperatures by the seepage experiment includes: measuring the starting pressure gradient of the heavy oil sample at different temperatures using the constant flow method.

[0015] More preferably, the experimental process for measuring the starting pressure gradient of heavy oil samples at different temperatures using the constant flow method includes: setting the experimental temperature to T, measuring the permeability and porosity of the core sample with saturated water, then replacing the water-saturated oil with ordinary heavy oil and aging for 22-26 hours; setting the flow rate, driving the crude oil with constant flow, and increasing the flow rate sequentially from low to high; recording the pressure of each experiment, plotting the flow rate-pressure gradient curve, and performing regression analysis on the flow rate-pressure gradient curve, the point where the flow rate-pressure gradient curve intersects the pressure gradient coordinate axis is the starting pressure; changing the experimental temperature and repeating the above process to obtain the starting pressure gradient corresponding to different temperatures.

[0016] Preferably, in step S2, the method for determining the inflection point temperature of the start-up pressure gradient curve includes: performing segmented fitting of the start-up pressure gradient data corresponding to different temperatures in a rectangular coordinate system, and the temperature corresponding to the intersection of the fitted curves is the inflection point temperature of the start-up pressure gradient curve.

[0017] Preferably, in step S3, the method for dividing the seepage zone between injection and production wells includes: based on the energy balance principle, determining the formation temperature T near the hot water injection well. h (r) is used to solve the problem, and based on this, the seepage zone between the injection and production wells is divided by combining the inflection point temperature of the pressure gradient curve.

[0018] Assuming that during hot water flooding: ① the oil layer is homogeneous; ② the oil layer has no vertical temperature difference, i.e., the vertical thermal conductivity is infinite; ③ the physical properties of the oil layer and the saturation of the fluid do not change with temperature; ④ heat conduction in the oil layer and surrounding rock is zero in the horizontal direction; ⑤ the injection temperature and injection rate are constant; and the heating zone area is of arbitrary shape; the location r of the hot water flooding heat wave and leading edge can be obtained by solving the energy balance equation using the Laplace transform and inverse transform. hThe calculation formulas are shown in equations (1) and (2):

[0019]

[0020]

[0021] Among them, Q i H represents the injection rate of hot water. s The enthalpy of the injected hot water is given by α, where α is the thermal diffusivity of the top and bottom layers, h is the formation thickness, and C is the thermal flux density. r For the heat capacity of the formation, T i The temperature of the injected hot water is T0, the original temperature of the formation is λ, the thermal conductivity of the top and bottom rocks is t, the time of hot water injection is r, and the distance from the hot water injection well is r.

[0022] The formation temperature T h The formula for calculating (r) is shown in equation (3):

[0023]

[0024] Compare the formation temperatures T at various locations near the hot water injection well. h (r) and the magnitude of the inflection point temperature obtained in step S2, if the formation temperature T h (r) If the temperature is higher than the inflection point temperature, it is classified as a Darcy flow zone; otherwise, it is classified as a non-Darcy flow zone.

[0025] Preferably, in step S4, the seepage resistance R of the Darcy seepage zone between the injection and production wells... d The calculation formula is shown in equation (4):

[0026]

[0027] Among them, K o For the effective permeability of the oil phase, μ o Let A be the viscosity of the crude oil, and let A be the cross-sectional area of ​​the seepage flow. d This refers to the distance from the leading edge of the Darcy seepage zone to the hot water injection well.

[0028] Preferably, in step S5, the pressure drop ΔP in the Darcy seepage zone between the injection and production wells... d The calculation method includes: based on the seepage resistance R of the Darcy seepage zone between the injection and production wells. d Based on the production capacity Q of the hot water flooding, the pressure drop ΔP in the Darcy flow zone between the injection and production wells is calculated using the Darcy formula. d The calculation formula is shown in formula (5):

[0029] ΔP d =QR d (5).

[0030] Preferably, in step S6, the length l of the non-Darcy flow zone between the injection and production wells is... nd The calculation process includes:

[0031] Combined with the pressure drop ΔP in the Darcy seepage zone between the injection and production wells d The pressure drop ΔP in the non-Darcy flow zone between the injection and production wells was obtained. nd The calculation formula is shown in equation (6):

[0032] ΔP nd =ΔP - ΔP d (6),

[0033] Where ΔP is the injection-production pressure difference;

[0034] Combined with the effective oil phase permeability K of the target block o With crude oil viscosity μ o Calculate the starting pressure gradient G of crude oil in the non-Darcy flow zone o The calculation formula is shown in equation (7):

[0035]

[0036] Where A and B are coefficients;

[0037] The temperature of the non-Darcy seepage zone is not higher than the inflection point temperature. When using the seepage mechanics equation for calculation, the starting pressure gradient needs to be considered. Its seepage balance equation is shown in equation (8):

[0038]

[0039] Where Q represents the production capacity of the hot water drive;

[0040] Solving equation (8) yields the length l of the non-Darcy flow zone between the injection and production wells. nd .

[0041] Preferably, in step S7, the calculation formula for the limiting well spacing L of the heavy oil reservoir for hot water flooding is shown in formula (9):

[0042] L = l d +l nd (9),

[0043] Among them, l d This refers to the distance from the leading edge of the Darcy seepage zone to the hot water injection well.

[0044] The beneficial effects of the present invention through the above technical solution are as follows:

[0045] The present invention provides a method for determining the limiting well spacing for hot water flooding in heavy oil reservoirs. Based on seepage experiments, it obtains initiation pressure gradient data at different temperatures. By fitting this data, it determines the inflection point temperature of the initiation pressure gradient. Then, combining this with calculated formation temperature distribution data near the injection wells, it divides the seepage zone for hot water flooding. Finally, considering the initiation pressure gradient in non-Darcy seepage zones, it determines the technical limiting well spacing based on the principle of equivalent seepage resistance. This method can effectively guide the efficient development of heavy oil thermal recovery and is of great significance for guiding the formulation of heavy oilfield development plans and ensuring good development results in heavy oilfields.

[0046] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0047] Figure 1 This is a flowchart of the method for determining the ultimate well spacing in the hot water drive of heavy oil reservoirs in this invention;

[0048] Figure 2 This is a schematic diagram illustrating the determination of the starting pressure gradient at 50°C in this invention;

[0049] Figure 3 This is a schematic diagram illustrating the determination of the inflection point temperature of the starting pressure gradient curve in this invention.

[0050] Figure 4 This is the formation temperature distribution near the hot water injection well in this invention;

[0051] Figure 5 This is a schematic diagram of the hot water drive seepage zone division results in this invention. Detailed Implementation

[0052] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0053] As mentioned above, the basic embodiment of the present invention provides a method for determining the limiting well spacing for hot water flooding in heavy oil reservoirs, such as... Figure 1 As shown, it includes the following steps:

[0054] S1. The starting pressure gradient corresponding to different temperatures was obtained by seepage test;

[0055] S2. Based on the starting pressure gradients corresponding to different temperatures obtained in step S1, determine the inflection point temperature of the starting pressure gradient curve.

[0056] S3. Based on the inflection point temperature of the pressure gradient curve, divide the seepage zone between injection and production wells;

[0057] S4. Based on the seepage zones defined in step S3, calculate the seepage resistance R of the Darcy seepage zone between injection and production wells. d ;

[0058] S5. Based on the seepage resistance R of the Darcy seepage zone between the injection and production wells d Calculate the pressure drop ΔP in the Darcy seepage zone between injection and production wells. d ;

[0059] S6. Based on the pressure drop ΔP in the Darcy seepage zone between the injection and production wells. d Calculate the length l of the non-Darcy flow zone between injection and production wells. nd ;

[0060] S7, based on the length l of the non-Darcy seepage zone nd Determine the limiting well spacing L for hot water flooding of the heavy oil reservoir.

[0061] In the description of the embodiments of the present invention, the determination of the limiting well spacing for hot water drive in heavy oil reservoirs is taken as an example. Specifically, heavy oil refers to crude oil with a specific gravity greater than 0.90 and a degassed crude oil viscosity of 100 mPa·s or higher at reservoir temperature. According to the viscosity of heavy oil, it can be divided into: ordinary heavy oil (degassed oil viscosity of 100-10000 mPa·s at reservoir temperature, specific gravity greater than 0.90) and extra-heavy oil (degassed oil viscosity of 1×10⁻⁶ mPa·s at reservoir temperature). 4 -5×10 4 mPa·s (specific gravity greater than 0.95) and extra-heavy oil (degassed oil viscosity at reservoir temperature is 5×10⁻⁶ mPa·s). 4 (above mPa·S, with a specific gravity greater than 0.98).

[0062] The determination method provided in the above basic embodiments of the present invention obtains the starting pressure gradient corresponding to different temperatures based on seepage experiments and determines the inflection temperature of the starting pressure gradient curve. Based on this, the seepage regions of the injection and production wells are divided, and finally, the length l of the non-Darcy seepage zone between the injection and production wells is determined. nd Determine the limiting well spacing L for hot water recovery in heavy oil reservoirs. This method can effectively guide the efficient development of heavy oil thermal recovery and is of great significance for guiding the formulation of heavy oil field development plans and ensuring good development results in heavy oil fields.

[0063] In one specific embodiment of the present invention, step S1, the method for obtaining the starting pressure gradient corresponding to different temperatures by the seepage experiment includes: measuring the starting pressure gradient of heavy oil samples at different temperatures using the constant flow method.

[0064] As a specific embodiment of the present invention, the experimental process for measuring the starting pressure gradient of heavy oil samples at different temperatures using the constant flow method includes: setting the experimental temperature to T, measuring the permeability and porosity of the core sample with saturated water, then replacing the water-saturated oil with ordinary heavy oil, and aging for 22-26 hours. The aging time can specifically be 22 hours, 24 hours, 26 hours, or any value between the aforementioned values; setting the flow rate, driving the crude oil with constant flow, and increasing the flow rate sequentially from low to high. For example, the flow rate can be set sequentially from low to high as 0.005 mL / min, 0.015 mL / min, 0.03 mL / min, and 0.05 mL / min; recording the pressure of each experiment, plotting the flow rate-pressure gradient curve, and performing regression analysis on the flow rate-pressure gradient curve. The point where the flow rate-pressure gradient curve intersects the pressure gradient coordinate axis is the starting pressure; changing the experimental temperature and repeating the above process to obtain the starting pressure gradient corresponding to different temperatures.

[0065] In one specific embodiment of the present invention, step S2, the method for determining the inflection point temperature of the startup pressure gradient curve includes: performing piecewise fitting of the startup pressure gradient data corresponding to different temperatures in a Cartesian coordinate system, and the temperature corresponding to the intersection of the fitted curves is the inflection point temperature of the startup pressure gradient curve. The above method can quickly and accurately obtain the inflection point temperature of the startup pressure gradient curve.

[0066] In one specific embodiment of the present invention, step S3, the method for dividing the seepage zone between injection and production wells includes: based on the energy balance principle, determining the formation temperature T near the injection well. h (r) is used to solve the problem, and based on this, the seepage zone between the injection and production wells is divided by combining the inflection point temperature of the pressure gradient curve.

[0067] Assuming that during hot water flooding: ① the oil layer is homogeneous; ② the oil layer has no vertical temperature difference, i.e., the vertical thermal conductivity is infinite; ③ the physical properties of the oil layer and the saturation of the fluid do not change with temperature; ④ heat conduction in the oil layer and surrounding rock is zero in the horizontal direction; ⑤ the injection temperature and injection rate are constant; and the heating zone area is of arbitrary shape; the location r of the hot water flooding heat wave and leading edge can be obtained by solving the energy balance equation using the Laplace transform and inverse transform. h The calculation formulas are shown in equations (1) and (2):

[0068]

[0069]

[0070] Among them, Q i H represents the injection rate of hot water. s The enthalpy of the injected hot water is given by α, where α is the thermal diffusivity of the top and bottom layers, h is the formation thickness, and C is the thermal flux density. rFor the heat capacity of the formation, T i The temperature of the injected hot water is T0, the original temperature of the formation is λ, the thermal conductivity of the top and bottom rocks is t, the time of hot water injection is r, and the distance from the hot water injection well is r.

[0071] The formation temperature T h The formula for calculating (r) is shown in equation (3):

[0072]

[0073] Compare the formation temperatures T at various locations near the hot water injection well. h (r) and the magnitude of the inflection point temperature obtained in step S2, if the formation temperature T h (r) If the temperature is higher than the inflection point temperature, it is classified as a Darcy flow zone; otherwise, it is classified as a non-Darcy flow zone.

[0074] In one specific embodiment of the present invention, in step S4, the seepage resistance R of the Darcy seepage zone between the injection and production wells... d The calculation formula is shown in equation (4):

[0075]

[0076] Among them, K o For the effective permeability of the oil phase, μ o Let A be the viscosity of the crude oil, and let A be the cross-sectional area of ​​the seepage flow. d This refers to the distance from the leading edge of the Darcy seepage zone to the hot water injection well.

[0077] In one specific embodiment of the present invention, in step S5, the pressure drop ΔP in the Darcy seepage zone between the injection and production wells... d The calculation method includes: based on the seepage resistance R of the Darcy seepage zone between the injection and production wells. d Based on the production capacity Q of the hot water flooding, the pressure drop ΔP in the Darcy flow zone between the injection and production wells is calculated using the Darcy formula. d The calculation formula is shown in formula (5):

[0078] ΔP d =QR d (5).

[0079] In one specific embodiment of the present invention, in step S6, the length l of the non-Darcy flow zone between the injection and production wells is... nd The calculation process includes:

[0080] Combined with the pressure drop ΔP in the Darcy seepage zone between the injection and production wells d The pressure drop ΔP in the non-Darcy flow zone between the injection and production wells was obtained. nd The calculation formula is shown in equation (6):

[0081] ΔP nd =ΔP - ΔP d (6),

[0082] Where ΔP is the injection-production pressure difference;

[0083] Combined with the effective oil phase permeability K of the target block o With crude oil viscosity μ o Calculate the starting pressure gradient G of crude oil in the non-Darcy flow zone o The calculation formula is shown in equation (7):

[0084]

[0085] Where A and B are coefficients;

[0086] Since the temperature in the Darcy flow zone is higher than the inflection point temperature of the starting pressure curve, the starting pressure gradient can be ignored. The flow of crude oil in the porous medium conforms to the Darcy flow law. However, the temperature in the non-Darcy flow zone is not higher than the inflection point temperature. Therefore, the starting pressure gradient needs to be considered when using the flow mechanics equation for calculation. Its flow balance equation is shown in equation (8):

[0087]

[0088] Where Q represents the production capacity of the hot water drive;

[0089] Solving equation (8) yields the length l of the non-Darcy flow zone between the injection and production wells. nd .

[0090] In one specific embodiment of the present invention, in step S7, the calculation formula for the limiting well spacing L of the heavy oil reservoir hot water drive is as shown in formula (9):

[0091] L = l d +l nd (9),

[0092] Among them, l d This refers to the distance from the leading edge of the Darcy seepage zone to the hot water injection well.

[0093] According to a particularly preferred embodiment of the present invention, a method for determining the timing of flue gas-assisted huff and puff injection is provided, such as... Figure 1 As shown, it includes the following steps:

[0094] S1. The constant flow method was used to measure the starting pressure gradient of heavy oil samples at different temperatures. The experimental procedure included: setting the experimental temperature to T, saturating the core with water to measure permeability and porosity, then replacing the water-saturated oil with ordinary heavy oil and aging for 22-26 hours; setting the flow rate, driving the crude oil with constant flow, and increasing the flow rate from low to high; recording the pressure of each experiment, plotting the flow rate-pressure gradient curve, and performing regression analysis on the flow rate-pressure gradient curve. The point where the flow rate-pressure gradient curve intersects the pressure gradient coordinate axis is the starting pressure; changing the experimental temperature and repeating the above process to obtain the starting pressure gradient corresponding to different temperatures.

[0095] S2. In a rectangular coordinate system, the starting pressure gradient data corresponding to different temperatures obtained in step S1 are piecewise fitted. The temperature corresponding to the intersection of the fitted curves is the inflection point temperature of the starting pressure gradient curve.

[0096] S3. Based on the principle of energy balance, the formation temperature T near the hot water injection well is... h (r) is used to solve the problem, and based on this, the seepage zone between injection and production wells is divided by combining the inflection point temperature of the pressure gradient curve.

[0097] Assuming that during hot water flooding: ① the oil layer is homogeneous; ② the oil layer has no vertical temperature difference, i.e., the vertical thermal conductivity is infinite; ③ the physical properties of the oil layer and the saturation of the fluid do not change with temperature; ④ heat conduction in the oil layer and surrounding rock is zero in the horizontal direction; ⑤ the injection temperature and injection rate are constant; and the heating zone area is of arbitrary shape; the location r of the hot water flooding heat wave and leading edge can be obtained by solving the energy balance equation using the Laplace transform and inverse transform. h The calculation formulas are shown in equations (1) and (2):

[0098]

[0099]

[0100] Among them, Q i H represents the injection rate of hot water. s The enthalpy of the injected hot water is given by α, where α is the thermal diffusivity of the top and bottom layers, h is the formation thickness, and C is the thermal flux density. r For the heat capacity of the formation, T i The temperature of the injected hot water is T0, the original temperature of the formation is λ, the thermal conductivity of the top and bottom rocks is t, the time of hot water injection is r, and the distance from the hot water injection well is r.

[0101] Formation temperature T h The formula for calculating (r) is shown in equation (3):

[0102]

[0103] Compare the formation temperature T at various locations near the hot water injection well. h(r) and the magnitude of the inflection point temperature obtained in step S2, if the formation temperature T h (r) If the temperature is higher than the inflection point temperature, it is classified as a Darcy flow zone; otherwise, it is classified as a non-Darcy flow zone.

[0104] S4. Based on the seepage zones defined in step S3, calculate the seepage resistance R of the Darcy seepage zone between injection and production wells. d The calculation formula is shown in equation (4):

[0105]

[0106] Among them, K o For the effective permeability of the oil phase, μ o Let A be the viscosity of the crude oil, and let A be the cross-sectional area of ​​the seepage flow. d This refers to the distance from the front edge of the Darcy seepage zone to the hot water injection well;

[0107] S5. Based on the seepage resistance R of the Darcy seepage zone between the injection and production wells d Based on the production capacity Q of the hot water flooding, the pressure drop ΔP in the Darcy flow zone between the injection and production wells is calculated using the Darcy formula. d The calculation formula is shown in formula (5):

[0108] ΔP d =QR d (5),

[0109] S6, Length of the non-Darcy flow zone between injection and production wells (l) nd The calculation process includes:

[0110] Combined with the pressure drop ΔP in the Darcy seepage zone between the injection and production wells d The pressure drop ΔP in the non-Darcy flow zone between the injection and production wells was obtained. nd The calculation formula is shown in equation (6):

[0111] ΔP nd =ΔP - ΔP d (6),

[0112] Where ΔP is the injection-production pressure difference;

[0113] Combined with the effective oil phase permeability K of the target block o With crude oil viscosity μ o Calculate the starting pressure gradient G of crude oil in the non-Darcy flow zone o The calculation formula is shown in equation (7):

[0114]

[0115] Where A and B are coefficients;

[0116] The temperature of the non-Darcy seepage zone is not higher than the inflection point temperature. When using the seepage mechanics equation for calculation, the starting pressure gradient needs to be considered. Its seepage balance equation is shown in equation (8):

[0117]

[0118] Where Q represents the production capacity of the hot water drive;

[0119] Solving equation (8) yields the length l of the non-Darcy flow zone between injection and production wells. nd ;

[0120] S7. The formula for calculating the ultimate well spacing L for hot water flooding in heavy oil reservoirs is shown in equation (9):

[0121] L = l d +l nd (9),

[0122] Among them, l d This refers to the distance from the leading edge of the Darcy seepage zone to the hot water injection well.

[0123] The method for determining the limiting well spacing of heavy oil reservoirs by hot water drive provided by the above preferred embodiments can effectively guide the efficient development of heavy oil thermal recovery and is of great significance for guiding the formulation of heavy oil field development plans and ensuring that heavy oil field development achieves good results.

[0124] The present invention will be described in detail below through embodiments.

[0125] The following example uses a heavy oil reservoir to determine the limiting well spacing for hot water flooding in a heavy oil reservoir. The basic parameters are: formation temperature of 75℃, average formation porosity of 0.31, and average formation permeability of 3512×10⁻⁶. -3 μm 2 The viscosity of the underground crude oil is 541 mPa·s, and the original formation pressure is 15.1 MPa. For example... Figure 1 As shown, the present invention provides a method for determining the limiting well spacing for hot water flooding in heavy oil reservoirs, comprising:

[0126] S1. The starting pressure gradient corresponding to different temperatures was obtained through seepage experiments. The starting pressure gradient of heavy oil samples at different temperatures was measured using the constant flow method. The specific process is as follows: 1. The initial experimental temperature was set to 50℃. Permeability and porosity were measured by saturating the core with water. Then, ordinary heavy oil was used to displace the water-saturated oil, and the samples were aged for 24 hours. 2. The displacement flow rate was set, and the crude oil was driven by constant flow. The flow rate was set from low to high as follows: 0.005 mL / min, 0.015 mL / min, 0.03 mL / min, and 0.05 mL / min. 3. The pressure of each experiment was recorded, and the flow rate-pressure gradient curve was plotted. The curve was regressed, and the point where the curve intersects the pressure gradient coordinate axis is the starting pressure gradient. A schematic diagram of the determination of the starting pressure gradient is shown below. Figure 2 As can be seen, the starting pressure gradient of the heavy oil sample at 50℃ is 0.45MPa / m; 4. The above process was repeated by changing the experimental temperature to 50℃-150℃, and the starting pressure gradients corresponding to different temperatures are shown in Table 1.

[0127] Table 1

[0128]

[0129] S2. Determine the inflection point temperature of the starting pressure gradient curve. In a Cartesian coordinate system, perform piecewise fitting on the starting pressure gradient data corresponding to different temperatures obtained in step S1. The temperature corresponding to the intersection of the fitted curves is the inflection point temperature of the starting pressure curve, such as... Figure 3 As shown, the inflection point temperature of the target block startup pressure gradient curve is 101.1℃.

[0130] S3. Delineate the seepage zone between injection and production wells. Based on the energy balance principle, solve for the formation temperature distribution near the injection well. Then, combine this with the inflection point temperature of the starting pressure gradient curve obtained in step S2 to delineate the seepage zone.

[0131] Assume that during hot water flooding: ① the oil layer is homogeneous; ② the oil layer has no vertical temperature difference, i.e., the vertical thermal conductivity is infinite; ③ the physical properties of the oil layer and the saturation of the fluid do not change with temperature; ④ heat conduction in the oil layer and surrounding rock is zero in the horizontal direction; ⑤ the injection temperature and injection rate are constant; and the area of ​​the heating zone is of arbitrary shape. Solving the energy balance equation using the Laplace transform and its inverse transform yields the location r of the hot water flooding heat wave and its leading edge. h The calculation formulas are shown in equations (1) and (2):

[0132]

[0133]

[0134] Among them, Q i The injection rate of hot water is expressed in kg / d; H2s ν is the enthalpy of the injected hot water, J / kg; a is the thermal diffusivity of the top and bottom layers, m. 2 / d; h is the formation thickness, in meters; C r The heat capacity of the formation, J / (m³) 3 ·℃); T i T0 is the temperature of the injected hot water, in °C; T0 is the original temperature of the formation, in °C; λ is the thermal conductivity of the top and bottom layers of rock, in W / (m·℃); t is the time for hot water injection, in d; r is the distance from the hot water injection well, in m.

[0135] Formation temperature T h The formula for calculating (r)(℃) is shown in equation (3):

[0136]

[0137] Enthalpy H of hot water injected into the target block s The heat capacity of the formation is 422 J / kg, the formation thickness h is 32 m, and the formation heat capacity C is... r It is 1.89 J / (m 3 ·℃), the temperature of the injected hot water T i The initial temperature of the formation was 150℃, the original temperature of the formation T0 was 75℃, and the thermal conductivity λ of the top and bottom rocks was 0.66W / (m·℃). After 1 year of production, the location r of the hot water drive heat front was calculated using equations (1) and (2). h The depth is 158m. Based on this, the formation temperature T near the hot water injection well is calculated using equation (3). h (r) distribution as Figure 4 As shown, it can be seen that the formation temperature decreases with increasing distance from the hot water well, and at the front edge of the hot water driving wave, the temperature decreases to the original formation temperature.

[0138] Compare the temperatures at various locations near the hot water injection well with the inflection point temperature of the starting pressure gradient curve obtained in step S2. If the temperature is higher than the inflection point temperature, the area is classified as a Darcy flow zone; otherwise, it is classified as a non-Darcy flow zone. The results of the hot water drive flow zone classification are as follows: Figure 5 As shown.

[0139] S4. Calculate the seepage resistance R in the Darcy flow zone between injection and production wells. d Based on the division of the seepage zone in step S3, the seepage resistance R of the Darcy seepage zone is calculated. d The calculation formula is shown in equation (4):

[0140]

[0141] In the formula, K o The effective permeability of the oil phase is expressed in mD and μ. o Where is the viscosity of crude oil, mPa·s; A is the cross-sectional area of ​​seepage, m³ / s.2 ;l d The distance, in meters, is the distance from the leading edge of the Darcy seepage zone to the hot water injection well.

[0142] according to Figure 5 It can be seen that the distance l from the front edge of the Darcy seepage zone to the hot water injection well is... d The seepage resistance R in the Darcy seepage zone is 78m. Using equation (4), the seepage resistance R in the Darcy seepage zone is calculated. d 0.04 MPa / (m 3 / d).

[0143] S5. Calculate the pressure drop ΔP in the Darcy flow zone between injection and production wells. d The seepage resistance R in the Darcy seepage zone obtained based on S4. d Based on the production capacity Q of the hot water flooding, the pressure drop ΔP in the Darcy zone between injection and production wells is calculated using the Darcy formula. d The calculation formula is shown in formula (5):

[0144] ΔP d =QR d (5),

[0145] The target block is designed to have a hot water drive capacity Q of 120 t / d, based on the seepage resistance R of the Darcy flow zone obtained in step S4. d The pressure drop ΔP in the Darcy seepage zone is calculated using equation (5). d It is 4.8 MPa.

[0146] S6. Calculate the length l of the non-Darcy flow zone between injection and production wells. nd The pressure drop ΔP in the Darcy seepage zone between injection and production wells, calculated in step S5, is used as a basis for further calculations. d The pressure drop ΔP in the non-Darcy flow zone between injection and production wells can be obtained from the injection-production pressure difference ΔP. nd The calculation formula is shown in equation (6):

[0147] ΔP nd =ΔP - ΔP d (6),

[0148] Combined with the formation permeability K of the target block o With crude oil viscosity μ o Calculate the starting pressure gradient G of crude oil in the non-Darcy flow zone o The calculation formula is shown in equation (7):

[0149]

[0150] Where A and B are coefficients.

[0151] For non-Darcy flow regions, consider the starting pressure gradient G of the crude oil in the non-Darcy flow region. oThe seepage equilibrium equation is shown in equation (8):

[0152]

[0153] Where Q represents the production capacity of the hot water drive;

[0154] Solving equation (8) yields the length l of the non-Darcy seepage zone. nd .

[0155] The injection-production pressure difference ΔP in the target block is 15.1 MPa, based on the pressure drop ΔP in the Darcy seepage zone calculated in step S5. d The pressure drop ΔP in the non-Darcy seepage zone is calculated using equation (6). nd The starting pressure gradient G in the non-Darcy seepage zone is calculated using equation (7) with a target block coefficient A = 0.159 and coefficient B = -2.036. o The pressure is 0.03 MPa / m; the length l of the non-Darcy seepage zone is calculated using equation (8). nd It is 96m.

[0156] S7. Determine the limiting well spacing L for hot water flooding of the heavy oil reservoir. Based on the length l of the non-Darcy flow zone obtained in step S6. nd Calculate the limiting well spacing L for hot water flooding in heavy oil reservoirs. The limiting well spacing is the sum of the lengths of the Darcy flow zone and the non-Darcy flow zone. The calculation formula is:

[0157] L = l d +l nd (9),

[0158] Among them, l d This refers to the distance from the leading edge of the Darcy seepage zone to the hot water injection well.

[0159] Based on the calculation results of step S6, the limit well distance L for hot water drive is calculated to be 174m using equation (9).

[0160] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for determining the thermal waterflood limit well spacing of a heavy oil reservoir, characterized in that, Includes the following steps: S1. The starting pressure gradient corresponding to different temperatures was obtained by seepage test; S2. Based on the starting pressure gradients corresponding to different temperatures obtained in step S1, determine the inflection point temperature of the starting pressure gradient curve. S3. Based on the inflection point temperature of the starting pressure gradient curve, divide the seepage zone between injection and production wells; S4. Based on the seepage area divided in step S3, the seepage resistance of the Darcy seepage area between injection and production wells is calculated R d ; S5, calculating the pressure drop Δ of the Darcy flow region between the injection well and the production well based on the flow resistance of the Darcy flow region between the injection well and the production well R d , calculating the pressure drop Δ of the Darcy flow region between the injection well and the production well based on the flow resistance of the Darcy flow region between the injection well and the production well P d ; S6、based on the pressure drop Δ of the Darcy flow zone between the injection and production wells P d , calculate the length of the non-Darcy flow zone between the injection and production wells l nd ; S7、based on the length of the non-Darcy seepage zone between the injection and production wells l nd , determine the limit well spacing of the hot water flooding of the heavy oil reservoir L ; In step S1, the method for obtaining the starting pressure gradient corresponding to different temperatures by the seepage experiment includes: measuring the starting pressure gradient of heavy oil samples at different temperatures using the constant flow method. The experimental procedure for determining the starting pressure gradient of heavy oil samples at different temperatures using the constant flow method includes: setting the experimental temperature to T, measuring the permeability and porosity of the core sample with saturated water, then replacing the water-saturated oil with ordinary heavy oil and aging for 22-26 hours; setting the flow rate, driving the crude oil with a constant flow, and increasing the flow rate sequentially from low to high; recording the pressure of each experiment, plotting the flow rate-pressure gradient curve, and performing regression analysis on the flow rate-pressure gradient curve. The point where the flow rate-pressure gradient curve intersects the pressure gradient coordinate axis is the starting pressure; changing the experimental temperature and repeating the above experimental procedure to obtain the starting pressure gradient corresponding to different temperatures; In step S3, the method for dividing the percolation area between the injection and production wells comprises: solving the formation temperature near the hot water injection well based on the energy balance principle T h ( r ) and dividing the percolation area between the injection and production wells based on the inflection point temperature of the starting pressure gradient curve. Assuming that in the hot water flooding process: ① the oil layer is uniform; ② the oil layer has no vertical temperature difference, i.e. the vertical heat conduction coefficient is infinite; ③ the oil layer properties and fluid saturation do not change with temperature; ④ in the oil layer and surrounding rock, the heat conduction is zero in the horizontal direction; ⑤ the injection temperature and injection rate are constant; the heating zone area is of arbitrary shape; using Laplace transform and inverse transform to solve the energy balance equation can obtain the hot water flooding heat wave and front position r h The calculation formula is shown in formula (1) and formula (2): （1）， （2）， wherein, Q i is the injection rate of hot water, H s is the enthalpy of the injected hot water, a is the thermal diffusivity of the top and bottom layers, h is the thickness of the formation, C r is the heat capacity of the formation, T i is the temperature of the injected hot water, T 0 is the original temperature of the formation, λ is the thermal conductivity of the top and bottom layers of rock, t is the time of injection of hot water, r is the distance from the injection well. the formation temperature T h ( r ) is shown in equation (3): （3）， comparing the formation temperature at each position near the water injection well T h ( r ) with the inflection point temperature obtained in step S2, if the formation temperature T h ( r ) is higher than the inflection point temperature, then it is classified as Darcy flow region, otherwise it is classified as non-Darcy flow region.

2. The determination method according to claim 1, characterized in that, In step S2, the method for determining the inflection point temperature of the starting pressure gradient curve includes: performing segmented fitting of the starting pressure gradient data corresponding to different temperatures in a rectangular coordinate system, and the temperature corresponding to the intersection of the fitted curves is the inflection point temperature of the starting pressure gradient curve.

3. The determination method according to claim 1, characterized in that, In step S4, the flow resistance of the Darcy flow zone between the injection well and the production well R d The calculation formula is shown as formula (4): （4）， wherein, K o is the effective permeability of the oil phase, μ o is the viscosity of the crude oil, A is the cross-sectional area of the flow, l d is the distance from the front of the Darcy flow zone to the hot water injection well.

4. The determination method according to claim 1, characterized in that, In step S5, the pressure drop Δ of the Darcy flow zone between the injection well and the production well is calculated using the Darcy formula based on the flow resistance of the Darcy flow zone between the injection well and the production well P d The calculation method includes: based on the flow resistance of the Darcy flow zone between the injection well and the production well R d , combining the thermal water drive productivity Q , using the Darcy formula to calculate the pressure drop Δ of the Darcy flow zone between the injection well and the production well P d The calculation formula is shown in formula (5): （5）。 5. The determination method of claim 1, wherein, In step S6, the length of the non-Darcy seepage zone between the injection and production wells is calculated l nd The calculation process includes: combining the pressure drop Δ P d of the non-Darcy flow region between the injection and production wells P nd , and the calculation formula is shown in equation (6): （6）， where ΔP is the injection-production differential pressure P as the injection-production differential pressure; Oil phase effective permeability of a target zone block K o Viscosity of crude oil μ o Computing the threshold pressure gradient of non-Darcy flow zone crude oil G o The computing formula is shown as formula (7): （7）， Where A and B are coefficients; The temperature of the non-Darcy seepage zone is not higher than the inflection point temperature. When using the seepage mechanics equation for calculation, the starting pressure gradient needs to be considered. Its seepage balance equation is shown in equation (8): （8）， wherein, Q Production capacity for hot water flooding; Solving equation (8) can obtain the length of the non-Darcy seepage zone between the injection and production wells l nd .

6. The determination method of claim 1, wherein, In step S7, the limit well spacing of the heavy oil reservoir thermal water flooding L The calculation formula is shown as formula (9): （9）， wherein, l d D is the distance from the front of the Darcy flow zone to the hot water injection well.

Images