Oil reservoir differential use and strata series recombination optimization method based on starting pressure gradient

Abstract

The invention discloses a starting pressure gradient-based oil reservoir differential use and strata series recombination optimization method, which comprises the following steps of: collecting a rock core, and carrying out a starting pressure gradient experiment; cleaning the test data, and removing abnormal values in the data set; starting pressure gradient and permeability data standardization; establishing a characterization model of the starting pressure gradient and the permeability; establishing a multilayer heterogeneous oil reservoir single-layer liquid production capacity model considering the starting pressure gradient; judging whether each oil layer of the target well can be effectively used or not; establishing a strata series recombination chart considering the starting pressure gradient; and based on the strata series recombination chart, carrying out strata series recombination and the like. According to the method, the matching relation between the maximum permeability and the minimum permeability which can be effectively utilized under different pressure difference conditions can be determined, more small layers can be started under the same production pressure difference condition of the same set of layer series, the reservoir which can be started under the same production pressure difference serves as one set of layer series, effective utilization of the small layers in the longitudinal direction is achieved through layer series recombination, and the stability of the reservoir is improved. And the water drive development effect is improved.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development engineering technology, specifically relating to a method for differentiated utilization and stratigraphic reorganization optimization of multi-layered complex oil reservoirs based on the starting pressure gradient, which is particularly suitable for complex oil and gas reservoirs with significant differences in starting pressure gradient. Background Technology

[0002] In complex, multi-layered offshore oil reservoirs, a combined production approach is often employed. However, due to differences in thickness, permeability, pore structure, and fluid properties among the vertical layers, traditional combined production methods suffer from severe inter-layer interference, uneven utilization, poor utilization of low-permeability layers, premature water or gas breakthrough in high-permeability layers, rapid breakthroughs, significant water cut increases, and poor development outcomes. Currently, offshore oilfields have limitations on the number of sand control sections during segmented sand control. Therefore, the subdivision of multi-layered, combined production reservoirs primarily focuses on determining the permeability and viscosity gradients within the sand control sections. However, in practice, even when the gradients of the sand control sections meet the theoretically defined limits, many small layers with poor physical properties within the sand control sections remain ineffective due to the initiation pressure. Therefore, there is an urgent need to establish a layer reorganization method that considers the initiation pressure gradient for complex, multi-layered offshore oil reservoirs. Summary of the Invention

[0003] This invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a reservoir differential activation and strata reorganization optimization method based on the starting pressure gradient.

[0004] This invention is achieved through the following technical solution: A method for differentiated mobilization and stratigraphic reorganization optimization of multi-layered complex reservoirs based on initiation pressure gradient includes the following steps: S1. Collect rock cores and conduct the initiation pressure gradient experiment; The core samples were selected from the main production layers, as well as core samples from different sub-layers and with different physical properties. The specific experimental method for the initiation pressure gradient experiment is as follows: S11. Measure the core length L; S12. Saturate the core with crude oil under high pressure; S13. Close one end and install a pressure gauge as the pressure measuring end. After the system pressure is balanced and stable, reduce the pressure value at the core venting end by 0.1 MPa and observe the change in pressure at the pressure measuring end within 30 minutes. S14. If the pressure at the measuring end does not change within 30 minutes, repeat step S13 until the pressure at the measuring end changes, and record the cumulative change in the venting end pressure. ; S15. Calculate the starting pressure gradient of the core. The formula for calculating the starting pressure gradient is: (1) In formula (1): The pressure gradient is used to initiate the process, and the unit is MPa / cm. The cumulative change in pressure at the venting end is expressed in MPa; L is the core length, expressed in cm. S16. Repeat the starting pressure gradient test three times for each core sample, and take the average of the three starting pressure gradients as the starting pressure gradient of the core sample.

[0005] S2. Cleaning Step: S1 starts the test data of the pressure gradient experiment and removes outliers in the dataset. Specifically, after sorting the obtained starting pressure gradient data in ascending order, the first quartile (Q1) and the third quartile (Q3) are the numbers at the 25th and 75th percentiles, respectively. Let the interquartile range be the difference between the third quartile and the first quartile, IQR = Q3 - Q1. Then, the values ​​between Q3 + 1.5 (IQR) and Q1 - 1.5 (IQR) are the acceptable values. Values ​​outside these two ranges are outliers and are removed. S3. Standardize the starting pressure gradient and permeability data of different dimensions to bring all data to the same scale. Specifically, the following steps are included: S31. Perform a logarithmic transformation on the permeability data. The transformation formula is as follows: (2) In formula (2): Logarithmic penetration rate, in mD; This represents the cumulative change in vent pressure, expressed in mD. S32. Calculate the average starting pressure gradient. Standard deviation of starting pressure gradient S R Log average penetration rate and the standard deviation of log permeability S K ; The average value of the starting pressure gradient The calculation formula is: (3) In formula (3): The average value of the starting pressure gradient is expressed in MPa / cm. denoted as the initiation pressure gradient of the i-th core sample, in MPa / cm; n represents the total number of core samples tested. The standard deviation of the starting pressure gradient S R The calculation formula is: (4) In equation (4): The standard deviation of the initiating pressure gradient is dimensionless. The average value of the starting pressure gradient is expressed in MPa / cm. denoted as the initiation pressure gradient of the i-th core sample, in MPa / cm; n represents the total number of core samples tested. The formula for calculating the average logarithmic permeability is as follows: (5) In equation (5): This is the average logarithmic permeability, in mD. denoted as logarithmic permeability of the i-th core sample, in mD; n represents the total number of core samples tested. The formula for calculating the standard deviation of the logarithmic permeability is as follows: (6) In formula (6): The standard deviation of the logarithmic penetration rate is dimensionless. This is the average logarithmic permeability, in mD. denoted as logarithmic permeability of the i-th core sample, in mD; n represents the total number of core samples tested. S33. Standardize the starting pressure gradient and log permeability data; The formula for calculating the standardized start-up pressure gradient is: (7) In equation (7): The initiation pressure gradient is standardized and dimensionless. The average value of the starting pressure gradient is expressed in MPa / cm. The starting pressure gradient of the i-th core sample is expressed in MPa / cm. The standard deviation of the initiating pressure gradient is dimensionless. The formula for calculating the standardized logarithmic penetration rate is as follows: (8) In equation (8): The standardized logarithmic penetration rate is dimensionless. The standard deviation of the logarithmic penetration rate is dimensionless. This is the average logarithmic permeability, in mD. Let be the logarithmic permeability of the i-th core sample, in mD; Through standardized calculations, the starting pressure gradient and permeability test data are transformed into dimensionless data with a mean of 0 and a standard deviation of 1.

[0006] S4. Establish a characterization model of the starting pressure gradient and permeability; Specifically, the following steps are included: S41. The data preprocessed in step S3 is randomly divided into a 70% training set and a 30% test set. The training set is used to apply the linear regression analysis algorithm, and the test set is used to evaluate the model performance. S42. In a rectangular coordinate system, with the standardized logarithmic permeability as the X-axis and the standardized starting pressure gradient as the Y-axis, establish a plane rectangular coordinate system and use a linear regression analysis algorithm to establish a characterization model of the starting pressure gradient and permeability. The characterization model of the initiation pressure gradient and permeability is as follows: (9) In equation (9): The initiation pressure gradient is standardized and dimensionless. The standardized logarithmic penetration rate is dimensionless; a and b are fitting parameters. S43. Substitute the standardized logarithmic permeability data of all data in the test set into the characterization model of starting pressure gradient and permeability, and calculate the coefficient of determination reflecting the accuracy of the model prediction. The formula for calculating the determination coefficient of the characterization model is as follows: (10) In formula (10): The coefficients of determination characterize the model and are dimensionless. The standardized startup pressure gradient for the test set, in MPa; The standardized initiation pressure gradient predicted by the model is expressed in MPa. is the normalized average starting pressure gradient of the test set, in MPa; m is the amount of test set data. S44. When the determination coefficient of the representation model When the value is greater than 0.8, the model can well characterize the correlation between the initiation pressure gradient and the permeability. When 0.6 < When the value is less than 0.8, the model can effectively characterize the correlation between the initiation pressure gradient and permeability. when When the gradient is less than 0.6, the correlation between the starting pressure gradient and the permeability of the sample is poor, and it is necessary to check whether the original data is reasonable.

[0007] S5. Based on the characterization model of starting pressure gradient and permeability, and according to Darcy's law, establish a single-layer production model for multi-layer heterogeneous reservoirs that considers the starting pressure gradient. The single-layer production model for multi-layer heterogeneous reservoirs considering the initiation pressure gradient is as follows: (11) In equation (11): This represents the liquid production rate of the i-th layer, in units of 10. -3 cm 3 / s; The permeability of the i-th layer is expressed in mD. The cross-sectional area of ​​the i-th layer is expressed in cm. 2 ; Formation pressure, in units of 10. -1 MPa; This refers to the bottom hole flowing pressure, in units of 10. - 1 MPa; is the starting pressure gradient of the i-th layer, in MPa / cm; L is the average well spacing, in cm; Let be the apparent viscosity of the i-th layer of oil-water two-phase fluid, in mPa·s; The apparent viscosity of the i-th layer of oil-water two-phase fluid The calculation formula is: (12) In equation (12): The relative permeability of the oil phase is dimensionless. The viscosity is the oil phase viscosity, in mPa·s. The relative permeability of the aqueous phase is dimensionless. The viscosity of the aqueous phase is expressed in mPa·s.

[0008] S6. Based on the values ​​calculated by the single-layer production model of multi-layer heterogeneous oil reservoir considering the starting pressure gradient established in step S5, determine whether each oil layer of the target well can be effectively utilized. Specifically, the following steps are included: S61. By querying the logarithmic permeability of each oil layer in the target well. The formulas for calculating the standardized start-up pressure gradient (Equation 7), the standardized logarithmic permeability (Equation 8), and the characterization model of start-up pressure gradient and permeability (Equation 9) were compiled and the relationship between start-up pressure gradient and permeability was derived. The start-up pressure gradient corresponding to each oil layer was then obtained. ; The starting pressure gradient corresponding to each oil layer The calculation formula is: (13) In equation (13): This represents the starting pressure gradient for each oil layer, in MPa / cm. The standard deviation of the initiating pressure gradient is dimensionless. The standard deviation of the logarithmic penetration rate is dimensionless. This is the average logarithmic permeability, in mD. The average starting pressure gradient is expressed in MPa / cm; a and b are fitting parameters. S62. Obtain the current formation pressure of the target well based on reservoir production data. Bottom hole flowing pressure And the average well spacing L, through the starting pressure gradient corresponding to each oil layer in step S61. The calculation formula calculates the starting pressure gradient corresponding to each oil layer under the current production pressure differential conditions. Does the oil reservoir meet the activation conditions? like The oil layer is usable; like This oil layer cannot be touched; The production pressure differential is the formation pressure. With bottom hole flowing pressure The difference, i.e. .

[0009] S7. Establish a stratification reorganization chart that takes into account the initiation pressure gradient; Specifically, the following steps are included: S71. Calculate the current production pressure differential start-up pressure gradient. ; The current production pressure differential start-up pressure gradient The calculation formula is: (14) In equation (13): The starting pressure gradient is based on the current production pressure differential, in MPa / cm. Formation pressure, in MPa; ρ represents the bottom hole flowing pressure, in MPa; L represents the average well spacing, in cm. S72. In a Cartesian coordinate system, establish a plane Cartesian coordinate system with the standardized logarithmic permeability as the X-axis and the standardized start-up pressure gradient as the Y-axis. Plot the curve showing the relationship between the start-up pressure gradient and permeability, and then plot the current production pressure differential and start-up pressure gradient. The calculation formula yields the current production pressure differential, and the starting pressure gradient is introduced onto the chart. The permeability corresponding to the intersection of this gradient and the curve is the current production pressure differential. Under these conditions, the minimum penetration rate K required for effective activation is... min ; S8. Based on the hierarchical restructuring diagram, perform hierarchical restructuring.

[0010] Specifically, the following steps are included: S81. Set the maximum number of groups m for the starting pressure gradient; m is usually divided based on actual production needs, such as distinguishing between thin and thick layers; distinguishing between low-permeability layers and high-permeability layers, etc. S82. When m=1, based on the diagram from step S7, determine the production pressure difference ( Under these conditions, the minimum permeability K that can be effectively utilized min It will be greater than K min All sub-layers are treated as a single development layer system; S83. When m>1, the production pressure difference ( Under these conditions, the permeability is greater than the minimum effective utilization rate K. min All the smaller layers are used as the first set of development layers, and then the current production pressure differential is used to start the pressure gradient. With maximum starting pressure gradient Each part is divided into m-1 parts, corresponding to the second to the mth development layers.

[0011] The beneficial effects of this invention are: This invention provides a reservoir-based differentiated utilization and layer reorganization optimization method based on the starting pressure gradient, achieving vertical balanced displacement and significantly improving waterflood development. This invention proposes a dynamic matching theory of "pressure difference-permeability," overcoming the limitations of existing technologies that only consider static permeability differences. It establishes a quantitative relationship model between production pressure difference and starting pressure gradient, revealing the dynamic utilization patterns of high and low permeability reservoirs under different pressure difference conditions, thus solving the key technical bottleneck of traditional methods' inability to predict interlayer interference during actual production. Furthermore, it establishes a subdivided layer intelligent decision-making map, constructing a three-dimensional optimization map integrating permeability differences, crude oil viscosity, and starting pressure gradient based on massive reservoir simulation data and machine learning algorithms. This represents a technological leap from "empirical division" to "quantitative optimization," fundamentally changing the "extensive synergistic production" development model of offshore oilfields. The results of this invention's subdivided layer analysis are more reasonable and reliable. Attached Figure Description

[0012] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a graph showing the relationship between the starting pressure gradient and permeability in Embodiment 1 of the present invention; Figure 3 This is a graph showing the change in the yield of different sublayers over time in Example 1 of the present invention; Figure 4 This is a permeability boundary chart of the subdivided layers in Embodiment 1 of the present invention.

[0013] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation

[0014] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0015] Example 1 like Figure 1 As shown, a differentiated mobilization and stratigraphic reorganization optimization method for multi-layered complex reservoirs based on the initiation pressure gradient includes the following steps: S1. Collect rock cores and conduct the initiation pressure gradient experiment; Experiments were conducted using core samples from different sub-layers and with varying physical properties within the main production stratigraphic layer. The specific experimental method is as follows: Before the experiment, the core length L was measured. The core was then saturated with crude oil under high pressure. One end was sealed and a pressure gauge was inserted as the measuring end. After the system pressure reached equilibrium and stabilized, the pressure at the venting end of the core was reduced by 0.1 MPa, and the pressure change at the measuring end was observed over 30 minutes. If no change was observed, the above steps were repeated, again reducing the pressure at the venting end by 0.1 MPa and observing the pressure at the measuring end, until a change in the pressure at the measuring end was observed. The cumulative change in pressure at the venting end was recorded. The starting pressure gradient of the test core can then be obtained.

[0016] The starting pressure gradient test was repeated three times for each core sample, and the average value was taken as the starting pressure gradient of that core sample.

[0017] In this embodiment, typical wells A-1 / A-2 / A-3 in the Bohai A oilfield were selected. Based on logging parameters, the thickness and permeability of the oil-bearing layers encountered in typical well sections of each well were determined. The starting pressure gradient values ​​under different reservoir properties were determined by the unsteady-state method, as shown in Table 1.

[0018] Table 1: Thickness and permeability of typical oil-bearing formations encountered during well drilling S2. Cleaning Step: S1 starts the test data of the pressure gradient experiment and removes outliers in the dataset. Specifically, the starting pressure gradient data obtained from the tests of typical wells A-1 / A-2 / A-3 in the Bohai A oilfield in the example were sorted in ascending order. The first quartile (Q1) and the third quartile (Q3) were the numbers at the 25th and 75th percentiles, respectively. Let the interquartile range be the difference between the third quartile and the first quartile, IQR = Q3 - Q1. Then, the values ​​between Q3 + 1.5 (IQR) and Q1 - 1.5 (IQR) are the acceptable values. Values ​​outside these two ranges are outliers and are removed.

[0019] S3. Standardize the starting pressure gradient and permeability data of different dimensions to bring all data to the same scale. Specifically, the following steps are included: S31. Perform a logarithmic transformation on the permeability data. The transformation formula is as follows: (2) In formula (2): Logarithmic penetration rate, in mD; This represents the cumulative change in vent pressure, expressed in mD. S32. Calculate the average starting pressure gradient. Standard deviation of starting pressure gradient S R Log average penetration rate and the standard deviation of log permeability S K ; The average value of the starting pressure gradient The calculation formula is: (3) In formula (3): The average value of the starting pressure gradient is expressed in MPa / cm. denoted as the initiation pressure gradient of the i-th core sample, in MPa / cm; n represents the total number of core samples tested. The standard deviation of the starting pressure gradient S R The calculation formula is: (4) In equation (4): The standard deviation of the initiating pressure gradient is dimensionless. The average value of the starting pressure gradient is expressed in MPa / cm. denoted as the initiation pressure gradient of the i-th core sample, in MPa / cm; n represents the total number of core samples tested. The formula for calculating the average logarithmic permeability is as follows: (5) In equation (5): This is the average logarithmic permeability, in mD. denoted as logarithmic permeability of the i-th core sample, in mD; n represents the total number of core samples tested. The formula for calculating the standard deviation of the logarithmic permeability is as follows: (6) In formula (6): The standard deviation of the logarithmic penetration rate is dimensionless. This is the average logarithmic permeability, in mD. denoted as logarithmic permeability of the i-th core sample, in mD; n represents the total number of core samples tested. S33. Standardize the starting pressure gradient and log permeability data; The formula for calculating the standardized start-up pressure gradient is: (7) In equation (7): The initiation pressure gradient is standardized and dimensionless. The average value of the starting pressure gradient is expressed in MPa / cm. The starting pressure gradient of the i-th core sample is expressed in MPa / cm. The standard deviation of the initiating pressure gradient is dimensionless. The formula for calculating the standardized logarithmic penetration rate is as follows: (8) In equation (8): The standardized logarithmic penetration rate is dimensionless. The standard deviation of the logarithmic penetration rate is dimensionless. This is the average logarithmic permeability, in mD. Let be the logarithmic permeability of the i-th core sample, in mD; Through standardized calculations, the starting pressure gradient and permeability test data of typical wells A-1 / A-2 / A-3 in the Bohai A oilfield of the example were transformed into dimensionless data with a mean of 0 and a standard deviation of 1.

[0020] S4. Establish a characterization model of the starting pressure gradient and permeability; Specifically, the following steps are included: S41. The data preprocessed in step S3 is randomly divided into a 70% training set and a 30% test set. The training set is used to apply the linear regression analysis algorithm, and the test set is used to evaluate the model performance. S42. In a rectangular coordinate system, with the standardized logarithmic permeability as the X-axis and the standardized starting pressure gradient as the Y-axis, establish a plane rectangular coordinate system and use a linear regression analysis algorithm to establish a characterization model of the starting pressure gradient and permeability. The characterization model of the initiation pressure gradient and permeability is as follows: (9) In equation (9): The initiation pressure gradient is standardized and dimensionless. The standardized logarithmic penetration rate is dimensionless; a and b are fitting parameters. S43. Substitute the standardized log permeability data of the test set into the characterization model of the starting pressure gradient and permeability, and calculate the coefficient of determination, which reflects the accuracy of the model prediction. The formula for calculating the determination coefficient of the characterization model is as follows: (10) In formula (10): The coefficients of determination characterize the model and are dimensionless. The standardized startup pressure gradient for the test set, in MPa; The standardized initiation pressure gradient predicted by the model is expressed in MPa. is the normalized average starting pressure gradient of the test set, in MPa; m is the amount of test set data. S44. When the determination coefficient of the representation model When the value is greater than 0.8, the model can well characterize the correlation between the initiation pressure gradient and the permeability. When 0.6 < When the value is less than 0.8, the model can effectively characterize the correlation between the initiation pressure gradient and permeability. when When the gradient is less than 0.6, the correlation between the starting pressure gradient and the permeability of the sample is poor, and it is necessary to check whether the original data is reasonable.

[0021] This embodiment selects three typical wells and typical layers for testing, and uses fitting as... Figure 2 As shown, where a = -0.6185, b = 0.6662, =0.8635 reflects that the model can well characterize the correlation between the initiation pressure gradient and permeability; S5. Based on the characterization model of starting pressure gradient and permeability, and according to Darcy's law, establish a single-layer production model for multi-layer heterogeneous reservoirs that considers the starting pressure gradient. The single-layer production model for multi-layer heterogeneous reservoirs considering the initiation pressure gradient is as follows: (11) In equation (11): This represents the liquid production rate of the i-th layer, in units of 10. -3 cm 3 / s; The permeability of the i-th layer is expressed in mD. The cross-sectional area of ​​the i-th layer is expressed in cm. 2 ; Formation pressure, in units of 10. -1 MPa; This refers to the bottom hole flowing pressure, in units of 10. - 1 MPa; is the starting pressure gradient of the i-th layer, in MPa / cm; L is the average well spacing, in cm; Let be the apparent viscosity of the i-th layer of oil-water two-phase fluid, in mPa·s; The apparent viscosity of the i-th layer of oil-water two-phase fluid The calculation formula is: (12) In equation (12): The relative permeability of the oil phase is dimensionless. The viscosity is the oil phase viscosity, in mPa·s. The relative permeability of the aqueous phase is dimensionless. The viscosity of the aqueous phase is expressed in mPa·s.

[0022] In this embodiment, four representative reservoir properties were selected, with permeabilities of 20mD, 50mD, 120mD, and 180mD, respectively. Based on the established model, the changes in production volume of each layer were obtained, such as... Figure 3 As shown: This indicates that after water is encountered in a high-permeability layer, the flowing pressure increases, which leads to a decrease in the production pressure differential of the relatively low-permeability layer and a reduction in output. When the production pressure differential is less than the starting pressure of a certain layer, that layer is not effectively utilized. In order to improve the utilization of layers with poor physical properties, layers belonging to different systems should be utilized to ensure that the same set of layers can start more layers with the same production pressure differential.

[0023] S6. Based on the values ​​calculated by the single-layer production model of multi-layer heterogeneous oil reservoir considering the starting pressure gradient established in step S5, determine whether each oil layer of the target well can be effectively utilized. Specifically, the following steps are included: S61. By querying the logarithmic permeability of each oil layer in the target well. The formulas for calculating the standardized start-up pressure gradient (Equation 7), the standardized logarithmic permeability (Equation 8), and the characterization model of start-up pressure gradient and permeability (Equation 9) were compiled and the relationship between start-up pressure gradient and permeability was derived. The start-up pressure gradient corresponding to each oil layer was then obtained. ; The starting pressure gradient corresponding to each oil layer The calculation formula is: (13) In equation (13): This represents the starting pressure gradient for each oil layer, in MPa / cm. The standard deviation of the initiating pressure gradient is dimensionless. The standard deviation of the logarithmic penetration rate is dimensionless. This is the average logarithmic permeability, in mD. The average starting pressure gradient is expressed in MPa / cm; a and b are fitting parameters. S62. Obtain the current formation pressure of the target well based on reservoir production data. Bottom hole flowing pressure And the average well spacing L, through the starting pressure gradient corresponding to each oil layer in step S61. The calculation formula calculates the starting pressure gradient corresponding to each oil layer under the current production pressure differential conditions. Does the oil reservoir meet the activation conditions? like The oil layer is usable; like This oil layer cannot be touched; The production pressure differential is the formation pressure. With bottom hole flowing pressure The difference, i.e. .

[0024] S7. Establish a stratification reorganization chart that takes into account the initiation pressure gradient; Specifically, the following steps are included: S71. Calculate the current production pressure differential start-up pressure gradient. ; The current production pressure differential start-up pressure gradient The calculation formula is: (14) In equation (13): The starting pressure gradient is based on the current production pressure differential, in MPa / cm. Formation pressure, in MPa; ρ represents the bottom hole flowing pressure, in MPa; L represents the average well spacing, in cm. S72. In a rectangular coordinate system, establish a plane rectangular coordinate system with permeability as the X-axis and the starting pressure gradient as the Y-axis. Plot the curve showing the relationship between the starting pressure gradient and permeability, and set the current production pressure difference and starting pressure gradient as the plotting parameters. The calculation formula yields the current production pressure differential, and the starting pressure gradient is introduced onto the chart. The permeability corresponding to the intersection of this gradient and the curve is the current production pressure differential. Under these conditions, the minimum penetration rate K required for effective activation is... min ; In this embodiment, a Cartesian coordinate system is established based on actual data, and a curve showing the relationship between the starting pressure gradient and permeability is plotted. Figure 4 ).

[0025] S8. Based on the hierarchical restructuring diagram, perform hierarchical restructuring.

[0026] Specifically, the following steps are included: S81. Set the maximum number of groups m for the starting pressure gradient; S82. When m=1, based on the diagram from step S7, determine the production pressure difference ( Under these conditions, the minimum permeability K that can be effectively utilized min It will be greater than K minAll sub-layers are treated as a single development layer system; S83. When m>1, the production pressure difference ( Under these conditions, the permeability is greater than the minimum effective utilization rate K. min All the smaller layers are used as the first set of development layers, and then the current production pressure differential is used to start the pressure gradient. With maximum starting pressure gradient Each part is divided into m-1 parts, corresponding to the second to the mth development layers.

[0027] In this embodiment, the target layer encountered a deep, inclined well section from 3717 meters to 3998 meters. The reservoir properties of the oil layer ranged from 12.2 mD to 755 mD, exhibiting strong heterogeneity. The minimum permeability of the target layer was 12.2 mD, and according to the chart, the maximum permeability that could ensure effective utilization of the entire well section was 113.1 mD. Therefore, the oil layer with permeability between 12.2 and 113.1 mD was developed as one set of layers, and the remaining oil layers with properties greater than 113.1 mD were developed as a second set of layers (as shown in Table 2).

[0028] Table 2: Detailed Layer Description of the Embodiments The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A reservoir differential activation and stratigraphic reorganization optimization method based on initiation pressure gradient, characterized in that: S1. Collect rock cores and conduct the initiation pressure gradient experiment; S2. Cleaning Step: S1 starts the test data of the pressure gradient experiment and removes outliers in the dataset. S3. Standardize the pressure gradient and permeability data. S4. Establish a characterization model of the starting pressure gradient and permeability; S5. Based on the characterization model of starting pressure gradient and permeability, and according to Darcy's law, establish a single-layer production model for multi-layer heterogeneous reservoirs that considers the starting pressure gradient. S6. Based on the values ​​calculated by the single-layer production model of multi-layer heterogeneous oil reservoir considering the starting pressure gradient established in step S5, determine whether each oil layer of the target well can be effectively utilized. S7. Establish a stratification reorganization chart that takes into account the initiation pressure gradient; S8. Based on the hierarchical restructuring diagram, perform hierarchical restructuring.

2. The reservoir differential activation and stratigraphic reorganization optimization method based on the starting pressure gradient according to claim 1, characterized in that: The core samples were selected from the main production layers, as well as core samples from different sublayers and with different physical properties.

3. The reservoir differential activation and stratigraphic reorganization optimization method based on the starting pressure gradient according to claim 1, characterized in that: The specific experimental method for the initiation pressure gradient experiment is as follows: S11. Measure the core length L; S12. Saturate the core with crude oil under high pressure; S13. Close one end and install a pressure gauge as the pressure measuring end. After the system pressure is balanced and stable, reduce the pressure value at the core venting end by 0.1 MPa and observe the change in pressure at the pressure measuring end within 30 minutes. S14. If the pressure at the measuring end does not change within 30 minutes, repeat step S13 until the pressure at the measuring end changes, and record the cumulative change in the venting end pressure. ; S15. Calculate the starting pressure gradient of the core. The formula for calculating the starting pressure gradient is: （1） In formula (1): The pressure gradient is set to MPa / cm. The cumulative change in pressure at the venting end is expressed in MPa; L is the core length, expressed in cm. S16. Repeat the starting pressure gradient test three times for each core sample, and take the average of the three starting pressure gradients as the starting pressure gradient of the core sample.

4. The reservoir differential activation and stratigraphic reorganization optimization method based on the starting pressure gradient according to claim 1, characterized in that: The specific method for removing outliers in step S2 is as follows: After sorting the test-obtained starting pressure gradient data in ascending order, the first quartile Q1 and the third quartile Q3 are the numbers located at the 25th and 75th percentiles after sorting, respectively; let the interquartile range be the difference between the third quartile and the first quartile, IQR = Q3 - Q1. Then the values ​​between Q3 + 1.5·IQR and Q1 - 1.5·IQR are the values ​​within the acceptable range. Numbers outside these two values ​​are outliers and are removed.

5. The reservoir differential activation and stratigraphic reorganization optimization method based on the starting pressure gradient according to claim 1, characterized in that: The standardization process in step S3 specifically includes the following steps: S31. Perform a logarithmic transformation on the permeability data. The transformation formula is as follows: （2） In formula (2): Logarithmic penetration rate, in mD; This represents the cumulative change in vent pressure, expressed in mD. S32. Calculate the average starting pressure gradient. Standard deviation of starting pressure gradient S R Log average penetration rate and the standard deviation of log permeability S K ; The average value of the starting pressure gradient The calculation formula is: （3） In formula (3): The average value of the starting pressure gradient is expressed in MPa / cm. denoted as the initiation pressure gradient of the i-th core sample, in MPa / cm; n represents the total number of core samples tested. The standard deviation of the starting pressure gradient S R The calculation formula is: （4） In equation (4): The standard deviation of the initiating pressure gradient is dimensionless. The average value of the starting pressure gradient is expressed in MPa / cm. denoted as the initiation pressure gradient of the i-th core sample, in MPa / cm; n represents the total number of core samples tested. The formula for calculating the average logarithmic permeability is as follows: （5） In formula (5): This is the average logarithmic permeability, in mD. denoted as logarithmic permeability of the i-th core sample, in mD; n represents the total number of core samples tested. The formula for calculating the standard deviation of the logarithmic permeability is as follows: （6） In formula (6): The standard deviation of the logarithmic penetration rate is dimensionless. This is the average logarithmic permeability, in mD. denoted as logarithmic permeability of the i-th core sample, in mD; n represents the total number of core samples tested. S33. Standardize the starting pressure gradient and log permeability data; The formula for calculating the standardized start-up pressure gradient is: （7） In equation (7): The initiation pressure gradient is standardized and dimensionless. The average value of the starting pressure gradient is expressed in MPa / cm. The starting pressure gradient of the i-th core sample is expressed in MPa / cm. The standard deviation of the initiating pressure gradient is dimensionless. The formula for calculating the standardized logarithmic penetration rate is as follows: （8） In equation (8): The standardized logarithmic penetration rate is dimensionless. The standard deviation of the logarithmic penetration rate is dimensionless. This is the average logarithmic permeability, in mD. Let be the logarithmic permeability of the i-th core sample, expressed in mD.

6. The reservoir differential activation and stratigraphic reorganization optimization method based on the starting pressure gradient according to claim 1, characterized in that: Step S4, establishing the characterization model of the initiation pressure gradient and permeability, specifically includes the following steps: S41. The data preprocessed in step S3 is randomly divided into a 70% training set and a 30% test set. The training set is used to apply the linear regression analysis algorithm, and the test set is used to evaluate the model performance. S42. In a rectangular coordinate system, with the standardized logarithmic permeability as the X-axis and the standardized starting pressure gradient as the Y-axis, establish a plane rectangular coordinate system and use a linear regression analysis algorithm to establish a characterization model of the starting pressure gradient and permeability. The characterization model of the initiation pressure gradient and permeability is as follows: （9） In equation (9): The initiation pressure gradient is standardized and dimensionless. The standardized logarithmic penetration rate is dimensionless; a and b are fitting parameters. S43. Substitute the standardized log permeability data of the test set into the characterization model of the starting pressure gradient and permeability, and calculate the coefficient of determination, which reflects the accuracy of the model prediction. The formula for calculating the determination coefficient of the characterization model is as follows: （10） In formula (10): The coefficients of determination characterize the model and are dimensionless. The standardized startup pressure gradient for the test set, in MPa; The standardized initiation pressure gradient predicted by the model is expressed in MPa. is the normalized average starting pressure gradient of the test set, in MPa; m is the amount of test set data. S44. Determine the effectiveness of the characterization model of the starting pressure gradient and permeability based on the coefficient of determination of the characterization model; When the determination coefficient of the representation model When the gradient is greater than 0.8, the model can well characterize the correlation between the initiation pressure gradient and permeability; when the gradient is less than 0.6... When <0.8, the model can well characterize the correlation between the initiation pressure gradient and permeability; when When the gradient is less than 0.6, the correlation between the starting pressure gradient and the permeability of the sample is poor, and it is necessary to check whether the original data is reasonable.

7. The reservoir differential activation and stratigraphic reorganization optimization method based on the starting pressure gradient according to claim 1, characterized in that: The single-layer production model for multi-layer heterogeneous reservoirs considering the initiation pressure gradient is as follows: （11） In equation (11): This represents the liquid production rate of the i-th layer, in units of 10. -3 cm 3 / s; The permeability of the i-th layer is expressed in mD. The cross-sectional area of ​​the i-th layer is expressed in cm. 2 ; Formation pressure, in units of 10. -1 MPa; This refers to the bottom hole flowing pressure, in units of 10. -1 MPa; is the starting pressure gradient of the i-th layer, in MPa / cm; L is the average well spacing, in cm; Let be the apparent viscosity of the i-th layer of oil-water two-phase fluid, in mPa·s; The apparent viscosity of the i-th layer of oil-water two-phase fluid The calculation formula is: （12） In equation (12): The relative permeability of the oil phase is dimensionless. The viscosity is the oil phase viscosity, in mPa·s. The relative permeability of the aqueous phase is dimensionless. The viscosity of the aqueous phase is expressed in mPa·s.

8. The reservoir differential activation and stratigraphic reorganization optimization method based on the starting pressure gradient according to claim 1, characterized in that: Step S6 specifically includes the following steps: S61. By querying the logarithmic permeability of each oil layer in the target well. The formulas for calculating the standardized start-up pressure gradient (Equation 7), the standardized logarithmic permeability (Equation 8), and the characterization model of start-up pressure gradient and permeability (Equation 9) were compiled and the relationship between start-up pressure gradient and permeability was derived. The start-up pressure gradient corresponding to each oil layer was then obtained. ; The starting pressure gradient corresponding to each oil layer The calculation formula is: （13） In equation (13): This represents the starting pressure gradient for each oil layer, in MPa / cm. The standard deviation of the initiating pressure gradient is dimensionless. The standard deviation of the logarithmic penetration rate is dimensionless. This is the average logarithmic permeability, in mD. The average starting pressure gradient is expressed in MPa / cm; a and b are fitting parameters. S62. Obtain the current formation pressure of the target well based on reservoir production data. Bottom hole flowing pressure And the average well spacing L, through the starting pressure gradient corresponding to each oil layer in step S61. The calculation formula calculates the starting pressure gradient corresponding to each oil layer under the current production pressure differential conditions. Does the oil reservoir meet the activation conditions? like The oil layer is usable; like This oil layer cannot be touched; The production pressure differential is the formation pressure. With bottom hole flowing pressure The difference, i.e. .

9. The reservoir differential activation and stratigraphic reorganization optimization method based on the starting pressure gradient according to claim 1, characterized in that: Step S7, establishing a stratification remodeling pattern that considers the initiation pressure gradient, specifically includes the following steps: S71. Calculate the current production pressure differential start-up pressure gradient. ; The current production pressure differential start-up pressure gradient The calculation formula is: （14） In equation (13): The starting pressure gradient is based on the current production pressure differential, in MPa / cm. Formation pressure, in MPa; ρ represents the bottom hole flowing pressure, in MPa; L represents the average well spacing, in cm. S72. In a Cartesian coordinate system, establish a plane Cartesian coordinate system with the standardized logarithmic permeability as the X-axis and the standardized start-up pressure gradient as the Y-axis. Plot the curve showing the relationship between the start-up pressure gradient and permeability, and assign the current production pressure differential and start-up pressure gradient to the appropriate values. The calculation formula yields the current production pressure differential, and the starting pressure gradient is introduced onto the chart. The permeability corresponding to the intersection of this gradient and the curve is the current production pressure differential. Under these conditions, the minimum penetration rate K required for effective activation is... min .

10. The reservoir differential activation and stratigraphic reorganization optimization method based on the starting pressure gradient according to claim 1, characterized in that: Step S8, performing layer reorganization based on the layer reorganization diagram, specifically includes the following steps: S81. Set the maximum number of groups m for the starting pressure gradient; S82. When m=1, based on the diagram from step S7, determine the production pressure difference ( Under these conditions, the minimum permeability K that can be effectively utilized min It will be greater than K min All sub-layers are treated as a single development layer system; S83. When m>1, the production pressure difference ( Under these conditions, the permeability is greater than the minimum effective utilization rate K. min All the smaller layers are used as the first set of development layers, and then the current production pressure differential is used to start the pressure gradient. With maximum starting pressure gradient Each part is divided into m-1 parts, corresponding to the second to the mth development layers.

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