Optimized production method for strong heterogeneous carbonate gas reservoir

Abstract

This invention discloses an optimized production allocation method for highly heterogeneous carbonate gas reservoirs, comprising: 1. Calculating the initial production capacity of the gas well; 2. Obtaining the original formation pressure before production and the production dynamic data after production, including the well oil pressure and stable production rate; 3. Obtaining the shut-in pressure of the gas well and identifying the reservoir type; 4. Calculating the dynamic reserves of the gas well based on the original formation pressure, production dynamic data, and shut-in pressure; 5. Plotting the dynamic reserves and stable production rate of the gas well and performing linear regression to determine whether the linear relationship between the dynamic reserves and stable production rate is within a set range; if so, proceeding to step 6; 6. Plotting the initial production capacity and dynamic reserves of the gas well, and performing linear regression on gas wells with different reservoir types to obtain the production allocation coefficients under different reservoir types, and optimizing the production allocation based on the production allocation coefficients and the initial production capacity of the gas well. This invention can more effectively determine the reasonable production allocation for gas wells.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration and development technology, and in particular relates to an optimized production method for highly heterogeneous carbonate gas reservoirs. Background Technology

[0002] Optimized gas well production allocation is one of the core tasks in the early and mid-stages of gas field development, aiming to ensure that gas field development meets relevant management requirements. Optimized gas well production allocation needs to comprehensively consider the balance between economic, social, and resource benefits based on factors such as reservoir size, reservoir type, and resource replacement capacity. It should be based on a certain level of economic benefit to meet the social demand for natural gas supply and maximize the extraction of underground natural gas resources.

[0003] Optimized production allocation for gas wells begins with the acquisition of geological data. The main idea is to find the optimal production target under certain economic and technical constraints, given a basic understanding of indicators such as gas well productivity and dynamic reserves. Figure 5 As shown, gas well optimization and production allocation are currently mainly based on experience and supplemented by science. It generally combines geological understanding and analogy with similar gas reservoirs to organize production at 1 / 6 to 1 / 3 of the absolute unobstructed flow rate. However, this production allocation method often lacks clear basis, resulting in an accuracy rate of only about 70%.

[0004] In addition, for low-permeability, highly heterogeneous gas reservoirs, there is a large difference between the early absolute unobstructed flow rate and the stable absolute unobstructed flow rate of the gas well, and 35% to 50% of the recoverable reserves can only be extracted during a long decline period. Therefore, how to allocate production at the optimal rate after the gas well is put into production has become a technical problem that needs to be solved.

[0005] Patent document CN111911115A discloses a dynamic production allocation method for shale gas wells, comprising: Step 1, constructing a single-well material balance equation for the shale gas well; Step 2, based on the actual reservoir properties of the shale gas well and combined with the material balance equation established in Step 1, establishing a relationship function between cumulative gas production and formation pressure; Step 3, calculating the cumulative gas production based on the current formation pressure; Step 4, establishing a binomial production capacity equation through production testing, and allocating production based on unobstructed flow rate; Step 5, drawing a chart of cumulative gas production versus formation pressure and single-well production allocation based on the production allocation results obtained in Step 4; Step 6, selecting the chart based on the cumulative gas production of different reservoirs in the shale gas well for production allocation. This method allows for rapid determination of a reasonable production allocation during gas well production by referring to the chart based on the well's current cumulative gas production. However, this method is applicable to shale gas reservoirs. Because the seepage of shale gas reservoirs differs from that of strongly heterogeneous carbonate gas reservoirs, this method cannot be applied to strongly heterogeneous carbonate gas reservoirs.

[0006] Furthermore, this method allocates production based on current production change information, without considering the influence of reservoir type, and cannot describe the relationship between current production allocation and dynamic gas well reserves. Therefore, its effect on optimizing production allocation is still poor. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned technical problems existing in the prior art and to provide an optimized production allocation method for highly heterogeneous carbonate gas reservoirs. This invention can more effectively determine the reasonable production allocation of gas wells.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] An optimized production method for highly heterogeneous carbonate gas reservoirs includes the following steps:

[0010] Step 1: Calculate the initial production capacity of the gas well based on the well testing data;

[0011] Step 2: Based on the conventional well test data of the gas well, obtain the original formation pressure before the gas well is put into production and the production dynamic data after production. The obtained production dynamic data includes the gas well oil pressure and stable production.

[0012] Step 3: Obtain the shut-in pressure of the gas well based on the special well test data of the gas well, and identify the reservoir type based on the interpretation results of the shut-in pressure recovery data;

[0013] Step 4: Calculate the dynamic reserves of the gas well based on the original formation pressure, production dynamic data, and shut-in pressure;

[0014] Step 5: Based on the dynamic reserves and stable production of gas wells, draw a chart of dynamic reserves and stable production of gas wells and perform linear regression to determine whether the linear relationship between dynamic reserves and stable production of gas wells is within the set range; if it is within the set range, proceed to step 6.

[0015] Step 6: Draw a graph of the initial production capacity and dynamic reserves of the gas well based on the initial production capacity and dynamic reserves of the gas well. Perform linear regression on the gas wells of different reservoir types based on the graph of the initial production capacity and dynamic reserves of the gas well to obtain the production allocation coefficient under different reservoir types. Optimize the production allocation based on the production allocation coefficient and the initial production capacity of the gas well.

[0016] In step 4, the dynamic reserves of the gas well are calculated using the material balance method based on the original formation pressure, production dynamic data, and shut-in pressure.

[0017] In step 4, the method for calculating the dynamic reserves of gas wells is as follows:

[0018]

[0019] in,

[0020]

[0021] In equations (1) and (2), p is the shut-in pressure, MPa; i Z represents the original formation pressure, Z is the natural gas deviation factor, which is dimensionless; C c The comprehensive compressibility coefficient of the gas reservoir is given in MPa. -1 G represents dynamic reserves, 10 8 m 3 G p To calculate the cumulative gas production, 10 8 m 3 C p C w These are the rock and formation water compressibility coefficients, respectively, in MPa. -1 S wc To constrain water saturation, decimal.

[0022] In step 5, the following relationship is obtained after linear regression:

[0023] lgG=0.8382lgq-0.1722 (3)

[0024] In equation (3), q is the wellhead production of the gas well, 10 4 m 3 / d.

[0025] In step 6, the production allocation coefficient is calculated as follows:

[0026]

[0027] in,

[0028]

[0029]

[0030] In equations (4)-(6), n is the production coefficient, which has no dimension; q AOF，初 For the initial absolute unobstructed flow rate of the gas well, 10 4 m 3 / d.

[0031] In step 1, the initial production capacity of the gas well is calculated based on the test production and test pressure of the gas well in the oil testing data.

[0032] In step 3, identifying the reservoir type based on the interpretation results of shut-in pressure recovery data means first obtaining the reservoir flow parameters based on the shut-in pressure interpretation, and then identifying the reservoir type based on the reservoir flow parameters.

[0033] In step 3, the method for identifying the reservoir type is as follows:

[0034] (1) The reservoir type was initially identified using well logging, core description, oil testing data and reservoir stimulation data;

[0035] (2) The reservoir type identified in step (1) is further identified by reservoir flow parameters;

[0036] (3) The reliability of fine identification is verified by combining production dynamic data, and the reservoir type is obtained after verification.

[0037] In step 3, the identified reservoir types include fracture-vuggy type I, fracture-vuggy type II, pore type I, pore type II, and porous type.

[0038] In step 5, if the linear relationship between the dynamic reserves and stable production of the gas well is not within the set range, repeat steps 1-4 until the linear relationship between the dynamic reserves and stable production of the gas well is within the set range.

[0039] The advantages of using this invention are:

[0040] This invention uses linear regression results of dynamic reserves and stable production rates of gas wells to create charts depicting the initial production capacity and dynamic reserves of gas wells in different reservoir types. The production allocation ratio is then determined through linear regression analysis. This transforms the current method of optimizing gas well production allocation, which is primarily based on experience with scientific support, into a method that is primarily based on science with experience as a supplement, achieving an accuracy rate of over 90%. Furthermore, this invention improves the stable production capacity of gas wells after production allocation, with the proportion of stable-producing gas wells reaching over 95%. Therefore, this invention can more effectively determine the reasonable production allocation for gas wells, ensuring maximum output. Attached Figure Description

[0041] Figure 1 This is a flowchart of the present invention;

[0042] Figure 2 This is a schematic diagram illustrating the linear relationship between dynamic reserves and stable production of gas wells in this invention.

[0043] Figure 3 This is a schematic diagram illustrating the relationship between dynamic reserves and initial production capacity of a gas well in this invention.

[0044] Figure 4 This is a schematic diagram illustrating the optimized production allocation of gas wells, which is based primarily on scientific principles and supplemented by empirical methods, according to the present invention.

[0045] Figure 5 This diagram illustrates the optimization of gas well production allocation, which is currently based primarily on experience and supplemented by scientific methods. Detailed Implementation

[0046] This invention discloses an optimized production method for highly heterogeneous carbonate gas reservoirs, such as... Figure 1As shown, its technical solution includes the following steps:

[0047] Step 1: Obtain the well test data and calculate the initial production capacity of the gas well based on the test production and test pressure data.

[0048] Step 2: Obtain conventional well test data of the gas well. Based on the conventional well test data of the gas well, obtain the original formation pressure before the gas well is put into production and the production dynamic data after production. The obtained production dynamic data includes the gas well oil pressure and stable production.

[0049] Step 3: Obtain specialized well test data for the gas well. Based on this data, determine the shut-in pressure of the gas well and identify the reservoir type based on the interpretation results of the shut-in pressure recovery data. Identifying the reservoir type based on the interpretation results of the shut-in pressure recovery data means first interpreting the reservoir flow parameters based on the shut-in pressure, and then identifying the reservoir type based on these parameters.

[0050] Furthermore, the method for identifying reservoir types is as follows:

[0051] (1) The reservoir type was initially identified using well logging, core description, oil testing data and reservoir stimulation data.

[0052] (2) The reservoir type identified in step (1) is further identified by reservoir flow parameters.

[0053] (3) The reliability of fine identification is verified by combining production dynamic data, and the reservoir type is obtained after verification.

[0054] Because carbonate gas reservoirs are highly heterogeneous, the identified reservoir types typically include:

[0055] (1) Type I fractured-vuggy reservoir: Both inner and outer zones have good reservoirs, high permeability and no order of magnitude difference between inner and outer zones.

[0056] (2) Fractured-vuggy type II: The reservoir is good inside and bad outside. The permeability is high in the near well area but the seepage capacity in the far well area is much worse than that in the near well area. There is an order of magnitude difference in permeability between the inner and outer areas.

[0057] (3) Type I Porous Reservoir: The reservoir is poor inside and good outside, and there is no order of magnitude difference in permeability between the inner and outer zones.

[0058] (4) Type II and Porous Type: Both the inner and outer zones of the reservoir have low permeability with no order of magnitude difference.

[0059] Step 4: Calculate the dynamic reserves of the gas well using the material balance method based on the original formation pressure, production dynamic data, and shut-in pressure.

[0060] Specifically, the calculation method for dynamic reserves of gas wells is as follows:

[0061]

[0062] in,

[0063]

[0064] In equations (1) and (2), p is the shut-in pressure, MPa; i Z represents the original formation pressure, Z is the natural gas deviation factor, which is dimensionless; C c The comprehensive compressibility coefficient of the gas reservoir is given in MPa. -1 G represents dynamic reserves, 10 8 m 3 G p To calculate the cumulative gas production, 10 8 m 3 C p C w These are the rock and formation water compressibility coefficients, respectively, in MPa. -1 S wc To constrain water saturation, decimal.

[0065] Step 5: Based on the dynamic reserves and stable production of the gas well, plot the dynamic reserves and stable production of the gas well and perform linear regression to determine whether the linear relationship between the dynamic reserves and stable production of the gas well is within the set range; if the linear relationship between the dynamic reserves and stable production of the gas well is within the set range... Figure 2 If the set range is within the specified range, proceed to step 6; if the linear relationship between the dynamic reserves and stable production of the gas well is not within the specified range, repeat steps 1-4 until the linear relationship between the dynamic reserves and stable production of the gas well is within the specified range.

[0066] In this step, the linear regression yields the following relationship:

[0067] lgG=0.8382lgq-0.1722 (3)

[0068] In equation (3), q is the wellhead production of the gas well, 10 4 m 3 / d.

[0069] After obtaining the relation (3), determine whether the linear relationship between the dynamic reserves and stable production of the gas well is within the set range based on the relation (3).

[0070] Step 6: First, draw a chart of the initial production capacity and dynamic reserves of the gas well based on the initial production capacity and dynamic reserves of the gas well. The drawn chart is as follows: Figure 3 As shown, linear regression is then performed on gas wells of different reservoir types based on the chart of initial gas well production capacity and dynamic gas well reserves to obtain the production allocation coefficient under different reservoir types. Finally, production allocation is optimized based on the production allocation coefficient and the initial gas well production capacity.

[0071] Specifically, the calculation method for the production allocation coefficient is as follows:

[0072]

[0073] in,

[0074]

[0075]

[0076] In equations (4)-(6), n is the production coefficient, which has no dimension; q AOF，初 For the initial absolute unobstructed flow rate of the gas well, 10 4 m 3 / d.

[0077] The method described in this invention, after being developed and designed by the applicant, has undergone years of experimentation and verification with numerous practical data. It is now effectively applicable to gas wells and can yield accurate production results. The following practical verification method is provided to validate this invention:

[0078] Verification conditions: Well GS001-X4 in the Dengsiqiang heterogeneous carbonate gas reservoir in the Sichuan Basin.

[0079] Verification process:

[0080] Step 1: First, obtain the well test data. The daily natural gas production of well GS001-X4 is 108.33 × 10⁻⁶. 4 m 3 With a stable oil pressure of 31.48 MPa per day, the initial production capacity of this well is calculated to be 180 × 10⁶ MPa. 4 m 3 / d.

[0081] Step 2: Based on the conventional well test data of the gas well, the original formation pressure before production was obtained as 56.64 MPa. Production dynamic data after production was recorded, with an initial oil pressure of 42.15 MPa and an initial stable production rate of 30 × 10⁻⁶ MPa. 4 m 3 The dynamic data from the / d recording shows that both oil pressure and output are gradually decreasing and cannot be stabilized.

[0082] Step 3: Obtain the shut-in pressure of the gas well based on the specialized well test data. Based on the shut-in pressure recovery data, interpret the permeability of the near and far well areas as 0.079 × 10⁻⁶. -3 μm 2 and 8.06×10 -3 μm 2 The reservoir type was determined to be type II fractured-vuggy reservoir.

[0083] Step 4: Based on the original formation pressure of 56.64 MPa, the shut-in pressure of the special well test of 30.70 MPa, and the cumulative gas production of 1.02 × 10⁻⁶ MPa... 8 m 3 The calculated dynamic reserves of the gas well are 3.01 × 10⁻⁶. 8 m 3 .

[0084] Step 5: Based on the initial production capacity and dynamic reserves of the gas well, draw a chart of the initial production capacity and dynamic reserves of the gas well. Determine the production allocation coefficient, which should be 10-21. Take 12-15 and optimize the production allocation to 12-15×10. 4 m 3 / d.

[0085] Verification results: Gas well production optimized to 12-15 × 10⁻⁶ 4 m 3 / d, production and oil pressure stabilized, then increased to 15×10 4 m 3 Stable production is maintained at a stable oil pressure of 15MPa per day.

[0086] In summary, this invention uses linear regression results of dynamic reserves and stable production of gas wells to create charts depicting the initial production capacity and dynamic reserves of gas wells in different reservoir types. Production allocation is then determined through linear regression diagrams to optimize gas well production. This essentially transforms the existing gas well optimization method, which is primarily based on experience and supplemented by scientific methods, into a more efficient approach. Figure 4 The gas well optimization production allocation method shown in this invention, which is based on scientific principles and supplemented by experience, has an accuracy rate of over 90%. Furthermore, after adopting this invention, the stable production capacity of gas wells after production allocation can be improved, and the proportion of stable production gas wells can reach over 95%. Therefore, this invention can more effectively determine the reasonable production allocation of gas wells.

[0087] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All features or steps in the disclosed methods or processes may be combined in any way, except for mutually exclusive features and / or steps.

Claims

1. A method for optimizing production allocation in a strongly heterogeneous carbonate gas reservoir, characterized in that Includes the following steps: Step 1: Calculate the initial production capacity of the gas well based on the well testing data; Step 2: Based on the conventional well test data of the gas well, obtain the original formation pressure before the gas well is put into production and the production dynamic data after production. The obtained production dynamic data includes the gas well oil pressure and stable production. Step 3: Obtain the shut-in pressure of the gas well based on the special well test data of the gas well, and identify the reservoir type based on the interpretation results of the shut-in pressure recovery data; Step 4: Calculate the dynamic reserves of the gas well based on the original formation pressure, production dynamic data, and shut-in pressure; Step 5: Based on the dynamic reserves and stable production of gas wells, draw a chart of dynamic reserves and stable production of gas wells and perform linear regression to determine whether the linear relationship between dynamic reserves and stable production of gas wells is within the set range; if it is within the set range, proceed to step 6. Step 6: Draw a chart of the initial production capacity and dynamic reserves of the gas well based on the initial production capacity and dynamic reserves of the gas well. Perform linear regression on the gas wells of different reservoir types based on the chart of the initial production capacity and dynamic reserves of the gas well to obtain the production allocation coefficient under different reservoir types. Optimize the production allocation based on the production allocation coefficient and the initial production capacity of the gas well. In step 4, the dynamic reserves of the gas well are calculated using the material balance method based on the original formation pressure, production dynamic data, and shut-in pressure. In step 4, the method for calculating the dynamic reserves of gas wells is as follows: （1） in, （2） In equations (1) and (2), p The shut-in pressure is in MPa. p i The original formation pressure, Z This is the natural gas deviation factor, which is dimensionless. The comprehensive compressibility coefficient of the gas reservoir is given in MPa. -1 ; G For dynamic reserves, 10 8 m 3 ; G p To calculate the cumulative gas production, 10 8 m 3 ; C p , C w These are the rock and formation water compressibility coefficients, respectively, in MPa. -1 ; S wc The bound water saturation is a decimal. In step 5, the following relationship is obtained after linear regression: （3） In equation (3), q For gas wellhead production, 10 4 m 3 / d; In step 6, the production allocation coefficient is calculated as follows: （4） in, （5） （6） In equations (4)-(6), n This is the production allocation coefficient, dimensionless; q AOF，初 For the initial absolute unobstructed flow rate of the gas well, 10 4 m 3 / d.

2. The optimized production method for strongly heterogeneous carbonate gas reservoirs according to claim 1, characterized in that: In step 1, the initial production capacity of the gas well is calculated based on the test production and test pressure of the gas well in the oil testing data.

3. The optimized production method for strongly heterogeneous carbonate gas reservoirs according to claim 1, characterized in that: In step 3, identifying the reservoir type based on the interpretation results of shut-in pressure recovery data means first obtaining the reservoir flow parameters based on the shut-in pressure interpretation, and then identifying the reservoir type based on the reservoir flow parameters.

4. The optimized production method for strongly heterogeneous carbonate gas reservoirs according to claim 3, characterized in that: In step 3, the method for identifying the reservoir type is as follows: (1) The reservoir type was initially identified using well logging, core description, oil testing data and reservoir stimulation data; (2) The reservoir type identified in step (1) is further identified by reservoir flow parameters; (3) Verify the reliability of fine identification by combining production dynamic data, and then determine the reservoir type.

5. The optimized production method for strongly heterogeneous carbonate gas reservoirs according to claim 1, characterized in that: In step 3, the identified reservoir types include fracture-vuggy type I, fracture-vuggy type II, pore type I, pore type II, and porous type.

6. The optimized production method for strongly heterogeneous carbonate gas reservoirs according to claim 1, characterized in that: In step 5, if the linear relationship between the dynamic reserves and stable production of the gas well is not within the set range, repeat steps 1-4 until the linear relationship between the dynamic reserves and stable production of the gas well is within the set range.

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