Method and device for evaluating productivity of gas reservoir

Abstract

The embodiment of the invention provides a method and a device for evaluating gas reservoir productivity, the method and the device are used for a heterogeneous gas reservoir, a to-be-evaluated gas reservoir is provided with a plurality of development wells, each development well is provided with a plurality of reservoirs, the method comprises the following steps: acquiring the permeability of the reservoirs, dividing the plurality of reservoirs into a first reservoir and a second reservoir according to the permeability, the permeability of the first reservoir is greater than that of the second reservoir; according to the ratio of the first reservoir to the second reservoir, the development well is divided into a first development well and a second development well, and the ratio of the first reservoir to the second reservoir in the first development well is higher than that of the second development well; for the first development well, obtaining a first theoretical productivity of the to-be-evaluated gas reservoir by using a theoretical formula method; for the second development well, obtaining a second theoretical productivity of the to-be-evaluated gas reservoir by using a formation coefficient analogy method; and evaluating the productivity of the to-be-evaluated gas reservoir through the first theoretical productivity and / or the second theoretical productivity. The method improves the accuracy of evaluating the productivity of the gas reservoir.

Description

Technical Field

[0001] The present invention relates to the field of gas reservoir development, and in particular to a method and device for evaluating gas reservoir productivity. Background Art

[0002] Productivity evaluation is an important part of gas reservoir development. It characterizes the relationship between gas well production and bottom hole flowing pressure, and also indicates the production capacity of a single well.

[0003] Before a production well is put into production, the single-well production capacity is calculated using a theoretical formula method based on different well types. This method first requires determining multiple physical parameters of the reservoir. After production, the single-well production capacity is determined through stable production tests of different systems, which requires stable production, bottomhole pressure, and formation pressure and other important parameters.

[0004] For heterogeneous gas reservoirs, the theoretical formula method blurs the differences in production capacity under different physical properties in the same gas reservoir. The production capacity obtained is the production capacity under relatively average physical properties, which deviates greatly from the actual production capacity. Production capacity analysis often needs to be carried out before a single well is put into production and in the early stages of production in order to better formulate a reasonable production system. Summary of the Invention

[0005] The purpose of the embodiments of the present invention is to provide a method and device for evaluating gas reservoir productivity, which improves the accuracy of evaluating gas reservoir productivity.

[0006] To achieve the above objectives, an embodiment of the present invention provides a method for evaluating gas reservoir productivity, which is used for a heterogeneous gas reservoir. The gas reservoir to be evaluated has multiple development wells, each of which has multiple reservoirs. The method includes:

[0007] obtaining a permeability of the reservoir, and dividing the plurality of reservoirs into a first reservoir and a second reservoir according to the permeability, wherein the permeability of the first reservoir is greater than that of the second reservoir;

[0008] dividing the development well into a first development well and a second development well according to a ratio of the first reservoir to the second reservoir, wherein the ratio of the first reservoir to the second reservoir in the first development well is higher than that in the second development well;

[0009] For the first development well, a first theoretical production capacity of the gas reservoir to be evaluated is obtained using a theoretical formula method; for the second development well, a second theoretical production capacity of the gas reservoir to be evaluated is obtained using a formation coefficient analogy method;

[0010] The productivity of the gas reservoir to be evaluated is evaluated using the first theoretical productivity and / or the second theoretical productivity.

[0011] Optionally, dividing the development well into a first development well and a second development well according to the ratio of the first reservoir to the second reservoir includes:

[0012] If the slope thickness ratio of the first reservoir in the development well is greater than the second threshold, the development well is the first development well;

[0013] If the slope thickness ratio of the first reservoir in the development well is not greater than the second threshold, the development well is the second development well.

[0014] Optionally, the first reservoir is a sweet spot reservoir, and the permeability of the sweet spot reservoir is greater than a first threshold;

[0015] The second reservoir is a low-permeability reservoir, and the permeability of the low-permeability reservoir is less than or equal to a first threshold.

[0016] Optionally, for the first development well, obtaining a first theoretical production capacity of the gas reservoir to be evaluated by using a theoretical formula method includes:

[0017] Determine the first theoretical production capacity of vertical wells, inclined wells and horizontal wells based on development well parameters;

[0018] The development well parameters include formation pressure, bottomhole flowing pressure, underground viscosity of natural gas, effective permeability of the formation, vertical thickness of the production layer, pressure under standard conditions, temperature under standard conditions, converted bottomhole radius of the horizontal well, converted gas supply radius of the horizontal well, natural gas compression coefficient, underground temperature, well inclination angle, length of the inclined well section, gas supply radius, converted bottomhole radius, pseudo-skin coefficient and skin coefficient generated by well inclination.

[0019] Optionally, the theoretical formula is:

[0020]

[0021]

[0022]

[0023] Among them, q d is the first theoretical production capacity of vertical wells and inclined wells, q g is the first theoretical production capacity of the horizontal well,

[0024] P R is the formation pressure, P wf is the bottom hole flowing pressure,

[0025] μ is the underground viscosity of natural gas, K is the effective permeability of the formation,

[0026] h is the vertical thickness of the production layer, P is the pressure under standard conditions,

[0027] T sc is the temperature under standard conditions, r eh is the converted bottom hole radius of the horizontal well,

[0028] rwh is the converted gas supply radius of the horizontal well,

[0029] Z is the natural gas compressibility coefficient, T is the underground temperature, L is the length of the inclined well section,

[0030] θ is the well inclination angle, r e is the air supply radius, r w is the converted radius of the well bottom,

[0031] S θ is the pseudo-skin coefficient generated by the well inclination angle θ, and S is the skin coefficient.

[0032] Optionally, for the second development well, obtaining a second theoretical production capacity of the gas reservoir to be evaluated by using a formation coefficient analogy method includes:

[0033] The second theoretical production capacity is obtained by analogy between the coefficient of the well to be developed and the coefficient of the developed well;

[0034] The coefficient of the well to be developed and the coefficient of the developed well both include the permeability and the oblique thickness of the first reservoir and the second reservoir.

[0035] Optionally, the step of comparing the coefficient of the well to be developed with the coefficient of the developed well to obtain the second theoretical production capacity includes:

[0036]

[0037] Among them, q2 is the second theoretical production capacity, q1 is the production capacity of the developed well,

[0038] K 11 , K 12 , K 13 , K 14 is the permeability of the four types of reservoirs in developed wells,

[0039] L 11 、L 12 、L 13 、L 14 The reservoir thickness of the four types of reservoirs in the developed wells is

[0040] K 21 , K 22 , K 23 , K 24 is the permeability of the four types of reservoirs to be developed,

[0041] L 21 、L 22 、L 23 、L 24 The reservoir thickness of the four types of reservoirs to be developed is

[0042] The four types of reservoirs include: reservoirs with permeability greater than 10mD are first-type reservoirs, reservoirs with permeability greater than 3mD and less than or equal to 10mD are second-type reservoirs, reservoirs with permeability greater than 1mD and less than or equal to 3mD are defined as third-type reservoirs, and reservoirs with permeability less than or equal to 1mD are fourth-type reservoirs. The first-type reservoir and the second-type reservoir are the first reservoir, and the third-type reservoir and the third-type reservoir are the second reservoir.

[0043] Optionally, the method also includes: obtaining the actual production capacity of the gas reservoir to be evaluated, determining the comprehensive capacity of the developed wells based on the theoretical capacity and the actual production capacity, and using the comprehensive capacity to draw a sweet spot capacity map and a low permeability capacity map for evaluating the theoretical capacity.

[0044] Optionally, the method of using the comprehensive production capacity to draw a sweet spot production capacity chart and a hypotonic production capacity chart for evaluating the theoretical production capacity includes:

[0045] Draw a relationship curve between sweet spot length, KL and production capacity based on the comprehensive production capacity;

[0046] Draw a sweet spot production capacity chart and a hypotonic production capacity chart according to the relationship curve;

[0047] The KL is the product of the formation coefficient and the reservoir oblique thickness.

[0048] On the other hand, the present invention also provides a device for evaluating gas reservoir productivity, which is used for a heterogeneous gas reservoir. The gas reservoir to be evaluated has multiple development wells, each of which has multiple reservoirs. The device includes:

[0049] an acquisition module, configured to acquire the permeability of the reservoir, and divide the plurality of reservoirs into a first reservoir and a second reservoir according to the permeability, wherein the permeability of the first reservoir is greater than that of the second reservoir;

[0050] a first processing module, configured to divide the development well into a first development well and a second development well according to a ratio of the first reservoir to the second reservoir, wherein the ratio of the first reservoir to the second reservoir in the first development well is higher than that in the second development well;

[0051] a second processing module, configured to obtain a first theoretical production capacity of the gas reservoir to be evaluated using a theoretical formula method for the first development well, and to obtain a second theoretical production capacity of the gas reservoir to be evaluated using a formation coefficient analogy method for the second development well;

[0052] The third processing module is configured to evaluate the productivity of the gas reservoir to be evaluated based on the first theoretical productivity and / or the second theoretical productivity.

[0053] Optionally, dividing the development well into a first development well and a second development well according to the ratio of the first reservoir to the second reservoir includes:

[0054] If the slope thickness ratio of the first reservoir in the development well is greater than the second threshold, the development well is the first development well;

[0055] If the slope thickness ratio of the first reservoir in the development well is not greater than the second threshold, the development well is the second development well;

[0056] The first reservoir is a sweet spot reservoir, and the permeability of the sweet spot reservoir is greater than a first threshold;

[0057] The second reservoir is a low-permeability reservoir, and the permeability of the low-permeability reservoir is less than or equal to a first threshold.

[0058] Optionally, for the first development well, obtaining a first theoretical production capacity of the gas reservoir to be evaluated by using a theoretical formula method includes:

[0059] Determine the first theoretical production capacity of vertical wells, inclined wells and horizontal wells based on development well parameters;

[0060] The development well parameters include formation pressure, bottom hole flowing pressure, underground viscosity of natural gas, effective formation permeability, vertical thickness of production layer, pressure under standard conditions, temperature under standard conditions, horizontal well bottom hole radius, horizontal well gas supply radius, natural gas compression coefficient, underground temperature, well inclination angle, length of inclined well section, gas supply radius, bottom hole radius, pseudo skin coefficient and skin coefficient generated by well inclination,

[0061] For the second development well, obtaining the second theoretical production capacity of the gas reservoir to be evaluated by using a formation coefficient analogy method includes:

[0062] The second theoretical production capacity is obtained by analogy between the coefficient of the well to be developed and the coefficient of the developed well;

[0063] The coefficient of the well to be developed and the coefficient of the developed well both include the permeability and the oblique thickness of the first reservoir and the second reservoir.

[0064] Optionally, the theoretical formula is:

[0065]

[0066]

[0067]

[0068] Among them, q d is the first theoretical production capacity of vertical wells and inclined wells, q g is the first theoretical production capacity of the horizontal well,

[0069] P R is the formation pressure, P wfis the bottom hole flowing pressure,

[0070] μ is the underground viscosity of natural gas, K is the effective permeability of the formation,

[0071] h is the vertical thickness of the production layer, P is the pressure under standard conditions,

[0072] T sc is the temperature under standard conditions, r eh is the converted bottom hole radius of the horizontal well,

[0073] r wh is the converted gas supply radius of the horizontal well,

[0074] Z is the natural gas compressibility coefficient, T is the underground temperature, L is the length of the inclined well section,

[0075] θ is the well inclination angle, r e is the air supply radius, r w is the converted radius of the well bottom,

[0076] S θ is the pseudo-skin coefficient generated by the well inclination angle θ, and S is the skin coefficient.

[0077] The second theoretical production capacity is obtained by analogy between the coefficient of the well to be developed and the coefficient of the developed well, including:

[0078]

[0079] Among them, q2 is the second theoretical production capacity, q1 is the production capacity of the developed well,

[0080] K 11 , K 12 , K 13 , K 14 is the permeability of the four types of reservoirs in developed wells,

[0081] L 11 、L 12 、L 13 、L 14 The reservoir thickness of the four types of reservoirs in the developed wells is

[0082] K 21 , K 22 , K 23 , K 24 is the permeability of the four types of reservoirs to be developed,

[0083] L 21 、L 22 、L 23 、L 24 The reservoir oblique thickness of the four types of reservoirs for the wells to be developed.

[0084] Optionally, the device further includes: an evaluation module, configured to obtain the actual production capacity of the gas reservoir to be evaluated, determine the comprehensive capacity of the developed wells based on the theoretical capacity and the actual production capacity, and use the comprehensive capacity to draw a sweet spot capacity chart and a low permeability capacity chart for evaluating the theoretical capacity;

[0085] The method of using the comprehensive capacity to draw a sweet spot capacity chart and a hypotonic capacity chart for evaluating the theoretical capacity includes: drawing a relationship curve between sweet spot length, KL and capacity according to the comprehensive capacity;

[0086] Draw a sweet spot production capacity chart and a hypotonic production capacity chart according to the relationship curve;

[0087] The KL is the product of the formation coefficient and the reservoir oblique thickness.

[0088] The present invention provides a method for assessing gas reservoir productivity for use in heterogeneous gas reservoirs, wherein the gas reservoir to be assessed has multiple development wells, each of which has multiple reservoirs. The method comprises: obtaining the permeability of the reservoirs, and dividing the multiple reservoirs into a first reservoir and a second reservoir based on the permeability, wherein the first reservoir has a greater permeability than the second reservoir; dividing the development wells into a first development well and a second development well based on the ratio of the first reservoir to the second reservoir, wherein the ratio of the first reservoir to the second reservoir in the first development well is greater than that in the second development well; for the first development well, obtaining a first theoretical productivity of the gas reservoir to be assessed using a theoretical formula method; for the second development well, obtaining a second theoretical productivity of the gas reservoir to be assessed using a formation coefficient analogy method; and assessing the productivity of the gas reservoir to be assessed using the first theoretical productivity and / or the second theoretical productivity. This method quantitatively distinguishes productivity calculation methods for development wells under different physical properties and different production systems, and comprehensively evaluates the final productivity of the development wells based on the theoretical productivity value and the actual production productivity value, thereby improving the accuracy of gas reservoir productivity assessment.

[0089] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the embodiments of the present invention, but do not constitute a limitation of the embodiments of the present invention. In the accompanying drawings:

[0091] Figure 1 It is a schematic flow chart of a method for evaluating gas reservoir productivity according to the present invention;

[0092] Figure 2 This is a schematic diagram of an embodiment of a tool for evaluating the production capacity of development wells in heterogeneous and thick gas reservoirs according to the present invention;

[0093] Figure 3 This is a schematic diagram of the relationship between the length of the first type of sweet spot and production capacity of the present invention;

[0094] Figure 4 This is a schematic diagram of the relationship between the optimized formation coefficient and production capacity. DETAILED DESCRIPTION

[0095] The following describes the specific implementation of the embodiment of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the embodiment of the present invention and is not used to limit the embodiment of the present invention.

[0096] Example 1

[0097] Figure 1 FIG. 1 is a flow chart of a method for evaluating gas reservoir productivity according to the present invention, as shown in FIG. Figure 1 As shown, a method for evaluating gas reservoir productivity according to the present invention is used for heterogeneous gas reservoirs. The gas reservoir to be evaluated has multiple development wells, each of which has multiple reservoirs. The method includes: Step S101 is to obtain the permeability of the reservoir, and based on the permeability, the multiple reservoirs are divided into a first reservoir and a second reservoir, wherein the permeability of the first reservoir is greater than that of the second reservoir. The method for evaluating gas reservoir productivity according to the present invention can be used for heterogeneous and thick gas reservoirs. The preferred method for obtaining the permeability of the reservoir is to calculate the average permeability of each type of reservoir by counting the thickness of each type of reservoir and then using a weighted average method.

[0098] According to a specific implementation method, the reservoirs drilled through by the development wells are classified according to the permeability differences in the logging interpretation results. Reservoirs with a permeability greater than 10mD are classified as first-category reservoirs, reservoirs with a permeability greater than 3mD and less than or equal to 10mD are classified as second-category reservoirs, reservoirs with a permeability greater than 1mD and less than or equal to 3mD are defined as third-category reservoirs, and reservoirs with a permeability less than or equal to 1mD are classified as fourth-category reservoirs. The first-category reservoir and the second-category reservoir are classified as the first reservoir, and the third-category reservoir and the third-category reservoir are classified as the second reservoir.

[0099] Specifically, the first reservoir is a sweet spot reservoir, the permeability of which is greater than a first threshold; the second reservoir is a low-permeability reservoir, the permeability of which is less than or equal to a first threshold. The first threshold is preferably 3 mD.

[0100] Step S102 is to divide the development well into a first development well and a second development well according to the ratio of the first reservoir to the second reservoir, wherein the ratio of the first reservoir to the second reservoir in the first development well is higher than that in the second development well.

[0101] Specifically, the development well is divided into a first development well and a second development well based on the ratio of the first reservoir to the second reservoir, including: if the slant thickness ratio of the sweet spot reservoir in the development well is greater than a second threshold (i.e., the ratio of the slant thickness value of the sweet spot reservoir in the development well to the slant thickness values of all reservoirs in the development well is greater than the second threshold), then the development well is the first development well; if the slant thickness ratio of the sweet spot reservoir in the development well is not greater than the second threshold (i.e., the ratio of the slant thickness value of the sweet spot reservoir in the development well to the slant thickness values of all reservoirs in the development well is not greater than the second threshold), then the development well is the second development well. Preferably, the second threshold is 20%.

[0102] According to a specific embodiment, the sweet spot reservoir has an slant thickness exceeding 20% of the slant thickness of all reservoirs, which is the first development well; the sweet spot reservoir has an slant thickness not exceeding 20% of the slant thickness of all reservoirs, which is the second development well.

[0103] Step S103 is to obtain a first theoretical production capacity of the gas reservoir to be evaluated using a theoretical formula method for the first development well.

[0104] Specifically, for the first development well, using a theoretical formula method to obtain a first theoretical production capacity of the gas reservoir to be evaluated includes determining the first theoretical production capacity of a vertical well, a deviated well, and a horizontal well based on development well parameters; the development well parameters include formation pressure, bottomhole flowing pressure, underground natural gas viscosity, effective formation permeability, vertical thickness of the production layer, pressure under standard conditions, temperature under standard conditions, converted bottomhole radius of the horizontal well, converted gas supply radius of the horizontal well, natural gas compressibility coefficient, underground temperature, well inclination angle, length of the deviated well section, gas supply radius, converted bottomhole radius, pseudo-skin coefficient generated by well inclination, and skin coefficient. The development well may be at least one of a vertical well, a deviated well, and a horizontal well, and the theoretical production capacity of the development well is obtained based on actual conditions.

[0105] According to a specific implementation, the theoretical formula is:

[0106]

[0107]

[0108]

[0109] Among them, q d is the first theoretical production capacity of vertical wells and inclined wells, q g is the first theoretical production capacity of the horizontal well, P R is the formation pressure, P wf is the bottom hole flow pressure, μ is the underground viscosity of natural gas, K is the effective permeability of the formation, h is the vertical thickness of the production layer, P is the pressure under standard conditions, T sc is the temperature under standard conditions, reh is the converted bottom hole radius of the horizontal well, r wh is the converted gas supply radius of the horizontal well, Z is the natural gas compression coefficient, T is the underground temperature, L is the length of the inclined well section, θ is the well inclination angle, r e is the air supply radius, r w is the converted radius of the well bottom, S θ is the pseudo-skin coefficient generated by the well inclination angle θ, and S is the skin coefficient.

[0110] Low permeability reservoirs in thick gas reservoirs are generally mined using inclined or horizontal wells. Therefore, the vertical thickness of the reservoir in the formation coefficient is optimized as the inclined thickness of the reservoir to evaluate the production capacity.

[0111] Step S104 is to obtain a second theoretical production capacity of the gas reservoir to be evaluated using a formation coefficient analogy method for the second development well.

[0112] Specifically, for the second development well, the second theoretical production capacity of the gas reservoir to be evaluated is obtained by using the formation coefficient analogy method, including: comparing the coefficient of the well to be developed with the coefficient of the developed well to obtain the second theoretical production capacity; the coefficient of the well to be developed and the coefficient of the developed well both include the permeability and reservoir oblique thickness of the first reservoir and the second reservoir.

[0113] The second theoretical production capacity is obtained by analogy between the coefficient of the well to be developed and the coefficient of the developed well, including:

[0114]

[0115] Among them, q2 is the second theoretical production capacity, q1 is the production capacity of the developed well, K 11 , K 12 , K 13 , K 14 is the permeability of the four types of reservoirs in developed wells, L 11 、L 12 、L 13 、L 14 is the reservoir thickness of the four types of reservoirs in the developed wells, K 21 , K 22 , K 23 , K 24 is the permeability of the four types of reservoirs to be developed, L 21 、L 22 、L 23 、L 24 The reservoir oblique thickness of the four types of reservoirs for the wells to be developed.

[0116] The four types of reservoirs include: reservoirs with permeability greater than 10mD are first-type reservoirs, reservoirs with permeability greater than 3mD and less than or equal to 10mD are second-type reservoirs, reservoirs with permeability greater than 1mD and less than or equal to 3mD are defined as third-type reservoirs, and reservoirs with permeability less than or equal to 1mD are fourth-type reservoirs. The first-type reservoir and the second-type reservoir are the first reservoir, and the third-type reservoir and the third-type reservoir are the second reservoir.

[0117] After the wells to be developed are put into production, the gas production and downhole pressure are collected according to different production systems, and the actual production capacity value is calculated using methods such as the one-point method, the binomial method, and the IPR curve fitting method.

[0118] Step S105 is to evaluate the productivity of the gas reservoir to be evaluated using the first theoretical productivity and / or the second theoretical productivity.

[0119] Specifically, if the development well is the first development well, the production capacity of the gas reservoir to be evaluated is evaluated using the first theoretical production capacity; if the development well is the second development well, the production capacity of the gas reservoir to be evaluated is evaluated using the second theoretical production capacity; if the development well includes both the first development well and the second development well, the production capacity of the gas reservoir to be evaluated is evaluated using the first theoretical production capacity and the second theoretical production capacity.

[0120] The method also includes: obtaining the actual production capacity of the gas reservoir to be evaluated, determining the comprehensive capacity of the developed wells based on the theoretical capacity and the actual production capacity, and using the comprehensive capacity to draw a sweet spot capacity map and a low permeability capacity map for evaluating the theoretical capacity.

[0121] Specifically, the use of the comprehensive capacity to draw the sweet spot capacity map and the low permeability capacity map for evaluating the theoretical capacity includes: drawing a relationship curve between the sweet spot length, KL and capacity according to the comprehensive capacity; drawing the sweet spot capacity map and the low permeability capacity map according to the relationship curve; the KL is the product of the formation coefficient and the reservoir oblique thickness.

[0122] According to one specific implementation method, after a development well is put into production, gas production and downhole pressure are collected according to different production systems. Actual production capacity is calculated using methods such as the one-point method, the binomial method, and the IPR curve fitting method. Data on stable production rates and corresponding bottomhole flowing pressures during the development well's actual production are collected. If only one stable production rate and corresponding bottomhole flowing pressure data point is available, the one-point method is used to calculate capacity; if multiple stable production rates and corresponding bottomhole flowing pressure data points are available, the binomial method is used. Furthermore, the IPR curve method in the PE Offices software can be used to fit multiple data points to determine a reasonable production capacity value for the development well.

[0123] Compare the theoretical production capacity value and the actual production capacity value calculated by the formula. If the difference is small, the final reasonable production capacity value is obtained. If the difference is large, the error size of each parameter acquisition method needs to be analyzed to determine the accurate production capacity value of the development well.

[0124] The present invention quantitatively distinguishes the productivity calculation methods of development wells under different physical properties and different production systems, comprehensively evaluates the final productivity value of the development well based on the theoretical productivity value and the actual production productivity value, and improves the accuracy of evaluating gas reservoir productivity.

[0125] Example 2:

[0126] Figure 2 It is a schematic diagram of a specific embodiment of the present invention, such as Figure 2 As shown in the figure, reservoirs are classified according to well logging interpretation results. Based on the reservoir inclination thickness, permeability, and reasonable production capacity data of multiple development wells, the development wells are divided into development wells with more sweet spots and development wells with more low-permeability reservoirs.

[0127] For example, when analyzing a gas reservoir, there are multiple development wells, each of which has multiple reservoirs, and the multiple development wells include well I and well II.

[0128] Among them, the inclined thickness of the Class I reservoir of Well I is 151.0m and the vertical thickness is 5.6m; the inclined thickness of the Class II reservoir is 157.5m and the vertical thickness is 17.6m; the inclined thickness of the Class III reservoir is 173.8m and the vertical thickness is 24.9m; the inclined thickness of the Class IV reservoir is 118.4m and the vertical thickness is 32.6m. The permeability of the Class I reservoir of Well I is 46.08 mD, the permeability of the Class II reservoir is 7.17 mD, the permeability of the Class III reservoir is 1.65 mD, and the permeability of the Class IV reservoir is 0.57 mD. Therefore, the Class I reservoir and the Class II reservoir of Well I are both sweet spot reservoirs, and the Class III reservoir and the Class IV reservoir are low permeability reservoirs. The slant thickness ratio of the sweet spot reservoir is: ((151+157.5) / (151+157.5+173.8+118.4))>20% (that is, greater than the second threshold value), so Well I is the first development well.

[0129] The oblique thickness of the Class I reservoir in Well II is 36.9m and the vertical thickness is 2.85m; the oblique thickness of the Class II reservoir is 116.2m and the vertical thickness is 9.4m; the oblique thickness of the Class III reservoir is 621.7m and the vertical thickness is 56.6m; the oblique thickness of the Class IV reservoir is 415.3m and the vertical thickness is 52.6m. The permeability of the Class I reservoir of Well II is 12.7 mD, the permeability of the Class II reservoir is 4.3 mD, the permeability of the Class III reservoir is 1.7 mD, and the permeability of the Class IV reservoir is 0.5 mD. Therefore, the Class I reservoir and the Class II reservoir of Well II are both sweet spot reservoirs, and the Class III reservoir and the Class IV reservoir are low permeability reservoirs. The slant thickness ratio of the sweet spot reservoir is ((36.9+116.2) / (36.9+116.2+621.7+415.3)) <20% (i.e., less than the second threshold value), so Well II is the second development well.

[0130] According to the reservoir classification results, the theoretical production capacity of Well I is calculated using the theoretical formula method (i.e., the first theoretical production capacity), and the theoretical production capacity of Well II is calculated using the formation coefficient analogy method (i.e., the second theoretical production capacity).

[0131] According to the inclined well production capacity formula

[0132]

[0133]

[0134]

[0135] Among them, q d is the first theoretical production capacity of vertical wells and inclined wells, q g is the first theoretical production capacity of the horizontal well, P R is the formation pressure, P wf is the bottom hole flow pressure, μ is the underground viscosity of natural gas, K is the effective permeability of the formation, h is the vertical thickness of the production layer, P is the pressure under standard conditions, T sc is the temperature under standard conditions, r eh is the converted bottom hole radius of the horizontal well, r wh is the converted gas supply radius of the horizontal well, Z is the natural gas compression coefficient, T is the underground temperature, L is the length of the inclined well section, θ is the well inclination angle, r e is the air supply radius, r w is the converted radius of the well bottom, S θ is the pseudo-skin coefficient generated by the well inclination angle θ, and S is the skin coefficient.

[0136] After superimposing the theoretical production capacity values of the four types of reservoirs of Well 1, the theoretical production capacity of Well 1 is 3.56 million cubic meters per day.

[0137] According to the formation coefficient analogy method, the actual production capacity of developed well A is known to be 2 million cubic meters per day. Substituting the reservoir thickness and permeability values of well A and well II into the formula:

[0138]

[0139] Among them, q2 is the second theoretical production capacity, q1 is the production capacity of the developed well, K 11 , K 12 , K 13 , K 14 is the permeability of the four types of reservoirs in developed wells, L 11 、L 12 、L 13 、L 14 is the reservoir thickness of the four types of reservoirs in the developed wells, K 21 , K 22 , K 23 , K 24 is the permeability of the four types of reservoirs to be developed, L 21 、L 22 、L 23 、L 24 The theoretical production capacity of Well II is 1.36 million cubic meters per day.

[0140] It should be noted that the permeability values in general well logging interpretation results need to be converted into effective permeability. If there are laboratory test values, they can be used directly. If there are no effective permeability values from actual tests, the empirical method or exploration well analogy method should be used to convert the well logging permeability into effective permeability, and then the formula should be used to calculate the theoretical production capacity value.

[0141] During the initial production phase of Wells I and II, trial production was conducted using different production systems. After obtaining the corresponding daily gas production and bottomhole pressure, the actual production capacity was calculated using the binomial method. The actual production capacity of Well I was 3.88 million cubic meters per day, while the actual production capacity of Well II was 1.42 million cubic meters per day. The binomial method is divided into pseudo-pressure, pressure, and pressure-balance methods. The binomial method is used to calculate actual production capacity after selecting the method based on formation temperature and pressure.

[0142] It should be noted that the bottom hole flowing pressure value is easier to obtain when there is a downhole pressure gauge in the development well. If there is no downhole pressure gauge, it can be converted from the wellhead oil pressure value after calculating the wellbore loss.

[0143] By comparing the theoretical production capacity and actual production capacity of Well I and Well II, it was found that the difference between the two was small. Therefore, it can be concluded that the production capacity of Well I is 3.8 million cubic meters / day and the production capacity of Well II is 1.4 million cubic meters / day.

[0144] Obtain the actual production capacity of the gas reservoir to be evaluated, determine the comprehensive capacity of the developed wells based on the theoretical capacity and the actual production capacity, and use the comprehensive capacity to draw a sweet spot capacity chart and a low permeability capacity chart to evaluate the theoretical capacity. Specifically, draw a relationship curve between the sweet spot length, KL and capacity based on the comprehensive capacity, such as Figure 3 and Figure 4 As shown, Figure 3 This is a development well with more sweet spot reservoirs (i.e., the first development well) Figure 4 For development wells with more low-permeability reservoirs (i.e., second development wells), a chart is drawn based on the relationship between the formation coefficient and productivity, and a chart is drawn based on the relationship between the length of the first type of sweet spot and productivity; the sweet spot productivity chart and the low-permeability productivity chart are drawn based on the relationship curves; the KL is the product of the formation coefficient and the reservoir oblique thickness.

[0145] The present invention comprehensively determines the reasonable production capacity of a single well through theoretical production capacity and actual production capacity, and forms a sweet spot production capacity plate and a low permeability production capacity plate for developed wells, respectively, to provide a reference for subsequent production capacity evaluation of new wells, thereby better guiding the reasonable development system of thick gas reservoirs.

[0146] Example 3

[0147] The present invention also proposes a device for evaluating the production capacity of a gas reservoir, which is used for a heterogeneous gas reservoir. The gas reservoir to be evaluated has multiple development wells, and each development well has multiple reservoirs. The device includes: an acquisition module, used to obtain the permeability of the reservoir, and divide the multiple reservoirs into a first reservoir and a second reservoir according to the permeability, and the permeability of the first reservoir is greater than that of the second reservoir; a first processing module, used to divide the development wells into a first development well and a second development well according to the ratio of the first reservoir to the second reservoir, and the ratio of the first reservoir to the second reservoir in the first development well is higher than that in the second development well; a second processing module, used to obtain a first theoretical production capacity of the gas reservoir to be evaluated for the first development well using a theoretical formula method, and for the second development well, obtain a second theoretical production capacity of the gas reservoir to be evaluated using a formation coefficient analogy method; and a third processing module, used to evaluate the production capacity of the gas reservoir to be evaluated based on the first theoretical production capacity and / or the second theoretical production capacity.

[0148] The first reservoir is a sweet spot reservoir, the permeability of which is greater than a first threshold; the second reservoir is a low-permeability reservoir, the permeability of which is less than or equal to the first threshold. The development well is divided into a first development well and a second development well based on the ratio of the first reservoir to the second reservoir, wherein: if the slant thickness ratio of the sweet spot reservoir in the development well is greater than a second threshold, the development well is classified as the first development well; if the slant thickness ratio of the sweet spot reservoir in the development well is not greater than the second threshold, the development well is classified as the second development well. The first threshold is preferably 3 mD, and the second threshold is preferably 20%.

[0149] For the first development well, the first theoretical production capacity of the gas reservoir to be evaluated is obtained using a theoretical formula method, including: determining the first theoretical production capacity of vertical wells, inclined wells and horizontal wells based on development well parameters; the development well parameters include formation pressure, bottomhole flowing pressure, underground viscosity of natural gas, effective permeability of the formation, vertical thickness of the production layer, pressure under standard conditions, temperature under standard conditions, converted bottomhole radius of the horizontal well, converted gas supply radius of the horizontal well, natural gas compression coefficient, underground temperature, well inclination angle, length of the inclined well section, gas supply radius, converted bottomhole radius, pseudo-skin coefficient and skin coefficient generated by well inclination.

[0150] The theoretical formula is:

[0151]

[0152]

[0153]

[0154] Among them, q d is the first theoretical production capacity of vertical wells and inclined wells, q g is the first theoretical production capacity of the horizontal well, P R is the formation pressure, P wf is the bottom hole flow pressure, μ is the underground viscosity of natural gas, K is the effective permeability of the formation, h is the vertical thickness of the production layer, P is the pressure under standard conditions, T sc is the temperature under standard conditions, r eh is the converted bottom hole radius of the horizontal well, r wh is the converted gas supply radius of the horizontal well, Z is the natural gas compression coefficient, T is the underground temperature, L is the length of the inclined well section, θ is the well inclination angle, r e is the air supply radius, r w is the converted radius of the well bottom, S θ is the pseudo-skin coefficient generated by the well inclination angle θ, and S is the skin coefficient.

[0155] For the second development well, the second theoretical production capacity of the gas reservoir to be evaluated is obtained by using the formation coefficient analogy method, including: comparing the coefficient of the well to be developed with the coefficient of the developed well to obtain the second theoretical production capacity; the coefficient of the well to be developed and the coefficient of the developed well both include the permeability and reservoir oblique thickness of the first reservoir and the second reservoir.

[0156] The second theoretical production capacity is obtained by analogy between the coefficient of the well to be developed and the coefficient of the developed well, including:

[0157]

[0158] Among them, q2 is the second theoretical production capacity, q1 is the production capacity of the developed well, K 11 , K 12, K 13 , K 14 is the permeability of the four types of reservoirs in developed wells, L 11 、L 12 、L 13 、L 14 is the reservoir thickness of the four types of reservoirs in the developed wells, K 21 , K 22 , K 23 , K 24 is the permeability of the four types of reservoirs to be developed, L 21 、L 22 、L 23 、L 24 The reservoir oblique thickness of the four types of reservoirs for the wells to be developed.

[0159] The device also includes: an evaluation module, which is used to obtain the actual production capacity of the gas reservoir to be evaluated, determine the comprehensive capacity of the developed wells based on the theoretical capacity and the actual production capacity, and use the comprehensive capacity to draw a sweet spot capacity map and a low permeability capacity map for evaluating the theoretical capacity; the use of the comprehensive capacity to draw the sweet spot capacity map and the low permeability capacity map for evaluating the theoretical capacity includes: drawing a relationship curve between the sweet spot length, KL and capacity based on the comprehensive capacity; drawing the sweet spot capacity map and the low permeability capacity map based on the relationship curve; the KL is the product of the formation coefficient and the reservoir oblique thickness.

[0160] The device quantitatively distinguishes the productivity calculation methods of development wells under different physical properties and different production systems. Based on the theoretical productivity value and the actual production productivity value, it comprehensively evaluates the final productivity value of the development well, thereby improving the accuracy of evaluating gas reservoir productivity.

[0161] The present invention provides a method for assessing gas reservoir productivity for use in heterogeneous gas reservoirs, wherein the gas reservoir to be assessed has multiple development wells, each of which has multiple reservoirs. The method comprises: obtaining the permeability of the reservoirs, and dividing the multiple reservoirs into a first reservoir and a second reservoir based on the permeability, wherein the first reservoir has a greater permeability than the second reservoir; dividing the development wells into a first development well and a second development well based on the ratio of the first reservoir to the second reservoir, wherein the ratio of the first reservoir to the second reservoir in the first development well is greater than that in the second development well; for the first development well, obtaining a first theoretical productivity of the gas reservoir to be assessed using a theoretical formula method; for the second development well, obtaining a second theoretical productivity of the gas reservoir to be assessed using a formation coefficient analogy method; and assessing the productivity of the gas reservoir to be assessed using the first theoretical productivity and / or the second theoretical productivity. This method quantitatively distinguishes productivity calculation methods for development wells under different physical properties and different production systems, and comprehensively evaluates the final productivity of the development wells based on the theoretical productivity value and the actual production productivity value, thereby improving the accuracy of gas reservoir productivity assessment.

[0162] The above describes in detail the optional implementation methods of the embodiments of the present invention in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above implementation methods. Within the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the scope of protection of the embodiments of the present invention.

[0163] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not further describe various possible combinations.

[0164] Those skilled in the art will understand that all or part of the steps in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a program, which is stored in a storage medium and includes a number of instructions for causing a single-chip microcomputer, chip or processor to execute all or part of the steps of the methods described in each embodiment of the present application. The aforementioned storage medium includes: a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and other media that can store program code.

[0165] In addition, various implementations of the embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed in the embodiments of the present invention.

Claims

1. A method for evaluating gas reservoir productivity, for use in heterogeneous gas reservoirs, characterized in that: The gas reservoir to be evaluated has multiple development wells, each of which has multiple reservoirs. The method includes: obtaining a permeability of the reservoir, and dividing the plurality of reservoirs into a first reservoir and a second reservoir according to the permeability, wherein the permeability of the first reservoir is greater than that of the second reservoir; dividing the development well into a first development well and a second development well according to a ratio of the first reservoir to the second reservoir, wherein the ratio of the first reservoir to the second reservoir in the first development well is higher than that in the second development well; For the first development well, a first theoretical production capacity of the gas reservoir to be evaluated is obtained using a theoretical formula method; For the second development well, a second theoretical production capacity of the gas reservoir to be evaluated is obtained using a formation coefficient analogy method; The productivity of the gas reservoir to be evaluated is evaluated using the first theoretical productivity and / or the second theoretical productivity.

2. The method according to claim 1, characterized in that The step of dividing the development well into a first development well and a second development well according to the ratio of the first reservoir to the second reservoir comprises: If the slope thickness ratio of the first reservoir in the development well is greater than the second threshold, the development well is the first development well; If the slope thickness ratio of the first reservoir in the development well is not greater than the second threshold, the development well is the second development well.

3. The method according to claim 1 or 2, characterized in that The first reservoir is a sweet spot reservoir, and the permeability of the sweet spot reservoir is greater than a first threshold; The second reservoir is a low-permeability reservoir, and the permeability of the low-permeability reservoir is less than or equal to a first threshold.

4. The method according to claim 1, wherein For the first development well, obtaining a first theoretical production capacity of the gas reservoir to be evaluated by using a theoretical formula method includes: Determine the first theoretical production capacity of vertical wells, inclined wells and horizontal wells based on theoretical parameters; The development well parameters include formation pressure, bottomhole flowing pressure, underground viscosity of natural gas, effective permeability of the formation, vertical thickness of the production layer, pressure under standard conditions, temperature under standard conditions, converted bottomhole radius of the horizontal well, converted gas supply radius of the horizontal well, natural gas compression coefficient, underground temperature, well inclination angle, length of the inclined well section, gas supply radius, converted bottomhole radius, pseudo-skin coefficient and skin coefficient generated by well inclination.

5. The method according to claim 4, characterized in that The theoretical formula is: Among them, q d is the first theoretical production capacity of vertical wells and inclined wells, q g is the first theoretical production capacity of the horizontal well, P R is the formation pressure, P wf is the bottom hole flowing pressure, μ is the underground viscosity of natural gas, K is the effective permeability of the formation, h is the vertical thickness of the production layer, P is the pressure under standard conditions, T sc is the temperature under standard conditions, r eh is the converted bottom hole radius of the horizontal well, r wh is the converted gas supply radius of the horizontal well, Z is the natural gas compressibility coefficient, T is the underground temperature, L is the length of the inclined well section, θ is the well inclination angle, r e is the air supply radius, r w is the converted radius of the well bottom, S θ is the pseudo-skin coefficient generated by the well inclination angle θ, and S is the skin coefficient.

6. The method according to claim 1, characterized in that For the second development well, obtaining the second theoretical production capacity of the gas reservoir to be evaluated by using a formation coefficient analogy method includes: The second theoretical production capacity is obtained by analogy between the coefficient of the well to be developed and the coefficient of the developed well; The coefficient of the well to be developed and the coefficient of the developed well both include the permeability and the oblique thickness of the first reservoir and the second reservoir.

7. The method according to claim 6, characterized in that The second theoretical production capacity is obtained by analogy between the coefficient of the well to be developed and the coefficient of the developed well, including: Among them, q2 is the second theoretical production capacity, q1 is the production capacity of the developed well, K 11 , K 12 , K 13 , K 14 is the permeability of the four types of reservoirs in developed wells, L 11 、L 12 、L 13 、L 14 The reservoir thickness of the four types of reservoirs in the developed wells is K 21 , K 22 , K 23 , K 24 is the permeability of the four types of reservoirs to be developed, L 21 , L 22 , L 23 , L 24 The reservoir thickness of the four types of reservoirs to be developed is The four types of reservoirs include: reservoirs with permeability greater than 10mD are first-type reservoirs, reservoirs with permeability greater than 3mD and less than or equal to 10mD are second-type reservoirs, reservoirs with permeability greater than 1mD and less than or equal to 3mD are defined as third-type reservoirs, and reservoirs with permeability less than or equal to 1mD are fourth-type reservoirs. The first-type reservoir and the second-type reservoir are the first reservoir, and the third-type reservoir and the third-type reservoir are the second reservoir.

8. The method according to claim 1, characterized in that The method further includes: The actual production capacity of the gas reservoir to be evaluated is obtained, and the comprehensive capacity of the developed wells is determined based on the theoretical capacity and the actual production capacity. The sweet spot capacity chart and the low permeability capacity chart are drawn using the comprehensive capacity to evaluate the theoretical capacity.

9. The method according to claim 8, characterized in that The method of using the comprehensive production capacity to draw a sweet spot production capacity chart and a hypotonic production capacity chart for evaluating the theoretical production capacity includes: Draw a relationship curve between sweet spot length, KL and production capacity based on the comprehensive production capacity; Draw a sweet spot production capacity chart and a hypotonic production capacity chart according to the relationship curve; The KL is the product of the formation coefficient and the reservoir oblique thickness.

10. A device for evaluating gas reservoir productivity, used in heterogeneous gas reservoirs, characterized in that: The gas reservoir to be evaluated has multiple development wells, each of which has multiple reservoirs. The device includes: an acquisition module, configured to acquire the permeability of the reservoir, and divide the plurality of reservoirs into a first reservoir and a second reservoir according to the permeability, wherein the permeability of the first reservoir is greater than that of the second reservoir; a first processing module, configured to divide the development well into a first development well and a second development well according to a ratio of the first reservoir to the second reservoir, wherein the ratio of the first reservoir to the second reservoir in the first development well is higher than that in the second development well; a second processing module, configured to obtain a first theoretical production capacity of the gas reservoir to be evaluated using a theoretical formula method for the first development well, and to obtain a second theoretical production capacity of the gas reservoir to be evaluated using a formation coefficient analogy method for the second development well; The third processing module is configured to evaluate the productivity of the gas reservoir to be evaluated based on the first theoretical productivity and / or the second theoretical productivity.

11. The device according to claim 10, characterized in that The step of dividing the development well into a first development well and a second development well according to the ratio of the first reservoir to the second reservoir comprises: If the slope thickness ratio of the first reservoir in the development well is greater than the second threshold, the development well is the first development well; If the slope thickness ratio of the first reservoir in the development well is not greater than the second threshold, the development well is the second development well; The first reservoir is a sweet spot reservoir, and the permeability of the sweet spot reservoir is greater than a first threshold; The second reservoir is a low-permeability reservoir, and the permeability of the low-permeability reservoir is less than or equal to a first threshold.

12. The device according to claim 10, characterized in that For the first development well, obtaining a first theoretical production capacity of the gas reservoir to be evaluated by using a theoretical formula method includes: Determine the first theoretical production capacity of vertical wells, inclined wells and horizontal wells based on development well parameters; The development well parameters include formation pressure, bottom hole flowing pressure, underground viscosity of natural gas, effective formation permeability, vertical thickness of production layer, pressure under standard conditions, temperature under standard conditions, horizontal well converted bottom hole radius, horizontal well converted gas supply radius, natural gas compressibility coefficient, underground temperature, well inclination angle, length of inclined well section, gas supply radius, bottom hole converted radius, pseudo-skin coefficient and skin coefficient generated by well inclination; For the second development well, obtaining the second theoretical production capacity of the gas reservoir to be evaluated by using the formation coefficient analogy method includes: The second theoretical production capacity is obtained by analogy between the coefficient of the well to be developed and the coefficient of the developed well; The coefficient of the well to be developed and the coefficient of the developed well both include the permeability and the oblique thickness of the first reservoir and the second reservoir.

13. The device according to claim 12, characterized in that The theoretical formula is: The second theoretical production capacity is obtained by analogy between the coefficient of the well to be developed and the coefficient of the developed well, including: Among them, q d is the first theoretical production capacity of vertical wells and inclined wells, q g is the first theoretical production capacity of the horizontal well, P R is the formation pressure, P wf is the bottom hole flowing pressure, μ is the underground viscosity of natural gas, K is the effective permeability of the formation, h is the vertical thickness of the production layer, P is the pressure under standard conditions, T sc is the temperature under standard conditions, r eh is the converted bottom hole radius of the horizontal well, r wh is the converted gas supply radius of the horizontal well, Z is the natural gas compressibility coefficient, T is the underground temperature, L is the length of the inclined well section, θ is the well inclination angle, r e is the air supply radius, r w is the converted radius of the well bottom, S θ is the pseudo-skin coefficient generated by the well inclination angle θ, S is the skin coefficient, q2 is the second theoretical production capacity, q1 is the production capacity of developed wells, K 11 , K 12 , K 13 , K 14 is the permeability of the four types of reservoirs in developed wells, L 11 、L 12 、L 13 、L 14 The reservoir thickness of the four types of reservoirs in the developed wells is K 21 , K 22 , K 23 , K 24 is the permeability of the four types of reservoirs to be developed, L 21 , L 22 , L 23 , L 24 The reservoir thickness of the four types of reservoirs to be developed is The four types of reservoirs include: reservoirs with permeability greater than 10mD are first-type reservoirs, reservoirs with permeability greater than 3mD and less than or equal to 10mD are second-type reservoirs, reservoirs with permeability greater than 1mD and less than or equal to 3mD are defined as third-type reservoirs, and reservoirs with permeability less than or equal to 1mD are fourth-type reservoirs. The first-type reservoir and the second-type reservoir are the first reservoir, and the third-type reservoir and the third-type reservoir are the second reservoir.

14. The device according to claim 10, characterized in that The device also includes: An evaluation module is used to obtain the actual production capacity of the gas reservoir to be evaluated, determine the comprehensive capacity of the developed wells based on the theoretical capacity and the actual production capacity, and use the comprehensive capacity to draw a sweet spot capacity chart and a low permeability capacity chart for evaluating the theoretical capacity; The method of using the comprehensive capacity to draw a sweet spot capacity chart and a hypotonic capacity chart for evaluating the theoretical capacity includes: drawing a relationship curve between sweet spot length, KL and capacity according to the comprehensive capacity; Draw a sweet spot production capacity chart and a hypotonic production capacity chart according to the relationship curve; The KL is the product of the formation coefficient and the reservoir oblique thickness.

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