A method and device for selecting favorable areas for karst gas reservoir development based on strike-slip faults

Abstract

The present invention relates to the technical field of oil and gas field development, and discloses a method and device for selecting favorable areas for karst gas reservoir development based on strike-slip faults. The method first divides the fault-controlled karst area into different fault-controlled areas, and then divides the fault-controlled area into different fault-controlled karst reservoir development pattern areas on a plane based on the divided fault-controlled areas and the direction of karst water flow. Finally, the stable production capacity of gas wells in the fault-controlled karst reservoir development pattern areas is evaluated, and the favorable areas for gas reservoir development are finally determined. Based on strike-slip faults, the present invention comprehensively evaluates sedimentation, karstity, and stable production capacity of gas wells, forming a new method in which the gas wells deployed by the method of the present invention not only test high production, but also achieve high and stable production of gas wells, which can effectively improve the overall development effect of the gas reservoir.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development, in particular to karst gas reservoir development, and in particular to a method and device for selecting favorable areas for karst gas reservoir development based on strike-slip faults. Background Art

[0002] The Sinian gas reservoirs in the Sichuan Basin are typical karst gas reservoirs both domestically and internationally, offering enormous development potential. However, 80% of the natural gas reserves are contained in ultra-low-porosity reservoirs with porosity below 5%. Influenced by multiple factors, such as sedimentation and karstification, the reservoirs are highly heterogeneous, making it extremely difficult to identify favorable development zones. Through years of exploration, a method has been developed to select favorable development zones, where the presence of hills and beaches and the quality of karst are key. While gas wells deployed in these zones, selected using this method, generally achieve high production rates, over 30% struggle to achieve both high and stable production. Consequently, production results are suboptimal, impacting the overall development of the reservoir.

[0003] The invention patent with publication number CN113513311A and publication date October 19, 2021 discloses a "method and device for dividing the internal structure of a carbonate strike-slip fault fracture zone". Its specific technical solution is: the method and device for dividing the internal structure of a carbonate strike-slip fault fracture zone provided by the present invention relate to the field of oil and gas reservoir development technology. The division method includes obtaining the characteristics of a carbonate strike-slip fault fracture zone; the characteristics include cracks, holes and caves; and dividing the carbonate strike-slip fault fracture zone into a first type, a second type and a third type according to the characteristics. The method and device for dividing the internal structure of a carbonate strike-slip fault fracture zone provided by the present invention can be used to guide drilling trajectory design and adjustment and optimization during drilling, by dividing the carbonate strike-slip fault fracture zone into a first type, a second type and a third type, while optimizing the drilling fluid, realizing early prediction of complex working conditions, and ensuring well control safety.

[0004] Although the above-mentioned existing technology mentions the concept of strike-slip faults and divides strike-slip fault fracture zones into three types, this technology is mainly used to identify strike-slip fault zones, classify faults, and guide the implementation of well location targets, but does not clearly guide the selection of favorable development areas. Summary of the Invention

[0005] In order to solve the problems and shortcomings existing in the above-mentioned prior art, the present invention proposes a method and device for optimizing favorable areas for karst gas reservoir development based on strike-slip faults. The gas wells deployed by this method can not only achieve high production, but also achieve stable production of the gas wells, which can effectively improve the overall development effect of the gas reservoir.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0007] A method for selecting favorable areas for karst gas reservoir development based on strike-slip faults comprises:

[0008] According to the fault development direction and geometric position between faults in the gas reservoir block, the fault-controlled karst area is divided into different fault-controlled areas;

[0009] According to the divided fault-controlled areas and the direction of karst water flow, the fault-controlled areas are divided into different fault-controlled karst reservoir development pattern areas on the plane;

[0010] The stable production capacity of gas wells in the fault-controlled karst reservoir development pattern area is evaluated to ultimately determine the favorable areas for gas reservoir development.

[0011] Preferably, the fault-controlled karst area is divided into different fault-controlled areas according to the fault development direction and the geometric position between the faults in the gas reservoir block, including:

[0012] Based on seismic, well logging and core data, the karst paleo-geomorphology of the gas reservoir is obtained using the impression method or the residual thickness method;

[0013] According to the karst development period and fault formation period and development characteristics, the first-level or second-level large faults formed before the karst period were selected, and the karst paleo-geomorphology and faults were superimposed using geological image processing software;

[0014] Determine the main direction of karst water flow based on the distribution characteristics of karst paleo-landforms;

[0015] According to the fault development direction and geometric position between faults in the gas reservoir block, the block is divided into different fault-controlled areas.

[0016] Preferably, the fault-controlled karst reservoir development pattern areas include three types in total, among which:

[0017] In the first type of area, algal mounds are developed and located in paleo-geomorphological residual mounds or slope break zones. The direction of karst water flow is parallel to the direction of fault development, and the areas on both sides of the fault are fault-controlled parallel zones.

[0018] Category II areas are areas where algal mounds are developed and are located in paleo-geomorphological residual mounds or slope-break zones, where the direction of karst water flow intersects with the direction of fault development, and the water flow does not cross the faults;

[0019] In the third type of area, algal mounds are developed and located in ancient landform residual hills or slope break zones. The direction of karst water flow intersects with the direction of fault development, and water flows through the fault area.

[0020] Preferably, the evaluation of the stable production capacity of gas wells within the fault-controlled karst reservoir development pattern area and the final determination of favorable areas for gas reservoir development include:

[0021] Four indicators, namely, the open flow rate of gas wells in the fault-controlled karst reservoir development pattern area, gas production per unit pressure drop of gas wells, dynamic reserves of single gas wells, and reservoir physical parameters interpreted by well test, were calculated respectively. Based on the existing understanding of geological characteristics such as sedimentary facies, structure, lithology, and karst landform, an evaluation chart for the stable production capacity of gas wells in areas with different fault-controlled karst reservoir development patterns was established in combination with the calculation results, and finally the favorable areas for gas reservoir development were determined.

[0022] Preferably, the open flow rate of the gas well is calculated as follows:

[0023] Using the binomial productivity equation established by the productivity test of a few gas wells in the entire gas reservoir development area, the α coefficient of the gas well is obtained by the following calculation expression based on the laminar coefficient and turbulent coefficient of the binomial productivity equation:

[0024]

[0025] Among them, q' AOF Indicates the open flow rate of gas wells in the gas reservoir development area where production capacity testing has been carried out, in units of 10 4 m 3 / d; A is the laminar coefficient, dimensionless; B is the turbulent coefficient, dimensionless;

[0026] According to the α coefficient and productivity coefficient KH of the gas well, a relationship curve is drawn, and the relationship between the α coefficient and the productivity coefficient KH value is obtained by regression.

[0027] α=0.0821ln(KH)-0.1 Formula (2);

[0028] Wherein, K is the effective permeability of the formation, obtained from well logging interpretation, in mD; H is the effective thickness of the formation, obtained from well logging interpretation, in m;

[0029] Substituting formula (2) into the "one-point method" production capacity prediction calculation expression, the following revised "one-point method" gas well production capacity prediction calculation expression is obtained. For gas wells in the gas reservoir development area that have not been tested for production capacity, their open flow rate is calculated according to the following calculation expression:

[0030]

[0031] Among them, P R is the formation pressure, in MPa; P wf is the bottom hole pressure, in MPa; q g is the gas well test production, unit is 10 4 m 3 / d.

[0032] Preferably, the method for calculating the gas production per unit pressure drop of the gas well is as follows:

[0033] When the gas well reaches quasi-steady-state production and the production is basically stable, the gas reservoir pressure drop funnel is a set of parallel curves. The formation pressure drop value Δp of the gas well from time t1 to time t2 is obtained by the following calculation expression:

[0034]

[0035] Wherein, Δp is the drop in formation pressure from production at time t1 to time t2, in MPa; p e1 is the reservoir boundary pressure at time t1, in MPa; p e2 is the gas reservoir boundary pressure at time t2, in MPa; p wf1 is the bottom hole flowing pressure of the gas well at time t1, in MPa; p wf2 is the bottom hole flowing pressure of the gas well at time t2, in MPa; p t1 is the wellhead oil pressure at time t1, in MPa; p t2 is the wellhead oil pressure at time t2, in MPa, Δp tubing1 is the wellbore loss pressure at time t1, in MPa; Δp tubing2 is the wellhead oil pressure at time t2, in MPa;

[0036] During the stable production of a gas well, the wellbore pressure loss at different time points is basically the same, Δp tubing1 ≈Δp tubing2 , so formula (4) can be simplified to

[0037]

[0038] The gas production per unit pressure drop from time t1 to time t2 can be calculated by the following expression

[0039]

[0040] Among them, J g is the gas production per unit pressure drop; q gi is the daily gas production on the i-th day when the gas well is in stable production.

[0041] Preferably, the calculation method of the single gas well dynamic reserves is as follows:

[0042] When the gas well enters the boundary control flow, the single well Blasingame curve is established using the production data and fitted with the theoretical characteristic curve. Any fitting point is selected and the actual fitting point (t ca ,q / Δp p ) M And the corresponding theoretical fitting points (t caDd ,q Dd ) MCalculate the dynamic reserves of the gas well according to the following calculation expression:

[0043]

[0044] Where G represents the geological reserves of natural gas, the unit is 10 8 m 3 ; C t Indicates the total compression coefficient of the formation, in MPa -1 ;t ca Indicates the pseudo-time of gas well material balance, in d; t caDd represents the dimensionless material balance pseudo-time of the Blasingame gas well, which is dimensionless; q represents the daily gas production of the gas well, in m 3 / d;Δp p represents the normalized pseudo-pressure difference, in MPa; q Dd represents the dimensionless production of Blasingame gas well, dimensionless; S w Indicates the water saturation of the gas reservoir, in %.

[0045] Preferably, the calculation method of the reservoir physical property parameters interpreted by the well test is as follows:

[0046] Based on the bottom hole pressure and production data of the gas well tested on site, the reservoir physical properties of the gas well are calculated using Pansystem or Saphir well test interpretation software.

[0047] Preferably, based on the existing understanding of the characteristics of sedimentary facies, structure, lithology, and karst landform, combined with the calculation results, a gas well stable production capacity evaluation chart for areas with different fault-controlled karst reservoir development patterns is established, and finally the favorable area for gas reservoir development is determined. This means that according to the established gas well stable production capacity evaluation chart, the area with better results of the four indicator parameters of gas well stable production capacity is selected as the favorable area for gas reservoir development.

[0048] A device for selecting favorable areas for karst gas reservoir development based on strike-slip faults, comprising:

[0049] The fault-controlled karst area division module is used to divide the fault-controlled karst area into different fault-controlled areas according to the fault development direction and the geometric position between faults within the gas reservoir block;

[0050] The fault control area division module is used to divide the fault control area into different fault-controlled karst reservoir development pattern areas on the plane according to the divided fault control area and the direction of karst water flow;

[0051] The evaluation module is used to evaluate the stable production capacity of gas wells in the fault-controlled karst reservoir development pattern area and ultimately determine the favorable areas for gas reservoir development.

[0052] A computer device includes a memory, a processor, and a computer program stored in the memory and executable in the processor. When the processor executes the computer program, the method for selecting favorable areas for karst gas reservoir development based on strike-slip faults described above is implemented.

[0053] A computer-readable storage medium stores a computer program, which, when executed in a computer processor, implements the above-mentioned method for selecting favorable areas for karst gas reservoir development based on strike-slip faults.

[0054] Beneficial effects of the present invention:

[0055] Traditional methods for selecting favorable development zones, based on the presence of hills and beaches and the quality of karst, generally result in high production rates for gas wells deployed in these favorable zones. However, over 30% of these wells struggle to achieve high and stable production, resulting in poor production outcomes and impacting overall reservoir development. Previous methods primarily sought high test yields for gas wells. This new method, based on strike-slip faults, integrates sedimentation, karst, and the evaluation of gas well stability, resulting in a new approach to selecting favorable zones. Practice has proven that this method not only achieves high test yields for gas wells but also achieves high and stable production, effectively improving overall reservoir development. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The foregoing and following detailed description of the present invention will become more apparent when read in conjunction with the following drawings, in which:

[0057] Figure 1 Flow chart of the method of the present invention;

[0058] Figure 2 It is a structural diagram of the device of the present invention;

[0059] Figure 3 This is a schematic diagram of the superposition of karst and fault landforms in the present invention;

[0060] Figure 4 This is a relationship curve diagram of the α coefficient and the production capacity coefficient KH of the present invention;

[0061] Figure 5 This is a schematic diagram of pressure distribution when the gas well enters a pseudo-steady state flow according to the present invention;

[0062] Figure 6 This is the gas well production performance curve of the present invention;

[0063] Figure 7 This is a gas well stable production capacity chart of the present invention;

[0064] Figure 8 This is the well location deployment diagram of Example 2 of the present invention. DETAILED DESCRIPTION

[0065] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the following will further illustrate the technical solutions for achieving the purpose of the present invention through several specific embodiments. It should be noted that the technical solutions claimed for protection by the present invention include but are not limited to the following embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0066] Karst oil and gas reservoirs, also known as karst reservoirs, are oil and gas accumulations formed in impermeable rock layers covering carbonate strata with ancient karst formations (such as caves, cavities, and crystal caves). Karst oil and gas reservoirs are denudation reservoirs and are often closely associated with ancient weathering surfaces, ancient buried hills, and ancient landforms. Karst oil and gas reservoirs, when rich in oil sources, often form large, high-pressure, and high-yield reservoirs.

[0067] Karst gas reservoirs have enormous development potential, but 80% of their natural gas reserves are held in ultra-low-porosity reservoirs with porosity below 5%. These reservoirs are highly heterogeneous, influenced by factors such as sedimentation and karstification, making it extremely difficult to identify favorable development zones. Through years of exploration, a method has been developed to select favorable development zones based on the presence of hills and beaches and the quality of karst. While gas wells deployed in these zones, selected using this method, generally achieve high production rates, over 30% struggle to achieve both high and stable production. Consequently, production results are suboptimal, impacting the overall development of the reservoir.

[0068] Based on this, this embodiment provides a method for selecting favorable areas for karst gas reservoir development based on strike-slip faults. On the basis of strike-slip faults, this method comprehensively evaluates sedimentation, karstity, and gas well stable production capacity to form a new method for selecting favorable areas. Practice has proved that gas wells deployed using this method not only test high production, but also achieve high and stable production of gas wells, which can effectively improve the overall development effect of the gas reservoir.

[0069] To facilitate understanding of this embodiment, a method for selecting favorable areas for karst gas reservoir development based on strike-slip faults disclosed in an embodiment of the present invention is first introduced in detail.

[0070] First, the professional terms involved in the embodiments of the present invention are explained:

[0071] Fault-controlled karst: Fault-controlled karst refers to the dissolution and expansion with the fault fracture zone as the core.

[0072] Bottomhole Flowing Pressure: Bottomhole flowing pressure, short for bottomhole flow pressure, is the bottomhole pressure during oil and gas well production. It represents the residual pressure after oil and gas flow from the formation to the bottom of the well. For flowing wells, it is also the starting pressure for oil and gas to flow from the bottom of the well to the surface.

[0073] Productivity coefficient: The product KH of the effective permeability K of the formation and the effective thickness H of the formation is called the productivity coefficient, which is a parameter that represents the productivity of oil and gas wells.

[0074] The embodiment of the present invention discloses a method for selecting favorable areas for karst gas reservoir development based on strike-slip faults. Figure 1 , the method specifically comprises the following steps:

[0075] Step S101: Divide the fault-controlled karst area into different fault-controlled areas.

[0076] First, based on seismic, well logging, core and other data, the karst paleo-geomorphology of the gas reservoir is obtained using the impression method or residual thickness method. At the same time, the karst development period and fault formation period and development characteristics are clarified, and large-scale first- or second-order faults formed before the karst period are selected.

[0077] Then, the karst paleo-landforms and faults were superimposed by geological image processing software (such as Shiwen, GeoMap, etc.) (refer to the appendix of the manual). Figure 3 ), according to the distribution characteristics of karst landforms and the natural law of water flowing from high to low, the main direction of karst water flow is determined. Figure 3 The middle karst paleo-geomorphology is characterized by being high in the east and low in the west, so the direction of karst water flow is from east to west;

[0078] Finally, different fault control areas are divided according to the fault development direction and the geometric position between faults in the block (such as Figure 3 in the partitions).

[0079] In this embodiment, it should be noted that the use of the impression method or the residual thickness method to obtain the karst paleo-geomorphology of the gas reservoir is a conventional method known to those skilled in the art and is not an invention of the present invention.

[0080] In this embodiment, it should also be noted that the superposition of the karst paleo-landform and the fault is a superposition on a two-dimensional plane.

[0081] Step S102: Based on the divided fault-controlled areas and in combination with the direction of karst water flow, the fault-controlled areas are divided into different fault-controlled karst reservoir development pattern areas on the plane.

[0082] According to the fault-controlled areas divided above, the karstification caused by karst water flow, and the direction of karst water flow, the fault-controlled areas are further divided into three types of fault-controlled karst reservoir development pattern areas on the superimposed two-dimensional plane map, including type I area, type II area and type III area, among which:

[0083] Type I area: Algal mounds are developed and located in paleo-geomorphological residual hills or slope break zones. The direction of karst water flow is parallel to the direction of fault development. The areas on both sides of the fault are fault-controlled parallel zones (i.e. Figure 3 Zone I in

[0084] Category II: Algal mounds are developed and located in paleo-geomorphological residual mounds or slope-break zones. The direction of karst water flow intersects with the direction of fault development, and the water flow does not pass through the fault area ( Figure 3 Zones III and IV in the

[0085] Category III: Algal mounds are developed and located in ancient landform residual hills or slope break zones. The direction of karst water flow intersects with the direction of fracture development. Water flows through the fracture area ( Figure 3 II and V in the .

[0086] Step S103: Evaluate the stable production capacity of gas wells within the fault-controlled karst reservoir development pattern area, and ultimately determine the favorable area for gas reservoir development.

[0087] Four indicators, namely, the open flow rate of gas wells in the fault-controlled karst reservoir development pattern area, gas production per unit pressure drop of gas wells, dynamic reserves of single gas wells, and reservoir physical property parameters interpreted by well testing, were calculated respectively. Based on the existing understanding of geological characteristics such as sedimentary facies, structure, lithology, and karst landform, an evaluation chart of the stable production capacity of gas wells in areas with different fault-controlled karst reservoir development patterns was established in combination with the calculation results of the four indicator parameters. Based on the established evaluation chart, the areas with better results of the four indicator parameters representing gas well productivity were selected as the final favorable areas for gas reservoir development.

[0088] In this embodiment, four index parameters characterizing gas well productivity are the open flow rate of the gas well, the gas production per unit pressure drop of the gas well, the dynamic reserves of the single gas well, and the reservoir physical property parameters interpreted by the well test.

[0089] In this embodiment, the open flow rate of the gas well is calculated as follows:

[0090] For deep, highly heterogeneous karst gas reservoirs, the reservoir heterogeneity is strong and the burial depth is generally deep. Well testing is not only time-consuming and costly, but also difficult to carry out on a large scale. It is also difficult to directly determine the stable production capacity of gas wells that have not been tested for interpretation. Therefore, using the binomial production capacity equation established by the few gas wells in the entire gas reservoir development area that have been tested for production capacity, and based on the laminar coefficient and turbulent coefficient of the binomial production capacity equation, the α coefficient of the gas well can be obtained through the following calculation expression.

[0091]

[0092] Among them, q' AOF Indicates the open flow rate of gas wells in the gas reservoir development area where production capacity testing has been carried out, in units of 10 4 m 3 / d; A is the laminar coefficient, dimensionless; B is the turbulent coefficient, dimensionless; α is the dimensionless coefficient;

[0093] According to the α coefficient and productivity coefficient KH of the gas well, draw a relationship curve (refer to the attached Figure 4 ), the relationship between the α coefficient and the capacity coefficient KH value is obtained by semi-logarithmic regression

[0094] α=0.0821ln(KH)-0.1 Formula (2);

[0095] Wherein, K is the effective permeability of the formation, obtained from well logging interpretation, in mD; H is the effective thickness of the formation, obtained from well logging interpretation, in m;

[0096] Substitute formula (2) into the following "one-point method" capacity forecast calculation expression:

[0097]

[0098] The following modified “one-point method” gas well productivity prediction calculation expression can be obtained. For gas wells in the gas reservoir development area that have not been tested for productivity, their open flow rate can be calculated according to the following calculation expression:

[0099]

[0100] Among them, P R is the formation pressure, in MPa; P wf is the bottom hole pressure, in MPa; q g is the gas well test production, unit is 10 4 m 3 / d.

[0101] In this embodiment, it should be noted that the binomial production capacity calculation expression for a gas well is a group of production capacity equations known to those skilled in the art.

[0102] In this embodiment, it should be noted that the open flow rate is a parameter and index used to evaluate the gas production capacity of a gas well.

[0103] In this embodiment, it is necessary to further explain that the relationship between the α coefficient and the capacity coefficient KH value obtained by regression is obtained by using a semi-logarithmic regression method, and the specific calculation method is a conventional means known to those skilled in the art.

[0104] In this embodiment, the method for calculating the gas production per unit pressure drop of the gas well is as follows:

[0105] Traditional methods for calculating gas production per unit pressure drop require multiple well tests or long-term shut-in pressure measurements. This is not only costly but also impacts normal gas well production. Data errors are significantly affected by operational factors, making it difficult to implement on a large scale during gas reservoir development. Therefore, this embodiment calculates gas production per unit pressure drop by selecting ecological dynamic data from a gas well during quasi-steady-state production.

[0106] Refer to the instruction manual Figure 5 and Figure 6 When the gas well reaches quasi-steady-state production and the production is basically stable, the gas reservoir pressure drop funnel is a set of parallel curves. The formation pressure drop value Δp of the gas well from time t1 to time t2 is obtained by the following calculation expression:

[0107]

[0108] Wherein, Δp is the drop in formation pressure from production at time t1 to time t2, in MPa; p e1 is the reservoir boundary pressure at time t1, in MPa; p e2 is the gas reservoir boundary pressure at time t2, in MPa; p wf1 is the bottom hole flowing pressure of the gas well at time t1, in MPa; p wf2 is the bottom hole flowing pressure of the gas well at time t2, in MPa; p t1 is the wellhead oil pressure at time t1, in MPa; p t2 is the wellhead oil pressure at time t2, in MPa; Δp tubing1 is the wellbore loss pressure at time t1, in MPa; Δp tubing2 is the wellhead oil pressure at time t2, in MPa;

[0109] During the stable production of a gas well, the wellbore pressure loss at different time points is basically the same, so Δp tubing1 ≈Δp tubing2 , so formula (4) can be simplified to

[0110]

[0111] Therefore, the gas production per unit pressure drop from time t1 to time t2 can be calculated by the following expression:

[0112]

[0113] Among them, J g is the gas production per unit pressure drop; q gi is the daily gas production on the i-th day when the gas well is in stable production.

[0114] In this embodiment, it should be noted that the daily gas production data of the i-th day during stable production of the gas well can be obtained through an on-site flow meter.

[0115] In this embodiment, the calculation method of the single-well dynamic reserves of the gas well is as follows:

[0116] When the gas well enters the boundary control flow, the single well Blasingame curve is established using the production data and fitted with the theoretical characteristic curve. Any fitting point is selected and the actual fitting point (t ca ,q / Δp p ) M And the corresponding theoretical fitting points (t caDd ,q Dd ) M Calculate the dynamic reserves of the gas well according to the following calculation expression:

[0117]

[0118] Where G represents the geological reserves of natural gas, the unit is 10 8 m 3 ; C t Indicates the total compression coefficient of the formation, in MPa -1 ;t ca Indicates the pseudo-time of gas well material balance, in d; t caDd represents the dimensionless material balance pseudo-time of the Blasingame gas well, which is dimensionless; q represents the daily gas production of the gas well, in m 3 / d;Δp p represents the normalized pseudo-pressure difference, in MPa; q Dd represents the dimensionless production of Blasingame gas well, dimensionless; S w Indicates the water saturation of the gas reservoir, in %.

[0119] In this embodiment, it should be noted that the daily gas production data of the gas well can be obtained through an on-site flow meter. During the calculation of this embodiment, several fitting points can be obtained.

[0120] In this embodiment, the calculation method of the reservoir physical property parameters interpreted by the well test is as follows:

[0121] By using the bottom hole pressure and production data of gas wells tested on site and using well test interpretation software such as Pansystem and Saphir, the reservoir physical properties of the gas wells can be calculated.

[0122] In this embodiment, it should be noted that the reservoir physical property parameter refers to the average permeability of the reservoir.

[0123] Refer to the instruction manual Figure 7 The stable production capacity of gas wells in the fault-controlled karst zone has obvious differences, including:

[0124] Class I area: mainly developed fracture-pore reservoirs, with an average open flow rate of 151.18×10 4 m 3 / d, the average gas production per unit pressure drop is 1991.41×10 4 m 3 / MPa, dynamic reserve 15.87×10 8 m 3 , well test interpretation reservoir average permeability is 0.4mD, mainly in zone I;

[0125] Category II area: mainly developed porous reservoirs, with an average open flow rate of 125.81×10 4 m 3 / d, average gas production per unit pressure drop, average dynamic reserves 12.70×10 8 m 3 , well test interpretation shows that the average reservoir permeability is 0.15mD, mainly in Zone III and Zone IV;

[0126] Category III area: mainly porous reservoirs are developed, with an average open flow rate of 76.76×10 4 m 3 / d, the average gas production per unit pressure drop is 151.37×10 4 m 3 / MPa, average dynamic reserves 3.3×10 8 m 3 The well test interpretation shows that the average reservoir permeability is 0.05mD, mainly in Zone II and Zone V.

[0127] Based on the fault-controlled karst zoning formed by the above-mentioned fault-controlled karst pattern, the stable production capacity of gas wells was evaluated. The hydrodynamic conditions in Class I and Class II areas are relatively strong, the gas wells have high open flow, large gas production per unit pressure drop, large dynamic reserves, and good stable production capacity. The hydrodynamic conditions in Class III areas are relatively weak, and gas well tests can achieve high production. However, the reservoir properties in the far-well area are poor, the fluid energy supply to the near-well area is weak, the gas production per unit pressure drop and dynamic reserves are small, and the stable production capacity of gas wells is poor. Therefore, Class I and Class II areas are favorable development areas.

[0128] In this embodiment, by comparing the four index parameters of the gas wells, namely, the open flow rate of the gas wells, the gas production per unit pressure drop of the gas wells, the dynamic reserves of the single gas wells, and the reservoir physical property parameters interpreted by the well test, the favorable areas for gas reservoir development can be basically determined; further, based on the obtained favorable areas for gas reservoir development, the established gas well stable production capacity evaluation chart can be used to reversely infer the geological characteristics of the favorable areas for gas reservoir development.

[0129] This technology, based on the well-defined distribution characteristics of strike-slip faults, integrates sedimentation, karstification, and gas well production stability evaluation to form a new method for selecting favorable areas. Its core purpose is to guide the selection of favorable development areas, thereby improving the overall development level of gas reservoirs.

[0130] Furthermore, based on the same inventive concept, an embodiment of the present invention also provides a preferred device for developing favorable areas of karst gas reservoirs based on strike-slip faults, as described in the following embodiments. As used below, the term "unit" or "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, it is also possible and conceivable to implement it in hardware, or in a combination of software and hardware. Specifically, refer to the attached manual. Figure 2 The device may include: a fault-controlled karst area division module 201, a fault-controlled area division module 202 and an evaluation module 203.

[0131] The structure is described in detail below.

[0132] The fault-controlled karst area division module 201 is used to divide the fault-controlled karst area into different fault-controlled areas according to the fault development direction and the geometric position between the faults in the gas reservoir block;

[0133] The fault control area division module 202 is used to divide the fault control area into different fault-controlled karst reservoir development pattern areas on the plane according to the divided fault control area and the direction of karst water flow;

[0134] The evaluation module 203 is used to evaluate the stable production capacity of gas wells in the fault-controlled karst reservoir development pattern area and ultimately determine the favorable area for gas reservoir development.

[0135] It should be noted that the systems, devices, models, or units described in the above embodiments can be implemented by computer chips or physical devices, or by products with certain functions. For ease of description, in this specification, the above devices are described as various units based on their functions. Of course, when implementing the present invention, the functions of each unit can be implemented in the same or multiple software and / or hardware components.

[0136] Furthermore, in this specification, adjectives such as first and second may be used merely to distinguish one element or action from another, without necessarily or implying any actual such relationship or order.

[0137] From the above description, it can be seen that the embodiment of the present invention provides a method for selecting favorable areas for karst gas reservoir development based on strike-slip faults. Based on strike-slip faults, it comprehensively evaluates sedimentation, karstity and gas well stable production capabilities to form a new method for selecting favorable areas. Practice has proved that the gas wells deployed by this method not only test high production, but also achieve high and stable production of gas wells, which can effectively improve the overall development effect of the gas reservoir.

[0138] Furthermore, an embodiment of the present invention also provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and executable in the processor. When the processor executes the computer program, the steps of any of the above methods are implemented.

[0139] Furthermore, an embodiment of the present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed in a computer processor, the steps of any of the above methods are implemented.

[0140] The computer device may be a desktop computer, notebook computer, PDA, cloud server, etc. The computer device may include, but is not limited to, a processor and a memory. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0141] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor, or the processor may be any conventional processor, etc. The memory may be an internal storage unit of the electronic device, such as a hard disk or memory of a terminal device. The memory may also be an external storage device of the electronic device, such as a plug-in hard disk equipped on the electronic device, a smart media card (SMC), a secure digital (SD) card, a flash memory card, etc. Furthermore, the memory may include both the internal storage unit of the electronic device and an external storage device. The memory is used to store the computer program and other programs and data required by the electronic device. The memory may also be used to temporarily store data that has been output or is to be output.

[0142] The devices or modules illustrated in the above embodiments can be specifically implemented by computer chips or entities, or by products with certain functions. For the convenience of description, the above devices are described in terms of functions and are divided into various modules and described separately. Of course, when implementing the present invention, the functions of each module can be implemented in the same or multiple software and / or hardware, or the module that implements the same function can be implemented by a combination of multiple sub-modules. The device embodiments described above are merely schematic. For example, the division of the modules is only a logical function division. In actual implementation, there may be other division methods, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0143] Those skilled in the art will also appreciate that, in addition to implementing the controller in pure computer-readable program code, it is entirely possible to implement the same functionality by logically programming the method steps in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, embedded microcontrollers, and the like. Therefore, such a controller can be considered a hardware component, and the devices included therein for implementing various functions can also be considered structures within the hardware component. Alternatively, the devices for implementing various functions can be considered both software modules implementing the method and structures within the hardware component.

[0144] Example 2

[0145] This embodiment takes the well location deployment of a certain project as an example to further illustrate the solution of the present invention.

[0146] Under the condition that reservoir sedimentary properties, karst landforms and other conditions are basically similar, two development wells are deployed on both sides of the fault. Well W1 deployed in the second-class area is located in the area where water flow does not pass through the fault, with a good degree of karstification. The open flow rate of the gas well is 106.24×10 4 m3 / d, daily gas production is 24×10 4 m 3 , gas production per unit pressure drop reaches 2200×10 4 m 3 / MPa, and the dynamic reserve is 17.18×10 8 m 3 The permeability is 0.172mD and the drilling thickness is 180m. The W2 well deployed in the third category area is a water flow through the fracture area with poor karstity. The open flow rate of the gas well is 96.24×10 4 m 3 / d, daily gas production is 11.45×10 4 m 3 , gas production per unit pressure drop reaches 520×10 4 m 3 / MPa, dynamic reserves of 5.02×108 m 3 , permeability is 0.032mD, and drilling thickness is 147.20m.

[0147] By comparing the two wells, we can see that the gas wells deployed in the two areas have relatively favorable sedimentary environments and paleogeomorphological locations, and the gas well test production is comparable. However, due to the influence of faults, the production effect of Well W1 is significantly better than that of Well W2. Therefore, the Class II area is a favorable development area.

[0148] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for selecting favorable areas for karst gas reservoir development based on strike-slip faults, characterized in that: include: According to the fault development direction and geometric position between faults in the gas reservoir block, the fault-controlled karst area is divided into different fault-controlled areas; According to the divided fault-controlled areas and the direction of karst water flow, the fault-controlled areas are divided into different fault-controlled karst reservoir development pattern areas on the plane; Evaluate the stable production capacity of gas wells in the fault-controlled karst reservoir development pattern area and ultimately determine the favorable areas for gas reservoir development; The fault-controlled karst reservoir development model area includes three types: In the first type of area, algal mounds are developed and located in paleo-geomorphological residual mounds or slope break zones. The direction of karst water flow is parallel to the direction of fault development, and the areas on both sides of the fault are fault-controlled parallel zones. Category II areas are areas where algal mounds are developed and are located in paleo-geomorphological residual mounds or slope-break zones, where the direction of karst water flow intersects with the direction of fault development, and the water flow does not cross the faults; Category III areas are areas where algal mounds are developed and are located in paleo-geomorphological residual mounds or slope-break zones, where the direction of karst water flow intersects with the direction of fault development, and water flows through the fault area; The evaluation of the stable production capacity of gas wells in the fault-controlled karst reservoir development pattern area and the final determination of favorable areas for gas reservoir development include: Four index parameters, namely, open flow rate, gas production per unit pressure drop, dynamic reserves of single gas wells, and reservoir physical property parameters interpreted from well tests, were calculated for gas wells in areas with fault-controlled karst reservoir development patterns. Based on the existing understanding of geological characteristics such as sedimentary facies, structure, lithology, and karst landforms, the calculation results of the four index parameters were combined to establish a stable production capacity evaluation chart for gas wells in areas with different fault-controlled karst reservoir development patterns, ultimately determining favorable areas for gas reservoir development. The reservoir physical property parameter refers to the average reservoir permeability. The open flow rate of the gas well is calculated as follows: Using the binomial productivity equation established by the productivity test of a few gas wells in the entire gas reservoir development area, the laminar coefficient and turbulent coefficient of the binomial productivity equation are used to obtain the gas well's coefficient Formula (1); in, Indicates the open flow rate of gas wells in gas reservoir development areas where productivity testing has been carried out; is the laminar flow coefficient, dimensionless; is the turbulence coefficient, dimensionless; According to the gas well Coefficient and capacity coefficient , draw a relationship curve, and get Coefficient and capacity coefficient The relationship between the values Formula (2); in, is the effective permeability of the formation, obtained from well logging interpretation; is the effective thickness of the formation, obtained from well logging interpretation; Substituting formula (2) into the "one-point method" production capacity prediction calculation expression, the following modified "one-point method" gas well production capacity prediction calculation expression is obtained. For gas wells in the gas reservoir development area that have not been tested for production capacity, their open flow rate is calculated according to the following calculation expression: Formula (3); in, is the formation pressure; is the bottom hole flowing pressure; Testing gas well production; The specific method for calculating the gas production per unit pressure drop of the gas well is as follows: When the gas well reaches the quasi-steady state production and the production is basically stable, the gas reservoir pressure drop funnel is a set of parallel curves. Production time to Formation pressure drop at time From the following calculation expression we can get Formula (4); in, for Production time to The formation pressure drop value at the moment; for Gas reservoir boundary pressure at the moment; for Gas reservoir boundary pressure at the moment; for The bottom hole flow pressure of the gas well at any moment; for The bottom hole flow pressure of the gas well at any moment; for Wellhead oil pressure at all times; for Wellhead oil pressure at all times; for Momentary wellbore loss pressure; for Wellhead oil pressure at all times; During the stable production of a gas well, the wellbore pressure loss at different time points is basically the same. , so formula (4) is simplified to Formula (5); from Production time to The unit pressure drop gas production at the time is obtained by the following calculation expression: Formula (6); in, is the gas production per unit pressure drop; For stable production of gas wells Daily gas production; The calculation method of the dynamic reserves of a single gas well is as follows: When the gas well enters the boundary control flow, the single well Blasingame curve is established using the production data and fitted with the theoretical characteristic curve. Any fitting point is selected and the actual fitting point is recorded. And the corresponding theoretical fitting points Calculate the dynamic reserves of the gas well according to the following calculation expression: Formula (7); in, Indicates the geological reserves of natural gas; Indicates the total compressibility of the formation; represents the pseudo-time of material balance of gas well; represents the dimensionless material balance pseudo-time of the Blasingame gas well; Indicates the daily gas production of the gas well; represents the normalized pseudo-pressure difference; It indicates the dimensionless production of Blasingame gas well; Indicates the water saturation of the gas reservoir.

2. The method for selecting favorable areas for karst gas reservoir development based on strike-slip faults according to claim 1, characterized in that: According to the fault development direction and geometric position between faults in the gas reservoir block, the fault-controlled karst area is divided into different fault-controlled areas, including: Based on seismic, well logging and core data, the karst paleo-geomorphology of the gas reservoir is obtained using the impression method or the residual thickness method; According to the karst development period and fault formation period and development characteristics, the first-level or second-level large faults formed before the karst period were selected, and the karst paleo-geomorphology and faults were superimposed using geological image processing software; Determine the main direction of karst water flow based on the distribution characteristics of karst paleo-landforms; According to the fault development direction and geometric position between faults in the gas reservoir block, the block is divided into different fault-controlled areas.

3. The method for selecting favorable areas for karst gas reservoir development based on strike-slip faults according to claim 1, characterized in that: The calculation method of the reservoir physical property parameters interpreted by the well test is as follows: Based on the bottom hole pressure and production data of the gas well tested on site, the reservoir physical properties of the gas well are calculated using Pansystem or Saphir well test interpretation software.

4. The method for selecting favorable areas for karst gas reservoir development based on strike-slip faults according to claim 1, characterized in that: The method of establishing a gas well stable production capacity evaluation chart for different fault-controlled karst reservoir development pattern areas based on the existing understanding of the geological characteristics of sedimentary facies, structure, lithology, and karst landform and combining the calculation results of four index parameters, and finally determining the favorable area for gas reservoir development means selecting, based on the established gas well stable production capacity evaluation chart, areas with better results of the four index parameters for gas well stable production capacity as favorable areas for gas reservoir development.

5. The method for selecting favorable areas for karst gas reservoir development based on strike-slip faults according to claim 2, characterized in that: The superposition of the karst paleo-landform and the fault is a superposition on a two-dimensional plane.

6. The method for selecting favorable areas for karst gas reservoir development based on strike-slip faults according to claim 1, characterized in that: By semi-logarithmic regression Coefficient and capacity coefficient The relationship between the values.

7. The method for selecting favorable areas for karst gas reservoir development based on strike-slip faults according to claim 1, characterized in that: The daily gas production of the gas well is obtained by collecting data using an on-site flow meter.

8. A device for selecting favorable areas for karst gas reservoir development based on strike-slip faults, characterized in that: The device is used to implement the method for selecting favorable areas for karst gas reservoir development based on strike-slip faults as described in any one of claims 1 to 7, comprising: The fault-controlled karst area division module is used to divide the fault-controlled karst area into different fault-controlled areas according to the fault development direction and the geometric position between faults within the gas reservoir block; The fault control area division module is used to divide the fault control area into different fault-controlled karst reservoir development pattern areas on the plane according to the divided fault control area and the direction of karst water flow; The evaluation module is used to evaluate the stable production capacity of gas wells in the fault-controlled karst reservoir development pattern area and ultimately determine the favorable areas for gas reservoir development.

9. A computer device, characterized in that: The method comprises a memory, a processor, and a computer program stored in the memory and executable in the processor, wherein when the processor executes the computer program, the method according to any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed in a computer processor, the method according to any one of claims 1 to 7 is implemented.

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