Method for analyzing productivity contribution of outer zone of shale condensate gas well volume fracturing

Abstract

The present application relates to a kind of shale condensate gas well volume fracturing outer zone productivity contribution analysis method, method includes the following steps: based on the complex fracture network characteristics and oil-gas two-phase flow characteristics in the fracturing development process of shale condensate gas well, establish mathematical physics model based on three linear flow theory, the complex fracture network of shale condensate gas well is equivalent to be handled into fracturing reconstruction body, fracturing reconstruction body includes artificial main fracture, fracturing reconstruction inner zone and fracturing reconstruction outer zone;Based on the mathematical physics model of three linear flow theory, the history matching of shale condensate gas well dynamic production is carried out, and typical shale and fracturing crack parameter is obtained;Based on typical shale and fracturing crack parameter, the contribution degree of fracturing reconstruction outer zone to productivity under the condition of different fracturing reconstruction outer zone boundary length, different fracturing reconstruction outer zone permeability is analyzed, to give reasonable well spacing considering the contribution degree of fracturing reconstruction outer zone.

Description

Technical Field

[0001] This invention relates to a method for analyzing the contribution of volumetric fracturing to the production capacity of shale condensate gas wells in the outer zone, belonging to the field of oil and gas exploration and development technology. Background Technology

[0002] Shale oil and gas fields are important mineral resources for oil and gas development. However, due to the extreme density of shale and the matrix permeability ranging from tens to hundreds of nadareses, it is generally believed that the matrix outside the fracturing zone contributes very little to production and can be ignored. Therefore, when determining the reasonable well spacing of shale oil and gas wells, theoretical calculations and microseismic monitoring of fracturing fractures are often the main methods. Based on shale physical properties, brittleness, and in-situ stress, and construction designs such as displacement, fractures are simulated to determine the achievable fracture half-length. Reservoir engineering professionals analyze the impact of parameters such as fracture half-length, conductivity, and matrix permeability on production and economics using reservoir engineering methods or numerical simulation methods to optimize the theoretically optimal well spacing. Theoretical optimization design also needs to be combined with field fracture monitoring. Based on the fracture morphology and distribution range of the fracturing fractures monitored by microseismic monitoring, twice the fracture half-length is taken as the reasonable well spacing. However, in reality, the well spacing of horizontal shale gas wells in North America has been continuously optimized based on geological, fluid, and technological factors.

[0003] Based on actual production data from condensate gas wells in Eagle Ford, North America, this application found that, within the same region and under essentially the same fracturing parameters, the production decline decreased with increasing well spacing. Figure 1 As shown, this indicates that areas outside the fracturing reservoir (SRV) also supply gas to the reservoir, thereby increasing gas well production and reducing the oil and gas decline rate. How to assess the impact of areas outside the SRV on oil and gas production is an urgent problem to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for analyzing the production contribution of shale condensate gas wells in the outer zone of volumetric fracturing. This method establishes a mathematical and physical model based on trilinear flow theory, taking into account the complex fracture network characteristics and oil-gas two-phase flow characteristics during the fracturing development process of shale condensate gas wells. Based on historical fitting of the dynamics of producing shale condensate gas wells, typical shale and fracturing fracture parameters are obtained. Based on this, the production contribution analysis of the outer zone of fracturing stimulation is carried out.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for analyzing the productivity contribution of shale condensate gas wells in the outer zone of volumetric fracturing includes the following steps:

[0007] Based on the complex fracture network characteristics and oil-gas two-phase flow characteristics in the fracturing development process of shale condensate gas wells, a mathematical and physical model based on the trilinear flow theory is established. This model treats the complex fracture network of shale condensate gas wells as equivalent to a fracturing body, which includes an artificial main fracture, an inner fracturing zone, and an outer fracturing zone.

[0008] Based on the mathematical and physical model of trilinear flow theory, the dynamics of shale condensate gas wells in production are historically fitted to obtain typical shale and fracturing parameters.

[0009] Based on typical shale and fracturing fracture parameters, this study analyzes the contribution of the fracturing outer zone to production capacity under different boundary lengths and permeabilities of the fracturing outer zone, thus providing a reasonable well spacing that takes into account the contribution of the fracturing outer zone.

[0010] The method for analyzing the contribution of shale condensate gas well volumetric fracturing to production capacity in the outer zone, preferably, establishes a mathematical and physical model based on the trilinear flow theory based on the following assumptions:

[0011] The shale reservoir is horizontal and of uniform thickness, with horizontal wells located in the center of the reservoir and fractures running through the entire reservoir.

[0012] Considering the compressibility of oil and gas, the compressibility of rocks is ignored;

[0013] The adsorption and desorption of gases follow the Langmuir monolayer adsorption model. Since the adsorption mechanism of condensate is not yet clear, it is not considered separately.

[0014] The fluid consists of two components: oil and gas. The gas component exists only in the gas phase, while the oil component can exist in both the oil and gas phases simultaneously.

[0015] The method for analyzing the productivity contribution of the outer zone in volumetric fracturing of shale condensate gas wells, preferably, uses the following equation for the fracturing stimulation of the outer zone:

[0016] The fracturing-modified outer zone is the matrix zone, and the adsorption and desorption of gases are described using Langmuir theory.

[0017]

[0018] In the formula, V L The volume is the Langfurter volume; P L ρ is the Landau pressure; p is the pressure; V is the amount of gas adsorbed per unit volume of rock.

[0019] The differential equations for the seepage of oil and gas in the fracturing-enhanced outer zone are as follows:

[0020] Gas components:

[0021]

[0022] Oil components:

[0023]

[0024] In the formula, k Arg k represents the relative permeability of the outer gas phase. Ar o represents the relative permeability of the oil phase in the outer zone; k A φ represents the permeability of the outer matrix. A S represents the porosity of the outer matrix. Ag S represents the gas saturation level in the outer region. Ao Oil saturation in the outer zone; μ g μ is the gas viscosity. o B represents crude oil viscosity. g B is the gas volume coefficient; o p is the crude oil volume coefficient; A External zone pressure; t is production time; R v V represents the content of dissolved condensate oil in the gas phase; L p is the Langevin volume; L y represents the Langmuir pressure; y is the coordinate direction.

[0025] The method for analyzing the productivity contribution of the outer zone of shale condensate gas well volumetric fracturing, preferably, involves a dual-medium fracturing zone. An unsteady-state mass transfer model is used, treating the medium as a flat plate. The influence of adsorbed gas content is referenced to the outer zone. Therefore, the flow equation in the matrix is:

[0026] Gas components:

[0027]

[0028] Oil components:

[0029]

[0030] In the formula, k mrg k represents the relative permeability of the gas phase in the inner matrix. mro k represents the relative permeability of the oil phase in the inner matrix. m φ represents the permeability of the inner matrix. m S represents the internal matrix porosity. mg S represents the gas saturation in the inner matrix. mo Oil saturation in the inner zone matrix; p m denoted as α, where α is the matrix pressure in the inner region; z is the coordinate direction.

[0031] The method for analyzing the productivity contribution of the outer zone of shale condensate gas wells via volumetric fracturing, preferably, involves the following: Since the fractures in the inner zone of the fracturing stimulation zone have matrix and are supplied by the outer zone of the fracturing stimulation zone, the flow equation in the matrix is:

[0032] Gas components:

[0033]

[0034] Oil components:

[0035]

[0036] In the formula, k frg k represents the relative permeability in the secondary fractures within the inner zone. fro k represents the relative permeability of the oil phase in the secondary fracture zone within the inner region. f Permeability of secondary fractures in the inner zone; φ f Porosity of secondary fractures in the inner zone; S fg S represents the gas saturation in the secondary fractures within the inner zone. fo p represents the oil saturation in the secondary fractures within the inner zone. f For the secondary fracture pressure in the inner zone; q gmf q represents the mass of gas flowing into a unit volume of secondary fracture from the matrix system within the inner zone per unit time; gAf The value represents the mass of gas flowing into a unit volume of secondary fracture from the outer zone matrix system per unit time; x represents the coordinate direction.

[0037] The method for analyzing the productivity contribution of the outer zone of shale condensate gas wells via volumetric fracturing, preferably, takes into account the fluid exchange from the fracturing-enhanced inner zone fractures to the artificial fractures, then the seepage equation in the artificial fractures is:

[0038] Gas components:

[0039]

[0040] Oil components:

[0041]

[0042] In the formula, k Frg k represents the relative permeability in the artificial fracture. Fr o represents the relative permeability of the oil phase in the artificial fracture; k F The permeability of the artificial fracture; φ F S represents the porosity of artificial cracks. Fg S represents the gas saturation in the artificial fracture. Fo Oil saturation in artificial fractures; p F For artificial crack pressure; q gfF q represents the mass of gas flowing into a unit volume of artificial fracture from a secondary fracture per unit time; ofF The value represents the mass of crude oil flowing into a unit volume of artificial fracture from secondary fractures per unit time; x represents the coordinate direction.

[0043] The method for analyzing the productivity contribution of the outer zone of shale condensate gas wells via volumetric fracturing, preferably includes typical shale and fracturing parameters such as: fracture half-length, secondary fracture permeability, matrix permeability in the inner / outer zone, artificial fracture conductivity, and matrix block width in the fracturing-enhanced inner zone.

[0044] The present invention has the following advantages due to the adoption of the above technical solutions:

[0045] 1. This invention addresses the complex fracture network characteristics and oil-gas two-phase flow characteristics during the fracturing development of shale condensate gas wells. It establishes a mathematical and physical model based on trilinear flow theory. By historically fitting the dynamics of producing shale condensate gas wells, it obtains typical shale and fracturing fracture parameters. Based on this, it conducts a production capacity contribution analysis of fracturing stimulation areas.

[0046] 2. The research results of the analytical method of this invention show that fracturing and stimulation of the outer zone contributes to the production capacity of shale condensate gas wells, and the contribution increases with the increase of matrix permeability. In the first 5 years of production, the outer zone within 40m contributes to the production capacity, with the main contribution within 20m; after 30 years of production, the contribution of the fracturing and stimulation of the outer zone to the production capacity is concentrated within 60m. Based on the analysis of the production contribution of the outer zone in the first 5 and 30 years, it is believed that in the Yingtan shale condensate gas area, the range of the outer zone can be appropriately considered when optimizing well spacing, but it should not be too large, and should be controlled within 20m as much as possible. The analytical method of this invention can provide a reference for the development of shale condensate gas in China. Attached Figure Description

[0047] Figure 1 A comparison chart of oil production from condensate gas wells with well spacing of 500 meters and 150 meters provided for this embodiment of the invention;

[0048] Figure 2 This is a mathematical and physical model diagram of a trilinear flow in a shale fracturing horizontal well provided in this embodiment of the invention, where Xe is the outer boundary range, and y e For the outer boundary range, y F The length of the artificial crack is half its length;

[0049] Figure 3 This is the bottom-hole flowing pressure diagram of the shale S1 well provided in this embodiment of the invention;

[0050] Figure 4 This is the gas-oil ratio in the initial stage of the shale S1 well provided in this embodiment of the invention;

[0051] Figure 5 This is a fitting and prediction diagram of the oil production of shale S1 well provided in this embodiment of the invention;

[0052] Figure 6 This is a fitting and prediction diagram of the gas production of the shale S1 well provided in this embodiment of the invention;

[0053] Figure 7 This is a graph showing the change in gas production / cumulative gas production over time for different outer zone lengths provided in this embodiment of the invention.

[0054] Figure 8 This is a graph showing the change in oil production / cumulative oil production over time under different outer zone lengths provided in this embodiment of the invention.

[0055] Figure 9 This is a graph showing the relationship between the gas production contribution rate and the length of the outer zone under different outer zone permeability in the first 5 years, provided by this embodiment of the invention.

[0056] Figure 10 This is a graph showing the relationship between oil production contribution rate and outer zone length under different outer zone permeability conditions provided in this embodiment of the invention.

[0057] Figure 11 This embodiment of the invention provides a graph showing the relationship between the gas production contribution rate and the length of the outer zone over the first 30 years under different outer zone permeability.

[0058] Figure 12 This is a graph showing the relationship between the oil production contribution rate and the length of the outer zone over the first 30 years under different outer zone permeability levels, provided in this embodiment of the invention. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0060] This invention addresses the issue of neglecting the contribution of the matrix outside the fracturing zone to production in existing shale oil and gas field development processes. Instead, it proposes a method for analyzing the production contribution of the outer zone of shale condensate gas wells through volumetric fracturing. This method establishes a mathematical and physical model based on trilinear flow theory, taking into account the complex fracture network characteristics and oil-gas two-phase flow characteristics during the fracturing development process of shale condensate gas wells. Based on historical fitting of the dynamics of producing shale condensate gas wells, typical shale and fracturing fracture parameters are obtained. Based on this, the production contribution analysis of the outer zone of fracturing is carried out.

[0061] The Yingtan Shale Oil and Gas Field is located in the Gulf Basin of South Texas, USA. Its main shale oil and gas producing layer is the Yingtan Formation, which is vertically divided into upper and lower sections. In the early stages of development, the lower section of the Yingtan Formation was the primary producing layer. In recent years, with advancements in fracturing and other development technologies, localized attempts have been made to develop the upper section of the Yingtan Formation with some success. The Yingtan Formation's sedimentary environment was controlled by multiple tectonic events, developing in a Middle to Late Cretaceous paleooceanic continental shelf sedimentary environment approximately 85 Ma ago, directly overlying Late Triassic and Jurassic carbonate strata. The lower section of the Yingtan Formation has relatively good preservation conditions. Its overlying strata consist of mudstone from the upper section of the Yingtan Formation, locally Austin Cretaceous limestone; the underlying strata are Buda limestone, locally Del Rio marl. The Yingtan Formation is buried at depths of approximately 1500–4900 m on land, with an average thickness of 76 m. The lower section of the Yingtan Formation consists of black shale / mudstone, with an average carbonate mineral content of 58% and an average clay mineral content of 16.5%, averaging 4.23%. Type II1 kerogen is the main component. From northwest to southeast, the Ro value of the lower section of the Yingtan Formation gradually increases. Based on production data from over 20,000 producing wells, this invention divides the Yingtan Shale area into five oil and gas producing zones according to the initial gas-oil ratio: black oil, volatile oil, condensate gas, wet gas, and dry gas. Regional oil and gas production is mainly controlled by the maturity of organic matter. This invention focuses on the condensate gas zone.

[0062] The method for analyzing the contribution of volumetric fracturing to the production capacity of shale condensate gas wells involved in this invention is as follows:

[0063] 1. Establish a mathematical and physical model based on the theory of trilinear flow.

[0064] Microseismic data from extensive hydraulic fracturing processes at Yingtan indicate that shale condensate gas wells, after hydraulic fracturing, form highly complex fracture networks within the shale formation. Based on previous research by Wu Yonghui et al., these complex fracture networks can be equivalently represented as a fracturing reforming body (SRV), consisting of an artificial main fracture, an inner fracturing reforming zone, and an outer fracturing reforming zone, such as... Figure 2 As shown. The inner zone of the fracturing stimulation mainly considers the complex fracture network system formed by fracturing, treating it as a dual-medium system. Due to the low inherent permeability of the matrix, existing unsteady flow models such as Kazemi can be used. The outer zone of the fracturing stimulation, since it has not been fractured, is treated as a single-pore medium. In each zone, the fluid flow is treated as linear flow, i.e., fluid in the outer zone flows linearly into the fracture matrix in the inner zone, fluid in the inner zone matrix flows linearly into the fracture medium in the inner zone, and then flows linearly from the inner zone fractures into the artificial fractures (e.g., Figure 2 (As shown).

[0065] Based on the complex fracture network characteristics and hydrocarbon two-phase flow characteristics during the fracturing development of shale condensate gas wells, a mathematical-physical model based on trilinear flow theory is established. This model is based on the following assumptions:

[0066] (1) The shale reservoir is horizontal and of uniform thickness, with horizontal wells located in the center of the reservoir and fractures penetrating the entire reservoir.

[0067] (2) Consider the compressibility of oil and gas, and ignore the compressibility of rocks;

[0068] (3) The adsorption and desorption of gases follow the Langmuir monolayer adsorption model. Since the adsorption mechanism of condensate is not yet clear, it is not considered separately.

[0069] (4) The fluid consists of two components: oil and gas. The gas component exists only in the gas phase, while the oil component can exist in both the oil and gas phases at the same time.

[0070] 1.1 The equation for the fracturing stimulation of the outer zone is:

[0071] The fracturing-modified outer zone is the matrix zone, and the adsorption and desorption of gases are described using Langmuir theory.

[0072]

[0073] In the formula, V L The volume is the Langfurter volume; P L ρ is the Landau pressure; p is the pressure; V is the amount of gas adsorbed per unit volume of rock.

[0074] The differential equations for the seepage of oil and gas in the fracturing-enhanced outer zone are as follows:

[0075] Gas components:

[0076]

[0077] Oil components:

[0078]

[0079] Initial conditions:

[0080] p A | t＝0 =p i (4)

[0081] External boundary conditions:

[0082]

[0083] Inner boundary conditions:

[0084]

[0085] In the formula, p i This represents the original formation pressure.

[0086] 1.2 The fracturing-stimulated inner zone is a dual-medium system. Using an unsteady-state mass transfer model (Kazemi model), the medium is treated as a flat plate. The influence of adsorbed gas content is referenced to the fracturing-stimulated outer zone. Therefore, the flow equation in the matrix is:

[0087] Gas components:

[0088]

[0089] Oil components:

[0090]

[0091] Initial conditions:

[0092] p m | t＝0 =p i (9)

[0093] External boundary conditions:

[0094]

[0095] Inner boundary conditions:

[0096]

[0097] In the formula, h m The width of the matrix block.

[0098] 1.3 Due to the presence of matrix in the fracturing inner zone and supply from the fracturing outer zone, the flow equation in the matrix is:

[0099] Gas components:

[0100]

[0101] Oil components:

[0102]

[0103] Initial conditions:

[0104] p f | t＝0 =p i (14)

[0105] External boundary conditions:

[0106]

[0107] Inner boundary conditions:

[0108]

[0109] 1.4 Considering the fluid exchange between the fractures in the fracturing inner zone and the artificial fractures (denoted by the subscript F), the seepage equation in the artificial fractures is:

[0110] Gas components:

[0111]

[0112] Oil components:

[0113]

[0114] Initial conditions:

[0115] p F | t＝0 =p i (19)

[0116] External boundary conditions:

[0117]

[0118] Inner boundary conditions:

[0119] p F | y＝0 =p wf (twenty one)

[0120] In the formula, p wf This refers to the bottom-hole flowing pressure.

[0121] 2. Inversion of fracture and reservoir parameters in typical shale condensate gas wells

[0122] Taking the condensate gas well S1 in the shale as the research object, the production rate of the condensate gas well was fitted using the dynamic historical fitting method of production data. The change in bottom hole pressure (see the graph) Figure 3 It can be seen that the pressure is unstable throughout the production stage, and the pressure changes significantly due to the opening and closing of wells. The overall trend is that the bottom hole pressure gradually decreases. Figure 4 The initial production gas-oil ratio of the well shows that it has remained relatively stable over the past two years. Figure 5 , Figure 6 The fitting results for oil and gas production are presented. Overall, the fitting effect is good, except for the poor fitting of oil production before and after well shut-in. The fitted fracture parameters are shown in Table 1. The fitted parameter values ​​are within the allowable error range, indicating a good fitting effect. Table 1 shows the inverted reservoir and fracture parameters.

[0123] Table 1 Reservoir and fracture parameter inversion

[0124]

[0125]

[0126] 3. Analysis of Productivity Contribution and Reasonable Well Spacing in the External Zone after Fracturing Stimulation

[0127] Based on the typical shale and fracturing parameters given in Table 2, this paper analyzes the contribution of the outer zone to production capacity under different outer zone boundary lengths and different outer zone permeabilities, and thus provides a reasonable well spacing recommendation that takes into account the contribution of the outer zone.

[0128] Table 2 Formation Parameters for Condensate Gas Wells

[0129] parameter Value parameter Value Original formation pressure, MPa 38 Stratum thickness, m 20 Original formation temperature, K 387 Horizontal segment length, m 2000 Bottom hole pressure, MPa 6 Inner / outer zone matrix porosity 0.10 Number of fracturing stages 20 Secondary crack porosity 1.0 Crack half length, m 100 Artificial crack porosity 0.5 Artificial suture drainage capacity, D.cm 5 Inner zone matrix permeability, mD 5e-4 Secondary fracture permeability, mD 2 Original gas saturation 1.0

[0130] 3.1 The Impact of Outer Zone Size on Production Capacity

[0131] Fracturing significantly increases the productivity of shale oil and gas wells, while the outer fracturing zone also contributes to productivity. Therefore, it is necessary to clarify the contribution of the outer fracturing zone to productivity under different sizes and permeabilities. Thus, we set the inner and outer fracturing zone permeability to 5e-4mD, the artificial fracture length to 100m, and the outer fracturing zone sizes to 0m, 20m, 40m, 60m, 80m, and 100m, respectively, to analyze the contribution of different outer fracturing zone sizes to productivity. Figure 7 The curves showing the change of gas production / cumulative gas production over time for different outer zone lengths show that in the early stage of production, the outer zone length has little impact on the instantaneous gas production, while in the later stage of production, the longer the outer zone length, the greater the cumulative gas production. Figure 8 The curves showing the change in oil production / cumulative oil production over time for different outer zone lengths reveal that in the early stages of production, the outer zone length has a relatively small impact on instantaneous oil production. However, in the later stages of production, a longer outer zone length results in a greater cumulative oil production. (Summary) Figure 7 and Figure 8 They believe that without considering the contribution of external regions to production capacity, the production capacity forecast will be too low; external regions contribute little to production capacity in the first 5 years, but contribute to production in the later period. As external regions increase, production increases, but the rate of increase gradually decreases.

[0132] 3.2 Contribution of Outer Zones to Production (Graphical Representation)

[0133] To provide a more intuitive understanding of the contribution of the outer zone to production capacity in the initial stage (first 5 years), a chart was created showing the contribution of typical outer zone matrix permeability and outer zone size to production capacity. Therefore, the inner zone matrix permeability was set to 5e-4mD, and the outer zone permeabilities were set to 5e-4mD, 2.5e-4mD, 1e-4mD, and 5e-5mD, with outer zone sizes of 0m, 20m, 40m, 60m, 80m, and 100m, respectively.

[0134] Figure 9The graphs show the relationship between the gas production contribution rate and the length of the outer zone for the first five years under different outer zone permeability. When the outer zone length is less than 40m, the gas production contribution rate increases rapidly with the increase of the outer zone length; when the outer zone length is greater than 40m, the gas production contribution rate basically no longer increases with the increase of the outer zone length. The higher the outer zone permeability, the more rapidly the gas production contribution rate increases, and the higher the gas production contribution rate is for the same outer zone length. Figure 10 The curves show the relationship between oil production contribution rate and outer zone length under different outer zone permeability. When the outer zone length is less than 40m, the oil production contribution rate increases rapidly with increasing outer zone length; when the outer zone length is greater than 40m, the oil production contribution rate no longer increases with increasing outer zone length. The higher the outer zone permeability, the more rapidly the oil production contribution rate increases, and the higher the oil production contribution rate is for the same outer zone length. (Summary) Figure 9 and Figure 10 In the first 5 years of production, the outer area size within 40m made a certain contribution to the production capacity, and the main contribution was within 20m, while the part larger than 40m made almost no contribution to the production capacity; the greater the penetration rate of the outer area, the greater the contribution to the production capacity.

[0135] To provide a more intuitive understanding of the contribution of the outer zone to 30 years of production, a chart was created showing the contribution of different outer zone matrix permeability and outer zone size to production capacity. Therefore, the following settings were used: the inner zone matrix permeability was 5e-4, and the outer zone permeabilities were 5e-4mD, 2.5e-4mD, 1e-4mD, and 5e-5mD, with outer zone sizes of 0m, 20m, 40m, 60m, 80m, and 100m.

[0136] Figure 11 The curves show the relationship between the gas production contribution rate and the length of the outer zone over the first 30 years under different outer zone permeabilities. When the outer zone length is less than 20m, the gas production contribution rate of different outer zone permeabilities increases with the increase of the outer zone length at the same rate; when the outer zone length is greater than 20m, the higher the outer zone permeability, the higher the gas production contribution rate; the longer the outer zone length, the flatter the gas production contribution rate curve becomes. Figure 12 The curves show the relationship between the oil production contribution rate and the length of the outer zone over the first 30 years under different outer zone permeability. When the outer zone length is less than 20m, the oil production contribution rate of different outer zone permeability increases with the outer zone length at the same rate; when the outer zone length is greater than 20m, the higher the outer zone permeability, the higher the oil production contribution rate; the longer the outer zone length, the flatter the oil production contribution rate curve becomes. (Summary) Figure 11 and Figure 12 Under the condition of 30 years of production, the larger the outer area, the greater the contribution to production capacity, mainly concentrated within the first 60 meters; the larger the penetration rate ratio of the outer area to the inner area, the greater the contribution to production capacity.

[0137] The impact of external areas on production capacity for condensate gas wells in the Yingtan Formation shale:

[0138] (1) The external region contributes to the production capacity to a certain extent, but the contribution value is not large;

[0139] (2) The higher the penetration rate in the outer area, the greater the contribution to production capacity;

[0140] (3) The larger the outer zone, the greater its contribution to production capacity;

[0141] (4) In the early stage of production (5 years), the outer area within 40m has a certain contribution to the production capacity, and the main contribution is within 20m; after 30 years of production, the larger the outer area, the greater the contribution to the production capacity, but it is still mainly concentrated in the first 40-60 meters.

[0142] Recommendations for optimizing well spacing in mines:

[0143] (1) When optimizing well spacing, the range of the outer zone can be appropriately considered, but it should not be too large and should be controlled within 20m as much as possible;

[0144] (2) Reasonable well spacing ≤ 2×(y F +20m).

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing the contribution of volumetric fracturing to the productivity of shale condensate gas wells in the outer zone, characterized in that, Includes the following steps: Based on the complex fracture network characteristics and oil-gas two-phase flow characteristics in the fracturing development process of shale condensate gas wells, a mathematical and physical model based on the trilinear flow theory is established. This model treats the complex fracture network of shale condensate gas wells as equivalent to a fracturing body, which includes an artificial main fracture, an inner fracturing zone, and an outer fracturing zone. Based on the mathematical and physical model of trilinear flow theory, the dynamics of shale condensate gas wells in production are historically fitted to obtain typical shale and fracturing parameters. Based on typical shale and fracturing fracture parameters, this paper analyzes the contribution of the fracturing outer zone to production capacity under different fracturing outer zone boundary lengths and different fracturing outer zone permeability conditions, and thus provides a reasonable well spacing that takes into account the contribution of the fracturing outer zone. The equation for the fracturing stimulation of the outer zone is: The fracturing-modified outer zone is the matrix zone, and the adsorption and desorption of gases are described using Langmuir theory. (1) In the formula, The volume is the Langevin volume. For Langevin pressure; For pressure; This represents the amount of gas adsorbed per unit volume of rock. The differential equations for the seepage of oil and gas in the fracturing-enhanced outer zone are as follows: Gas components: Oil components: In the formula, The relative permeability of the outer gas phase; The relative permeability of the oil phase in the outer zone; The permeability of the outer matrix; The porosity of the outer matrix; The gas saturation level in the outer zone; The oil saturation level in the outer zone; Gas viscosity; Crude oil viscosity; This is the gas volume coefficient; This is the crude oil volume coefficient; external pressure; t For production time; This represents the content of dissolved condensate oil in the gas phase; The volume is the Langevin volume. For Langevin pressure; y The coordinate direction is indicated by .

2. The method for analyzing the contribution of shale condensate gas well volumetric fracturing capacity in the outer zone according to claim 1, characterized in that, The mathematical and physical model of trilinear flow theory is based on the following assumptions: The shale reservoir is horizontal and of uniform thickness, with horizontal wells located in the center of the reservoir and fractures running through the entire reservoir. Considering the compressibility of oil and gas, the compressibility of rocks is ignored; The adsorption and desorption of gases follow the Langmuir monolayer adsorption model. Since the adsorption mechanism of condensate is not yet clear, it is not considered separately. The fluid consists of two components: oil and gas. The gas component exists only in the gas phase, while the oil component can exist in both the oil and gas phases simultaneously.

3. The method for analyzing the contribution of shale condensate gas well volumetric fracturing capacity in the outer zone according to claim 1, characterized in that, The fracturing-induced inner zone is a dual-medium system. Using an unsteady-state mass transfer model, the medium is treated as a flat plate. The effect of adsorbed gas content is referenced to that of the fracturing-induced outer zone. Therefore, the flow equation in the matrix is: Gas components: Oil components: In the formula, The relative permeability of the gas phase in the inner matrix; The relative permeability of the oil phase in the inner matrix; The inner zone matrix permeability; The porosity of the inner matrix; This represents the gas saturation level in the inner matrix. The oil saturation in the inner zone matrix; For the inner zone matrix pressure; z The coordinate direction is indicated by .

4. The method for analyzing the contribution of shale condensate gas well volumetric fracturing capacity in the outer zone according to claim 3, characterized in that, Since the fractures in the inner zone of the fracturing zone are supplied by the matrix and the fractures in the outer zone, the flow equation in the matrix is: Gas components: Oil components: In the formula, The relative permeability in the secondary fractures within the inner zone; The relative permeability of the oil phase in the secondary fracture zone of the inner region; Permeability of secondary fractures in the inner zone; Porosity of secondary cracks in the inner zone; The gas saturation in the secondary fractures within the inner zone; The oil saturation in the secondary fractures within the inner zone; For the pressure of secondary fractures in the inner zone; The mass of gas flowing into a unit volume of secondary fracture from the matrix system in the inner zone per unit time; The mass of gas flowing into a unit volume of secondary fracture from the outer zone matrix system per unit time; x The coordinate direction is indicated by .

5. The method for analyzing the contribution of shale condensate gas well volumetric fracturing capacity in the outer zone according to claim 4, characterized in that, Considering the fluid exchange from the internal fractures to the artificial fractures in the fracturing stimulation zone, the seepage equation in the artificial fractures is: Gas components: Oil components: In the formula, The relative permeability in the artificial fracture; The relative permeability of the oil phase in the artificial fracture; The permeability of artificial cracks; Porosity of artificial cracks; The gas saturation level in the artificial crack; The oil saturation in the artificial crack; Artificial crack pressure; The mass of gas flowing into a unit volume of artificial crack from a secondary crack per unit time; The mass of crude oil flowing into a unit volume of artificial fracture from secondary fractures per unit time; x The coordinate direction is indicated by .

6. The method for analyzing the contribution of shale condensate gas well volumetric fracturing capacity in the outer zone according to claim 4, characterized in that, Typical shale and fracturing parameters include: fracture half-length, secondary fracture permeability, matrix permeability in the inner / outer zone, artificial fracture conductivity, and matrix block width in the fracturing-modified inner zone.

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