Induced dynamic fracture numerical characterization method based on dynamic embedded discrete fracture

Abstract

The invention belongs to the technical field of oil-gas exploration and development, and particularly relates to an induced dynamic fracture numerical characterization method based on dynamic embedded discrete fractures. A dynamic embedded discrete fracture-based induced dynamic fracture numerical characterization method is characterized by comprising the following steps: determining an initial position for inducing the growth and extension of a dynamic fracture, and generating a dynamic embedded discrete fracture sheet for describing the growth and extension or closing process of the dynamic fracture at the moment by moment according to a time sequence by taking the initial position as a starting point; space splicing is achieved on the common boundary of the adjacent dynamic embedded discrete fracture pieces, the fracture is kept continuous as a whole, and then a dynamic embedded discrete fracture model covering and inducing the whole life cycle of the dynamic fracture is formed. Effective simulation of the water injection induced dynamic fracture growth extension and closing process in the energy storage and permeability enhancement injection process of the ultra-low permeability reservoir is achieved, and therefore effective technical guidance is provided for implementation of an energy storage and permeability enhancement technology mine field of the ultra-low permeability reservoir.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration and development technology, specifically relating to a numerical characterization method for induced dynamic fractures based on dynamic embedded discrete fractures. Background Technology

[0002] The ultra-low permeability oilfields such as Yanchang and Changqing are located in the Shaanxi-Gansu-Ningxia region of the Ordos Basin. Some development blocks have crisscrossing gullies, and factors such as water shortage and immature water injection conditions prevent the formation energy from being effectively replenished. To address this, the technology of energy storage and permeability enhancement for ultra-low permeability reservoirs to improve stage recovery rate has been proposed. The main principle of this technology is to combine the dual mechanisms of fracturing and water injection. In a short period of time, large displacement and large fluid volume injection will generate water-induced dynamic fractures near the bottom of the injection well and form a high-pressure zone distributed along the dynamic fractures. Through well stagnation and permeation exchange and well opening displacement, the goal of increasing oil well production can be achieved. Meanwhile, long-term water injection development practices in domestic ultra-low permeability reservoirs have shown that water injection-induced dynamic fractures have become a new geological attribute in the development of ultra-low permeability reservoirs. This has two sides to the development of ultra-low permeability reservoirs. On the one hand, the generation of water injection-induced dynamic fractures easily forms water channeling and water flooding channels between injection and production wells, exacerbating the ineffective circulation of injected water. Simultaneously, the generation of water injection-induced dynamic fractures intensifies the horizontal and vertical heterogeneity of the reservoir, forming residual oil-rich areas within the reservoir and reducing the reservoir development effect. On the other hand, the generation of water injection-induced dynamic fractures during the energy storage and permeation enhancement injection process in ultra-low permeability reservoirs has a positive effect. The generation of water injection-induced dynamic fractures effectively improves the seepage capacity of ultra-low permeability reservoirs and increases the pressure wave volume during energy storage and permeation enhancement injection. Therefore, the generation of the induced dynamic fracture system greatly improves the reservoir's seepage conditions. At the same time, well suffocation and seepage absorption promote the effective replacement of oil and water in the reservoir, greatly increasing single-well production and stage recovery rate. Therefore, accurately characterizing and simulating the dynamic changes of water-induced dynamic fractures in ultra-low permeability reservoirs, effectively utilizing the advantages brought by water-induced dynamic fractures, and avoiding the disadvantages brought by water-induced dynamic fractures have become the key and difficult points in the research on improving the reservoir development effect of energy storage and permeability enhancement technology in ultra-low permeability reservoirs. At present, the research on water-induced dynamic fractures is mainly based on the equivalent numerical characterization method of traditional static fractures, such as local mesh refinement and discrete fracture models. However, traditional numerical characterization methods cannot perform dynamic characterization of the morphology and attribute parameters of induced dynamic fractures, which has strong limitations. Therefore, it is urgent to explore a numerical characterization method of induced dynamic fractures based on dynamic embedded discrete fractures. Summary of the Invention

[0003] The present invention aims to address the above-mentioned problems by proposing a numerical characterization method for induced dynamic cracks based on dynamically embedded discrete cracks.

[0004] The technical solution of this invention is as follows: The numerical characterization method for induced dynamic cracks based on dynamic embedded discrete cracks is as follows: the starting position of the growth and extension of the induced dynamic crack is determined, and dynamic embedded discrete crack slices describing the growth, extension or closure process of the induced dynamic crack at that moment are generated step by step according to the time series starting from the starting position; spatial splicing is realized on the common boundary of adjacent dynamic embedded discrete crack slices to maintain the overall continuity of the crack, thereby forming a dynamic embedded discrete crack model covering the entire life cycle of the induced dynamic crack.

[0005] The specific process for determining the starting position of the induced dynamic fracture growth and extension is as follows: if there is no original fracture in the injection well at the initial moment, the starting position of the induced dynamic fracture growth and extension is the location of the perforated section of the injection well in the wellbore; if there is an original fracture in the injection well at the initial moment, the starting position of the induced dynamic fracture growth and extension is the location of the dynamically embedded discrete fracture piece away from the perforated section of the injection well in the wellbore at the initial moment.

[0006] The dynamic embedded discrete crack sheet includes three types: Type 1: the crack height and crack aperture remain constant, and only the crack length changes with time; Type 2: the crack height remains constant, and the crack length and crack aperture change with time; Type 3: the crack length, crack height, and crack aperture all change with time.

[0007] The specific process of achieving spatial stitching on the common boundary of adjacent dynamically embedded discrete slit pieces is as follows: For the dynamic embedded discrete cracks of types 1, 2 and 3, at each time step, the next dynamic embedded discrete crack will grow and extend along the vertical boundary of the current dynamic embedded discrete crack, and the vertical boundary of the next dynamic embedded discrete crack will coincide with that of the current dynamic embedded discrete crack. Using the coordinates of dynamically embedded discrete crack sections { P 1 ( X 1 、Y 1 、Z 1) 、P 2 ( X 2 、Y 2 、Z 2) 、P 3 ( X 3 、Y 3 、Z 3) 、P 4 ( X 4 、 Y 4 、Z 4) Numerical characterization of crack length and crack height is performed.

[0008] Let T0 be the initial time, and T t T is the time when growth extension ends. end The termination time of the closure is T0~Tt The time is the growth extension stage, with T t ~T end This is the closed phase.

[0009] When simulating the induced dynamic crack growth and extension process, at time T1, only one dynamic embedded discrete crack sheet is generated vertically at the starting position of the induced dynamic crack growth and extension, which is denoted as the dynamic embedded discrete crack sheet at time T1. At time T2, the dynamic embedded discrete crack sheet that grows and extends forward with the vertical boundary of the terminating edge of the dynamic embedded discrete crack sheet at time T1 as the vertical boundary of the starting edge of the dynamic embedded discrete crack sheet at time T2 is denoted as the dynamic embedded discrete crack sheet at time T2. Type 1: The crack length of the dynamic embedded discrete crack plate at time T2 is different from that of the dynamic embedded discrete crack plate at time T1, but the crack opening and crack height are the same. The starting coordinate of the dynamic embedded discrete crack plate at time T2 coincides with the ending coordinate of the dynamic embedded discrete crack plate at time T1. Type 2: The crack length and crack aperture of the dynamically embedded discrete crack disc at time T2 are different from those of the dynamically embedded discrete crack disc at time T1, but the crack height is the same. Type 3: The crack length, crack aperture, and crack height of the dynamically embedded discrete crack disc at time T2 are different from those of the dynamically embedded discrete crack disc at time T1. Similarly, complete T3~T t By splicing together dynamically embedded discrete crack segments, the crack aperture of each dynamically embedded discrete crack segment decreases monotonically during the growth and extension process; thus, a dynamic embedded discrete crack model is completed in the process of inducing dynamic crack growth and extension.

[0010] When simulating the induced dynamic crack closure process, T t+1 The vertical boundary of the starting edge of the dynamic embedded discrete crack sheet at time and T t The vertical boundary of the termination edge of the dynamic embedded discrete crack plate coincides (in type 1, T) t+1 The starting coordinates of the dynamic embedded discrete crack plate at any given time and T t (The termination coordinates of the dynamically embedded discrete crack plate coincide at any given time). Similarly, complete T... t+2 ~T end The dynamic embedded discrete crack segments are spliced ​​together at all times; during the closure process, the crack opening of each dynamic embedded discrete crack segment is 0m; thus, the dynamic embedded discrete crack model in the process of inducing dynamic crack closure is completed.

[0011] The generation process of the dynamic embedded discrete crack patch is as follows: by combining microseismic monitoring and interpretation, numerical simulation of induced dynamic cracks under geostress, or dynamic monitoring and interpretation analysis, the generation time, crack morphology parameters, and crack attribute parameters of induced dynamic cracks at different times are obtained, and then the dynamic embedded discrete crack patch at that time is generated.

[0012] The process of generating the initial dynamic embedded discrete fracture patch is as follows: combining microseismic monitoring interpretation data, unsteady well test interpretation and production dynamic analysis results to analyze and interpret the original fracture morphology and attribute parameters of the injection well, and then generating the initial dynamic embedded discrete fracture patch to characterize the original fracture of the injection well at the initial moment.

[0013] The specific crack morphology parameters include: the starting position and direction of the growth, extension or closure of induced dynamic cracks at different times, crack length, crack height, crack aperture, crack dip angle and crack azimuth angle; the crack attribute parameter is crack permeability.

[0014] The fracture permeability includes the permeability along the long side of the dynamically embedded discrete fracture sheet. k fci and the permeability along the short side of the dynamically embedded discrete crack. k fdi ; Permeability along the long side of a dynamically embedded discrete slit plate k fci The specific calculation process is as follows: k fci = ξk fc · oh f 3 / oh fo 3 Permeability along the short side of a dynamically embedded discrete slit plate k fdi The specific calculation process is as follows: k fdi = ξk fd · oh f 3 / oh fo 3 In the formula: k fci The permeability along the long side of a dynamically embedded discrete crack plate. μm 2 ; xThis is a permeability correction factor, dimensionless. k fc The permeability along the long side at the starting position of the dynamically embedded discrete crack plate. μm 2 ; oh f For crack opening, μm ; oh fo This refers to the crack aperture at the starting position of a dynamically embedded discrete crack sheet. μm ; k fdi The permeability along the short side of a dynamically embedded discrete crack plate. μm 2 ; k fd The permeability along the short side at the starting position of the dynamically embedded discrete crack plate. μm 2 .

[0015] The technical effects of this invention are as follows: This invention characterizes the fracture morphology and fracture attribute parameters of water-induced dynamic fractures during the energy storage and permeability enhancement injection process in ultra-low permeability reservoirs. It solves the current problem that the fracture morphology and fracture attribute parameters of water-induced dynamic fractures cannot be characterized. It realizes the effective simulation of the growth, extension and closure process of water-induced dynamic fractures during the energy storage and permeability enhancement injection process in ultra-low permeability reservoirs, thereby providing effective technical guidance for the field implementation of energy storage and permeability enhancement technology in ultra-low permeability reservoirs. Attached Figure Description

[0016] Figure 1 This is a dynamic embedded discrete fracture profile at the initial T0 moment of the injection well in the X-measure well group, as shown in a specific application case.

[0017] Figure 2 This is a schematic diagram of the dynamic embedded discrete fracture sheet at time T1 of the injection well in the X-measure well group in a specific application case.

[0018] Figure 3 This is a cross-sectional view of the dynamically embedded discrete fracture fragment at time T1 of the injection well in the X-measure well group in a specific application case.

[0019] Figure 4 In a specific application case, the T1~T of the injection well in the X-measure well group 10 A top view of a dynamically embedded discrete slit sheet.

[0020] Figure 5 In a specific application case, the T1~T of the injection well in the X-measure well group 10 Cross-sectional view of a dynamically embedded discrete crack section.

[0021] Figure 6 This is a comparison chart of pressure simulations characterized by dynamic embedded discrete crack sections and embedded discrete crack sections. Detailed Implementation

[0022] Example 1 The numerical characterization method for induced dynamic cracks based on dynamic embedded discrete cracks is as follows: the starting position of the growth and extension of the induced dynamic crack is determined, and dynamic embedded discrete crack slices describing the growth, extension or closure process of the induced dynamic crack at that moment are generated step by step according to the time series starting from the starting position; spatial splicing is realized on the common boundary of adjacent dynamic embedded discrete crack slices to maintain the overall continuity of the crack, thereby forming a dynamic embedded discrete crack model covering the entire life cycle of the induced dynamic crack.

[0023] Example 2 Based on Example 1, it also includes: The specific process for determining the starting position of the induced dynamic fracture growth and extension is as follows: if there is no original fracture in the injection well at the initial moment, the starting position of the induced dynamic fracture growth and extension is the location of the perforated section of the injection well in the wellbore; if there is an original fracture in the injection well at the initial moment, the starting position of the induced dynamic fracture growth and extension is the location of the dynamically embedded discrete fracture piece away from the perforated section of the injection well in the wellbore at the initial moment.

[0024] Example 3 Based on Example 2, it also includes: The dynamic embedded discrete crack sheet includes three types: Type 1: the crack height and crack aperture remain constant, and only the crack length changes with time; Type 2: the crack height remains constant, and the crack length and crack aperture change with time; Type 3: the crack length, crack height, and crack aperture all change with time.

[0025] The specific process of achieving spatial stitching on the common boundary of adjacent dynamically embedded discrete slit pieces is as follows: For the dynamic embedded discrete cracks of types 1, 2 and 3, at each time step, the next dynamic embedded discrete crack will grow and extend along the vertical boundary of the current dynamic embedded discrete crack, and the vertical boundary of the next dynamic embedded discrete crack will coincide with that of the current dynamic embedded discrete crack. Using the coordinates of dynamically embedded discrete crack sections { P 1 ( X 1 、Y 1 、Z 1) 、P 2 ( X 2 、Y 2 、Z 2) 、P 3 ( X 3 、Y 3、Z 3) 、P 4 ( X 4 、 Y 4 、Z 4) Numerical characterization of crack length and crack height is performed.

[0026] Let T0 be the initial time, and T t T is the time when growth extension ends. end The termination time of the closure is T0~T t The time is the growth extension stage, with T t ~T end This is the closed phase.

[0027] When simulating the induced dynamic crack growth and extension process, at time T1, only one dynamic embedded discrete crack sheet is generated vertically at the starting position of the induced dynamic crack growth and extension, which is denoted as the dynamic embedded discrete crack sheet at time T1. At time T2, the dynamic embedded discrete crack sheet extends forward with the vertical boundary of the terminating edge of the dynamic embedded discrete crack sheet at time T1 as the vertical boundary of the starting edge of the dynamic embedded discrete crack sheet at time T2. The extended dynamic embedded discrete crack sheet is denoted as the dynamic embedded discrete crack sheet at time T2. Type 1: The crack length of the dynamic embedded discrete crack plate at time T2 is different from that of the dynamic embedded discrete crack plate at time T1, but the crack opening and crack height are the same. The starting coordinate of the dynamic embedded discrete crack plate at time T2 coincides with the ending coordinate of the dynamic embedded discrete crack plate at time T1. Type 2: The crack length and crack aperture of the dynamically embedded discrete crack disc at time T2 are different from those of the dynamically embedded discrete crack disc at time T1, but the crack height is the same. Type 3: The crack length, crack aperture, and crack height of the dynamically embedded discrete crack disc at time T2 are different from those of the dynamically embedded discrete crack disc at time T1. Similarly, complete T3~T t By splicing together dynamically embedded discrete crack segments, the crack aperture of each dynamically embedded discrete crack segment decreases monotonically during the growth and extension process; thus, a dynamic embedded discrete crack model is completed in the process of inducing dynamic crack growth and extension.

[0028] When simulating the induced dynamic crack closure process, T t+1 The vertical boundary of the starting edge of the dynamic embedded discrete crack sheet at time and T t The vertical boundary of the termination edge of the dynamic embedded discrete crack plate coincides (in type 1, T) t+1 The starting coordinates of the dynamic embedded discrete crack plate at any given time and T t (The termination coordinates of the dynamically embedded discrete crack plate coincide at any given time). Similarly, complete T... t+2 ~T endThe dynamic embedded discrete crack segments are spliced ​​together at all times; during the closure process, the crack opening of each dynamic embedded discrete crack segment is 0m; thus, the dynamic embedded discrete crack model in the process of inducing dynamic crack closure is completed.

[0029] Example 4 Based on Example 3, it also includes: The generation process of the dynamic embedded discrete crack patch is as follows: by combining microseismic monitoring and interpretation, numerical simulation of induced dynamic cracks under geostress, or dynamic monitoring and interpretation analysis, the generation time, crack morphology parameters, and crack attribute parameters of induced dynamic cracks at different times are obtained, and then the dynamic embedded discrete crack patch at that time is generated.

[0030] The process of generating the initial dynamic embedded discrete fracture patch is as follows: combining microseismic monitoring interpretation data, unsteady well test interpretation and production dynamic analysis results to analyze and interpret the original fracture morphology and attribute parameters of the injection well, and then generating the initial dynamic embedded discrete fracture patch to characterize the original fracture of the injection well at the initial moment.

[0031] Example 5 Based on Example 4, it also includes: The specific crack morphology parameters include: the starting position and direction of the growth, extension or closure of induced dynamic cracks at different times, crack length, crack height, crack aperture, crack dip angle and crack azimuth angle; the crack attribute parameter is crack permeability.

[0032] The fracture permeability includes the permeability along the long side of the dynamically embedded discrete fracture sheet. k fci and the permeability along the short side of the dynamically embedded discrete crack. k fdi ; Permeability along the long side of a dynamically embedded discrete slit plate k fci The specific calculation process is as follows: k fci = ξk fc · oh f 3 / oh fo 3 Permeability along the short side of a dynamically embedded discrete slit plate k fdi The specific calculation process is as follows: k fdi = ξk fd · oh f 3 / oh fo 3 In the formula: k fci The permeability along the long side of a dynamically embedded discrete crack plate. μm 2 ; x This is a permeability correction factor, dimensionless. k fc The permeability along the long side at the starting position of the dynamically embedded discrete crack plate. μm 2 ; oh f For crack opening, μm ; oh fo This refers to the crack aperture at the starting position of a dynamically embedded discrete crack sheet. μm ; k fdi The permeability along the short side of a dynamically embedded discrete crack plate. μm 2 ; k fd The permeability along the short side at the starting position of the dynamically embedded discrete crack plate. μm 2 .

[0033] A specific experimental case study—taking the X-measure well group in the Z area of ​​the Ordos Basin as an example.

[0034] The main development layer of the X-measure well group is the Triassic Yanchang Formation, length 61. 1 This small reservoir has an average burial depth of 1490m. It primarily develops a deltaic front subfacies, with a single subaqueous distributary channel sand body as the main reservoir sand body. The main source direction is NE-SW. The target reservoir has an average porosity of 11.5% and an average permeability of 0.55 × 10⁻⁶ m. -3 μm 2 The X-measure well group is a diamond-shaped inverted nine-point injection-production well network, with a well spacing of 470.0 × 150.0 m. The injection wells are located at a length of 61 m. 1-3 The No. 1 sand body corresponds to 7 production wells. In the early stages of production, all wells in the group were production wells, with high fluid and oil production. However, the depletion-type development led to a rapid decline in well production.

[0035] The X-measure well group employs high-capacity, high-pressure pump injection equipment for rapid water injection to enhance permeability, with a daily injection volume of 480.0-720.0 m³. 3 Between these values, the injection volume is 1.1-1.3m³. 3 / min, cumulative injection 5000.0m3 During the injection period, the wellhead injection pressure was 13.6-15.3 MPa, which was greater than the extension pressure of the original artificial fracturing fracture at the bottom of the injection well. After the measures were taken, the bottom pressure of the corresponding five oil wells increased by an average of more than 1.3 MPa. After stable production, the daily oil production increased by more than 2 times, achieving a good development effect.

[0036] The numerical characterization method for induced dynamic fractures based on dynamic embedded discrete fractures provided by this invention is used to characterize the fractures, thereby simulating the growth and extension process of induced dynamic fractures in injection wells during the energy storage and permeability enhancement injection process in ultra-low permeability reservoirs. The specific process is as follows: (1) Numerical characterization of the original fracture parameters of the injection well at the initial time In the X-measure well group, the injection wells were originally oil production wells, put into production using fracturing. Therefore, the injection wells initially had original fractures; the original fracturing section was 61 meters long. 1 The fracturing layer has a perforation section of 1526.0-1532.0m and a total hydraulic fluid injection volume of 96.5m³. 3 25.0m of proppant (quartz sand) 3 Average displacement 2.1~2.3m 3 / min, average sand ratio 29.6%, maximum pump pressure on the construction ground 30.4MPa, working pressure 22.5~18.5MPa, and pump stop pressure 6.5MPa; During the energy storage and permeability enhancement measures, large-volume, high-displacement injection operations were carried out in the injection wells. Based on microseismic monitoring and interpretation data, as well as unsteady puncture test interpretation, it was determined that the original fracture extension direction of the injection wells in the X-measure well group was 65° east of north, with a fracture half-length of approximately 70.0 m and a fracture height of approximately 15.0 m (the thickness of the reservoir sand body where the perforated section is located). The permeability of the induced dynamic fractures was 2500.0 × 10⁻⁶. -3 μm 2 .

[0037] (2) Generation of dynamically embedded discrete cracks at different times 1) Parameters of the injection process during the daily stage of energy storage and permeability enhancement in the injection well During the daily injection phase of the energy storage and permeability enhancement injection well, a high-pressure pump truck was used for large-volume, high-displacement injection. Detailed data is shown in Table 1. It can be seen that induced dynamic fractures were generated during the daily injection phase of the energy storage and permeability enhancement injection well. The generation of these induced dynamic fractures effectively improved the fluid's seepage capacity and expanded the swept volume of the injected water. Table 1 is a statistical table of injection process parameters for the daily injection phase of the energy storage and permeability enhancement injection wells in the X-measure well group. Table 1. Statistical Table of Injection Process Parameters for Energy Storage and Permeability Enhancement in Injection Wells of the X-Measure Well Group (Daily Stage) ; 2) Generation of dynamically embedded discrete fractures after the injection phase of the energy storage and permeability enhancement stage in the injection well. After the injection phase of the energy storage and permeability enhancement project in the injection well is completed, the instantaneous pressure drop curve at the bottom of the well is used to account for the dynamic changes in the filtration coefficient. G Functional interpretation and logarithmic interpretation of induced dynamic fracture well testing were used to interpret the fracture morphology and attribute parameters of the induced dynamic fractures after the injection of the well during the daily stage of energy storage and permeability enhancement. Specifically, this included the fracture length and fracture permeability of the induced dynamic fractures. Table 2 shows the values ​​for all daily stages of the injection well (T1~T2). 10 A statistical table of crack morphology parameters and crack attribute parameters of induced dynamic cracks, as interpreted after the injection at the specified time. Table 2. Statistical Table of Crack Morphology Parameters and Crack Attribute Parameters ; Based on specific reservoir properties and field injection parameters, the induced dynamic fractures generated during the energy storage and permeation enhancement injection process of the injection well have constant fracture height and fracture aperture, with only fracture length increasing over time, satisfying the type 1 dynamic embedded discrete fracture sheet. Therefore, the dynamically embedded discrete fracture patch generated at the initial time T0 of the original fracture in the injection well is used as { P 0 - 1 ( X 1 、Y 1 、 Z 1) 、P 0 - 2 ( X 2 、Y 2 、Z 1) 、P 0 - 3 ( X 3 、Y 3 、Z 2) 、P 0 - 4 ( X 4 、Y 4 、Z 2) Characterize the original fracture morphology parameters, and numerically characterize the fracture attribute parameters using fracture permeability; the dynamic embedded discrete fracture section profile at the initial time T0 is shown below. Figure 1 As shown; After injection at time T1, the starting position of the induced dynamic fracture growth and extension was the location of the dynamically embedded discrete fracture fragment furthest from the perforated section of the injection well at the initial time T0. The extension direction was consistent with the original fracture direction, at 65° east of north. The interpreted fracture half-length of the induced dynamic fracture was 10.0 m, and the fracture height was consistent with the original fracture height. { P 11-1 ( X 2 、Y 2 、Z 1) 、P 11-2( X 2 + 9.06 、Y 2 + 4.23 、Z 1) P 11-3 ( X 3 + 9.06 、Y 3 + 4.23 、Z 2) P 11-4 ( X 3 、Y 3 、 Z 2)}、{ P 12-1 ( X 1 、Y 1 、Z 1) P 12-2 ( X 1 - 9.06 、Y 1-4.23 、Z 1) 、P 12-3 ( X 4-9.06 、Y 4 - 4.23 、Z 2) 、P 12-4 ( X 4 、Y 4 、 Z 2) Numerical characterization of fracture morphology parameters of the induced dynamic fractures at time T1 after injection in the injection well was performed, and the interpreted fracture permeability was 2400.0 × 10⁻⁶. -3 μm 2 Generate a dynamically embedded discrete fracture plate after injection at time T1, assuming the permeability along the long side of the dynamically embedded discrete fracture plate. k fci Permeability along the short side of the dynamically embedded discrete slit sheet k fdi Consistent, see details Figure 2 and Figure 3 As shown. Similarly, complete all daily stages of the injection well (T2~T) 10 The interpretation of crack morphology parameters and crack attribute parameters of the induced dynamic cracks after the injection at time (T1~T2) is then used to generate all daily stages (T1~T3). 10 The dynamically embedded discrete cracks after the injection at time (T1~T2) are denoted as T1~T2. 10 Real-time dynamic embedded discrete crack sheet, see details Figure 4 and Figure 5 As shown.

[0038] (3) Spatial splicing of dynamic embedded discrete slit sections T1~T 10 The dynamic embedded discrete crack slices are spatially spliced ​​to form a dynamic embedded discrete crack model that covers the entire life cycle of induced dynamic cracks, thereby realizing the numerical characterization of crack generation, growth and extension processes. During the spatial splicing process, the starting position for inducing dynamic fracture growth and extension is taken as the location of the dynamically embedded discrete fracture sheet at the initial time T0, which is farthest from the perforated section of the injection well. The injection wells T1~T 10 The dynamic embedded discrete crack pieces at time T1 are spatially stitched together; the starting coordinates of the dynamic embedded discrete crack piece at time T1 coincide with the ending coordinates of the dynamic embedded discrete crack piece at the initial time T0, i.e. P 11-1 and P 0-2 coincide 、P 11-4 and P 0-3 coincide, P 12-1 and P 0-1 coincide 、P 12-4 and P 0-4 By overlapping, the numerical characterization of the dynamically embedded discrete crack after the injection at time T1 is completed is achieved; similarly, the characterization from T2 to T... 10 Numerical characterization of dynamic embedded discrete cracks after time injection is achieved, realizing numerical characterization of crack generation, growth and extension processes.

[0039] Figure 6 This study simulates the energy storage and permeability enhancement injection process of a square inverse nine-point injection-production well network using both dynamic embedded discrete fractured sections and embedded discrete fractured sections, with a reservoir matrix permeability of 0.5 × 10⁻⁶. -3 μm 2 The injection well injects 500.0 m³ per day. 3 / d, injected for a total of 10 days, with a cumulative injection volume of 5000.0m. 3As can be seen from the simulated pressure plane diagram, when using dynamic embedded discrete fracture slices for simulation, the fracture length of the induced dynamic fractures changes dynamically, and the pressure field spreads outwards from the reservoir in an elliptical shape. This is more consistent with the propagation characteristics of the pressure field during energy storage and permeability enhancement injection. However, when using embedded discrete fracture slices for simulation, the fracture length of the induced dynamic fractures remains unchanged during energy storage and permeability enhancement injection, which causes the injected pressure field to spread outwards from the reservoir in a circular shape. This does not conform to the propagation characteristics of the pressure field after the induced dynamic fractures expand during energy storage and permeability enhancement injection. Therefore, using dynamic embedded discrete fracture slices for numerical characterization of induced dynamic fractures has better adaptability and provides good guidance for optimizing and adjusting the energy storage and permeability enhancement injection parameters of low-permeability and ultra-low-permeability reservoirs.

Claims

1. A numerical characterization method for induced dynamic cracks based on dynamically embedded discrete cracks, characterized in that, The method is as follows: Determine the starting position of the induced dynamic crack growth and extension, and generate dynamic embedded discrete crack slices describing the induced dynamic crack growth, extension or closure process at each time step according to the time series, starting from the starting position; realize spatial splicing on the common boundary of adjacent dynamic embedded discrete crack slices to maintain the overall continuity of the crack, and thus form a dynamic embedded discrete crack model covering the entire life cycle of the induced dynamic crack.

2. The numerical characterization method for induced dynamic cracks based on dynamically embedded discrete cracks according to claim 1, characterized in that, The specific process for determining the starting position of the induced dynamic fracture growth and extension is as follows: if there is no original fracture in the injection well at the initial moment, the starting position of the induced dynamic fracture growth and extension is the location of the perforated section of the injection well in the wellbore; if there is an original fracture in the injection well at the initial moment, the starting position of the induced dynamic fracture growth and extension is the location of the dynamically embedded discrete fracture piece away from the perforated section of the injection well in the wellbore at the initial moment.

3. The numerical characterization method for induced dynamic cracks based on dynamically embedded discrete cracks according to claim 1, characterized in that, The dynamic embedded discrete crack sheet includes three types: Type 1: the crack height and crack aperture remain constant, and only the crack length changes with time; Type 2: the crack height remains constant, and the crack length and crack aperture change with time; Type 3: the crack length, crack height, and crack aperture all change with time.

4. The numerical characterization method for induced dynamic cracks based on dynamically embedded discrete cracks according to claim 3, characterized in that, The specific process of achieving spatial stitching on the common boundary of adjacent dynamically embedded discrete slit pieces is as follows: For the dynamic embedded discrete cracks of types 1, 2 and 3, at each time step, the next dynamic embedded discrete crack will grow and extend along the vertical boundary of the current dynamic embedded discrete crack, and the vertical boundary of the next dynamic embedded discrete crack will coincide with that of the current dynamic embedded discrete crack. Type 1: The next dynamic embedded discrete crack strip has a different crack length than the current dynamic embedded discrete crack strip, but the crack opening and crack height are the same. Type 2: The next dynamic embedded discrete crack strip has a different crack length and crack opening than the current dynamic embedded discrete crack strip, but the same crack height. Type 3: The next dynamic embedded discrete crack strip differs from the current dynamic embedded discrete crack strip in terms of crack length, crack aperture, and crack height.

5. The numerical characterization method for induced dynamic cracks based on dynamically embedded discrete cracks according to claim 1, characterized in that, The generation process of the dynamic embedded discrete crack patch is as follows: by combining microseismic monitoring and interpretation, numerical simulation of induced dynamic cracks under geostress, or dynamic monitoring and interpretation analysis, the generation time, crack morphology parameters, and crack attribute parameters of induced dynamic cracks at different times are obtained, and then the dynamic embedded discrete crack patch at that time is generated.

6. The numerical characterization method for induced dynamic cracks based on dynamically embedded discrete cracks according to claim 2, characterized in that, The process of generating the initial dynamic embedded discrete fracture patch is as follows: combining microseismic monitoring interpretation data, unsteady well test interpretation and production dynamic analysis results to analyze and interpret the original fracture morphology and attribute parameters of the injection well, and then generating the initial dynamic embedded discrete fracture patch to characterize the original fracture of the injection well at the initial moment.

7. The numerical characterization method for induced dynamic cracks based on dynamically embedded discrete cracks according to claim 5, characterized in that, The specific crack morphology parameters include: the starting position and direction of the growth, extension or closure of induced dynamic cracks at different times, crack length, crack height, crack aperture, crack dip angle and crack azimuth angle; the crack attribute parameter is crack permeability.

8. The numerical characterization method for induced dynamic cracks based on dynamically embedded discrete cracks according to claim 7, characterized in that, The fracture permeability includes the permeability along the long side of the dynamically embedded discrete fracture sheet. k fci and the permeability along the short side of the dynamically embedded discrete crack. k fdi ; Permeability along the long side of a dynamically embedded discrete slit plate k fci The specific calculation process is as follows: k fci = ξk fc · ω f 3 / ω fo 3 Permeability along the short side of a dynamically embedded discrete slit plate k fdi The specific calculation process is as follows: k fdi = ξk fd · ω f 3 / ω fo 3 In the formula: k fci The permeability along the long side of a dynamically embedded discrete crack plate. μm 2 ; ξ This is a permeability correction factor, dimensionless. k fc The permeability along the long side at the starting position of the dynamically embedded discrete crack plate. μm 2 ; ω f For crack opening, μm ; ω fo This refers to the crack aperture at the starting position of a dynamically embedded discrete crack sheet. μm ; k fdi The permeability along the short side of a dynamically embedded discrete crack plate. μm 2 ; k fd The permeability along the short side at the starting position of the dynamically embedded discrete crack plate. μm 2 .

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