Coal bed gas crossing fracturing demonstration and optimization method

Abstract

The invention discloses a coal bed gas crossing fracturing demonstration and optimization method, which comprises the following steps: acquiring an underground rock core, carrying out mechanical and physical property parameter tests on a coal bed and an interlayer, and constructing a longitudinal multi-thin interbed geologic model based on a full-three-dimensional structured grid, including mechanical characteristics and stress characteristics of each thin layer; the positions of perforation points are changed, a segmented clustering scheme is completed, and the longitudinal layer penetrating effect of cracks is simulated; the fracturing construction parameters are optimized with the longitudinal crossing effect as a target, and the fracturing construction parameters comprise the displacement, the sand adding amount, the number of single-cluster holes, the gap distance and the number of intra-segment clusters; simulating the overall fracture form and fracture parameters through a full-three-dimensional fracture propagation simulation platform; micro-seismic testing is carried out to monitor the fracture crossing effect, and the effectiveness of fracture crossing fracturing construction parameters is demonstrated. According to the embodiment of the invention, aiming at a thin interbed type coal bed gas reservoir, horizontal well crack longitudinal crossing fracturing construction parameters are optimized, the coal bed gas yield is improved, and higher economic benefits are obtained.

Description

Technical Field

[0001] The present application relates to the technical field of coalbed methane development, and in particular to a coalbed methane through-layer fracturing demonstration and optimization method based on full three-dimensional structured grid simulation. Background Art

[0002] Fracturing transformation is a necessary technology to increase coalbed methane production. The coalbed methane reservoir area is affected by geological tectonic movements, with many types of gas-controlling structures and many coal seams, high coal seam gas content, high resource abundance, high reservoir pressure and ground stress, as well as large coalbed methane resources, large coal grade changes, large changes in coal seam permeability and large vertical changes in geological conditions. Coalbed methane reservoirs are characterized by "many layers, thin thickness, and clustered distribution", and some blocks have high clay mineral content in the strata. It is difficult for hydraulic fracturing cracks to expand vertically, and it is difficult to accurately demonstrate the effect of crack penetration. Establishing an integrated geological and engineering model and demonstrating the effect of vertical crack penetration is of great significance to effectively guide the deployment of new wells for coalbed methane mining and the optimal design of fracturing schemes.

[0003] In the process of on-site fracturing, due to the large number of thin interlayers in the coalbed methane reservoir and the large differences between layers, the difficulty of longitudinal penetration of fractures in different perforation sections varies greatly. The matching of perforation scheme, construction parameters and reservoir is not yet clear. Therefore, a coalbed methane cross-layer fracturing demonstration and optimization method is proposed. Summary of the invention

[0004] The technical problem to be solved by the present invention is: how to solve the problems in the existing technology of on-site fracturing, such as the large number of thin longitudinal interlayers in the coalbed methane reservoir, large differences between layers, large differences in the difficulty of longitudinal penetration of fractures in different perforation sections, and unclear matching of perforation schemes, construction parameters and reservoirs. A method for demonstrating and optimizing coalbed methane penetration fracturing is provided.

[0005] The present invention solves the above technical problems through the following technical solutions: a coalbed methane cross-layer fracturing demonstration and optimization method based on full three-dimensional structured grid simulation, which can optimize the vertical cross-layer fracturing scheme for coalbed methane reservoirs with a large number of thin interlayers, increase coalbed methane production, and obtain higher economic benefits.

[0006] A coalbed methane interlayer fracturing demonstration and optimization method based on full three-dimensional structured grid simulation includes the following steps:

[0007] Step 1: Obtain underground cores and conduct mechanical and physical parameter tests of coal seams and interlayers;

[0008] Step 2: construct a vertical multi-thin interlayer geological model based on a full three-dimensional structured grid;

[0009] Step 3: Change the perforation point position, set the segmentation and clustering scheme, and simulate the longitudinal penetration effect of the fracture;

[0010] Step 4, optimizing the fracturing operation parameters including displacement, sand addition, number of single cluster holes, fracture spacing and number of clusters within a segment through orthogonal simulation test of fracture extension;

[0011] Step 5, simulating the overall crack morphology and crack parameters through a full three-dimensional crack extension simulation platform;

[0012] Step 6: Conduct microseismic testing to monitor the crack penetration effect and demonstrate the effectiveness of the crack penetration fracturing construction parameters.

[0013] In step 1, underground cores are obtained, and mechanical and physical parameters of coal seams and interlayers are obtained based on uniaxial / triaxial compression tests, tensile strength tests, ground stress tests, and clay mineral content tests;

[0014] In step 2, a full 3D structured grid is constructed based on the logging data to cover the small layer interface inside the vertical box, and the indoor test data is used in combination with the well point stratification correction; the plane grid accuracy of the multi-thin interlayer 3D geological model is 50m×50m, and the vertical grid accuracy is 0.5m; based on the existing logging interpretation results, the logging data is collected, sorted and loaded, and the geological model of the work area where the horizontal well is located is established in the Gohfer platform, including: permeability model, porosity model; establish a 3D lithology and physical property parameter model; establish a 3D geostress model;

[0015] In step 3, by changing the perforation point position and setting different segmentation and clustering schemes, the longitudinal penetration effect of the fracture is simulated;

[0016] In step 4, through the orthogonal simulation test of fracture extension, the fracturing operation parameters are optimized with the vertical penetration effect as the goal, including displacement, sand addition amount, number of single cluster holes, fracture spacing and number of clusters in a segment;

[0017] In step 5, the overall crack morphology is simulated through a full three-dimensional crack extension simulation platform, and crack parameters are counted to compare the longitudinal penetration effect of the crack;

[0018] In step 6, ground microseismic testing is carried out during the on-site fracturing construction process to monitor the crack penetration effect and demonstrate the effectiveness of the crack penetration fracturing construction parameters.

[0019] Compared with the prior art, the present invention has the following advantages: the coalbed methane interlayer fracturing demonstration and optimization method, the invention obtains underground cores and conducts mechanical parameter tests of coal seams and interlayers, and constructs a longitudinal multi-thin interlayer geological model based on a full three-dimensional structured grid, including the mechanical characteristics and stress characteristics of each thin layer; changes the position of the perforation point, completes the segmentation and clustering scheme, and simulates the longitudinal interlayer effect of the fracture; and optimizes the fracturing construction parameters with the longitudinal interlayer effect as the goal, including displacement, sand addition, single cluster hole number, seam spacing and number of clusters in the segment; simulates the overall fracture morphology and fracture parameters through a full three-dimensional fracture expansion simulation platform; conducts microseismic testing to monitor the fracture interlayer effect and demonstrates the effectiveness of the construction parameters. The embodiments of this specification can be used to optimize the longitudinal interlayer fracturing construction parameters of horizontal well fractures for thin interlayer coalbed methane reservoirs, increase coalbed methane production, and obtain higher economic benefits, making the system more worthy of popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the downhole core and test result diagram of the present invention;

[0021] Figure 2 It is a three-dimensional geological model diagram of the longitudinal thin interbeds of the present invention;

[0022] Figure 3 It is the segmentation clustering result of the present invention Figure 1 ;

[0023] Figure 4 It is the segmentation clustering result of the present invention Figure 2 ;

[0024] Figure 5 It is the segmentation clustering result of the present invention Figure 3 ;

[0025] Figure 6 It is the segmentation clustering result of the present invention Figure 4 ;

[0026] Figure 7 This is a diagram demonstrating the effect of longitudinal layer penetration of the present invention;

[0027] Figure 8 It is a construction parameter optimization result diagram of the present invention;

[0028] Fig. 9 It is the result of three-dimensional fracture expansion in the horizontal well of the present invention. DETAILED DESCRIPTION

[0029] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0030] like Figure 1 to Figure 6As shown, this embodiment provides a technical solution: a coalbed methane through-layer fracturing demonstration and optimization method, including the following steps.

[0031] As shown in the figure, underground cores are obtained, and the mechanical and physical parameters of coal seams and interlayers are obtained based on uniaxial / triaxial compression tests, tensile strength tests, ground stress tests and clay mineral content tests.

[0032] like Figure 2 As shown in the figure, based on the logging data, a full three-dimensional structured grid is constructed to cover the small layer interface inside the vertical box, and the indoor test data is used in combination with the well point stratification correction; the plane grid accuracy of the multi-thin interlayer three-dimensional geological model is 50m×50m, and the vertical grid accuracy is 0.5m; based on the existing logging interpretation results, the logging data is collected, sorted and loaded, and the geological model of the work area where the horizontal well is located is established in the Gohfer platform, including: permeability model, porosity model; a three-dimensional lithology and physical property parameter model is established; and a three-dimensional geostress model is established.

[0033] like Figure 3 As shown, based on the three-dimensional geological model of multiple thin interbeds in step 2, the longitudinal extension range of the fracture under different relative positions of wellbore trajectories and coal seams is obtained to simulate the longitudinal penetration effect of the fracture.

[0034] like Figure 4 As shown, a reservoir model is established based on the geomechanical model in step 2. Through orthogonal simulation tests of fracture extension, the fracturing construction parameters are optimized with the vertical penetration effect as the goal, including displacement, sand addition amount, number of single cluster holes, fracture spacing and number of clusters within a segment.

[0035] like Figure 5 As shown, according to the geological model established in step 2 and the longitudinal through-layer fracturing construction parameters optimized in step 4, based on the on-site segmentation and clustering scheme of the platform well, the physical property differences in the same layer, the geomechanical characteristics, and the influence of stress interference of multiple clusters of fractures are comprehensively considered. The clustering method is used to design the layer segment and the number of clusters where the perforations are located to complete the segmentation and clustering scheme. The YHF-1 well completion plan is as follows: the total length of the horizontal section is 640m, with a total of 8 fracturing sections, with a section length between 64m and 100m, an average section length of 80m, 2 clusters within the section, an average cluster spacing of 38.8m, each cluster is perforated 3m, and the hole density is 10 holes / m. Active water is used as the sand-carrying fluid, and the construction displacement is 12m 3 / min, 70 / 140 mesh, 40 / 70 mesh and 20 / 40 mesh quartz sand to support cracks, single-stage sand volume 57.7m 3 , sand ratio 5% to 10%, single stage liquid volume 1687m 3 .

[0036] like Figure 6As shown in the figure, based on the completion scheme and construction parameters in step 5, the overall fracture morphology is simulated through the full three-dimensional fracture extension simulation platform, and the fracture parameters are counted to compare the longitudinal penetration effect of the fracture.

[0037] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0038] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0039] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A coalbed methane interlayer fracturing demonstration and optimization method, characterized in that: The following steps are involved: Step 1: Obtain downhole cores, conduct mechanical and physical parameter tests on coal seams and interlayers, and obtain logging data; Step 2: Based on the acquired logging data, a full 3D structured grid is constructed to construct a vertical multi-thin interbedded 3D geological model; Step 3: Change the perforation point position, set the segmentation and clustering scheme, and simulate the longitudinal penetration effect of the fracture; Step 4: Optimize fracturing operation parameters through orthogonal simulation test of crack extension; Step 5, simulating the overall crack morphology and crack parameters through a full three-dimensional crack extension simulation platform; Step 6: Conduct microseismic testing to monitor the crack penetration effect and demonstrate the effectiveness of the crack penetration fracturing construction parameters.

2. A coalbed methane cross-layer fracturing demonstration and optimization method according to claim 1, characterized in that: The test methods for obtaining underground cores and conducting mechanical and physical parameter tests of coal seams and interlayers in step 1 include rock mechanics tests, geostress tests, and clay mineral content tests.

3. A coalbed methane cross-layer fracturing demonstration and optimization method according to claim 1, characterized in that: In step 2, the full three-dimensional structured grid constructed based on the logging data covers the small layer interface inside the reservoir vertically, and uses indoor test data and well points to perform stratification correction; The plane grid accuracy of the multi-thin interlayer 3D geological model is 50m×50m, and the vertical grid accuracy is 0.5m.

4. A coalbed methane cross-layer fracturing demonstration and optimization method according to claim 1, characterized in that: In step 2, based on the existing logging interpretation results, the logging data are collected, sorted and loaded, and a multi-thin interlayer three-dimensional geological model of the work area where the horizontal well is located is established in the Gohfer platform. The multi-thin interlayer three-dimensional geological model includes: a permeability model, a porosity model, a three-dimensional lithology and physical property parameter model, and a three-dimensional geostress model.

5. A coalbed methane cross-layer fracturing demonstration and optimization method according to claim 1, characterized in that: The simulation process in step 3 is based on the multi-thin interbedded three-dimensional geological model in step 2, and needs to comprehensively consider the physical property differences of the same layer, the geomechanical characteristics, and the influence of stress interference of multiple clusters of fractures; Then, the perforation point position is changed, the segmentation and clustering scheme is set, the pumping program for on-site construction is input, the calculation example is designed, and finally the longitudinal penetration effect of the fracture is simulated.

6. A coalbed methane cross-layer fracturing demonstration and optimization method according to claim 1, characterized in that: Based on the three-dimensional geological model of multiple thin interbeds in step 2, the longitudinal extension range of the fracture under different relative positions of wellbore trajectories and coal seams is obtained to simulate the longitudinal penetration effect of the fracture.

7. A coalbed methane cross-layer fracturing demonstration and optimization method according to claim 1, characterized in that: The optimized fracturing construction parameters in step 4 include displacement, sand addition amount, number of single cluster holes, seam spacing and number of clusters within a segment.

8. A coalbed methane cross-layer fracturing demonstration and optimization method according to claim 1, characterized in that: In step 5, according to the geological model established in step 2 and the longitudinal through-layer fracturing construction parameters optimized in step 4, based on the on-site segmentation and clustering scheme of the platform well, the physical property differences of the same layer, the geomechanical characteristics, and the influence of stress interference of multiple clusters of fractures are comprehensively considered, and the clustering method is adopted to design the layer section and the number of clusters for perforation, and complete the segmentation and clustering scheme.

9. A coalbed methane through-layer fracturing demonstration and optimization method according to claim 1, characterized in that: Based on the completion plan and construction parameters in step 5, the overall fracture morphology is simulated through the full 3D fracture extension simulation platform, and the fracture parameters are counted to compare the longitudinal penetration effect of the fracture.

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