Coal bed gas through layer fracturing demonstration and optimization method

Abstract

The application discloses a coal bed gas through-layer fracturing demonstration and optimization method, comprising the following steps: obtaining downhole cores and carrying out coal bed and interlayer mechanical and physical property parameter tests, constructing a longitudinal multi-thin interbedded geological model based on a full three-dimensional structured grid, including the mechanical characteristics and stress characteristics of each thin layer, changing the perforation point position, completing a segmented cluster scheme, simulating the longitudinal through-layer effect of the fracture, taking the longitudinal through-layer effect as a target to optimize fracturing construction parameters, including the displacement, sanding amount, single cluster hole number, seam spacing and cluster number in the segment, simulating the overall fracture shape and fracture parameters through a full three-dimensional fracture propagation simulation platform, carrying out microseismic test to monitor the fracture through-layer effect, and demonstrating the effectiveness of the fracture through-layer fracturing construction parameters. According to the embodiment of the specification, the horizontal well fracture longitudinal through-layer fracturing construction parameters can be optimized for the thin interbedded coal bed gas reservoir, the coal bed gas production 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 particularly relates to a coalbed methane through-layer fracturing demonstration and optimization method based on full three-dimensional structured grid simulation. BACKGROUND

[0002] Fracturing reconstruction is a necessary technology for improving coalbed methane production. The coalbed methane reservoir region is affected by geological structure movement, and has many types of gas-controlling structures, many coal layers, high coalbed methane content, high resource abundance, high reservoir pressure and ground stress, and large coalbed methane resource, large coal rank variation, large coalbed permeability variation and large vertical geological condition variation. The coalbed methane reservoir has the characteristics of'many layers, thin thickness and group distribution', and the stratum clay mineral content of some blocks is high, so it is difficult for the hydraulic fracturing cracks to expand in the vertical direction, and the crack through-layer effect cannot be accurately demonstrated. It is of great significance to establish a geological engineering integrated comprehensive model and demonstrate the crack vertical through-layer effect for effectively guiding the deployment of new coalbed methane production wells and the optimization design of fracturing schemes.

[0003] In the process of implementing fracturing on site, since the coalbed methane reservoir has many vertical thin interbeds, the interlayer difference is large, the crack vertical through-layer construction difficulty of different perforation sections is large, and the matching of the perforation scheme, construction parameters and the reservoir is not clear, therefore, a coalbed methane through-layer fracturing demonstration and optimization method is provided. SUMMARY

[0004] The technical problem to be solved by the present application is how to solve the problem in the prior art that in the process of implementing fracturing on site, since the coalbed methane reservoir has many vertical thin interbeds, the interlayer difference is large, the crack vertical through-layer construction difficulty of different perforation sections is large, and the matching of the perforation scheme, construction parameters and the reservoir is not clear, and a coalbed methane through-layer fracturing demonstration and optimization method is provided.

[0005] The present application solves the above technical problems by the following technical scheme, a coalbed methane through-layer fracturing demonstration and optimization method based on full three-dimensional structured grid simulation, which can optimize the vertical through-layer fracturing scheme for the coalbed methane reservoir with many thin interbeds, improve the coalbed methane production, and obtain higher economic benefits.

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

[0007] Step 1, obtaining downhole cores, and testing the mechanical and physical parameters of the coalbed and interlayer;

[0008] Step 2, constructing a vertical multi-thin interbed geological model based on a full three-dimensional structured grid;

[0009] Step 3, changing the perforation point position, setting a segmented cluster scheme, and simulating the crack vertical through-layer effect.

[0010] Step 4, optimize the fracturing operation parameters including displacement, sanding amount, single cluster hole number, inter-well spacing and cluster number in the segment through crack propagation orthogonal simulation test;

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

[0012] Step 6, carry out microseismic test to monitor the crack through-layer effect and demonstrate the effectiveness of the crack through-layer fracturing operation parameters.

[0013] In step 1, obtain downhole core, and obtain the mechanical and physical parameters of coal seams and interlayers based on single / three-axis compression test, tensile strength test, in-situ stress test and clay mineral content test;

[0014] In step 2, based on logging data, build a full three-dimensional structured grid covering the small layer interface inside the vertical box, and use laboratory test data combined with well point layer correction; the plane grid precision of the multi-thin interbedded three-dimensional geological model is 50m x 50m, and the vertical grid precision is 0.5m; based on the existing logging interpretation results, collect, organize and load logging data, and establish the geological model of the working area where the horizontal well is located in the Gohfer platform, including: permeability model, porosity model; establish three-dimensional lithology and physical property attribute parameter model; establish three-dimensional in-situ stress model;

[0015] In step 3, simulate the longitudinal through-layer effect of the crack by changing the perforation point position and setting different segmentation and clustering schemes;

[0016] In step 4, optimize the fracturing operation parameters including displacement, sanding amount, single cluster hole number, inter-well spacing and cluster number in the segment through crack propagation orthogonal simulation test and taking the longitudinal through-layer effect as the target;

[0017] In step 5, simulate the overall crack morphology through the full three-dimensional crack propagation simulation platform, and count the crack parameters to compare the longitudinal through-layer effect of the crack;

[0018] In step 6, carry out ground microseismic test during the fracturing operation process to monitor the crack through-layer effect and demonstrate the effectiveness of the crack through-layer fracturing operation parameters.

[0019] Compared with the existing technology, the present invention has the following advantages: the coalbed methane interlayer fracturing demonstration and optimization method obtains downhole cores and conducts mechanical parameter tests of coal seams and interlayers, 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 to complete the segmented clustering scheme and simulate 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 amount, number of single cluster holes, fracture spacing and number of clusters within a 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 promotion 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 This is the segmented clustering result of the present invention Figure 1 ;

[0023] Figure 4 This is the segmented clustering result of the present invention Figure 2 ;

[0024] Figure 5 This is the segmented clustering result of the present invention Figure 3 ;

[0025] Figure 6 This is the segmented clustering result of the present invention Figure 4 ;

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

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

[0028] Figure 9 This is the result of the 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 based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0030] like Figures 1-6As 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, downhole 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, a full 3D structured grid covering the small layer interface inside the vertical box is constructed based on logging data, and indoor test data is used in combination with well point stratification correction; the plane grid accuracy of the multi-thin interbedded 3D geological model is 50m×50m, and the vertical grid accuracy is 0.5m; based on the existing logging interpretation results, logging data is collected, organized and loaded, and a geological model of the horizontal well area is established in the Gohfer platform, including: permeability model, porosity model; 3D lithology and physical property parameter model is established; and 3D 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 in Figure 2, a reservoir model is established based on the geomechanical model in step 2. Through orthogonal simulation tests 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 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, taking into account the differences in physical properties of the same layer, geomechanical characteristics, and the influence of stress interference of multiple clusters of fractures, a clustering method is used to design the layer segment and number of clusters for perforation, and complete the segmentation and clustering scheme. The completion plan of the YHF-1 well is as follows: the total length of the horizontal section is 640m, with a total of 8 fracturing sections, the section length is between 64m and 100m, the average section length is 80m, there are 2 clusters in the section, the average cluster spacing is 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 the crack, 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 plan and construction parameters in step 5, the full 3D fracture propagation simulation platform is used to simulate the overall fracture morphology, calculate the fracture parameters, and compare the longitudinal penetration effect of the fracture.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0038] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean 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 can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

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

Claims

1. A coalbed methane through-layer 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 generated to construct a vertical multi-thin interbedded 3D geological model; Step 3: Change the perforation point position and set the segmentation and clustering scheme to simulate the longitudinal penetration effect of the fracture; Step 4: Optimize fracturing parameters through orthogonal simulation test of crack propagation; Step 5: Simulate the overall crack morphology and crack parameters through a full three-dimensional crack propagation 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. The coalbed methane through-layer fracturing demonstration and optimization method according to claim 1, characterized in that: The test methods for obtaining downhole cores and conducting mechanical and physical parameter tests of coal seams and interlayers in step 1 include rock mechanics testing, geostress testing, and clay mineral content testing.

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

4. The method for demonstrating and optimizing coalbed methane through-layer fracturing according to claim 1, characterized in that: In step 2, based on the existing logging interpretation results, the logging data are collected, organized and loaded, and a multi-thin interbedded 3D geological model of the work area where the horizontal well is located is established in the Gohfer platform. The multi-thin interbedded 3D geological model includes: a permeability model, a porosity model, a 3D lithology and physical property parameter model, and a 3D geostress model.

5. The coalbed methane through-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 3D geological model in step 2, and needs to comprehensively consider the physical property differences of the same layer, geomechanical characteristics, and the influence of stress interference of multiple clusters of fractures; Then, the perforation point position was changed, a segmented and clustered scheme was set, the on-site pumping program was input, a case study was designed, and finally the longitudinal penetration effect of the fracture was simulated.

6. The coalbed methane through-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. The method for demonstrating and optimizing coalbed methane through-layer fracturing according to claim 1, characterized in that: The optimized fracturing operation parameters in step 4 include displacement, sand addition amount, number of single cluster holes, fracture spacing and number of clusters within a segment.

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

9. The 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 was simulated using a full 3D fracture propagation simulation platform. Fracture parameters were then statistically analyzed to compare the longitudinal penetration effects of the fractures.

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