Fracturing method for ground inclined shaft of steeply inclined coal seam

Abstract

The invention provides a steeply inclined seam ground inclined shaft fracturing method which comprises the following steps: monitoring overlying strata fracture release energy through micro-seismic monitoring equipment, and selecting a rock stratum with the maximum fracture release energy as a fracturing target layer; obtaining a loess layer movement line according to the loess layer thickness and the loess layer movement angle above the fracturing target layer; obtaining a rock stratum movement line according to the loess layer movement line and the goaf upper end point; drilling is conducted between the ground and a fracturing target layer, and a fracturing well vertical section is obtained; and inclined fracturing is conducted on the fracturing target layer between the end point of the vertical section of the fracturing well and the lower end point of the to-be-mined area, and the inclined section of the fracturing well is obtained. According to the method, the drilling position of the fractured well is determined according to the spatial position of the fractured well and the rock stratum movement line, and the well leakage accident rate and the well building cost are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of steeply inclined coal seam mining, in particular to a ground inclined well fracturing method for steeply inclined coal seams. Background Art

[0002] The occurrence conditions and fracture movement laws of steeply inclined coal seams are complex. Under the influence of the "three highs and one disturbance" in the deep, the impact tendency is high and rock burst accidents occur frequently. The use of ground inclined well fracturing can effectively prevent and control them. However, during the construction of fracturing wells, due to the complexity of geological conditions, well leakage accidents occur frequently, which not only consumes a lot of materials and prolongs the well construction period, but may also cause complex situations such as well collapse, blowout, and drill stuck, causing major engineering accidents. Therefore, it is very necessary to design a ground inclined well fracturing method for steeply inclined coal seams. Summary of the invention

[0003] The purpose of the present invention is to provide a method for fracturing a steeply inclined coal seam surface inclined well, so as to determine the drilling position of the fracturing well according to the spatial position of the fracturing well and the rock formation movement line, thereby reducing the leakage accident rate and the well construction cost.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A method for fracturing a steeply inclined coal seam surface inclined well, comprising the following steps:

[0006] The energy released by the overburden fracture is monitored by microseismic monitoring equipment, and the rock layer with the largest energy released by fracture is selected as the target layer for fracturing;

[0007] The loess layer movement line is obtained according to the loess layer thickness and loess layer movement angle above the fracturing target layer;

[0008] The rock layer movement line is obtained according to the loess layer movement line and the upper end point of the goaf;

[0009] Drilling a hole between the ground and the target layer for fracturing to obtain a vertical section of the fracturing well;

[0010] The target layer is subjected to inclined fracturing between the end point of the vertical section of the fracturing well and the lower end point of the planned production area to obtain the inclined section of the fracturing well.

[0011] Optionally, the specific steps of obtaining the rock layer movement line according to the loess layer movement line and the upper end point of the goaf are: connecting the lower end point of the loess layer movement line with the upper end point of the goaf to obtain a connecting straight line and using the connecting straight line as the rock layer movement line.

[0012] Optionally, in the direction of the extended axis of the inclined section of the fracturing well, the ratio of the distance between the end point of the vertical section of the fracturing well and the upper end point of the planned mining area and the rock formation movement line is 1:2.

[0013] Optionally, the ratio of the normal distance between the inclined section of the fracturing well and the upper and lower surfaces of the fracturing target layer is 2:1.

[0014] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: the present invention provides a method for fracturing a steeply inclined coal seam on the ground inclined well, the method comprising: monitoring the energy released by the breaking of the overburden through microseismic monitoring equipment, selecting the rock layer with the largest breaking energy release as the target layer for fracturing; obtaining the loess layer movement line according to the thickness of the loess layer above the target layer for fracturing and the loess layer movement angle; obtaining the rock layer movement line according to the loess layer movement line and the upper end point of the goaf; drilling between the ground and the target layer for fracturing to obtain a vertical section of the fracturing well; performing inclined fracturing on the target layer for fracturing between the end point of the vertical section of the fracturing well and the lower end point of the area to be mined to obtain an inclined section of the fracturing well. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0016] Figure 1 This is a flow chart of a method for fracturing a steeply inclined coal seam surface inclined well according to an embodiment of the present invention;

[0017] Figure 2 This is a position diagram of the vertical section and inclined section of a fracturing well according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 1 As shown, the present invention takes the ground fracturing of a steeply inclined coal seam in a mine in Gansu as an example. This embodiment provides a ground inclined well fracturing method for a steeply inclined coal seam, including the following steps:

[0021] Step 100: Monitor the energy released by overburden fracture by using microseismic monitoring equipment, and select the rock layer with the largest energy released by fracture as the target layer for fracturing.

[0022] Step 200: Obtaining a loess layer movement line according to the loess layer thickness above the fracturing target layer and the loess layer movement angle.

[0023] Specific as Figure 2 As shown in the figure, by consulting the relevant geological data of the location of the fracturing target layer, the thickness of the loess layer in the well construction area is obtained to be 32m, the loess layer movement angle β is 45°, and the farthest surface fracture development point is c. With point c as the starting point, a loess layer movement line with an angle of 45° to the horizontal plane is drawn to obtain the lower end point b of the loess layer movement line. The inclination angle α of the fracturing target layer is 60°.

[0024] Step 300: Obtain the rock layer movement line according to the loess layer movement line and the upper end point of the goaf.

[0025] Specifically, the upper end point a of the goaf is on the same horizontal line as the upper elevation B of the proposed mining area. The upper elevation B of the proposed mining area is +1450m. The lower end point b of the loess layer movement line is connected to the upper end point a of the goaf to obtain a connecting straight line and use the connecting straight line as the rock layer movement line.

[0026] Step 400: Drilling a hole between the ground and the target layer for fracturing to obtain a vertical section of the fracturing well.

[0027] Specifically, the vertical section length L1 of the fracturing well is 223 m.

[0028] Step 500: performing inclined fracturing on the target layer between the end point of the vertical section of the fracturing well and the lower end point of the planned production area to obtain an inclined section of the fracturing well.

[0029] Specifically, the starting point of the inclined section of the fracturing well is connected to the end point of the vertical section of the fracturing well, and the end point of the inclined section of the fracturing well is on the same horizontal line as the lower elevation A of the proposed mining area. The lower elevation A of the proposed mining area is +1403m. The inclination angle of the inclined section of the fracturing well and the target layer of the fracturing are both 60°. The length L2 of the inclined section of the fracturing well is 71m.

[0030] More specifically, the axis extension line of the inclined section of the fracturing well intersects with the rock formation movement line, the distance from the starting point of the inclined section of the fracturing well along the axis extension line to the intersection of the axis extension line and the rock formation movement line is C2, and the distance from the starting point of the inclined section of the fracturing well along the axis extension line beyond the upper elevation B of the planned mining area is C1. The ratio of C1 to C2 is 1: 2. In this embodiment, C2 is 28.2 m and C1 is 14.3 m.

[0031] More specifically, the normal distance between the inclined section of the fracturing well and the upper surface of the fracturing target layer is Z2, and the normal distance between the inclined section of the fracturing well and the lower surface of the fracturing target layer is Z1. The ratio of Z1 to Z2 is 1: 2. In this embodiment, Z2 is 21.6 m and Z1 is 10.8 m.

[0032] The beneficial effects of the present invention are as follows:

[0033] 1) According to the spatial position relationship between the fracturing well and the rock formation movement line, the layout mode and parameters of the vertical section and inclined section of the fracturing well are determined, which greatly reduces the wellbore leakage phenomenon during the well construction process, effectively prevents well leakage accidents, and reduces the well construction cost;

[0034] 2) The fracturing method is simple, highly applicable and has a wide range of applications.

[0035] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0036] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for fracturing a steeply inclined coal seam surface inclined well, characterized in that: The steps include: The energy released by the overburden fracture is monitored by microseismic monitoring equipment, and the rock layer with the largest energy released by fracture is selected as the target layer for fracturing; Obtaining a loess layer movement line according to the loess layer thickness and loess layer movement angle above the fracturing target layer; Obtaining a rock layer movement line according to the loess layer movement line and the upper end point of the goaf; Drilling a hole between the ground and the target layer for fracturing to obtain a vertical section of the fracturing well; The target layer of the fracturing is subjected to inclined fracturing between the end point of the vertical section of the fracturing well and the lower end point of the planned production area to obtain the inclined section of the fracturing well.

2. The method for fracturing a steeply inclined coal seam surface inclined well according to claim 1, characterized in that: The specific steps of obtaining the rock layer movement line according to the loess layer movement line and the upper end point of the goaf are: connecting the lower end point of the loess layer movement line with the upper end point of the goaf to obtain a connecting straight line and using the connecting straight line as the rock layer movement line.

3. The method for fracturing a steeply inclined coal seam surface inclined well according to claim 1, characterized in that: In the direction of the extended axis of the inclined section of the fracturing well, the ratio of the distance between the end point of the vertical section of the fracturing well and the upper end point of the planned mining area and the rock formation movement line is 1:

2.

4. The method for fracturing a steeply inclined coal seam surface inclined well according to claim 1, characterized in that: The ratio of the normal distance between the inclined section of the fracturing well and the upper and lower surfaces of the fracturing target layer is 2:1.

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