Soft and hard interaction coal seam horizontal well staged fracturing gas advanced extraction method

Abstract

The invention relates to a soft and hard interaction coal seam horizontal well staged fracturing gas advanced extraction method. The method comprises the steps that a vertical well is constructed in the deep structure of a protection coal pillar, and the cave position of the vertical well is located in a hard coal layer of a soft and hard interaction coal seam; a horizontal well set in butt joint with the vertical well is constructed in the direction of a protection coal pillar between planned coal faces, and the horizontal section of the horizontal well set is located in a hard coal layer of the soft and hard interaction coal seam; the horizontal well is subjected to staged perforation fracturing construction in a retreating mode, and high-speed jet flow of the staged perforation fracturing construction induces water flow to break through a hard coal layer and then enter a soft coal layer; and after the staged perforation fracturing construction, gas extraction is conducted on the horizontal well, and drainage operation is conducted on the vertical well. According to horizontal well planning and deployment, the influence of later-stage coal mining activities is considered, coal mining and gas mining integrated design is achieved, and the purpose of coordinated development of coal and coal bed gas is achieved.

Description

technical field [0001] The invention relates to a gas extraction method in advance, belonging to the technical field of gas extraction, in particular to a gas extraction method for staged fracturing of a horizontal well in a soft-hard alternating coal seam. Background technique [0002] Soft and hard coal seam refers to a type of coal seam in which soft coal and hard coal exist alternately. This kind of coal seam is widely distributed in my country and has a huge amount of gas resources. The gas drainage in it is conducive to curbing coal mine gas disasters and ensuring safe production in coal mines. . At present, the method of gas pre-drainage in underground boreholes is generally used for gas control in mines where soft-hard intersecting coal seams develop. This method has problems such as large amount of engineering, difficult construction, low drainage volume, unbalanced drainage, and long time for drainage to reach the standard, etc. The problem is that the contradictio...

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Problems solved by technology

[0003] At present, the pre-drainage of vertical wells on the ground in soft-hard alternating coal seams generally presents the characteristics of poor drainage effect and low efficiency, and the mutual interference of coal mining and gas production makes it difficult to meet the needs of striped coal mines, rapid and efficient reduction of gas content

However, there are few successful cases of horizontal well staged fracturing and enhanced drainage in soft-hard alternating coal seams.

There are mainly the following difficulties: (1) The planning and deployment of horizontal wells is unreasonable, inconsistent with the integrated design concept of coal and gas production, which seriously affects the later coal mining activities; (2) It is difficult to control the wellbore trajectory in the drainage of horizontal wells , drilling in soft coal seams has poor wall stability, failure to form holes, and high drilling construction risks; (3) The fracturing construction is difficult, the extension of soft coal cracks is difficult, and the stimulation effect is poor, so it is difficult to realize simultaneous stimulation of soft and hard coal; ( 4) There are many accidents in drainage and gas production, frequent pump shutdown and maintenance, resulting in high cost of drainage and other problems

[0004] To sum up, at present, the deployment of advanced gas drainage in soft-hard interactive coal seams is unreasonable. It is difficult to control the drilling trajectory of horizontal wells, and the fracturing and drainage effects are poor. It is difficult to achieve the integration of coal and gas production, and it is difficult to achieve large-scale and rapid reduction. The gas content of the soft-hard alternating coal seam can achieve the purpose of strengthening the effect of gas drainage

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