Horizontal well forced gas drainage method with coal bed gas subjected to staged fracturing

Abstract

The invention relates to a horizontal well forced gas drainage method with coal bed gas subjected to staged fracturing. In order to solve the problems that hole forming performance of horizontal drilling in a coal bed is poor and buried drill accidents can happen easily and to achieve the forced gas drainage effect on tectonic soft coal, the well track of a horizontal well is controlled in mudstone or sand stone with a certain range above a coal bed top boundary, and the horizontal well is docked with a drainage vertical well at a far end. An ultra deep penetration perforating technology is used, according to the requirement for certain hole density and orientation, orientated perforating is conducted downwards on the horizontal well section in a segmented mode, a steel sleeve, a well cementation cement ring and a mudstone top plate are penetrated, and the horizontal well is communicated with a target coal layer below. Then, a clear water sand carrying fracturing technology is used, staged fracturing is conducted on the target coal bed according to the requirements for large discharge capacity, large liquid amount, high prepad fluid ratio, large sand amount and middle sand ratio, and the purpose of increasing production is achieved.

Description

technical field [0001] The invention belongs to the technical field of surface coal-bed methane development, and relates to a method for intensifying drainage of ground coal-bed methane by segmental fracturing and horizontal wells facing structurally soft coal. Background technique [0002] At present, CBM development in structurally soft coal mainly adopts surface vertical well development. Vertical well development has the characteristics of low gas production per well, high operating cost due to the large number of production wells, low drainage efficiency, and large land occupation. [0003] Traditionally, horizontal wells are used to exploit coalbed methane in coal seams with particularly good coal structure, and the wellbore trajectories are all in coal seams. More than 98% of horizontal wells are completed with open holes, and a very small number of wells are Casing and perforating are performed in the coal seam to complete wells, and then staged fracturing is perform...

AI Technical Summary

Problems solved by technology

Due to the repeated kneading and extrusion of the coal seam under the action of strong structural stress, the structure and structure of the coal are greatly different from those of the original structure coal. The soft structure of the coal body is its remarkable feature. Poor porosity, easy to cause accidents such as buried drilling, high construction risk

[0005] To sum up, the current conventional coalbed methane development technology has low drainage efficiency, and it is difficult to quickly reduce the content of coalbed methane in structural soft coal and achieve the purpose of enhancing the effect of coalbed methane drainage

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