Drainage method of non-cell-cementation cased-hole-completion coal bed gas horizontal well

Abstract

The invention discloses a drainage method of a non-cell-cementation cased-hole-completion coal bed gas horizontal well. The method includes: a U-shaped butted well is used, the horizontal section of the horizontal well is deployed along the declination direction of a coal bed and a direction parallel to the minimum main stress of the coal bed, and well completion is performed by using casing running and an external self-expansion casing packer in a non-cell-cementation manner; the setting section, perforation and fracturing section of the external casing packer of the horizontal well are optimized; perforation is performed in a large-displacement and fixed-direction hydraulic abrasive perforation manner, and slug insertion type sand-carrying fracturing is performed on the horizontal well section by section in a large-displacement, large-scale, high-prepad-fluid-ratio and medium-sand-ratio manner; draining is performed at the wellhead of a drainage vertical well, and gas production is performed at the wellhead of the horizontal well. The drainage method has the advantages that pollution of a coal reservoir and production and operation costs can be lowered, the fracturing transformation effect and draining and gas production effect of the non-cell-cementation cased-hole-completion horizontal well are improved, the drainage efficiency and effect of the horizontal well are increased, the coal bed gas content of soft, broken and low-permeability coal beds can be lowered in a large-range and fast manner, and intensified coal bed gas drainage is achieved.

Description

technical field [0001] The invention relates to the technical field of surface coalbed methane development, in particular to a non-cementing casing completion coalbed methane horizontal well drainage method. Background technique [0002] With the continuous development of horizontal well development technology, breakthroughs have been made in the development effect of coalbed methane horizontal wells, which shows that horizontal wells are an effective method to realize rapid and efficient extraction of coalbed methane. At present, more than 95% of horizontal wells are completed using open hole and non-fracturing methods, and the horizontal section is drilled in coal seams, which has problems such as well wall collapse, drilling fluid pollution, and formation blockage, which also exposes unstable gas production. , low yield, fast decay and other characteristics. In order to improve the development effect of horizontal wells, casing completion was explored, and then staged fr...

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Problems solved by technology

[0003] In view of the poor bonding strength between the cement sheath and the coal seam during the cementing of coalbed methane wells, resulting in unqualified cementing quality, and there are also problems such as cement slurry polluting the coal seam. At present, horizontal wells are completed with casing and no cementing.

In the development of CBM horizontal wells under non-cementing conditions, the uniform segmentation method is basically adopted based on the number of fracturing stages of the horizontal well, and the selection of fracturing segments is not targeted; the fracturing technology of non-cementing horizontal wells is still not perfect, The problem of channeling outside the fracturing pipe cannot be solved. The fracturing scale and sanding intensity carried by clean water are very small, and the fracturing effect of the coal seam is poor. The impact is serious, and under the condition of no cementing, the sand and pulverization of the coal seam are serious, resulting in the frequent occurrence of pump jamming and gas lock of the drainage equipment, which restricts the smooth progress of drainage and gas recovery of the coalbed methane horizontal well, and seriously affects the coalbed methane horizontal well. development effect

[0004] To sum up, the current non-cementing casing completion CBM horizontal well development technology has poor drainage effect and low drainage efficiency, and it is difficult to achieve large-scale and rapid reduction of CBM content in broken, soft and low-permeability coal seams, and it is difficult to achieve enhanced drainage. The purpose of mining coalbed methane effect

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