Method for drilling and completion of horizontal branched well for coal bed gas

Abstract

The invention discloses a method for drilling and completion of a horizontal branched well for coal bed gas. The method comprises the following steps: step 1: drilling a first-opening surface layer section, a second-opening straight well section and an incline angle buildup section of the horizontal branched well by adopting a conventional drilling tool combination, and after finishing drilling, arranging casing pipes so as to fix the well; step 2: drilling a third-opening coal bed horizontal section by adopting a casing pipe well drilling tool combination until a designed well depth is reached, and pulling out a directional drilling tool combination at the bottom of the well from the casing pipe with a steel wire fishing device; and step 3: adopting a radial lateral well drilling tool with a super-short radius so as to mill the casing pipe and drill the branched well in a coal bed. According to the method disclosed by the invention, pumping termination time can be shortened during drilling a main well hole of the coal bed, the coal bed can be effectively supported, the swabbing effect of well drilling is avoided, and accidents of collapse of a horizontal well and burying of the drilling tools are reduced; a well drilling technology of the branched well is greatly simplified, the well drilling risk of the branched well is reduced, the operation period is shortened, and the cost of drilling the branched well for the coal bed gas is reduced.

Description

technical field [0001] The invention belongs to the technical field of drilling, and in particular relates to a drilling and completion method for a coalbed gas horizontal branch well. Background technique [0002] Horizontal branch well technology is one of the most important means of increasing production in coalbed methane mining. It mainly has the advantages of large single well controlled reserves, high production, high penetration, longer completion section than vertical well, and larger pressure relief area. , has the advantages of directional control and length control that hydraulic fracturing cannot create. [0003] However, coal has a lower elastic modulus and a higher Poisson's ratio than conventional reservoirs, which is likely to cause wellbore collapse. The risk of CBM horizontal branch wells increases significantly with the extension of the horizontal section length and the prolongation of the open hole vacancy time. The performance of soft coal seams is mor...

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Problems solved by technology

[0003] However, coal has a lower elastic modulus and a higher Poisson's ratio than conventional reservoirs, which is likely to cause wellbore collapse. The risk of CBM horizontal branch wells increases significantly with the extension of the horizontal section length and the prolongation of the open hole vacancy time. The performance of soft coal seams is more prominent. In addition, the cost of horizontal well branch drilling is high, and the drilling technology of horizontal well branch wells seriously affects the development benefits of coalbed methane.

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