Double circulation relay type coal seam drilling method

Abstract

The invention discloses a dual-cycle relay coal bed well drilling method. The method comprises the following steps: (1) drilling and extracting: carrying out well cementation and enlarging a cave in a coal bed after drilling and completion twice and running casing; (2) drilling a horizontal multilateral well: through drilling and completion twice, after the second drilling and completion, running dual-casing to suspend and center an internal casing in an external casing, and placing the terminal of an internal casing on a place which is 0.5-10m far away from the casing shoe of the external casing; bypassing an extraction well while the third drilling is carried out, disconnecting the extraction wheel, and then drilling the extraction wheel after the construction of a horizontal multilateral well is finished; and (3) shutting in the well and putting into production in commission: cementing a plug, sealing the well head of the horizontal multilateral well, and pumping, draining and producing coal gas by using the extraction well. According to the drilling method, the double circulation above the casing shoe is formed, and coal dust at a horizontal naked eye section accelerates upward movement by virtue of the dual-circulation effect after the coal dust reaches the casing shoe, so that the stability and return flow of the drilling returning fluid can be improved, the sand-carrying capacity can be improved, and pipe-sticking accidents can be reduced or eliminated.

Description

technical field [0001] The invention relates to the technical field of coal bed methane drilling engineering, in particular to a double-circulation relay coal seam drilling method. Background technique [0002] At present, in the exploration and development of coalbed methane, the drilling technology at home and abroad generally adopts the combination of drilling horizontal branch wells and drainage wells. see figure 1 At present, the main process of drilling and completion is as follows: [0003] 1. Drilling and drainage wells: one spud (hereinafter referred to as "first spud") drilling and completion, casing running and cementing, and then secondary spud (hereinafter referred to as second spud) drilling and completion, casing running and cementing , and then expand the coal seam cave; 2. Drill the horizontal branch well, run the casing and cement the well before entering the horizontal section, and then drill a section of horizontal open hole with the drill bit at the bo...

AI Technical Summary

Problems solved by technology

[0005] The object of the present invention is to provide a coal seam drilling method for the exploration and development of coal bed methane to solve the problems of unstable air circulation, large annulus, low return velocity and weak sand-carrying capacity in drainage wells, and at the same time eliminate The impact of gas injection coal seams in drainage wells is prone to collapse, reducing or eliminating the occurrence of stuck pipe accidents

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