Single-well coal bed gas multi-branch horizontal well drilling and completion method

Abstract

The invention provides a single-well coal bed gas multi-branch horizontal well drilling and completion method. The method includes the steps that a vertical shaft section, an angle building section, an angle maintaining section and a hole angle increasing section are sequentially drilled from the ground, the tail end of the hole angle increasing section reaches a target coal bed, then at least one horizontal branch which is connected to a horizontal section is drilled in sequence along the target coal bed, and the hole drift angle of the horizontal branch is made to be larger than or equal to the hole drift angle of any point on the angle maintaining section and the hole angle increasing section; moreover, every time one horizontal branch is drilled, a sieve tube is tripped into the horizontal branch, and an annular gap is formed between the sieve tube and the horizontal branch; the upper portion of the angle maintaining section is used for placing water drainage and gas production equipment, and the angle maintaining section and the hole angle increasing section below the water drainage and gas production equipment are used as a bag. The single-well coal bed gas multi-branch horizontal well drilling and completion method changes the well drilling sequence of a traditional well drilling method, the sieve tube is tripped into each horizontal branch, thus safety production is achieved, and yield is increased.

Description

technical field [0001] The invention relates to the field of coalbed methane development, in particular to a method for drilling and completing wells for multi-branched horizontal wells for single borehole coalbed methane. Background technique [0002] At present, there are two main well types for the horizontal well exploitation of coalbed methane, which are multi-branch horizontal wells and U-shaped wells. [0003] Multi-branch horizontal well refers to constructing a vertical well at a well site on the ground, and then constructing a horizontal well at a well site at a certain distance from the vertical well. Hirai branch. Drainage equipment is installed in vertical wells during production, and horizontal wells are used to provide drainage, decompression and analysis channels for coal seams for drainage and gas recovery. In the process of drilling vertical wells for this multi-branch horizontal well, it is necessary to drill a pocket of about 60 meters to collect coal p...

AI Technical Summary

Problems solved by technology

[0007] First, due to the fact that the instability of the target coal seam is very common, during drilling, there will be shedding, falling blocks, or even collapse at the site, which will easily cause wellbore blockage, which will continue to affect the later drainage construction and reduce the life of coalbed methane drainage. It is the bottleneck restricting the development of coalbed methane industry

[0008] Second, because the drilling sequence of existing multi-branch horizontal wells is to drill the farthest branch first, gradually retreat to the next farth branch, and finally drill the central branch, this drilling method determines that even if the supporting casing is run It can only be downloaded to one of the branches, and it is impossible to determine which branch it will be downloaded into, so only one branch can only guarantee the production continuity

[0009] Third, due to the high production cost of existing multi-branch horizontal wells, it is difficult to run screens in all branches of the current multi-branch horizontal wells and ensure that each branch can be connected. When collapse occurs during the drainage process, the drilled passages are blocked, which cannot satisfy the gas reservoir to obtain sufficient gas production passages, which affects the gas production of a single well and virtually increases the production cost

[0010] Fourth, due to the influence of many parameters such as the structure of the production layer, reservoir pressure, water content, permeability and porosity, in the production of coalbed methane, especially the production of medium-rank coal and low-rank coal, the medium- and low-rank Due to the poor diagenesis and soft characteristics of rank coal seams, the method of open hole completion can easily lead to the collapse of the wellbore coal seam and affect the gas production of a single well

[0011] Fifth, when any point on one of the horizontal branches collapses, the collapse at the point closest to the wellhead may block the branch wellbore far from the wellhead, and the pay zone from the collapse point to the end of the branch is opposite to the The gas production of a single well cannot directly contribute, directly affecting the production decline of a single well

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