A method for transforming coalbed methane wells into coal-measure gas wells

Abstract

Disclosed is a method for transforming a coal-bed gas well into a coal-measure gas well. The method comprises the following steps that (1) the ground coal-bed gas well to be transformed is selected; (2) an indoor reservoir damage test is conducted on coal rock samples collected by coring the ground coal-bed gas well in the step (1), and a low damage fracturing fluid is prepared; (3) a layer section to be transformed is determined according to the ground stress profile, the TOC profile and the rupture pressure profile, and a re-perforating perforation layer is determined according to the relative position relationship of early-stage coal-bed perforation situations, coal rock body structures and the low damage fracturing fluid with the anti-swelling rate and coal rock layers of mud rock, anda re-perforating perforation plan is established; (4) a fracturing mode of transforming each layer section for multi-layer section transforming is determined, except for the uppermost layer section,the rest of the layer sections adopt oil pipe + packer fracturing, and the fractured layer sections are blocked by using sand filling or a packer; and (5) the low damage fracturing fluid and a supporting agent are pump-cast by stages.

Description

technical field [0001] The invention belongs to the field of coal-measure gas exploration and development, and in particular relates to a method for transforming a coal-bed gas well into a coal-measure gas well. Background technique [0002] As an unconventional energy source, coalbed methane has been developed in my country for nearly 40 years. There are currently about 16,000 coalbed methane wells under construction, of which only one-third of the coalbed methane wells can achieve commercial production. In addition to the resource conditions in areas where a few coalbed methane wells are located are not conducive to development, most coalbed methane wells have problems such as incomplete reconstruction and serious reservoir damage. [0003] The target of coalbed methane well reconstruction is coal seam, a considerable part of which is soft coal (crushed coal, mylonitic coal), it is difficult to establish fluid migration and production channels through hydraulic fracturing, ...

AI Technical Summary

Problems solved by technology

[0002] As an unconventional energy source, coalbed methane has been developed in my country for nearly 40 years. There are currently about 16,000 coalbed methane wells under construction, of which only one-third of the coalbed methane wells can achieve commercial production. In addition to the resource conditions in the areas where a few coalbed methane wells are located are not conducive to development, most of the coalbed methane wells have problems such as incomplete transformation and serious reservoir damage

[0003] The target of coalbed methane well reconstruction is coal seam, a considerable part of which is soft coal (crushed coal, mylonitic coal), it is difficult to establish fluid migration and production channels through hydraulic fracturing, even if the transformed coal seam is fragmented coal, although It has a certain degree of reformability, but when the depth of the coal seam is close to 1000 m, the minimum in-situ stress of the coal seam is much higher than the compressive strength of the coal, which makes it prone to serious proppant embedding into the coal seam in the later stage of drainage, and then cause the support cracks to lose their conductivity

At the same time, the active water fracturing fluid used in coalbed methane well stimulation often only considers the prevention and treatment of reservoir water-sensitive damage, while ignoring the serious impact of water lock damage and velocity-sensitive damage on stimulation, and the compatibility between fracturing fluid and formation is poor

When tubing fracturing is used, the active water fracturing fluid tends to generate high friction in the pipeline, resulting in high construction pressure and difficulty in increasing construction displacement

In addition, the constant displacement pumping method used in fracturing can only establish a single type of fracture channel in the direction of the maximum principal stress of the reservoir, and it is difficult to realize the overall reconstruction of low-permeability reservoirs. Low, both have adverse effects on the transformation effect

The above-mentioned reasons may be the main reasons why most CBM wells cannot achieve commercial production

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