Pressure-controlled drainage gas production method and system for coal-bed gas well

By adopting a specific first-day drainage volume and pressure-compensating medium injection strategy in coal-bed methane wells, the problem of difficulty in determining the drainage rate is solved, reservoir permeability damage is avoided, and the mining efficiency and gas production of coal-bed methane wells are improved.

CN109322644AActive Publication Date: 2019-02-12CHINA PETROLEUM & CHEMICAL CORP +1
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
CHINA PETROLEUM & CHEMICAL CORP
Filing Date
2017-07-31
Publication Date
2019-02-12

AI Technical Summary

Technical Problem

In the existing drainage gas production technology of coalbed methane wells, the drainage speed is difficult to determine, which leads to damage to reservoir permeability and decrease in gas production. Regardless of the speed, there are problems with cost and investment payback period.

Method used

The first day's drainage is used for drainage, and the pressure-compensating medium is injected during the drainage process to maintain the daily decrease in bottom-hole flow pressure and avoid the shrinkage and closure of pores and cracks. Through the combined use of gas and liquid pressure-compensating media, respectively in the early stage of drainage and perform additional pressure later.

Benefits of technology

It achieves reasonable determination of drainage speed, avoids the closure of pores and fractures, improves the mining efficiency of coalbed methane wells, reduces reservoir damage and costs, and increases gas production.

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Abstract

The invention discloses a pressure-controlled drainage gas production method and system for a coal-bed gas well. The pressure-controlled drainage gas production method comprises the steps that drainage is conducted through the first daily drainage amount, wherein the first daily drainage amount meets the eliminating demand for production interference objects in a coal bed; and a pressure-supplementing medium is injected while drainage is conducted, and the downhole flow pressure daily drop amount is maintained as a first differential pressure value so as to avoid retracting and closing of pores and cracks in the coal bed. According to the pressure-controlled drainage gas production method for the coal-bed gas well, the drainage speed at the drainage state can be conveniently determined, the eliminating demands for drilling and completion fluids, pulverized coal and slack coal in the coal bed can be met, and meanwhile, retracting and closing of the pores and the cracks in the coal bed can also be avoided; and compared with the prior art, the pressure-controlled drainage gas production method is simple in process, the production efficiency of the coal-bed gas well can be greatly improved, and quite high practical value and popularization value are achieved.
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