Calculation method for quantitative optimization of working system of coal-bed gas well

Abstract

The invention discloses a calculation method for quantitative optimization of a working system of a coal-bed gas well. The calculation method comprises the following steps: (1) dividing a coal-bed gasproduction stage, namely sequentially dividing into a single-phase water flow stage, a gas-water two-phase flow stage and a single-phase gas flow stage; (2) establishing a drainage system optimization model; (3) optimizing a single-phase water flow stage drainage system; (4) optimizing a two-phase water flow stage drainage system; and (5) optimizing a single-phase airflow stage discharge and mining system. A working system optimization model established by the invention can reasonably guide the maximum bottom hole pressure reduction of the coal-bed gas well in the single-phase water flow stage and the gas-water flow stage, and the limit gas flow can effectively prevent the airlock caused by the large-scale desorption of the coal-bed gas until the average pressure of the reservoir reachesthe rebound pressure.

Description

Technical field [0001] The invention belongs to the technical field of development and utilization of coalbed methane wells, and specifically relates to a calculation method for quantitative optimization of a coalbed methane well working system. Background technique [0002] The drainage system plays a very important role in CBM production. The lower downhole flow pressure drop rate will lead to a prolonged CBM production cycle and reduce the economics of CBM production. On the contrary, a rapid drop in bottom hole pressure will cause stress sensitivity, pulverized coal migration, gas-water flow coupling and other problems in the early stage of production, which is not conducive to high CBM production. First of all, with the rapid exploitation of coalbed water in the single-phase flow stage, effective stress will have a greater impact on coal reservoirs, pores and cleats will be compacted, resulting in fracture closure and reservoir permeability reduction. Secondly, coal is eas...

AI Technical Summary

Problems solved by technology

[0004] However, the current formulation and adjustment of the coalbed methane drainage system is basically qualitative or semi-quantitative, and has not really been quantified.

In addition, there are relatively few studies on the influence of reasonable drainage system on the expansion of pressure drop funnel and the mechanism of coalbed methane productivity.

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