Physical Simulations of Gas Production Mechanism in Constant-Rate Co-production from Multiple Coal Reservoirs

Abstract

Coalbed methane co-production is an efficient technique for producing gas from multiple coal reservoirs. In this study, four large-scale specimens were connected in parallel to model a system of coalbed methane production. The results revealed that a low-pressure coal reservoir is disrupted owing to the pressure equilibrium, causing the cross-formational flow of gas through the wellbore. The production and productivity contribution rates were positively correlated with the initial reservoir pressure over a stable production period, forming a “dynamic supply” state among the coal reservoirs. The intensity of the interlayer interference was negatively correlated with reservoir pressure such that with significant interlayer interference, reverse gas flow or a halt in production could occur in the low-pressure coal reservoir. The constant-rate production value and the effect of interlayer interference had an inverse relationship in terms of production; the smaller the former, the greater was the latter. Increasing the constant-rate value can restrict large-scale production from the high-pressure coal reservoir and improve the productivity recovery rate and production distribution of the low-pressure coal reservoir.