The production schedule optimization of a multilayer superposed CBM system: An experimental study

There are obvious differences in the reservoir-forming mechanisms, flow mechanisms, and production trends between a multilayer superposed CBM system and a single CBM system. This paper performed large-scale physical simulations of CBM production in a multilayer superposed gas-bearing system. According to the experimental results, during commingled production, gas backfilling from a high initial reservoir pressure coal scam into a low reservoir pressure coal seam (LRPCM) occurred, which restrained or even shielded gas production from the low initial reservoir pressure coal seam. Progressive production effectively prevented gas backfilling by optimizing the gas production time of the coal seam, giving the coal seam a more reasonable productivity distribution. The permeability of the two production schedules showed obvious differences in the early stage, which gradually decreased in the middle and late stages. Different values of the coefficient D showed that progressive production provided a better production schedule. (C) 2020 Elsevier B.V. All rights reserved.