Experimental Study on Interlayer Interference Effect of Commingling Production of Cbm in a Multi-Pressure System Under Output Control Mode

Abstract

To comprehend the interlayer interference in a multi-pressure system under output control mode, this research adopted the self-developed test device to conduct tests. It analyzed the reservoir response and gas production characteristics in coalbed methane (CBM)'s commingling production and discussed the interlayer interference mechanism. The results revealed that the CBM's commingling production at the initial stage would generate the interlayer interference under the output control mode, causing the cross-fluids of interlayer fluids. The interlayer interference would form a gas-production state, that is, when the gas production of reservoirs with high fluid energy is excessive, that of the reservoirs with low fluid energy would be inhibited. When the gas production of reservoirs with high fluid energy is attenuated, that of reservoirs with low fluid energy would start recovering to maintain stable production. The reservoir pressure gradients positively influence interlayer interference. The greater the difference between the fluid energies of the reservoir aggravates, the more severer this interlayer interference. The output control values negatively influence the interlayer interference, as their increase would weaken the severity of interlayer interference. Therefore, the output control design should appropriately increase the output value or rationally select the reservoirs with slighter difference in fluid energies. The gas model can be divided into three: conventional type, inhibitory type, and reverse-flow type, and their production stage can be divided into five different phases: gas rise, gas inhibition, reverse flow, gas recovery, and gas attenuation.

Keywords: coalbed methane, Commingling production, Multi-pressure system, Output control mode, Interlayer interference effect