煤层气排采产气通道适度携煤粉理论

Analysis of pulverized coal migration during CBM production

考虑在煤储层中实际地层液混合流体中煤粉含量和煤粉颗粒群的悬浮分级,建立煤粉颗粒在产气通道内悬浮运移模型,给出煤粉悬浮排出的条件;打破以往以防煤粉为主的思想,基于液流携带建立煤层气排采产气通道内的适度携煤粉方法,基于液固两相流理论建立液流携带煤粉运移模型,并分析地层液参数和煤粉颗粒参数对适度携煤粉的影响。结果表明:煤粉颗粒粒径越小,地层液流速越大、黏度越大,煤粉在产气通道截面上分布越均匀,其悬浮排出能力越强,煤粉较易被地层液携带排出;煤层气井排采各个阶段(单相水流阶段、气水两相流阶段和单相气体流动阶段)地层液中气液固三相混合的比例不同导致地层液的黏度不同,造成排采过程中地层液携带煤粉的能力随着产气量的变化而变化。合理控制地层液的参数有利于煤粉适度排出,疏通产气通道增加其渗流能力,提高煤层气井产气量。

A model for migration of suspended pulverized-coals during coalbed methane（CBM） production in gas-channels was established with considerations of the suspending grade and content of pulverized-coals in the fluid mixture of CBM formations. The conditions for discharging the suspended pulverized-coals were described. The model was based on the liquidsolid two-phase flow theory and can be used to study the method for a moderate production rate of coal powders rather than to prevent it. The effects of different parameters on the carrying capability of pulverized coal by the formation liquid were analyzed,including the size of pulverized-coals,the velocity and viscosity of the formation fluid. Due to the differences of the gas-liquid-solid mixtures during different discharge-phases of CBM production,the apparent viscosity of the formation fluid is different,which has a great effect on the carrying capability of pulverized coal of the formation fluid,and being affected by the gas production rate. The gas production of CBM wells can be improved via moderately adjusting the flow behavior of the formation fluid for a proper discharging of pulverized coal,or increasing the percolation capacity of gas channels.