Study on the migration of pulverized coal in CBM wellbore

Abstract

A method using multi-fluid Eulerian computational fluid dynamics (CFD) model to study the migration of pulverized coal in coal-bed methane (CBM) wellbore is presented in this paper. The study aims to predict the condition of discharging pulverized coal out of CBM wellbore and decrease downhole failures such as low efficiency, pump leakage and stuck pump caused by the deposition of pulverized coal. On basis of production conditions of CBM wells in Ordos Basin of China, the transient model of pulverized coal-liquid two-phase flow in the annulus between sucker rod and tubing is established by CFD software, and the effects of pulverized coal size and well liquid inflow velocity on the output of pulverized coal are investigated. On the process of simulation, the distribution and volume fraction changes over time of pulverized coal in the annulus are analyzed, the critical drainage volume of CBM well for discharging pulverized coal is determined, and the output of pulverized coal in every case is predicted. Based on simulation results, the recycle water supplement technology to cleanout pulverized coal in the wellbore is put forward and tested in CBM field. The satisfactory performances of tests show the validity of the CFD study results and the practicability of the recycle water supplement technology.