Petroleum Reservoir Evaluation and Development ›› 2022, Vol. 12 ›› Issue (4): 580-588.doi: 10.13809/j.cnki.cn32-1825/te.2022.04.005

• Methodological and Theory • Previous Articles     Next Articles

Mechanism of coal wettability on storage state of undersaturated CBM reservoirs

ZHU Suyang1(),MENG Shangzhi2,PENG Xiaolong1,LI Xiangchen1,ZHANG Qiangui1,ZHANG Si1   

  1. 1. Petroleum Engineering School, Southwest Petroleum University, Chengdu, Sichuan 610500, China
    2. Zhonglian Coalbed Methane Co., LTD., Beijing 100000, China
  • Received:2022-05-24 Online:2022-08-26 Published:2022-09-02

Abstract:

The wettability decides the fluid distribution in porous media, and the wet-phase fluid will primarily occupy the smaller pore. Based on this principle, the paradox between laboratory test of coal wettability and state of fluids distribution is analyzed. On the view of wettability, two possible coalbed methane(CBM) storage types are proposed. When the coal is gas-phase wettability, owing to capillary pressure, the free gas and adsorption gas can be trapped in matrix (smaller pore system) by the water in cleat (larger pore system). In matrix system, the sorption of gas is in equilibrium state, but the storage of gas is in the undersaturated state. The critical desorption process results from the capability pressure of water and gas. When the coal is water-phase wettability, the matrix is saturated by water, and the coalbed methane can store in the matrix in liquid-phase sorption state. This study designs the experiment to validate the gas liquid-phase sorption. The results indicate that a mass of methane can be adsorbed in the matrix in the liquid-phase sorption mode.

Key words: coalbed methane(CBM), wettability, gas storage, liquid-phase sorption, undersaturated storage, underbalance sorption

CLC Number: 

  • TE122