Challenges and Opportunities of Coalbed Methane Development in China

Coalbed methane (CBM) resources in China have been estimated to exceed 36 Tcm. As of 2014, there were ∼9300 producing CBM wells in China with an annual production of ∼4.4 Bcm. To satisfy its need for energy and to transition to a low-carbon economy, China has a big need to accelerate CBM development. This paper gives an overview of the status of CBM development in China, identifies key technical challenges, and proposes solutions to overcome them. Our review of the literature has revealed that current CBM development in China faces several technical challenges. Current projects are focused on high-rank coals in the Qinshui and Ordos basins, which have major geological and engineering challenges. The former includes low permeability, subhydrostatic reservoir pressure, and a lack of understanding of the connectivity of coal seams, which leads to difficulty in sweet spot indication. The latter includes difficulty in hydraulic fracturing in vertical wells, because of the ductile nature of the coal seams in the Qinshui basin, bore hole instability and formation damage during drilling of horizontal wells. To remedy this situation, we propose a refocus on the more-abundant high-permeability low-rank coals in China and detailed coal seam characterization using current industry best practices of static and dynamic modeling of CBM reservoirs. This refocus on low-rank coal may lessen the need for hydraulic fracturing in vertical wells. For horizontal wells, research should focus on non-formation-damaging drilling fluids, incorporating geomechanics studies to reduce the risk of borehole collapse during drilling and production, and new horizontal well designs, which minimize the risk of collapse of the mother bore.