Enhanced CH 4 recovery and CO 2 storage via thermal stimulation in the CH 4 /CO 2 replacement of methane hydrate

Abstract

Abstract The replacement of CH 4 by CO 2 in methane hydrates is a promising method for simultaneously achieving CO 2 storage and CH 4 recovery for global warming mitigation and energy production, respectively. However, gas replacement is restricted to the slow diffusion-limited transport of CO 2 caused by the formation of a mixed hydrate layer, and little attention has been paid to the storage of CO 2 . Therefore, this study proposed a combination of CH 4 /CO 2 replacement and thermal stimulation to enhance CH 4 recovery and CO 2 storage. The effects of the methane hydrate saturation level, replacement zone, and freezing point on the replacement were analyzed. The CH 4 replacement percentage and energy efficiency were obtained and compared using the replacement and combined methods. The results suggested that the combined method effectively improved CH 4 recovery, with the CH 4 replacement percentage exhibiting an upper limit of 64.63%. Moreover, In CH 4 /CO 2 replacement, the total number of moles of CO 2 stored is unequal to CH 4 recovered, because the replacement is sensitive to the free water in the pores of the hydrate sediments. In addition, the CO 2 storage efficiency was first discussed. The results proved that the CH 4 /CO 2 replacement has obvious advantages in CO 2 storage, and a maximum CO 2 storage efficiency of 96.73% was achieved by combined method.