China's CCUS Progresses and a New Evaluation Method of CO2 Storage Capacity in Coalbed Reservoirs

Abstract

Carbon Capture Utilization and Storage (CCUS) is playing a significant role in dealing with the global climate change, such as CO2 Injects into coal bed reservoirs, it is proved that CCUS technology not only definitely reduce CO2 emissions, but also enhance coal bed methane (ECBM).Coalbed methane resources are very rich in China, its resources ranks the third in the world. The coal structure of coalbed methane reservoirs are very complicated, experimental results show that methane content is not the same between low coal rank and high coal rank, therefore, desorption and absorption laws of CO2 for two different coal ranks are obviously different. This study point out weaknesses of evaluation methods both at home and abroad, show clearly what problems existing in the previous evaluation results based on the actual production situations of China's coal bed methane. The new modified method has been used to estimate on operable capacity, practical capacity, effective capacity as well as theoretical capacity in coalbed basin of the whole China. The research takes fully into account the influence of various factors including proved ratio, replacement ratio of CO2 to CH4, recovery ratio, ash content and moisture, completion factor, efficient pores volume, gas saturation, etc. While estimating CO2 storage capacity, the proved ratio is deemed to a key factor influencing estimates. The authors think that not all the coal bed methane reservoirs can be used for CO2 storage and ECBM. According to actual situation of engineering practice, this paper forecasts the future of coalbed methane recovery, and then it is the first time to put forward that the depth limitation of the coal bed methane reservoirs. At present, CO2 store depth of 300m to 1000m is unreasonable because of the coal resources will be used by underground coal gasification technology. The new methods give full consideration to the reasonable depth of CBM reservoir. Experimental results show that CO2 / CH4 adsorption ratio is different along with the depth of reservoirs. CO2 storage capacities of China coalbed basins are calculated by using the method, the results exhibit CO2 accumulated operable capacity and practical capacity.