CO2 Sequestration Enhances Coalbed Methane Production

Since 1980s, petroleum engineers and geologists have conducted researches on Enhanced Coalbed Methane Recovery (ECBM). During this period, many methods are introduced to enhance the production of coalbed methane. One of the methods called CO2-ECBM, which is injecting CO2 into the coal seam to replace the coalbed methane adsorbed on the surface of coal matrix, attracted attention of many engineers. Injecting CO2 into coalbed formation serves a dual-purpose of enhancing production while sequestrating CO2. Nowadays, CO2 emission has been identified as major contributor to global warming effect which results in climate change. Therefore, in order to eliminate the detrimental effect of global warming, finding a way to permanently store venting CO2, at the meanwhile, to enhance the coalbed methane production thereby offset the cost of CO2 sequestration may be the best strategy for both environmental protection and petroleum industry. Researches for improving methane production by gas flooding, such as performance of CO2, N2 and fuel gas injection, changes in permeability and porosity caused by gas injection due to effects of swelling and shrinkage of coal and influence of coal rank have been done. Published papers had illustrated that CO2 sequestration to enhance coalbed methane production is feasible and practical. However, well completion is seldom taken in account. Thus, this thesis not only analyzes the effects of CO2 sequestration, but also focuses on determining the efficiency of CO2-ECBM, when applying hydraulic fracturing and horizontal well techniques as well completion. Through simulation works, the thesis evaluates production of coalbed methane from the reservoir applied CO2 sequestration and provides efficient and commercial well completion alternatives for production enhancement under CO2 sequestration condition.