Measuring CO2 in Coalbed Reservoirs
MacDonald, Steven1 (1) WellDog, Inc, Laramie, WY
CO2, whether natural occurring or introduced, can have significant effects on the production and subsequent handling of gas from coalbed reservoirs. CO2 has greater affinity for absorption onto coal than methane and thus displaces methane. This displacement, with naturally occurring CO2, will result in a reduction of the capacity of the coal to hold methane, and if not considered, will result in lower than predicted SCF/ton of methane storage. In systems of introduced CO2, such as flooding or enhanced recovery, the greater affinity of CO2 for the surface of the coal is used to drive off the methane and thus increase the production rate. In both cases, knowledge of the amount of CO2 in the system can affect the economics and operational procedures of producing the reservoir. Raman spectroscopy, a laser based spectroscopy used for chemical analysis, has been adapted to quantify and identify the chemical forms of CO2 in reservoir fluids.
AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana