Measuring CO2
in Coalbed Reservoirs
MacDonald, Steven1 (1)
WellDog, Inc,
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 Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California