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Impedance Analysis for Methane and CO2 Discrimination in Coalbeds
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 74th EAGE Conference and Exhibition incorporating EUROPEC 2012, Jun 2012, cp-293-00846
- ISBN: 978-90-73834-27-9
Abstract
We present a methodology to evaluate the use of Elastic Impedance (EI) to discriminate coals saturated with methane from coals saturated with CO2. We apply this methodology to a dataset of the Fruitland coals Fairway, San Juan Basin, U.S. In this project, we develop a proxy model of a 15.25m (50ft) coalbed at a depth of 914.4m (3000ft) over an area of 31.4km2. We obtain the production forecast of 24 wells during primary production and enhanced coalbed methane by CO2 injection, starting in 1999 and continuing until 2031. Based on the results of the fluid simulation, we perform a Gassmann fluid substitution to model the variation in Vp, Vs and density due to the changes of fluid saturations in the pore space, assuming 100% of brine saturation as the initial state. We present three cases: primary production, after two years of CO2 injection, and one year after stopping injection. We calculate EI and we observe a decrease in the zones around the injector wells that were associated with the movement of the CO2 flood. It was not possible to use EI to discriminate CO2 from methane in this study and the magnitudes of the changes of EI are small.