(204l) Differential Retention and Release of CO2 and CH4 in Kerogen Nanopores: Implications for Gas Extraction and Carbon Sequestration

Kerogen is the largest pool of organic matter on earth. During kerogen maturation, a considerable amount of CO2 is generated concurrently with petroleum products. Surprisingly, no one has reported any significant amount of CO2 for shale gas plays across the US. One explanation is that once CO2 is expelled from kerogen, it can be removed from the gas phase by mineral precipitation and dissolution. Therefore, fundamental investigation of the retention and expulsion of CO2 in kerogen is important to understand the fate of CO2 in sedimentary basins. In this talk we show that kerogen retains more CO2 than CH4 and that a large amount of the CO2 generated during kerogen maturation will not be released until the reservoir pressure decreases below CO2 supercritical pressure. Our results, derived from careful selection and validation of a simulation model, provide fundamental insight into the fate of CO2 generated in kerogen and potentially in organic matter in general. This research also investigates the introduction of CO2 into kerogen nanopores to mimic the potential use of CO2 to enhance gas recovery and CO2 sequestration scenarios. CO2 can migrate into kerogen nanopores even when the nanopore openings are blocked with water, and displace a large quantity of CH4.
Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.