Mapping Storage and Enhanced Gas Recovery for Organic Shale in the Midwest Regional Carbon Sequestration Partnership
Midwest Regional Carbon Sequestration Partnership teams are investigating the potential for CO2 storage and enhanced gas recovery in organic shales such as the Middle Devonian Marcellus Shale and Upper Ordovician Utica Shale in the Appalachian Basin. This work builds on past research on the Upper Devonian Ohio Shale in eastern Kentucky. For the Ohio Shale, Schmoker’s density model was found to accurately estimate total organic carbon (TOC) from density in downhole geophysical logs. Because there are always more logs than sample analyses, determining if TOC can be reasonably estimated from logs is beneficial for regional mapping. For the Ohio Shale, density logs could then be used to map regional TOC distribution and thereby calculate potential CO2 storage volume when used to enhance gas production. When Schmoker’s density model was tested on Marcellus and Utica Shale data, however, results were more variable. Different models were developed to estimate TOC from downhole log data for each shale. The Marcellus structure was mapped from 8900 well-log tops from southern New York southeast into Ohio and West Virginia. A net thickness map of the Marcellus Shale with net gamma ray greater than 180 API was constructed from 1,559 wells with gamma logs. A subset of 575 wells with density logs was used to model organic distribution. Mean (P50) TOC was contoured from an average of multiple wireline-based models. A gridded net thickness of shale with calculated TOC > 4% was mapped using the same data. General trends in the calculated TOC > 4% map compare well with the 180 API cutoff map, although a broader area of net organic-rich shale in northeastern Pennsylvania and southern New York is estimated from the TOC > 4% map. A potential Marcellus Shale volume of 2 billion acre-ft with a storage capacity of 1.1 to 3.7 billion tons of CO2 is estimated from the TOC > 4% map. CO2 storage capacity in the shale is based on the potential to use CO2 for enhanced gas recovery and retention of CO2 by adsorption on the organic-rich matrix. A similar set of maps is being generated for the Upper Ordovician Utica–Point Pleasant play and potential CO2 storage capacities will be estimated from the maps developed. Results to date show that different models are needed for estimating TOC in different organic-rich shales. Regional mapping of net organic thickness of the various shales will provide insight into the potential for CO2 storage with enhanced gas recovery across the region.
AAPG Datapages/Search and Discovery Article #90335 © 2018 AAPG 47th Annual AAPG-SPE Eastern Section Joint Meeting, Pittsburgh, Pennsylvania, October 7-11, 2018