Statewide Assessment of CO₂ Storage Capacity

for lower Paleozoic strata, Oklahoma

Anna M. Turnini and Matthew J. Pranter

School of Geosciences

Mewbourne College of Earth and Energy

University of Oklahoma

Abstract

Subsurface geological storage of CO₂,as part of carbon capture, utilization, and storage (CCUS) operations, is one option to reduce atmospheric CO₂ concentrations.  Oklahoma’s geological setting and unique history as an oil and gas producing state makes it an ideal location for subsurface geological storage of CO₂.  While the United States Geological Survey (USGS) completed and released a national assessment of geologic CO₂ storage resources (USGS Circular 1386, 2013), which provides an initial assessment of storage capacity on a regional basis, there are few, if any, published detailed assessments of CO₂ storage capacity for individual reservoirs at the state level.  Therefore, this study addresses the spatial distribution of reservoir rocks, pore volume, and CO₂ storage capacity for lower Paleozoic strata across the state including: 1) Arbuckle and Timbered Hills groups (Arbuckle zone); 2) Simpson Group and Viola Limestone (Ordovician zone); and 3) Hunton Group (Hunton zone).  Three-dimensional geological models of lithology, pore volume, CO₂ density, and CO₂ storage capacity were generated using well-log information from >80,800 wells and the U.S. Department of Energy (US-DOE) methodology.  CO₂ storage capacity by zone was determined using both site-specific and formation-level saline storage efficiency coefficients (E_Saline) and reported for the entire study area, by lithology and by measured depth.  Due to the historical correlation between wastewater injection and induced seismicity in the Arbuckle zone, this study highlights areas of higher risk for induced seismicity by integrating well data, wastewater-injection volumes, basement-seated faults, and historical earthquake locations and magnitudes.  Overall, this research provides a detailed assessment of the stratigraphic and geographic variability of lithology, pore space, and CO₂ storage capacity for the state of Oklahoma.  Key findings include 1) areas of enhanced porosity in the Arbuckle zone and areas at high risk of induced seismicity due to basement faults and proximity to wastewater injection wells; 2) areas with thick, high-porosity Ordovician sandstone at drilling depths above 10,000 ft, and 3) areas with high-porosity Hunton dolomite and depleted pressure that potentially contribute to higher storage capacity.  Areas with stacked storage reservoirs at appropriate depths for CO₂ could limit the numbers of required wells for injection; thus, limiting the surface footprint and cost for storage.

Biography

Matthew J. Pranter is Director of the School of Geosciences, Eberly Family Chair, and Professor of Geosciences at the University of Oklahoma (OU). He is also an affiliate faculty in the Mewbourne School of Petroleum and Geological Engineering at OU.  He was previously a geology professor at the University of Colorado Boulder, senior research geologist with ExxonMobil, and reservoir geologist with Conoco. He received a B.S. in geology from Oklahoma State University, B.S. in geological engineering from Colorado School of Mines, M.S. in geology from Baylor University, and Ph.D. in geology from the Colorado School of Mines. His research interests include petroleum geosciences, energy resources, reservoir characterization and modeling, and sedimentary geology.  He has been an active member of AAPG since 1986, is a member of the AAPG Executive Committee, and serves as AAPG Editor.