Abstract
This study reports on analyses of natural, geologic CO2 migration paths in Farnsworth Oil Field, northern Texas, where CO2 was injected into the Pennsylvanian Morrow B reservoir as part of enhanced oil recovery and carbon sequestration efforts. We interpret 2D and 3D seismic reflection datasets of the study site, which is located on the western flank of the Anadarko basin, and compare our seismic interpretations with results from a tracer study. Petroleum system models are developed to understand the petroleum system and petroleum- and CO2-migration pathways. We find no evidence of seismically resolvable faults in Farnsworth Field, but interpret a karst structure, erosional structures, and incised valleys. These interpretations are compared with results of a Morrow B well-to-well tracer study that suggests that inter-well flow is up-dip or lateral. Southeastward fluid flow is inhibited by dip direction, thinning, and draping of the Morrow B reservoir over a deeper, eroded formation. Petroleum system models predict a deep basin-ward increase in temperature and maturation of the source rocks. In the northwestern Anadarko Basin, petroleum migration was generally up-dip with local exceptions; the Morrow B sandstone was likely charged by formations both below and overlying the reservoir rock. Based on this analysis, we conclude that CO2 escape in Farnsworth Field via geologic pathways such as tectonic faults is unlikely. Abandoned or aged wellbores remain a risk for CO2 escape from the reservoir formation and deserve further monitoring and research.
Highlights
A phase of relatively rapid subsidence occurred during the Late Pennsylvanian- Early Permian, when the Anadarko Basin subsidence accelerated as part of foreland basin development [22,27,43,62,77]
Thicker sedimentary sequences or packages were included in the petroleum system models, except around the Morrowan reservoir of interest where layers decrease to thicknesses of tens of meters
Faults have been reported previously in the northwest Anadarko Basin, we found no direct evidence for tectonic faults in the reservoir or caprock in Farnsworth Field
Summary
In Farnsworth Field, northern TX (Figures 1 and 2), CO2 was injected into an existing porous petroleum reservoir (the Morrow B sandstone, at a depth of about 8000 feet) as part of an enhanced oil recovery operation in which the CO2 displaces and mobilizes oil. Mississippian System, Part 1 of Paleotectonic Investigations of the Mississippian Systems in the United States; Craig, L.C., Varnes, K.L., Eds.; USGS: Reston, VA, USA, 1979; Volume 1010-J, pp. F.; Pranter, M.J. Lithofacies, depositional, and diagenetic controls on the reservoir quality of the Mississippian mixed siliciclastic-carbonate system, eastern Anadarko Basin, Oklahoma, USA. K.S.; Amsden, T.W.; Denison, R.E.; Dutton, S.P.; Goldstein, A.G.; Rascoe, B., Jr.; Sutherland, P.K.; Thompson, D.M. Southern Midcontinent region. In Sedimentary Cover–North American Craton, U.S.; Sloss, L.L., Ed.; Geological Society of America: Boulder, CO, USA, 1988; pp. In Sedimentary Cover–North American Craton, U.S.; Sloss, L.L., Ed.; Geological Society of America: Boulder, CO, USA, 1988; pp. 307–359
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