An Investigation of Residual Oil Zones in the Permian Basin: Their Nature, Origins and Implications for Carbon Dioxide Capture, Utilization, and Storage
University of Texas, Jackson School of Geosciences, Austin, Texas USA
Residual Oil Zone (ROZs), oil accumulations that have been naturally displaced to near-residual oil saturation, are of interest both as a potentially large energy resource and opportunity for carbon dioxide (CO2) capture, utilization, and storage. ROZ is being produced already in several Permian Basin oil fields through CO2-enhanced oil recovery. Existing literature highlights several lines of evidence for regional tectonic uplift and resulting regional flow of meteoric groundwater through petroleum-bearing strata across the basin. These lines of evidence are consistent with the present theory of hydrodynamically-dominated ROZ formation mechanisms.
This study indicates that the Permian Basin has tilted an average of approximately 0.12˚ in the past 100 Ma, enough to generate regionally extensive ROZs by either hydrodynamic or buoyancy-driven processes. The distribution of secondary ROZ indicators, however, points to both a stratigraphic and spatial concentration of ROZs in specific formations and regions. Initial literature and core analysis indicates that flow-conducive units like fractured layers and specific dolomite units are important locally, but that regionally, structurally-controlled fracture zones, steepened uplift gradients, and stratigraphic juxtaposition of certain areas may also be a key controlling factor in ROZ distribution.
While ROZs have likely formed in numerous parts of the Permian Basin and present a large opportunity depending on economic conditions, they do not appear ubiquitous and each field may result from different processes. Further work will be important in better detailing basin development and oil migration routes to enable more accurate understanding and prediction of ROZ genesis and resource distribution across the Permian Basin.
AAPG Search and Discovery Article #90183©2013 AAPG Foundation 2013 Grants-in-Aid Projects