A holistic understanding of the Permian Basin unconventional reservoirs is important for efficient hydrocarbon exploration and development, the assessment of recoverable resources, and in understanding its role in oil and gas markets. For example, oil and gas companies may wish to compare the geologic and reservoir character of one unconventional region versus another and have this information readily available. To support these needs, a 3D geologic model was constructed that covers the entire Delaware Basin unconventional reservoir system of the late Pennsylvanian through Leonardian section. The model includes results from facies and stratigraphic analyses, structural interpretation, well coverage, petrophysical interpretations, geo-mechanical interpretations, and hydrocarbon properties.
Bone Spring and Wolfcamp formations were subdivided by major zones and mapped to depositional limits against the shelf edge or to the structural boundaries. The structural boundaries mark where regional dip is toward the basin center. A basement-involved fault model is used, supplemented by mapped Wolfcamp outcrop faults. Petrophysical analyses were incorporated from across the entire basin region. Hydrocarbon properties from pressure-volume-temperature laboratory analysis (PVT) and well production data allowed separation of hydrocarbon types into several different oil and gas-condensate categories. Gaussian simulation is used to generate most of the property models. Hydrocarbon-in-place estimations and uncertainty analyses were applied to all zones of the Bone Spring and Wolfcamp formations.
The resulting 3D geo-cellular model can be used as input for regional and detailed acreage assessments and to drive further research. The model supplies a basis for analyzing technically recoverable reserves, expected hydrocarbon recoveries, production development scenarios, and potential economic values. Sector models were cut from the regional model for detailed, dynamic simulation modeling, resource and development analysis. The model has been uploaded to 3D seismic datasets to assist comparison of structural interpretations and for attribute analysis. Lessons learned in construction of the Delaware Basin model are improving our design for building a regional, 3D geo-cellular model over the entire Midland Basin, Wolfcamp and Spraberry reservoirs, planned for completion by end of 2022.
Although the current results are especially useful, they also highlight where further improvements can be made. Planned future work includes refinement of the depositional limits by expanding our cross-section studies, incorporation of large, detrital geo-bodies mapped from well-log studies into the facies modeling, and addition of more salinity data, PVT analyses and geo-mechanical analyses. Production data is also being reviewed to improve the original-condition pressure and gas-oil ratio (GOR) data used in the model.