Print this pageStratigraphic Framework and "Well-Spacing" Controls on Reservoir Heterogeneity, Volumetric Calculations, and Synthetic-Seismic Response In a 3-D "Reservoir" Model: McKittrick Canyon, West Texas and New Mexico
TINKER, SCOTT W.
A primary challenge facing geoscientists and engineers in the petroleum industry today is the efficient and economic management of producing reservoirs. A key component of effective reservoir management is reservoir characterization, which typically results in the three-dimensional distribution of facies within a sequence-stratigraphic framework. Because data are always limited in the subsurface, studies of continuous outcrops, in which stratal surfaces and facies distributions can be described precisely, are very useful as analogs for reservoir description.
This work discusses results from a detailed study of the continuous, well-exposed shelf-to-basin outcrops of the carbonate-dominated Permian Seven Rivers, Yates and Capitan Formations in McKittrick Canyon, New Mexico and Texas. In general, the need for an accurate sequence-stratigraphic framework increases as a function of greater depositional topography of reservoir units. This is illustrated in McKittrick Canyon, where primary, basinward dips of reservoir-quality, outer-shelf units can exceed 10 degrees, and dips of shelf margin and upper slope units can exceed 60 degrees.
The measured sections and sample descriptions from McKittrick Canyon were used as input data in six "reservoir models" (Stratamodel{TM} software), three using 10-ac, 40-ac and 160-ac "well" spacings within a sequence-stratigraphic framework, and three using the same "well" spacings within a lithostratigraphic framework. Lithofacies distributions, volumetric calculations, and synthetic seismic are compared for each model. The models indicate that an erroneous lithostratigraphic framework interpretation and/or greater well spacing will have the same effect, each resulting in increased pore volume and decreased reservoir heterogeneity. An accurate sequence-stratigraphic framework can provide substantial additional opportunities for improved field management including identification of bypassed hydrocarbon zones, optimization of infill locations, improved volumetric calculations, more efficient secondary-recovery program design, and better reservoir-simulation results.