Assigning Petrophysical Properties in Gas Reservoir 3-D Geocelluar Modeling, by Integrating Geophysics, Geology, and Reservoir Engineering
Mark H. Holtz, Dr. Hongliu Zeng, Paul Knox, and Mike De Angelo Bureau of Economic Geology John A.& Katherine G. Jackson School of Geosciences The University of Texas at Austin
Complete Integration of geophysical, geologic, and reservoir engineering data results in the development of the most plausible model, completely populated by petrophysical properties. The 3-D seismic volume yields not only the structural architecture but also a large-scale distribution of shale volume that is based on neural network modeling of seismic and wireline data. Large-scale, seismically derived shale volume can be combined with a small-scale 3-D shale volume constructed from well control and geologic depositional facies description. Functions of the interrelationships between all salient petrophysical properties, including porosity, permeability, irreducible water saturation, capillary pressure, and residual gas saturation, are developed so that reservoir volumetrics can be calculated and then compared with material balance volumes. The 3-D model is then optimized to give the most geologically plausible sand-shale distribution while maintaining a petrophysical property distribution that is consistent with pressure and production data. Model optimization also includes the distribution of residual gas saturation values on a cell-by-cell basis so that material balance to aquifer influx is accounted for.