INTEGRATION OF GEOLOGICAL AND GEOPHYSICAL DATA FOR CHARACTERIZATION OF SUBSURFACE HETEROGENEITY IN THE MIOCENE TEMBLOR FORMATION, COALINGA AREA, CALIFORNIA

To characterize heterogeneity and improve resolution of subsurface stratigraphy of the Miocene Temblor Formation near Coalinga, California, three-dimensional seismic geophysical data have been integrated with three-dimensional geological computer models of lithofacies, scaled gamma-ray logs, and formation density logs. Four stratigraphic bounding surfaces, which represent unconformities, within the Temblor Formation were correlated and help to constrain the modeling: base of Temblor, top estuarine facies tract, top tide to wave dominated facies tract, and top Temblor. Based on scaled gamma-ray and normalized density geophysical logs, seven lithofacies groups were interpreted: thinly laminated sand, silt, and clay; sand; burrowed sand; calcareous cemented sand; fossiliferous sand and clay; burrowed clay; and limestone. Deterministic density models, deterministic scaled gamma-ray models, and stochastic lithofacies models were created. These geological models show truncation of lithofacies groups by the bounding surfaces and lateral discontinuities within the lithofacies groups.

Normalized density, sonic geophysical logs, and synthetic seismograms were created and used to compare geological correlations of the stratigraphic bounding surfaces with data from three-dimensional seismic surveys. This analysis shows that the truncation of some reflectors is related to position of the bounding surfaces. Sonic and normalized density curves were then used to estimate relative porosity and lithology. Integration of these results along with the deterministic and stochastic geological models provides improved representation of subsurface heterogeneity.