A NEW RESISTIVITY-BASED MODEL FOR IMPROVED HYDROCARBON SATURATION ASSESSMENT IN CLAY-RICH FORMATIONS USING QUANTITATIVE CLAY NETWORK GEOMETRY AND ROCK FABRIC

摘要

The importance of the clay-network conductivity inresistivity-based saturation assessment has been wellrecognized over the years. The existing shaly sandmodels are oversimplified by assuming that the clays arepresent in the rock predominantly as laminated,dispersed, or structural. This assumption, however, is notreliable in many clay-rich formations. Because, innature, clay minerals can have complex spatialdistributions. Furthermore, the conventional shaly sandresistivity models such as Waxman-Smits, Dual-Water,Simandoux, and Indonesia do not take into accountspatial distribution and connectivity of clay network.Spatial distribution of clay network can significantlyaffect resistivity of clay-rich formations andoversimplifying this distribution can lead to hugeuncertainties in estimates of water saturation in suchformations. In this paper, we introduce a new resistivitybasedmodel which quantitatively takes into account theactual clay-network geometry and distribution and typeof clay minerals. Reliable incorporation of spatialdistribution of clay network (i.e., not limited to extremecases of dispersed, layered, and structural) improvesreserves evaluation in clay-rich formations with complexclay network structure.