Title: A PETROPHYSICAL EVALUATION FOR PERMEABILITY OF A GAS RESERVOIR IN THE TARANAKI BASIN, NEW ZEALAND
Abstract: The goal of this study was to evaluate permeability and study the controls on permeability in a gas saturated formation. Conventional well logs, mineral identification crossplots and empirical models were applied to analyze different lithologic and diagenetic features and to examine the effect that these features may have on the reservoir. An unusual feature was observed, and required detailed examination: there existed (in two wells) five zones of lower resistivity (higher water saturation) above the gas-water contact. This is unexpected, as above that contact, the water is usually at irreducible water saturation. I conclude that the lower resistivity (the higher water saturation) is due to unusual mineralogy containing small grain size, ineffective microporosity and secondary porosity within specific grains, and support this conclusion with a variety of indicators.