Comparison of Core/Log and Well Test Permeabilities - A Closer Look "Sawan Tight Sands"

Abstract

Abstract Permeability values are available through many sources e.g. cores, logs and well testing. It is a usual practice to condition log data with core, but integration of well test data is usually left for later stages when building 3D reservoir models. It is often observed that core/log results do not agree with well test results. This becomes usually very prominent in tight sand wells. The usual suspect is formation damage during drilling and completion operations, but the real cause may only be revealed by an in-depth analysis of the available data. Core/log results usually give absolute permeabilities, whereas well tests provide effective permeabilities for the fluid under consideration. The role of cut-offs is very important when core/log permeabilities are calculated e.g. porosity, water saturation, clay volume etc. To compare with Well test permeabilities, the effect of over burden pressure, the gas slippage effect and relative permeability effect should be considered. The noticeable difference in core/log permeabilities and well test permeabilities is analyzed in this paper and compared with other industry reported cases.