Journal of Earth Science & Climatic Change
Open Access

Abstract

The calculation of saturation is reliable when connate water resistivity (Rw) and Archie?s parameters, such as saturation exponent (n) and cementation exponent (m), are available. However, rock-core measurements or chemical analysis of formation water are not always available. A new joint inversion method with borehole spontaneous potential (SP) log and High Definition Induction Log (HDIL) is proposed for accurate estimation of Rw, and the Archie?s parameters. In order to accurately simulate SP, the generated position of the membrane and diffusion potential, which are assumed as main contributors of SSP, are identified through simulation of fresh-water mud invasion. Then a five-parameter model is built up for precise construction of the complex resistivity distribution while fresh mud invasion happens. In so doing, the formation is divided into three zones: flushed zone, transition zone and virgin zone. The resistivity profile of transition zone is assumed to be a parabola shape, which is more consistent with the actual change of formation resistivity, especially when a low resistivity annulus occurs. Then the invasion profile is rebuilt with the five-parameter method, and Rw is also calculated with the SSP and mud resistivity (Rm). m and n are estimated by Archie or dual-water equations. We successfully applied this method to an oil field in western China. Values of Rw , m and n yielded are consistent with those obtained from a traditional method. The method proposed here is an effective alternative to obtain water saturation wherein rock-core measurements or chemical analysis not available or questionable.

Biography

Li Hu is a PhD. student in China University of Petroleum School of Geosciences. He is a member of SPE and SEG. He is engaging in Applied Geophysics and Electromagnetic Logging method research