Response Characteristics Of The New Multicomponent Induction Logging Tool, 3Dexsm

Electrically anisotropic reservoirs are encountered<br>frequently in hydrocarbon exploration. For accurate<br>saturation estimation and optimum hydrocarbon<br>recovery from these reservoirs, it is essential to detect<br>and properly describe their electrical properties. For<br>example, in laminated sand/shale sequences or sands<br>with different grain size distributions the resistivity<br>parallel to the formation bedding is usually smaller<br>than the resistivity perpendicular to the bedding.<br>Conventional induction logging tools with the<br>transmitter and receiver orientation parallel to the<br>borehole axis provide insufficient information to<br>accurately evaluate hydrocarbon saturations in<br>anisotropic reservoirs. These reservoirs that usually<br>show low resistivities in conventional induction logs,<br>despite their hydrocarbon content being economically<br>significant, are called “low resistivity pay." Under the<br>sponsorship of Shell Technology EP, Baker Atlas<br>commercialized a new induction logging tool that<br>comprises three mutually orthogonal transmitterreceiver<br>configurations.<br>In this paper we discuss the underlying basic physics<br>of the new multicomponent induction logging tool,<br>3DEXSM. We examine the different response<br>characteristics of the new coil arrangements in<br>vertical and horizontal wells in anisotropic media. A<br>sensitivity analysis documents that the new coplanar<br>magnetic field data together with the standard coaxial<br>field responses allows us to de-couple horizontal and<br>vertical resistivities in vertical, deviated and<br>horizontal wells. However, the new coplanar coils<br>exhibit a stronger borehole and near zone effects than<br>the standard coaxial coil arrangements in conductive<br>mud systems. These effects can be dramatically<br>reduced by combining single frequency data into dual<br>frequency responses.