Abstract: Advantages of "Real-time" LWD Dipmeter Data

GRAYSON, STEVE, Schlumberger Wireline and Testing, Ventura, CA;JIM EZELL, JON SCHWALBACH, and DALTON LOCKMAN, Exxon Co., U.S.A., Thousand Oaks, CA;TIM QUINLAN, DAVID ROSE, Schlumberger Geoquest, Bakersfield, CA

Advances in Logging While Drilling (LWD) technology now make it possible to acquire formation bed dip information while drilling, using Anadrill's RAB (Resistivity At Bit) tool. The use of button resistivity electrodes mounted on a rotating LWD tool provides the data for a resistivity image of the borehole. These images are the basis for ongoing structural interpretation as a well is drilling and can be used to "geosteer" the wellbore to an optimal location.

A well recently drilled in the Santa Ynez Unit of offshore California (U.S.), illustrates an application of this technology. A highly deviated well path (77 degrees from vertical) was designed to intersect a gently dipping (5 degrees) Monterey Formation target. This nearly parallel borehole-strata geometry provides little room for error when attempting to intersect reservoir intervals at specific elevations. In this case, the RAB data collected and processed at each bit trip indicated that formation dips were quite different than expected due to structural features small enough to fall below the resolution of the seismic data. The geologic model was modified while drilling, as was the drilling plan. In response to the RAB dip information, the well trajectory was modified to encounter the reservoir zone within the oil column, resulting in a successful completion.

Other applications of the RAB data include precise location of faults and structural culminations, and in some cases the identification of highly fractured intervals. When integrated with other LWD data, and mud logs, well paths can be directed as drilling progresses, avoiding costly sidetracks and redrills.

AAPG Search and Discovery Article #90935©1998 AAPG Pacific Section Meeting, Ventura, California