Oil and Gas

Biography

Biography: Kajal Sheth

Abstract

A new logging-while-drilling (LWD) technology has been developed and field-tested, which introduces directional electromagnetic (EM) measurements through the use of tilted and transverse current-loop antennas. The multispacing and multifrequency directional measurements enable monitoring distance to formation boundaries and their orientation to facilitate proactive well placement. In combination with conventional LWD resistivity, these directional EM measurements allow for accurate structure and formation resistivity interpretation around the wellbore, independent of mud type. Furthermore, specific antenna combinations provide the capability to detect and characterize resistivity anisotropy in near-vertical wells while drilling. The directional EM tool is designed with a symmetrical transmitter-receiver configuration that optimizes the sensitivity to the desired formation parameters. While canceling the influence of anisotropy and formation dip, adding the symmetrical directional measurements together maximizes the sensitivity to bed boundaries, which is optimal forgeo steering. The fact that the antennas are mounted on a conductive collar significantly reduces the large borehole effects that are normally associated with transverse EM measurements in conductive mud. In addition to exploring the physics of the new directional propagation measurements, we will demonstrate their unique applications with field test examples. By detecting and tracking, in real time, formation boundaries up to 15 ft around the wellbore, the directional propagation tool allows for sufficient time to make trajectory adjustments and stay within the reservoir. The bedding orientation information also answers the question, in what direction to steer, which is often ambiguous when relying on traditional propagation measurements. Particularly interesting applications are the placement of wells in thin oil rims and in reservoirs with complex structures such as intra-bedded shale silts. Field test examples will also be shown of the enhanced formation evaluation capabilities offered by directional measurements in high-angle and horizontal wells, where formation resistivities can now be determined while accurately accounting for proximate bed boundaries. The ability to measure resistivity anisotropy in near vertical wells will be demonstrated by a field test example where the anisotropy measurement was confirmed by comparing with a conventional propagation resistivity measurement run in a near-by high-angle well.