Gyro

SPE 63274 Development of a Robust Gyroscopic Orientation Tool for MWD Operations
R. A. Estes, SPE, and D. M. Epplin / Baker Hughes INTEQ

Copyright 2000, Society of Petroleum Engineers Inc. This paper was prepared for presentation at the 2000 SPE Annual Technical Conference and Exhibition held in Dallas, Texas, 1–4 October 2000. This paper was selected for presentation by an SPE ProgramCommittee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPEmeetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not becopied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax 01-972-952-9435.

Abstract The allure of a gyroscopic directional sensor for MWD (Measurement While Drilling) operations has spanned over two decades now. The authors first investigated potential sensors for MWDapplications in 1982 and were disappointed to find technological limitations precluded such a device. Why is it so difficult to build a gyroscope into an MWD tool, and why don’t we have one available for commercial use in the industry today? Also, what should oil companies expect from a service company who promises an “MWD Gyro Tool” in the next year or two? Currently there are several servicecompanies working on directional modules that incorporate some type of gyroscopic sensor and promise to provide an indication of “True North” direction in conjunction with MWD tools. This paper is intended to establish realistic expectations for the performance that might be delivered by these early gyroscopic tools in the harsh MWD environment. The paper also describes the investigation, specification,design decisions, and testing done in the development of a tool to meet the most common application requirements for an MWD Gyro. Initial testing of the tool has proven it surprisingly accurate and at least as robust as existing conventional mag/accel sensors. Extensive qualification testing in both lab and field settings has proven the instrument capable of surviving the harsh MWD environment.Introduction Directional drilling instruments (particularly MWD tools) have benefited during the past two decades from application of aerospace sensors known as quartz servo accelerometers and fluxgate magnetometers. Adopting these sensors put an end to the previous malady of continually shifting biases, which

caused directional errors. These solid state devices offer much higher reliability thanthe older electromechanical inclination and compass sensors. Buoyed by improvements in the ruggedness of accelerometers and magnetometers, MWD tools became the standard for guiding and surveying our more highly-deviated and horizontal wells. This sensor reliability has set a hurdle for introduction of new MWD sensors: they must maintain accuracy, even in the face of extremely harsh environmentalconditions. Global deployment mandates that directional tools remain stable for months, or even years, without need for repair or recalibration. Magnetic compass-based directional tools do not work well when placed near steel casing or steel drill string components. This is due to the magnetic interference caused by these materials. Therefore, is sometimes necessary to use a gyroscopic-based...