This paper describes a radically new wellbore survey system based upon the principle of rate gyrocompass i rig. While the basic concept has been applied for many years in such applications as the initial alignment of inertial platform navigators, it is only recently that repetitive rate gyrocom-passing has been developed in its own right as a means to obtain directional survey data.

The benefits of this approach are that an extremely rugged and reliable sensor can be built into a 1–3/4" o.d. pressure housing as opposed to the 3–5/8" to 10-5/8" pressure housings necessary to contain currently available inertial platform designs. This is of great importance in regards to the versatility of the system to handle all directional survey requirements from orientation to surveys in production tubing.

In addition, the time to acquire a survey will in many cases be significantly reduced by virtue of the high traverse speeds possible and freedom from time dependent gyro drift sampling necessary with directional gyros. Field results to date indicate that positional accuracy is also consistently improved by elimination of systematic errors due to initial gyro alignment, gyro drift and accelerometer bias.

Keywords:
assembly, upstream oil & gas, inclination, field calibration, elimination, surface computer, axis, latitude, laboratory, requirement
Subjects:
Well Planning, Formation Evaluation & Management, Information Management and Systems, Trajectory design
Copyright 1982, Society of Petroleum Engineers of AIME
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