As outlined above, Gyro Survey Tools were initially and primarily introduced into the industry, to provide a means of obtaining or checking borehole attitude, when the wellbore was already cased, negating the application or repeated use of magnetic based tools (Lease Scandals). Similar conditions were to foster the requirement for reduced diameter tools when later legal argument ensued over deeper smaller diameter wells. However, the primary motivation for technology advancement has been the requirement to survey ever deeper, higher angle boreholes (beyond horizontal), with significant azimuthal change at greater latitudes.
The first gyros used by the industry had no means of inner gimbal/spin axis control but the surveyor could determine its approximate position from the film record at each survey station. These gyros were originally intended for use up to 20 – 30 degs inclination. However, as borehole inclinations increased, hardware improvements were made and operational techniques were developed which enabled these tools to be used successfully beyond 60 degs inclination. As noted above, Gimbal Tilt control and Drift Curve correction methods were refined to better account for the increasingly difficult operating conditions encountered and its interactive effects on gyro stability and data quality at a relatively early stage.
Feedback
Post your comment on this topic.