engleski

A Retrofitting Control System Design Suitable for Deep Borehole Drilling Using Legacy Draw-Works Mechanical Brake Hardware

Deep drilling operations are typically needed when producing deep wells for hydrocarbon exploitation or geothermal energy applications. Since a notable portion of existing deep drilling rigs are still fielding manually operated draw-works (hoist) drum mechanical brake actuators, their usage puts notable constraints on the quality of borehole production and corresponding production rates. By retrofitting such mature drilling rigs with a suitable brake actuator servo mechanism, completely automatic drilling operation can be facilitated, thus also achieving borehole production efficiency improvements and meeting the increasingly stringent requirements on drilling control system performance. To this end, this paper presents the development of an automatic drilling control system based on an electrical servoactuator of the draw-works mechanical brake, with the control system arranged in the so-called cascade control system structure, and an automatic tuning procedure having been devised as well. Its robustness has been tested by means of root locus plots and simulation analysis of dominant closed- loop dynamics effects. The proposed control system has been verified by means of simulations first, which has been followed by a thorough experimental verification on an actual deep drilling rig retrofitted with electrical servodrive based- actuator of the winch drum mechanical brake. Field results have indicated that the proposed control system can maintain the drill-bit normal force within 10% (+/-) of the target value during normal operation, with penetration rate variations typically being two to three times smaller compared to the case of human operator controlling the drilling process.

Deep drilling rig ; weight-on-bit ; rate-of-penetration ; retrofitting ; mechanical brake servomechanism ; cascade control system ; proportional-integral control ; field testing

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