Since the decline of the cable-tool rig, well construction operations have been performed exclusively with some variation of steel tubulars. Recently a drilling system that combines composite coiled-tubing technology and hydraulic workover technology has been introduced. This paper examines the benefits of the combined system.

A newly developed composite coiled-tubing drillstring with embedded conductors allows this revolutionary drilling system to achieve uninterrupted, real-time, two-way communication with the downhole tools. This allowed a step-change improvement in the knowledge of dynamic wellbore conditions and in the overall control of downhole drilling assemblies and systems. Subsequently, new procedures were developed to assimilate and use this increased functionality. These procedures include both geosteering and real-time system diagnostics from remote locations.

Incorporating a hydraulic workover (HWO) jacking system as an integral part of the unit expanded the operating envelope and functionality of the entire system. The HWO unit allows for jointed pipe drilling in both underbalanced and overbalanced situations. The HWO unit also serves as a platform to perform jointed pipe completions. When combined with the composite coiled-tubing drilling unit, the resultant "hybrid" drilling system greatly expands the options now available for developing hydrocarbon reserves.

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