ADVANCED TOOLS FOR ADVANCED WELLS - ROTARY CLOSED-LOOP DRILLING SYSTEM - RESULTS OF PROTOTYPE FIELD TESTING

In the next few years, a revolutionary well-steering system will arriv e to face the ''advanced wells'' challenge. After an extensive period of field testing, the ''rotary closed-loop system'' (RCLS) seems very close to having the capability of operating in any extended-reach, dee p horizontal, or complex multilateral well and in a high-pressure/high -temperature (HPHT) environment. Additionally, mainly because of the e limination of a sliding operation, conventional directional wells will , in many cases, also greatly benefit. The RCLS was designed to contro l automatically well geometry during directional drilling, even while rotating the drill-string. Hydraulically powered, electronically contr olled, expandable ribs, which generate a radial steering contact force to the borehole wall, adjust the wellpath. All parts, except a short steering sleeve, work continuously in rotation. The RCLS may be operat ed with or without a downhole motor. Several subsystems, e.g., the hyd raulic components, most electronic modules, and the bottom-to-surface communication, were field tested during 1994 and 1995. The first field trial of the complete unit, drilling a total of 1067 m, was conducted in late 1995 at Montrose, Scotland. The field test program was contin ued in early 1996 to compare RCLS drilling and directional performance with the introduction of broadened operating parameters. During this prototype testing period, the efficacy of all major functions was full y verified.