PowerDrive Xtra The world's first onshore slimhole rotary steerable well recently drilled for Occidental Petroleum-Oman made history and is a harbinger of things to come.

The results from geosteering execution of a 4712 ft, 61/8" lateral well in the Safah field reflect high, better-than-expected performance. Longer directional wells can now be drilled in the Oman region with maximum reservoir drainhole penetration.

This latest field test of the Schlumberger PowerDrive Xtra 475* rotary steerable system was run to determine the ability of such a system in slimhole conditions to aid in satisfying energy industry objectives in Oman.

The goal of energy players in Oman is to reduce project time and deliver increased oil production from fewer wells, and at the same time, reduce the occurrence of produced water. The 3D steerability offered by this new technology in combination with unique continuous rotation capabilities gives clients the option of taking new approaches to complex well designs.

''We recognise that new technology such as this should deliver a more effective result by reducing drilling time and time to market on production,'' according to Hal Owens, drilling manager, Occidental Petroleum-Oman.

''We were pleased that a tool just out of engineering performed so well on its first run and delivered on all of our requirements.

''To penetrate the planned targets using our current standard systems,'' continued Owens, ''requires drilling in the slide mode, in our case, 30 per cent of the time. During these periods, our penetration rates drop by two-thirds. The PowerDrive Xtra system allows us to maximise our penetrate rate. Also staying in rotary mode allows for additional lateral length to be reached when needed.

''Based on our success with the system to date, we will utilise the PowerDrive Xtra system on two additional wells with the second well getting under way within a few weeks.''

Added Ken Feather, marketing manager for Schlumberger Oilfield Services-Oman: ''As Oman's E&P industry focuses more on enhanced oil recovery techniques, while maintaining low lifting costs, operators are looking to drill fewer smarter wells. PowerDrive Xtra allows a single drain hole to be placed in parts of the reservoir previously unreachable. This new capability will help in the effort of increasing production and ultimate recovery.''

Conventional technology can produce an uneven well path when changing from sliding to rotating mode. Continuously rotating the drill string while steering reduces the chance of producing an uneven path and results in faster, more controllable well placement. By enabling greater control of directional drilling using constant rotation, the new rotary steering technology makes it possible to intersect more targets in a longer hole section and minimises the risk of stuck pipe. In fact, advanced planning between the two companies enabled real-time monitoring of the geologic orientation in the reservoir, which delivered information used to make steering decisions.

The new technology also operates independent of mud weight and depth, allowing for longer runs and fewer trips. This unique capability, used in conjunction with real-time drilling and geological data, offers a distinct advantage to oil and gas operators to reduce field development costs.

''Although the Safah 198 well had significant gas influx from a nearby injector well, all horizons registered as planned and log responses proved accurate,'' remarked Dominic Carrington, operations manager-Oman, Schlumberger Drilling & Measurements.

''To respond to the gas influx, mud weight had to be greatly increased and drilling rates had to be controlled at times. Use of conventional mud motors on the well would have proved slow and we may not have been able to reach TD.''

Services used in addition to the PowerDrive Xtra system included the VISION475* 434" measurement-while-drilling and logging-while-drilling system and INFORM* integrated modeling. A real-time geosteering screen was used and the well was drilled using a 61/8" Schlumberger Sabre drill bit.