The PowerDrive Xtra system reduced the hole inclination from 0.47° to 0.03° at the begin- ning of the fi rst run and maintained an overall inclination of 0.15° over the course of two runs of the tool. The well was drilled 2.5 days ahead of the schedule specifi ed in the authorization for expenditure (AFE), saving US$ 750,000. Working together, Petrobras and Schlumberger used the PowerDrive Xtra tool to drill the well according to technical specifications and ahead of plan, which improved the financial impact of this endeavor. In light of these results, Petrobras plans to deploy PowerDrive Xtra technology in at least 40% of the more than 100 offshore wells slated for drilling during 2004.
Openhole Sidetracking in Complicated Formations Tool reliability, steerability and durability are key factors when drilling complicated well tra- jectories in harsh drilling environments. Rotary steerable systems are a natural fit for these operations because full rotation of the systems lessens the likelihood of operational mishaps, such as mechanical sticking.
The reliability and durability of the PowerDrive Xceed rotary steerable system for harsh, rugged environments make it suitable for drilling the most diffi cult wells (right). The sys- tem incorporates electronics from the proven, durable PowerPulse measurements-while-drilling (MWD) telemetry system, which can operate more than 1,000 hours without failure. Steerability of the PowerDrive Xceed system is regulated by an internal steering mechanism and through traditional three-point contact with the borehole wall. The internal steering mecha- nism is completely enclosed to provide a greater degree of accuracy than a tool with an external steering mechanism because the internal steer- ing mechanism limits interaction between the tool and the hole. Only rotating elements contact the borehole, so directional drilling is controlled by the tool instead of the shape of the
11. Rotary steerable systems have been used in the Njord
eld to drill extremely complicated wells, including a W- shaped well. For more information: Downton et al, reference 5.
For more on the Njord eld:
http://www.hydro.com/en/our_business/oil_energy/ production/oil_gas_norway/
njord.html (viewed January 12, 2004).
12. von Flatern R: “ Rotary Steerables Ready for the Mainstream,” Offshore Engineer 28, no. 4 (April 2003): 32– 34, 36.
hole. This independence of the rotary steerable system from the borehole facilitates complicated drilling applications, drilling with bicenter bits and drilling openhole sidetracks with great reli- ability, even at high build rates. In addition, the limited contact between the tool and the bore- hole improves hole quality and maximizes ROP. The PowerDrive Xceed system is designed specifically for tough environments. Enclosed components and stationary internal seals protect the tool in wellbore temperatures to 302° F, highly abrasive formations, all types of fl uids, and high- shock environments. Its minimal contact with the borehole wall makes the tool less susceptible to wear in abrasive formations. In addition, the tool can build angle up to 8° /100 ft [8° /30 m], which allows it to drill demanding trajectories. Many of these advantages of the rotary steer- able system were tested in the Njord fi eld, in the Norwegian sector of the North Sea (next page).11 Numerous faults separate the reservoir into compartments that must be tapped individually, but determining the location and extent of the compartments is a difficult task. Some of the rocks are extremely abrasive, while others are prone to instability. Njord operator Hydro used the PowerDrive Xceed system to perform an openhole sidetrack in the A-10 BY3H well. The system successfully drilled the sidetrack from open hole at 91° incli- nation. The plan called for a drop in inclination from 91° to 88.5° , while turning from an azimuth of 179° to 170° . The section was drilled from openhole sidetrack to total depth in one run, a feat never previously achieved in this fi eld. This saved approximately two days of rig time. The PowerPulse system measured downhole vibrations, which were lower in quantity and degree than comparable runs,
indicating
improved drilling efficiency. Performing more than 90% of the tool settings while drilling with the tool on bottom also enhanced effi ciency by reducing nonproductive time.
13. For more on slimhole systems: Kuyken C, van der Plas K, Frederiks K, Williams M and Cockburn C: “ Developing and Using Slimhole Rotary Steerable Systems in the North Sea Changing the Economics of Mature Asset Drilling,” paper SPE 83948, presented at the SPE Offshore Europe 2003 Meeting, Aberdeen, Scotland, September 2– 5, 2003.
Steering section: assembly continuously orients the tilted bit shaft to control the drilling direction and the dogleg severity of the borehole.
Power-generation module: turbine-driven alternator supplies power for steering and control.
Control system: electronics and sensor package take measurements to control steering assembly.
> PowerDrive Xceed rotary steerable system. The power-generation module supplies power for steering and control. The control unit contains electronics and sensors that take measurements to control the steering assembly. The steering section continuously orients the tilted bit shaft to control the drilling direction and build angle.
8
Oilfi eld Review
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