ROP
220 200 180 160 140 120 100 80 60 40 20 0
Inclination
Azimuth
Build angle
7 6 5 4
2 3
1 0
1,700 1,900 2,100
13 3⁄ 8-in. casing at 1,692 m measured depth (MD)
2,300 Depth, m Voador field Plan Actual 2,500 2,700 2,900 -1
Total depth 3,336 m MD 9 5⁄ 8-in. casing at 2,885 m MD
SOUTH AMERICA
> Voador eld, Campos basin, offshore Brazil (bottom right). Petrobras used the PowerDrive Xtra system to drill a pilot hole to establish reservoir boundaries, and a sidetrack hole to optimize heavy-oil production (bottom left). The tool drilled the 84° inclination of the sidetrack hole with maximum build angle of 6.5° /30 m [6.5° /100 ft] into the target formation as planned (top), with an average rate of penetration (ROP) of 35 to 40 m/hr [115 to 131 ft/hr], which was double that of the steerable motor deployed in offset wells.
LWD images acquired during the trip out of the hole were downloaded at surface. When compared with images acquired at different times, for example, during drilling, these time- lapse images confirmed wellbore-stability problems in the shales, which were first indi- cated by the cuttings morphology and increasing drag. In this well, the PERFORM process helped engineers determine that the mud weight was too low and that hole cleaning was suboptimal. The well was drilled successfully to total depth by managing both parameters while drilling. Petrobras took PowerDrive Xtra technology in a different direction when the company
planned a vertical, deepwater exploration well, 1-RJS-600, near a salt dome. The company wanted to drill close to the salt dome, where for- mation dip was greater than 20° , but also wanted the well to penetrate the reservoir verti- cally. Keeping the borehole perfectly vertical, rather than deviating and correcting back to vertical, would produce a smoother wellbore. A smoother wellbore facilitates running larger casing, and offers the possibility of using an extra string of casing at some later stage in the operation. Although a vertical drilling tool could have done the job, Petrobras wanted to use a PowerDrive Xtra system to ensure that the drill- string would rotate
throughout drilling
operations while allowing application of the maximum weight on bit to maintain the highest possible penetration rates.
8. For an example of rotary steerable drilling in a marginal
eld: Musa MB, Wai FK and Kheng LL: “ Fit-for-Purpose Technologies Applications in Commercialising a Marginal Oil Field,” paper SPE 80462, presented at the SPE Asia Paci c Oil and Gas Conference and Exhibition, Jakarta, Indonesia, April 15– 17, 2003.
9. For an example of the roles of LWD and rotary steerable systems in well placement: Tribe IR, Burns L, Howell PD and Dickson R: “ Precise Well Placement With Rotary Steerable Systems and Logging-While-Drilling Measurements,” SPE Drilling & Completion 18, no. 1 (March 2003): 42– 49.
10. For more on the PERFORM process: Aldred W, Plumb D, Bradford I, Cook J, Gholkar V, Cousins L, Minton R, Fuller J, Goraya S and Tucker D: “ Managing Drilling Risk,” Oil eld Rev iew 11, no. 2 (Summer 1999): 2– 19.
Spring 2004
7
ROP, m Inclination or azimuth, °
Build angle, °
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