On a recent high stepout 3D well for Unocal, the Halliburton Geo-Pilot rotary steerable system, equipped with a new FM3000 PDC bit design from Security DBS, yielded outstanding results, Halliburton says.
Unocal drilled the well in the Ship Shoal area of the Gulf of Mexico where high ROPs are common. The challenge was to increase ROP even further, while keeping up with the rate of cuttings being generated in the 9 7/8-in. hole, which would generate even more cuttings volume compared to offset wells drilled with a smaller 8 1/2-in. diameter. This required the highest level of borehole quality to eliminate cuttings traps normally created by non-stabilized bits, outstanding cuttings transport properties in the drilling fluid, no interruptions for rotary steerable communications, and high rate cuttings handling and treatment (drying) at the surface. All of these goals were met, the company says, allowing 5,843 ft to be drilled in the first 24 hours and the entire 10,107-ft interval to be drilled in one run.
The operation required coordination between Baroid personnel, who supplied the mud additives for Unocal's synthetic base fluid; Brandt, which Halliburton subcontracted for their high-speed cuttings dryers; Sperry-Sun for the Geo-Pilot system; and Security DBS for bit design. The well profile called for building angle to 48°, which is right in the critical 45°-55° range for hole cleaning problems, and then turning the well 118° in azimuth. A 7 5/8-in. casing with a maximum diameter of 7.775 in. was then run successfully, Halliburton says. The weight of the casing string and the hole profile made it unlikely that the casing string could have been retrieved had it gotten hung up before reaching total depth, but due to the unsurpassed hole quality and hole cleaning achieved, the casing went straight to bottom.
