Avoid extra run in deep water

Hole enlargement while drilling is a common practice in deepwater wells in the Gulf of Mexico that typically results in a rathole of more than 100 ft at TD. In deepwater drilling, the reamer is positioned above the long, complex LWD string so that the enlarged borehole will not degrade the accuracy of formation evaluation measurements.

To open the long rathole to the larger borehole size, the usual practice is to trip the drilling BHA back to surface and perform a dedicated cleanout run, which adds a day or more to the well construction timeline. Noble Energy wanted to avoid an extra cleanout run in the 12 1/4-in by 14 1/2-in hole section of a well it was drilling in deepwater Gulf of Mexico.

Design a dual-reamer BHA

Schlumberger designed an integrated dual reamer drilling system for this operation. The Rhino RHE dual-reamer system comprises a hydraulically actuated reamer positioned above the Schlumberger MLWD tools, and a near-bit on-demand reamer positioned below the tools and above a PowerDrive X6 RSS and MDi716 PDC drill bit from Smith Bits, a Schlumberger company. Optimal reamer placement and surface operating parameters were determined by modeling the drilling system in i-DRILL engineered drilling system design. The directional response of the PowerDrive X6 RSS was also modeled to ensure that placement of the near-bit reamer did not interfere with the directional capabilities of the RSS.

During drilling of the section, the blocks of the Rhino XC reamer were locked at 1⁄8-in undergauge from the 12 1/4-in bit size to avoid interfering with the drilling operation. The reamer's cutter blocks were special cement cleanout blocks with a minimum number of cutters on the gauge surface that would be passive when retracted during normal drilling mode.