Schlumberger

Case Study: Rhino XS Reamer and Stabilizer Eliminate Additional Downhole Trip Offshore Brazil

Combination successfully drills and underreams to TD in one trip and confirms hole calibration with reduced torque and vibration

Challenge: Drill and underream to TD in a single trip in an interbedded presalt formation offshore Brazil.

Solution: Deploy a Rhino XS hydraulically expandable reamer with stabilizer blocks for reduced torque and vibration during hole enlargement.

Result:

  • Underreamed while drilling to planned TD in one run.
  • Delivered superior BHA stabilization for reduced torque and vibration levels.
  • Set 18-in liner without issues.

Underream through challenge interbedded layers a single trip

To investigate a potentially hydrocarbon-bearing basin offshore Brazil, an operator planned to drill a vertical well. To ensure a proper setting of an 18-in liner, a borehole enlargement was required from 18 1/8 in to 22 in.

During two previous operations in the same area, the operator encountered severe wear on the reamer cutter blocks while using standard drillstring stabilizers. Therefore, the operator planned to drill in two runs, changing out the bit and reamer before reaching the well’s final depth.

Deploy proven reamer and stabilizer for hole enlargement

The operator chose to deploy a BHA that included the Rhino XS reamer (22-in opening size), a specialized stabilizer (21-in opening size), and an 181/8-in PDC bit to perform the underreaming-while-drilling (UWD) job. An 181/8-in Borrox AP advanced-performance sealed-bearing reamer was also used to reduce torque in the challenging presalt play. The stabilizer for the Rhino XS reamer provides concentric, stable points of contact in the enlarged section and minimizes cutter block wear by stabilizing the reamer, ensuring optimal performance of the Rhino XS reamer.

The OptiLog BHA dynamics recorder sub, placed directly above the reamer, was chosen to provide correlation data and record triaxial vibration, rotation, and temperature.

Mitigate torque and vibration for reduced cutter block wear

Drilling began in shale at 5–9 m/h, with 50% weight on the bit and 50% weight on the reamer. Vibration was monitored through a real-time drilling optimization service. The vibration monitoring results and the OptiLog recorder sub indicated that vibration was worse at a higher rpm. At 140 rpm, the BHA was receiving more medium- and high-risk lateral vibration (2 to 4 gn) and more erratic torque. Upon recognizing this, the operator chose to reduce rpm to preserve the BHA.

From 4,080-m MD, the torque increased sharply as the reamer entered the next formation. At this point, WOB and rpm were reduced to preserve equipment and help avoid stall out. When underreaming through carbonates, from 4,120 m to 4,413 m, the OptiLog recorder sub confirmed medium- and high-risk levels of lateral and whirl vibrations (3 to 4 gn).

The bit reached the top of the anhydrite salt layer at 4,413 m, which was characterized by the drastic reduction in torque recorded at surface. At 4,451 m, the reamer reached the anhydrite salt top, and high levels of vibration (whirl, lateral, and stick/slip) were observed. These levels were reduced once the reamer entered the salt formation with the bit.

The UWD operation continued until TVD was reached at 4,646-m MD in one run. The 18-in liner was set successfully.

According to the operational program, a bit and reamer replacement was planned for 4,321 m. However, the performance of the Rhino XS reamer exceeded expectation, reaming an in-gauge hole to TD in a singe run. The 21-in system stabilizer proved essential in stabilizing and protecting the reamer’s cutter blocks.

The OptiLog recorder sub and predrill models generated by the IDEAS integrated dynamic design and analysis platform optimized and refined drilling procedures and strategies for future runs. The ability to provide postrun feedback regarding the effectiveness of mitigation procedures used while drilling also proved beneficial.


Download: Rhino XS Reamer and Stabilizer Eliminate Additional Downhole Trip Offshore Brazil (0.49 MB PDF)

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