Dual RFID Activated Reamers Reduce Vibration in Deepwater Well

Abstract

Simultaneous drilling and enlargement is common in deepwater Gulf of Mexico projects. It controls equivalent circulating density, manages pore pressure anomalies, and ensures that casing strings and liners reach total depth (TD). Common hole-enlargement-while-drilling (HEWD) bottomhole assemblies (BHAs) place a concentric hydraulic underreamer above the rotary steerable system (RSS) and measurement-while-drilling/logging-while-drilling (MWD/LWD) package. Although this placement is effective, it could leave up to 200 ft (61 m) of under gauge rathole at TD, which often leads to a dedicated trip to eliminate the rathole. This underreamer placement with the bit off bottom also has limited underreaming capabilities because of vibration caused by drill string instability. These vibrations typically make underreaming an existing pilot hole more difficult than simultaneous drilling and reaming.

On a job for a sidetracked well in the Gulf of Mexico, a drilling team had challenges in a 12 1/4- × 14 1/2-in. section. The team encountered significant vibration and torque when underreaming 423 ft (129 m) of an existing 12 1/4-in. pilot hole in a salt section. After this operation proved unsuccessful, due to low rate of penetration (ROP) caused by severe torque spikes and high shocks and vibrations, the team opted for an alternative solution to achieve the section objectives.

The team designed a unique BHA that included two intelligent underreamers. The first placed above the MWD assembly, and the second placed below the MWD assembly. Historically, placing underreamers below the MWD package and near the bit creates problems because the inside diameter (ID) of the MWD/LWD tools restricts balls that activate the underreamer, and flow-operated underreamers can prematurely activate or fail to activate.

In the new dual-reamer design, radio-frequency identification (RFID) technology provided the capability of activating and opening each underreamer and underreaming with both simultaneously. Wiring through the underreamer below the MWD package connected the rotary-steerable and MWD tools for communication.

The team ran the RFID underreamer below the MWD/LWD package and activated the cutter blocks at the correct depth. The team used both reamers concurrently to ream the 423-ft (129-m) section and then tripped into the hole using the upper reamer to continue drilling the below-salt formation. The operation continued as planned until 500 ft (152 m) before the planned well depth. At that point, downhole problems resulted in losing the BHA in the hole, cementing the openhole interval, and sidetracking the well.

The innovative dual-reamer design delivered a stable BHA to enlarge a wellbore section in one run, which could not have been done using a conventional ball-drop underreamer and BHA design. The drill string operated at 15,000 ft-lb (20,337 N·m) less torque spikes than with the previous design.