Intelligent Near-Bit Reamer Affords Same-Trip Drilling, Hole Enlargement and Rathole Reduction for Optimal Deepwater Well Construction

Abstract

Simultaneous drilling and hole enlargement in deepwater wells helps set casing strings deeper in the well. Common BHA designs place an underreamer above the MWD/LWD package, which ensures reliable mechanical activation of the underreamer, but also leaves up to 200 feet of undergauge rat hole to TD. An intelligent underreamer is presented with RFID and pressure cycle activation capabilities. Placed closer to the bit, this underreamer minimizes the rat hole to ensure deeper casing setting.

The intelligent drilling reamer is a concentric mass-balance underreamer that enlarges wellbores below casing restrictions. The reamer simultaneously drills and enlarges when deployed with rotary-steerable systems or rotary BHAs. Unlike ballactivated underreamers, the intelligent reamer is activated via RFID, in which RFID tags are pumped downhole to transmit instructions to an electronic reader on the reamer. The reamer can also be activated with a pressure cycle, which opens or closes a solenoid-operated valve to lock or unlock the reamer. With this dual actuation feature, the tool can be installed just behind the bit, where it significantly reduces rathole length.

An operator working offshore Malaysia deployed the intelligent underreamer to enlarge a highly deviated, slimhole wellbore from 6-¾ in. to 8-½ in. The tool was run in the lower part of the directional BHA, near the bit, to minimize the rathole. A set of RFID tags was dropped into the drill string at the same time that the pressure pulse activation sequence began. The RFID tag activation code was not received at the expected time, an indication that the tags were not able to easily pass through the turbine-driven MWD tools. However, the reamer was activated by the pressure pulse sequence and the rathole elimination operation commenced.

The reamer reduced the rathole length from 180 ft to 10 ft (55 m to 3 m), allowing the operator to achieve its completion and reservoir inflow requirements without changing drilling practices or replacing any BHA components. The operation eliminated the need for a dedicated run to enlarge the hole. The single run also minimized openhole time, which reduced borehole instability risks. In total, this single-trip drilling and reaming run reduced rig time by approximately 20 hours, equivalent to a cost savings of approximately USD125K.

The intelligent reamer is the only one of its kind capable of actuation via RFID tags or pressure pulse cycling, which provides on-demand control for nearly unlimited activation and deactivation when tripping and drilling. It also provides a backup activation option when the primary RFID method fails. The tool's RFID-activated automatic battery savings mode increases battery life by up to four to eight times, which ensures longer reaming runs in the same trip.