New Dual Digital On-Command Under Reamer Solution Performed Multiple Activation Cycles in Challenging Exploration Well Not Compromising Acoustic Measurements
Authors: Grymalyuk S. , Herlitzius J. , Schimanski M. 
Published: April 2017

This paper presents and discusses the results of a field application where the new under reamer technology was used in a vertical exploration well in the Jangkrik field in Indonesia. The challenging soft formation required a lean casing profile by the customer. A rathole elimination was needed to set the casing close to total depth and manage the critical formation pressure zones. The past run was utilized with a conventional ball drop main reamer with single activation and deactivation. After 1,640 ft (500 m) the bottom hole assembly (BHA) reached a critical section. Multiple attempts to continue drilling simultaneously with main reamer and bit didn't succeed. The client decided to pull out of hole and continue drilling with a dual on-command digital reamer configuration.
The on-command digital, expandable under reamer is fully integrated into the BHA and can be monitored and controlled from the surface. The under reamer tool has unlimited activation cycles that provide the capability of selective reaming. The flexible placement of multiple reamers in the BHA enables near-bit and main reaming applications, and a combination of both. The real-time feedback from the reamer includes tool vibration and stick slip (VSS) data, and confirmation of blade activation status and blade position (being fully retracted, fully extended, or transiting between the two). The extended blade position is pre-configured to a certain position on surface and the reamer will open up to this position when activated, after which reaming operations will begin. The real-time feedback reduces operational uncertainty by allowing the operator to adjust drilling parameters instantly during reaming operations and saves time for a shoulder test.
During restarting at the critical 12 ¼-in. section the main digital reamer was not activated and the BHA drilled successfully with the bit only. After 8 stands of continuous drilling the BHA reached a significantly different formation observed by the resistivity and acoustic measurements. The BHA was pulled back into the critical section, the main reamer was activated via downlink and enlarged the pre-drilled hole to 14 ½-in. After that drilling was continued with main reamer and bit simultaneously to TD. To eliminate the rat hole the BHA was pulled back to the edge ofthe main reamer and the near bit reamer was activated.
In order to drill the critical exploration well a rotary steerable BHA including resistivity and acoustic measurements combined with a dual configuration of the new on-command digital reamer was deployed. The distance between the acoustic measurement and the main reamer was 45.6 ft (13.9 m) and no impact on the acoustic measurements was observed. The acoustic reading was used for detailed pore pressure predictions during this exploration well.
With the dual reamer setup 1650 ft (503 m) were reamed with the main reamer and the rathole was reduced down to 15.1 ft (4.6 m) with the near bit reamer. This dual reamer solution solved the challenges which couldn't be solved by a conventional reamer. Additionally the near bit reamer saved the customer a two day trip for a dedicated rathole run.
Due to formation challenges both reamers were opened and closed multiple times. The real time VSS and diagnostics data was successfully used to optimize the reaming operation.
The paper will summarize and describe the results and features in detail, and will demonstrate how they can help the operators to reduce operational risks and save cost.