Schlumberger

Case Study: Operator Completes Milling at 300 degF Using DynaForce TT Motor with Proprietary Elastomer

Two-well, 21-hour campaign was successfully completed by replacing an accelerated-chunking motor with thru-tubing motor in the Eagle Ford Shale

Challenge: Complete a two-well milling campaign with downhole temperatures of 300 degF in a low-pressure reservoir using 60% N2 flow without losing motor power.

Solution: Use DynaForce TT high-performance thru tubing motor with NBR-HR proprietary elastomer to complete the job without risk of chunking or degraded power.

Result: Completed a two-well campaign, milling for 21 h at 300 degF with 60% N2 content and demonstrating excellent operational condition after pulling out of hole.

Complete millout campaign in harsh downhole environment

An operator needed to complete a two-well campaign to mill out cement and some organic residues in a 300-degF field in the Eagle Ford Shale play. The reservoir was depleted, so high N2 flow was needed. Several attempts were conducted in previous wells, but the company's current motor fleet was chunking in a few hours because of a susceptibility to high temperatures and rapid gas decompression (RDG) on the motor's elastomer. The operator commissioned a coiled tubing (CT) services company to use a Schlumberger thru-tubing motor for the millout operation.

Deploy optimal combination of thru-tubing motor and proprietary elastomer

Schlumberger recommended the use of its 1 11/16-in 4-stage DynaForce TT thru-tubing motor in a 5/6-lobe configuration with the proprietary NBR-HR elastomer and a 1-loose fit, achieved by installing an undersized rotor (1US). The NBR-HR elastomer has a controlled expansion ratio and holds its hardness at high temperatures to deliver optimal power while limiting the N2 invasion factor, minimizing the risk of premature chunking. The possibility of a debonded stator at such high bottomhole temperatures is reduced by the implementation of specially formulated adhesives.

Run motor for 21 h without chunking

A single Schlumberger downhole motor was used to complete more than 21 h of combined work on two wells with a constant flow of brine and 60% N2. After Schlumberger confirmed postjob full motor functionality and performance at surface, the motor was disassembled for further inspection. No wear, evidence of chunking, or elastomer degradation were found following the work in the harsh environment.


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