Schlumberger

Case Study: OSC Monitoring Avoids Potential Twist-Off Through Early Washout Detection

Intervention Eliminates Delays and NPT

Challenge: Convince customer to pull out of hole (POOH) to avoid a potential twist-off and finish drilling the 8 1/2-in section within targeted time.

Solution: Used OSC interactive drilling operations to provide 24-hour monitoring to detect the washout and provide data to confirm the need to POOH.

Result: Avoided a potential twist-off through early detection of washout, saved time that would have been needed for fishing and sidetracking, and successfully drilled the section 1 day earlier than the planned AFE of 7 days.

OSC monitoring detects potential washout

During drilling of an 8 1/2-in section in a well in Abu Dhabi using a BHA, the operation support engineer (OSE) at the Operation Support Center (OSC) noticed a drop in turbine rpm while the standpipe pressure was continuing to increase. The drop in turbine rpm suggested a washout in the drillstring, which the increase in standpipe pressure seemed to contradict.

Data offers proof for decision making

The OSE recommended that the rig crew check the surface system and the mud parameters. Mud weight had been gradually increasing, so mixing mud was stopped to monitor the standpipe pressure, which continued to increase.

The TeleScope high-speed telemetry-while-drilling service provided real-time information that allowed logging the borehole sections in greater detail. Based on this data, charts and logs were prepared and sent to the customer. A technical chart that showed the correlation between the flow and turbine rpm at various mud weights provided proof of a washout with up to 150 galUS/min not passing through the tools.

Early detection avoids twist-off

Based on the information provided, the operator decided to POOH, and a washout was found in the PBL sub. A potential twist-off—which would have resulted in delays for fishing and sidetracking—and NPT were avoided. Drilling continued using PowerDrive Xceed RSS to maximize ROP and reach TD in less time. The section was completed 1 day earlier than the planned AFE of 7 days, including the 20-hour turnaround time for the washout trip.


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