Schlumberger

Performance Report: KLA-SHIELD System Performs Exceptionally in Elk Hills Bakersfield, CA

Challenge: Experience from offset wells showed that shale and claystone are very reactive when drilling with conventional water-base mud, resulting in pack-offs, stuck logging tools, tight hole while running casing, lost circulation and stuck pipe. The formations responded well when drilled with oil-base mud and a 12% KCL polymer/water mud system.

Completion problems with oil/water-emulsion mud precluded further drilling with oil-base fluid. The 12% KCL polymer mud system performed almost as well as the oil-base system, but like the oil-base product, special electric logging tools were necessary due to high chloride concentration in the mud.

Solution: The KLA-SHIELD water-base drilling-fluid system with only 6% KCL was proposed to minimize the problem. The system was expected to be sufficiently inhibitive but with lower concentrations of chlorides to facilitate running conventional electric logs.

Result: The KLA-SHIELD system performed very well while drilling through the anticipated reactive shales and claystones.

It is well known that reactive shale formations are prone to instability when left open for a long period of time. This wellbore showed very good stability on all of the five bit trips. The BHA and bit came out clean on every trip, and there were no reports of bit balling.

Unlike some of the offset wells, where pack-offs, stuck logging tools and tight-hole problems while running casing were experienced, this interval, was drilled to TD and the logs and casing program were carried out with no hole-instability problems.

The fluid was maintained with low solids content, the MBT was kept below 10 ppb. The fluid will be utilized in the next well, which represents a cost savings to the client.


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