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Case Study: SonicScope Multipole LWD Service Demonstrates Consistent Slow Shear Capabilities in Malaysia

High-quality slow shear data acquired in soft formation where monopole acquisition would be limited

Challenge: Acquire high-quality compressional and slow shear data in very soft formation to reduce uncertainty in surface seismic.

Solution: Use SonicScope multipole sonic-while-drilling service in four closely spaced wells to acquire high-quality data.

Result: Acquired reliable, repeatable compressional and slow shear data in four wells, enabling correction of the time-depth conversion to accurately identify geological layers and potential hazards.

Slow shear data needed in slow formation

An operator in Malaysia planned to drill four wells in close proximity and needed to acquire accurate time-depth information in real time to reduce uncertainty in the surface seismic. The team knew that critical data needed to be acquired in a very soft and shallow drilling environment challenging for sonic data acquisition.

Multipole sonic LWD service used to reduce uncertainty in surface seismic

For this project, Schlumberger provided SonicScope multipole sonic-while-drilling service, which is capable of high-quality monopole and quadrupole measurements for compressional and shear slownesses in soft formations. TeleScope telemetry-while-drilling service was included in the BHA for real-time transmission to surface.

This technology combination was run in the shallow 12 1/4-in section drilled from the conductor, acquiring data to complement velocity measurements planned in deeper sections of the wells.

Reliable, repeatable shear data acquired in real time

The operator was able to acquire reliable, repeatable compressional and slow shear data using the SonicScope service in all four wells, despite very soft formation that would prevent high-quality measurements with a conventional sonic acquisition tool. The compressional slownesses were extracted through a Leaky-P processing technique that is unique to the SonicScope service. The quadrupole acquisition provided consistent shear slownesses results. Comparison of results between the four wells showed consistent compressional and shear data including slow shear up to 960 us/ft.

A slowness-time-coherence (STC) plot showed that the high-quality, real-time data matched recorded data. Additionally, data was used for a Poisson's ratio cross plot to be able to identify the sweet spots within gas bearing sands.


Download: SonicScope Multipole LWD Service Demonstrates Consistent Slow Shear Capabilities in Malaysia (1.33 MB PDF)

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