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Case Study: Geostopping Enables CNOOC to Core 100% of Target Zone

Real-time resistivity-at-the-bit measurements accurately identify top of interval of interest in South China Sea appraisal well

Challenge: Identify top of interval to be cored without penetrating it.

Solution: Measure resistivity at the bit in real time with geoVISION imaging-while-drilling service.

Result: Accurately identified top of interval to be cored. Enabled core recovery from 100% of target interval. Avoided additional coring above interval.

Identify coring point

After drilling an exploration well, Chinese National Offshore Oil Corporation (CNOOC) Shenzhen identified a new reservoir in the South China Sea and decided to drill an appraisal well to core the zone of interest for reservoir characterization. A thick shale interval above the zone and a lack of obvious formation markers made identifying the exact top of the zone a challenge. If standard MWD and LWD tools were used, their sensors would be so far from the bit that significant penetration of the zone of interest would occur before its top was identified.

Measure resistivity at the bit

Use of the geoVISION imaging-while-drilling service to measure resistivity at the bit in real time enabled CNOOC Shenzhen to identify the top of the zone of interest without any significant zone penetration. When the geoVISION service detected a change in resistivity less than 0.3 m from the bit, drilling was stopped and two cores, totaling 26.6 m, were recovered over the zone of interest.

Make precise geostopping decision

The accurate, real-time, geoVISION resistivity-at-the-bit measurement made it possible for CNOOC Shenzhen to make a precise geostopping decision and begin coring operations at the top of the zone of interest. There was no need to core additional formation above the zone to avoid penetrating it. Cores were recovered over 100% of the zone of interest, enabling CNOOC Shenzhen to confirm the presence of oil and evaluate formation properties.


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Geostopping Enables CNOOC to Core 100% of Target Zone
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