Near-Bit Gamma Ray Service Provided Optimum Wellbore Placement

Baker Hughes identified key zones with minimal penetration

North Sea production well

While drilling a shale/sandstone/chalk sequence in the Tor formation in a North Sea production well, an operator needed stratigraphic control while drilling the 12¼-in. section. The plan also called for obtaining a base evaluation of the Palaeocene sand reservoir section, if present. The operator wanted to use the Baker Hughes near-bit gamma ray service to clearly define the top of the Tor formation and to minimize losses in the reservoir section.

Using the near-bit gamma ray service to correctly identify the top of the Tor formation would allow the 95⁄8-in. casing to be set into the reservoir with minimum penetration into the reservoir. By identifying the top of the zone with the gamma ray, it would not be necessary to wait for samples to be circulated to the surface to confirm penetration of the target zone.

Key zone identification

To meet the operator’s objectives and provide longer reservoir sections, Baker Hughes deployed the AutoTrak rotary closed-loop steering system with gamma ray detectors positioned above the AutoTrak steering unit. The unit was deployed without any HS&E incidents, and the near-bit gamma ray service successfully identified the key zones with minimum penetration and reduced the waiting time on samples.

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