Schlumberger

Case Study: At-Bit Image Gamma and Inclination Allow Quick Interpretation for Steering Decisions

MLWD technologies provide advanced measuring and imaging capabilities for accurate well positioning in North America shale play

Challenge: Geosteer within a shale wellbore lateral to maintain and optimize position in the target zone.

Solution: Use iPZIG at-bit inclination, gamma ray, and imaging service with a customized drilling assembly to quickly interpret formation bed boundaries and PayZone Steering well placement service to accurately geosteer the horizontal section.

Result: Successfully geosteered the horizontal section, staying in the target zone 100% of the time.

Abrasive formation in North America shale

An operator was drilling a lateral section in a very abrasive formation in a North America shale play. The abrasiveness caused excessive wear on the drilling equipment and required a specialized design. To geosteer within the lateral and stay in the target zone, the operator selected the MWD survey and total natural gamma ray (fixed-collar directional service), coupled with the iPZIG service, based on its unique at-bit sensors that provide real-time bed boundary measurements.

The iPZIG service positions the image natural gamma ray and dynamic inclination measurements close to the bit to reduce the reaction time for making critical geosteering decisions and maintaining the wellbore in the targeted zone. Measurements of the bed boundary were characterized within the target interval, allowing for new calculation of apparent and true bed dip and direction. The close proximity of the service to the bit enabled quick geosteering decisions to adjust the well trajectory and reduce risks while navigating through critical hole sections and maintaining the wellbore in the target zone.

Advanced measuring, imaging, and modeling

When the borehole intersects a geologic feature, it appears as a sinusoid on the borehole natural gamma ray image. By fitting the sinusoid to the image data, apparent and true dip angle and dip direction can be quantitatively determined. Post processing of the image natural gamma ray using the PayZone Steering service generates an earth model based on offset data. Dynamic inclination and image gamma ray 8–16 sector data from the iPZIG service provides the drilling and geological teams with accurate real-time at-bit information. This allows for quick directional and geological interpretation of the wellbore to maintain the correct position within the defined target interval.

Accurate geosteering

The iPZIG service allowed for greater directional control and confidence in time‐critical decision making relative to the wellbore trajectory to maximize in‐zone exposure. Geological features observed from the 8-sector real-time images aided in the geosteering interpretations. This in-depth information gained from the combined technologies helped the operator correctly determine the position and accurately direct the drilling, staying within the target interval.


Download: At-Bit Image Gamma and Inclination Allow Quick Interpretation for Steering Decisions (1.86 MB PDF)

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At-Bit Service Enables Staying in Target Zone

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