Multilayer Mapping-While-Drilling Service Doubles Detection Range, Offshore China | Schlumberger
Case Study
Location
China, Asia, Offshore
Details

An operator drilling two wells in the Chenghai Block in Bohai Bay, China, used PeriScope Edge multilayer mapping-while-drilling service to increase reservoir understanding in sandstone and PowerDrive Archer high build rate rotary steerable system to effectively steer the horizontal section of the wells. The technologies helped the operator make effective real-time geosteering decisions and improve net-to-gross (NTG) ratios.

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Multilayer Mapping-While-Drilling Service Doubles Detection Range, Offshore China

Increased reservoir understanding improves NTG ratios in two wells

Improve geosteering and stay within the sand body

The operator faced drilling challenges where the development wells shift from targeting the center of the sand body to the end. In the previous two wells, because of the large sedimentary changes and sand body discontinuities, the NTG ratios were lower than expected. The average thickness of sand bodies is approximately 8 m. With previous technology, the depth of investigation was around 2 to 3 m, making it difficult to clearly depict the whole sand body. The rapidly changing reservoir structure makes geosteering and staying within the sand body more challenging.

Increase reservoir understanding and make informed decisions

Schlumberger recommended using the PeriScope Edge service, which increases the depth of investigation to 6 m. The service doubled the detection range in the field compared with previous-generation technology. The tool mapped the whole sand body, increased reservoir understanding, and enabled the operator to make informed decisions for maximizing the NTG ratio for each well, which greatly improved the productivity of the wells.

By providing higher-resolution mapping, the PeriScope Edge service revealed the internal layering and quality variation within the reservoir, optimizing the well path and production. PowerDrive Archer high build rate rotary steerable system enabled the operator to effectively steer the horizontal section of the wells to handle the abrupt structure changes and target multiple sand bodies in one well.

Optimize well path

PeriScope Edge service was first used in the reservoir section of Well A. The service mapped the top of target sand 2.1 m away and the base of target sand 5.2 m away as soon as it came out of the casing shoe. PeriScope Edge service mapped the top and the base of the sand body throughout the section, clearly showing the pinchout of the sand body. The well was drilled for 256 m inside the sand body, with 50-m/h average ROP while achieving 100% NTG.

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PeriScope Edge service mapped the top and the base of the sand body throughout the section, clearly showing the pinchout of the sand body. The well was drilled for 256 m inside the sandy body, with 50 m/h average ROP while achieving 100% NTG.

Well B was drilled in an area lacking control wells, causing uncertainties about the thickness and dip of the reservoir structure. At 2,960-m MD, PeriScope Edge service mapped the abrupt upward dip change of the base of the current sand body, enabling the operator to build inclination of the well path and avoid drilling out of the current good quality sand. At 3,030-m MD, PeriScope Edge service mapped the top of the sand body and a poor-quality layer at the upper part of the reservoir. The geosteering team dropped the inclination and avoided drilling into the poor-quality zone at the top. At 3,123-m MD, the PeriScope Edge service inversion showed that the formation dip changed from 0.5 downward to 8.5 upward. The operator called for TD based on this information. For this well, the team achieved a 91.5% NTG ratio, drilling 215 m in sand for the total horizontal section of 235 m.

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PeriScope Edge service mapped the abrupt upward dip change of the base of the current sand body, enabling the operator to build inclination of the well path and avoid drilling out of the current good-quality sand.

"PeriScope Edge service has improved the detection range significantly. It can clearly depict the internal property changes inside the reservoir, providing reliable guidance for the real-time geosteering operation. The PowerDrive Archer rotary steerable system provided high-accuracy trajectory control, ensured the smoothness of wellbore, and improved drilling efficiency."

—Senior Geology Advisor

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