Case Study: New Multilayer LWD Service Helps Achieve 100 Percent Net-to-Gross Ratio

PeriScope HD service detects reservoir layers to accurately place well within 3 m of upper boundary

Challenge: Geosteer within 3 m of upper boundary, differentiating between overlapping dipping channel sands and the reservoir’s top structure, while avoiding any exits into overlying shale and ensuring the wellbore is steered within set dogleg severity (DLS).

Solution: Employ PeriScope HD multilayer bed boundary detection service to identify multiple geological layers and precisely place the well.


  • Achieved 100 percent net-to-gross (NTG) ratio
  • Drilled with an average of 3 m of the upper boundary
  • Mapped top of reservoir and identified internal layering continuously and simultaneously

Detect challenging reservoir layers to accurately place subsea well

BHP Billiton aimed to drill and complete a well within the oil-bearing sandstones of the Pyrenees development. In order to maximize the intersection of the reservoir, the well was to be positioned within 3 m of the upper boundary. Observation of offset data and previous experience in the same field showed that the well’s main zone of interest comprised varied resistivity profiles. The reservoir target consists of a series of dipping sand progrades, truncated at the top by an unconformity, resulting in an angular unconformity between the overlying shale and the reservoir sands. With a stark contrast in resistivity, BHP Billiton needed a bed boundary detection service that would enable precise placement of the drain hole beyond conventional capabilities.

Increase understanding of complex reservoir geometry to reduce wellbore tortuosity

Schlumberger provided a BHA with the new PeriScope HD service to minimize potential standoff with respect to the unconformable overlying shale. PeriScope HD enabled identification of multiple resistivity layers and delivered continuous mapping of reservoir boundaries and internal geometry. In addition to formation evaluation measurements acquired from real-time bed boundary mapping, gamma ray, resistivity, bulk density, and neutron porosity measurements were used to optimally place the well.

Mapped different layers while identifying upper boundary for a 100 percent NTG ratio

Well placement engineers worked together with BHP Billiton to successfully drill and place the well. The PeriScope HD service’s unique depth of investigation (DOI) coupled with the multilayer detection capability provided an increased understanding of the complex reservoir geometry, optimizing well placement in the reservoir. PeriScope HD service was able to continuously map the upper boundary of the reservoir while simultaneously identifying internal layering and mapping several dipping progrades.

The well was drilled with an average of 3 m below the top of the unconformable reservoir and achieved a 100 percent NTG ratio—remaining within the sweet spot.

BHP Billiton is planning to use the PeriScope HD service in two more horizontal wells within the field.

Download: New Multilayer LWD Service Helps Achieve 100 Percent Net-to-Gross Ratio (0.88 MB PDF)

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High-Definition Reservoir Mapping Service Identifies Multiple Resistivity Layers

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Precise Detection of Multiple Reservoir Layers for Advanced Well Placement

PeriScope HD Multilayer Bed Boundary Detection Service
High-definition LWD service identifies multiple resistivity profiles in real time for increased understanding of complex reservoir geometry.
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