Tech Paper: Wellbore Placement in the Middle Bakken Formation Using an Azimuthal Gamma-Ray Measurement

Identify shearing or faulting early using an azimuthally sensitive natural gamma-ray tool

The Bakken formation is a large, unconventional resource located in North Dakota. Horizontal wells are drilled from pads at tight spacings, and placement within the target formation is critical to ultimate recovery rates. Geologic placement is established by evaluating the natural gamma-ray tool response and comparing it to a representative gamma-ray log from a vertical wellbore. Typically, a bulk gamma-ray detector is used, and small gamma-ray differences are used to infer stratigraphic placement. This paper presents the current geosteering methodology, as well as the use of an azimuthally sensitive gamma-ray sensor, to place the well more accurately in the target formation.

Accurate stratigraphic placement is necessary to achieve optimum production rates and to avoid a shale strike in the formations above and below the middle Bakken member. Shale strikes can result in hole-condition problems and may require sidetracks or the use of oil-based drilling fluid instead of water-based drilling fluid, which increases the cost of the well.

The azimuthally sensitive natural gamma-ray tool transmits a real-time gamma-ray image of the wellbore. The wellbore image can be used to infer relative stratigraphic movement of the drilling assembly through the formation. Additionally, the image can be used to identify shearing or faulting across the wellbore and relative formation dip.

Click below to view further details and download the technical paper (PDF).

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Source: Unconventional Resources Technology Conference, 1-3 August, San Antonio, Texas, USA

Authors: Dan Carson (Petro-Hunt) | Susana Gutierrez Carrilero (Halliburton) | Tim Parker (Halliburton) | David Hinz (Halliburton) | Eric Shearer (Halliburton)

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