Distribution and Character of Fractures in the Lisburne Group, Northeastern Brooks Range, Alaska

The Carboniferous Lisburne Group is a thick, heterogeneous and highly fractured sequence of carbonate rocks that acts as the reservoir horizon for the Lisburne oil field of the North Slope. It also is widely exposed throughout northern Alaska as an important element of the Brooks Range fold-and-thrust belt. The Lisburne Group was recognized as a potential reservoir horizon very early during petroleum exploration of northern Alaska and was considered by many to be the primary exploration target during the early phases of drilling on the North Slope.

As in many carbonate reservoirs, naturally-occurring fractures in the Lisburne Group play a major role in hydrocarbon production by providing both porosity and permeability. However, the distribution, density and character of fractures within the Lisburne are highly variable and difficult to predict, and may depend on the lithology of the host rock, the structural setting of the reservoir and/or other unidentified factors. In the Lisburne oil field, less than 10% of the 2 billion barrels in place is recoverable at the present time. A clearer understanding of the distribution, character and origin of fractures has the potential to aid in the development of secondary and tertiary recovery programs for this large, but difficult to produce, reservoir.

This study uses examples of the Lisburne Group exposed in the northeastern Brooks Range to determine the relationship between lithology, structural position, and fracture patterns within this carbonate sequence. This information will help predict the distribution and effect of fractures on hydrocarbon production within the Lisburne Group of the North Slope.

Funded by DOE and Sandia National Labs Grant AG-4303.
Scientific personnel: C. Hanks; A. Krumhardtand J. Lorenz (Sandia National Labs); and L. Teufel (New Mexico Institute of Technology and Sandia National Labs)

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