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What We Know
Fracture mapping has been effectively utilized to better understand fracture growth behavior for two decades. This has helped the industry to understand what was achieved with fracture treatments in a wide range of reservoirs across the United States.
At this time, only a limited amount of fracture mapping data has been published about hydraulic fracture growth in the Bakken formation. The availability of reliable, high-resolution, downhole microseismic fracture mapping data is somewhat limited due to the large well-to-well offset distances, which make it hard to set up projects where the microseismic hearing distance of 2,500 – 3,000 ft is not major limiting factor in a project.
From these fracture mapping datasets, the following general fracture growth behavior for treatments in the Bakken formation appears:
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The dominant fracture orientation for Bakken fracture systems is about N 50°E.
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Unlike fracture systems in the Barnett Shale and some other resource plays, fracture growth is not necessarily complex, meaning that fracture growth is often just dominant in a single direction.
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Diversion and placement of a fracture treatment in its intended stage position along the horizontal lateral has been spotty. In some early single stage “Hail Mary” fracture treatments, some authors have observed fracture treatments that only effectively treated the toe and heel of the lateral. In treatments where lateral stage lengths were in excess of 500 ft, only portions of the intended lateral sections appear to have been effectively treated.
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Fracture growth is predominantly upward in nature, with fracture growth of several hundreds of feet upward from the wellbore into the Lodgepole Limestone. Downward growth is often limited to only about 100 ft. It is therefore often uncertain whether the Three Forks formation, which is located about 80 ft below the Middle Bakken, is stimulated during the Bakken fracture treatment, and whether the Three Forks interval will actually contribute to the production response of a Bakken fracture treatment.
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Fracture half-length from the wellbore depends largely on treatment volume and lateral stage length, but has been observed to be between 200 and 500 ft.
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