Continental: Bakken's giant scope underappreciated

By OGJ editors
HOUSTON, Feb. 16 -- The Bakken play in the Williston basin could become the world’s largest discovery in the last 30-40 years, a senior manager at Continental Resources Inc. said Feb. 16.

Ultimate recovery from the overall play is now estimated at 24 billion bbl of oil, compared with US reserves of nearly 20 billion bbl, he told the NAPE Expo in Houston.

The 24 billion bbl figure is five times the US Geological Survey’s 2008 estimate and compares with the 151 million bbl the survey put forth as recently as the mid-1990s, said Jack Stark, Continental senior vice-president, exploration (OGJ, Apr. 21, 2008, p. 37).

Close to 2 billion bbl of the 24 billion will come from the underlying Three Forks, which Continental helped prove to be a separate reservoir, Stark noted (OGJ Online, July 10, 2008).

The increases resulted as technology evolved over a 20-year span from marginal or uneconomic vertical wells to open hole stimulations in single, dual, and trilaterals to liners with staged fracs that are resulting in 50% rates of return today, Stark said. Industry also began drilling into the Middle Bakken dolomite, which is more porous and permeable than the upper and lower Bakken shale source rocks.

Production exceeds 400,000 b/d including Montana and North Dakota, Stark estimated, and smaller volumes are being produced in Canada. So recovery of that volume of oil will take years.

Industry has completed 2,750 horizontal wells since 2000. It is running 165 rigs that likely will drill 1,800 more wells in 2011, and production could reach as much as 1 million b/d within a few years, Stark said. The Bakken is continuous under nearly 15,000 sq miles.

The play’s numerous operators are drilling 18,000-21,000-ft wellbores that include 9,500-ft laterals and applying 18-30 frac stages/well, said Stark.

In general, higher initial potential producing rates indicate higher estimated ultimate recoveries, but the correlation isn’t 1:1 “due to overriding geological factors,” he said. Operators seem to reach a point of diminishing returns between 18 and 24 frac stages and are still seeking the ideal number of stages, he said.