By OGJ editors
HOUSTON, May 22 -- A well on the Williston basin Nesson anticline in Dunn County, ND, was completed flowing oil, gas, and water from the Devonian Three Forks/Sanish formation.
Only 52 wells have produced from little-known Three Forks/Sanish in the US part of the basin. Continental Resources Inc., Enid, Okla., and other operators are attempting such completions to determine whether the Three Forks/Sanish formation may be a separate reservoir not drained by a horizontal completion in the more heavily drilled Middle Bakken zone above it.
Another consideration is whether a horizontal well bore in the Three Forks/Sanish might recover oil by gravity drainage from the Middle Bakken, necessitating fewer overall wells.
The US Geological Survey (USGS) included the Three Forks/Sanish interval in its April 2008 assessment as part of the "Bakken composite continuous fractured reservoir." The USGS used estimated ultimate recoveries (EUR) from the basin's Bakken/Sanish completions to estimate the undiscovered resource in the Nesson-Little Knife Structural Assessment Unit (see map, OGJ, Apr. 21, 2008, p. 37).
Vertical wells perforated in the Bakken and Sanish had high EUR relative to vertical wells that only produced from the Bakken, so matrix contribution from the porous Sanish is extremely favorable, said Richard Pollastro, USGS geologist and Bakken formation task leader.
Sanish wells "certainly had a resulting effect on the final mean volume of 909 million bbl assessed" for the Nesson-Little Knife unit, Pollastro said.
Continental Resources reported a 7-day average flow of 618 b/d of oil, 543 Mcfd of gas, and 662 b/d of load water with 1,352 psi on a 24/64-in. choke at the Bice 1-29H well, in 29 and 32-146n-95w, Dunn County, ND.
The distance between a horizontal well bore in the Middle Bakken, if drilled, and the horizontal lateral in the Three Forks/Sanish in the Bice 1-29H is 60 ft, Continental Resources said.
Almost all of the Three Forks/Sanish completions are in Antelope field in McKenzie County, the USGS said
The Bice well is in an undrilled spacing unit. To learn whether the two formations are in communication, Continental would need stabilized production from a Three Forks/Sanish lateral followed by drilling a Middle Bakken lateral and running a frac job. Some models show that a frac will not penetrate the Middle Bakken.