Title: Sweet Spot Localization of Production From Fractured “Shales” in Rocky Mountain Basins
Speakers: Richard Inden, LSSI, Ltd. Denver, CO, and William Pearson, Pearson Technologies, Inc, Golden, CO
Date: November 20, 2009
Publication: The Outcrop, November 2009, p. 29
Hydrocarbon production from shales is dependent upon source quality, maturation, fracturability, tectonic fracturing, and in many cases, the amount of structural dip. Definition of which interval(s) might be good candidates as shale gas or oil targets is determined by laboratory analyses, but where to drill and recover the most hydrocarbons is reliant upon geologic history, mapping, the understanding the fracture system affecting the intervals of interest, as well as drilling and completion technology.
To date, drilling in the Rockies suggests that the potential for finding a resource
type shale play such as the Barnett, Haynesville, or Marcellus look-alike is elusive.
It appears from existing recently discovered and historic production that fractured shale production in the Rocky Mountain area bears a direct relationship to either major wrench faults, or the intersections of more localized fault systems, and as such, falls more in the realm of conventional traps.
Interpretations of filtered aeromagnetic data illustrate the faulting, and thus potential for extensive fracturing in fields that produce from numerous Cretaceous shales, and the Bakken Shale (Dev.) of the Williston Basin.
Bakken production in the Williston Basin is tied to certain faults, many of which were rejuvenated through time. The thick dolomite of the Bakken middle member in Richland Co., Montana that sets up the 100 MMB Elm Coulee Field follows a set of NW oriented regional faults. Likewise numerous rapid changes in isopach trends and thickness occur along major regional faults. Other excellent production from the Bakken, such as Parshall Field and Sanish Fields on the east side of the basin, occurs along a major NE oriented fault system.
The Niobrara at Puerto Chiquito (east flank of the San Juan Basin) has produced over 25 MMBO from fractured shales along a N-S system of faults; the field appears to be limited in extent by NE oriented shear zones. Verde Field, has produced 7.5 MMBO, and displays similar relationships. Numerous other fractured shale fields in the San Juan Basin, the Paradox Basin, and other areas also appear to a large degree to be dependent upon, and related to, fault/fracture systems identifiable on high-resolution aeromagnetic data.