Sweet Spot Localization of Production from Fractured Shales

Pearson, Willaim¹ and Richard Inden^2
1Pearson Technologies Incorporated, Denver, CO
²LSSI, Ltd, Denver, CO

     Definition of intervals that qualify as good shale gas or oil targets are determined by laboratory analyses, but where to drill the high-graded candidates and recover economic hydrocarbons relies more upon mapping, and on an understanding of fracture distribution. It appears from existing production that Rocky Mountain fractured shale production bears a relationship to either major wrench faults, or the intersections of these and more localized fault systems, and thus zones of more intense fracturing.
     Interpretations of filtered aeromagnetic data readily illustrate faulting, and thus the potential for extensive fracturing in fields that produce from Cretaceous shales, the Williston basin Bakken Shale, and Pennsylvanian shales of the Paradox basin, where prolific production from the Cane Creek Shale lies along a prominent N-NE oriented fault.
     The Puerto Chiquito Field in the San Juan Basin has produced over 25 MMBO from the Niobrara Formation along a N-S system of faults. The field appears to be limited in extent by NE oriented shear zones. Numerous other fractured shale fields in the San Juan, Powder River Basin (Mowry Shale), and other basins bear similar relationships.
     Bakken production in the Williston Basin is associated with rejuvenated regional wrench faults. 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 EOG's Parshall Field on the east side of the basin, occurs along a major NE oriented fault system.

AAPG Search and Discovery Article #90071 © 2007 AAPG Rocky Mountain Meeting, Snowbird, Utah