La Pointe, Paul¹, Jan Hermanson², Mike Dunleavy³ 
(1) Golder Associates Inc, Redmond, WA 
(2) Golder Associates AB, Stockholm, Sweden 
(3) Marathon Oil Company, Cody, WY

ABSTRACT: Development and Validation of a Fractured Reservoir Model for the Circle Ridge Field, Wind River Basin, WY

The Circle Ridge Field is part of a doubly-plunging, fault-breeched, fault-propagation fold with production from the Phosphoria, Tensleep and Amsden Formations. Despite more than 50 years of production, it is estimated that less than 20% of the OOIP has been recovered. Water cuts approach 97%. The Field is a potential candidate for gravity drainage via gas injection and de-watering, all of which are very sensitive to fracture connectivity and permeability. 
A 3D Discrete Fracture Netowrk (DFN) model was developed for the Tensleep and Phosphoria Formations from outcrop fracture studies, subsurface image log data, new cross sections and a 3D palinspastic reconstruction of the faulting and folding. It was found that during the initial folding of the Field, the rock did not bend continuously, but tended to break into panels of more or less constant dip. The hinges between panels became zones of greatly increased fracturing. These hinge zones formed both subhorizontal zones related to the upwarp and flattening of the rock, as well as dip-parallel radial hinge zones probably related to the contraction in the doubly plunging ends of the Field. Nitrogen injection and Bromide tracer tests carried out in both the hanging wall and footwall portions of the Field show breakthrough patterns consistent with the location of these hinge zones. 
The validated DFN model was then calibrated to transient wells tests and used to produce fracture permeability, porosity and sigma factor maps for the Tensleep and Phosphoria Formations. These results, together with the maps derived from the DFN model showing predicted fracture intensity and fracture orientations, are being used to plan well location and completion strategies, as well as to provide input for numerical simulation of secondary and tertiary recovery processes.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.