Caroline M. Burberry
Date of this Version
Khatri, S. (2017). Controls on Fracture Network Characteristics of the Middle Member of the Bakken Formation, Elm Coulee Field, Williston Basin, USA. Master's Thesis. University of Nebraska-Lincoln.
The Bakken formation in the Elm Coulee Field of the Williston Basin consists of three members: 1) upper shale member, 2) middle silty dolostone member, and 3) lower shale member. The upper and lower members act as excellent source rocks and the main reservoir is the middle member with an average porosity of 3 to 9% and average permeability of 0.04md. The Bakken oil play in this area is a stratigraphic trap with a pinch-out to the southwest and a diagenetic facies change in the northeast. The main production is interpreted to come from matrix permeability in the field area. However, the first year production trends from the Elm Coulee Field show areas of anomalously high production.
This study used 3D seismic data from Crane Field, which is located in the southeastern part of the Elm Coulee Field, to investigate structures which might be responsible for the anomalous production trends at the Elm Coulee Field. We used post stack seismic conditioning and seismic attributes to amplify the structure of the basement. Further investigation revealed the presence of a pop-up structure in the central portion overlying a zone of basement deformation. This zone of deformation was interpreted to be composed of a left lateral wrench faulting system based on a model-driven approach. This study goes on further to map the structure and faults in 3 dimensions using a model driven approach, which reveals that the pop-up structure evolved from an obtuse angle left lateral step over system in the basement. In addition, the presence of this left lateral wrench fault network is interpreted to be related to a regional left lateral strike slip system – the Brockton Froid Fault Zone The fracture network characteristics in the middle member of the Bakken Formation are directly related to the local stresses generated by the interpreted left lateral wrench fault system in the study. There are two fracture sets- NE-SW and NW-SE. The structure and fracture network characteristics help explain the presence of regions of anomalously high EUR [CB1] values in the Elm Coulee Field. The regions of anomalously high EURs in the Elm Coulee Field may be regions where the middle member of the Bakken Formation has increased natural fracturing related to the local stresses induced by left-lateral oblique slip strike slip faults.
Advisor: Caroline Burberry