Tight Oil Reservoirs Williston Basin

Williston Basin operators over the past few years have been targeting the Bakken section especially in the North Dakota area of the play. Numerous cores and well performance data have been collected and analyzed in the area. However, recent activity has been pushing the Bakken Play into northern Montana where the formation is not as well characterized. Also, operators have begun drilling pilot wells and horizontals evaluating the evolving Three Forks Play. There are also other horizontal candidates in the basin that operators are taking a look at, such as the Red River, Interlake, lower Lodgepole, Mission Canyon, Tyler, and others. Consequently, this study will focus on the Bakken Play extension, Three Forks, and all other potential liquids-rich, reservoirs that are horizontal candidates (Figure 1).

The Integrated Reservoir Solutions Division of Core Laboratories is proposing to interested companies participation in a multi-company, geo-engineering, regional study of the prospective formations in the Williston Basin. This project consists of the characterization and evaluation of numerous conventional cores and rotary sidewall cores taken from multiple wells targeting the zones of interest.

Project Objectives

The primary objective of this project is to provide operators with measured geological, petrophysical, geomechanical, geochemical, and production properties of the prospective formations in order to improve their formation evaluation and to optimize stimulation and production. Our work suggests that understanding the similarities and differences in the section on a regional basis is the key to successful exploration and exploitation. The resultant database will be an invaluable tool to operators in evaluating, comparing, and designing completion and stimulation methods. Specifically, the project objectives are as follows:

• Geologically characterize the cored intervals in terms of depositional facies, environment of deposition, and rock types.
• Characterize and classify the stratigraphic sections in terms of lithology, mineralogy, clay content, clay types, and pore structure including macro- and micro-fractures.
• Measure the various petrophysical properties such as porosity, permeability, grain density, and saturations (i.e. water saturation, gas saturation, oil saturation, hydrocarbon filled porosity and bound water).
• Measure and characterize the organic content of the source-rock mudstones in terms of total organic content (TOC), Rock Eval pyrolysis, and vitrinite reflectance.
• Measure the key geomechanical properties that are required for optimizing fracture designs and/or horizontal wells such as Young's Modulus, Poisson's Ratio, Bulk Modulus, horizontal stress, and proppant embedment.
• Determine rock-fluid compatibility and fracture conductivity of proppant and fluid- carrier systems in support of hydraulic fracture stimulation.
• Core-log calibration of open-hole logs for the development of petrophysical models to determine potential "pay" zones for stimulation.
• Integrate the core data with well logs, fracture stimulation techniques, and production test results to aid companies in their evaluation and exploitation of the reservoirs.
• Provide a regional assessment of the various reservoir attributes to aid in exploration and exploitation.
• Develop relationships from the database to aid in evaluating and comparing the various rock properties.
• Provide operators with a searchable database for reservoir properties that can be used as analogs to aid in the appraisal and exploitation of new areas as the play expands.