|Subtask 1.7 – Evaluation of Key Factors Affecting Successful Oil Production in the Bakken Formation, North Dakota – Phase 2
||Last Reviewed 11/15/2011
DE-FC26-08NT43291 – 01.7
This project expands on recently completed Bakken Formation investigations. The project goal is to quantitatively describe and understand the Bakken Formation in the Williston Basin by collecting and analyzing a wide range of data (including geomechanical and geochemical data) that impact well productivity and oil recovery.
Energy & Environmental Research Center (EERC), Grand Forks, ND 58202-9018
The Bakken Formation has emerged as an important source of oil and gas in the Williston Basin. Operators are realizing production from the middle Bakken and Three Forks formations which are sourced from the organic-rich shale units within the Bakken formation. Total organic carbon (TOC) within these shale units may be as high as 40%, with estimates of total hydrocarbon generation potential across the entire Bakken Formation ranging from 200 to 400 billion barrels. The Bakken play is noteworthy because a wide variety of approaches and technologies have been applied. Areas that were initially using single stage hydraulic fracturing have progressed to multi-stage approaches with as many as 40-stages within a 10,000 foot lateral well-bore; shallower depth areas are finding success with shorter laterals and fewer stages. Understanding the technologies, geology, and their interrelationships can help improve production for more challenged areas of the Bakken play. This project will implement a robust, systematic, scientific and engineering research effort to address challenges and unlock the vast resource potential of the Bakken Formation in the Williston Basin.
The EERC implemented and completed an initial four-pronged approach to evaluate and compare key attributes of the Bakken play in two North Dakota counties (Mountrail and Dunn) to enhance the understanding of key components critical for efficient resource development, and provide technical guidance to stakeholders regarding future production efforts. The research program focused on four topic areas: geology, geochemistry, geomechanics, and engineering. By comparing key geological and engineering attributes of the two counties, insights would be gained that could improve the productivity of Dunn County wells and/or provide guidance in exploring and exploiting new sub-plays.
The EERC is continuing the Bakken research as part of the ongoing EERC–U.S. Department of Energy (DOE) Joint Program on Research and Development for Fossil Energy-Related Resources Cooperative Agreement. EERC will conduct four major activities:
- Further development of the Bakken Decision Support System (BDSS) into a web-based geographic information system (GIS) analytical tool that includes a well file information database
- Development of geomechanical data sets to examine how macroscale stress and strain forces can affect the geomechanical properties of Bakken rocks and capitalize on the analytical methods developed earlier
- Continue geochemical evaluations of Bakken samples to evaluate potential relationships between geochemical and petrological properties of the Bakken and oil productivity
- Establish an industry advisory board for the project to meet with the EERC research team and provide guidance regarding the overall proposed research direction
It is anticipated that the activities will be coordinated with complementary, but separate, ongoing research efforts being conducted by the North Dakota Geological Survey (NDGS) and a consortium of petroleum production and service companies.
The results of this study will provide a clearer understanding of how to efficiently maximize production from the vast Bakken resources in the Williston Basin. The web-based BDSS will provide an interactive geographical database of wells that will allow the user to compare and analyze relevant information, including production and completion information, for all publically available data. A detailed comparison of the predictive utility of various collected data sets within different geological settings of the overall Bakken play will provide operators and stakeholders fresh insight regarding the roles that geologic structure and geomechanics play in the design and operation of a successful Bakken well in North Dakota.
The project has been completed. This study provides the technical characterizations that are necessary to improve knowledge, provide characterization, validate generalizations, and provide insight relative to hydrocarbon recovery in the Bakken and Three Forks Formations. Highlights from the study are as follows:
- Production in the Bakken and Three Forks Formations is undoubtedly benefiting from multistage hydraulic fracturing. Completion data collected from over 700 wells have clearly enumerated the engineering aspects of the play and suggest that there is room to further improve stimulation treatments with quality proppants and shorter treatment spacings along the lateral wellbore
- Water and oil saturation data coupled with water-cut data appear to be useful in identifying and evaluating productive and nonproductive areas along the eastern edge of the Bakken play. The correlation appears to be less applicable to production in the western portion of North Dakota, although more saturation data are necessary to fully evaluate this concept.
- The majority of identifiable porosity in thin-section samples was in partially healed microfractures or in residual hydrocarbon-filled accumulations.
- Pore structures in thin sections were observed to be highly disconnected while intragranular permeability was highly compacted and cemented. This supports the observation that productivity has historically been attributed to natural and/or induced fractures.
- Areas of North Dakota that have highly productive lithofacies within the middle Bakken tend to comprise geomechanically weaker rocks. Brittle rocks with high Young’s modulus tend to propagate longer fractures.
- Strength of middle Bakken rocks appears to be related to microstructure and facies. Structureless and weakly laminated samples tended to display higher peak strength, whereas strongly laminated or chaotically bedded samples were weaker.
- Geomechanical properties in the Three Forks vary widely because of the highly laminated nature of the rock. When not highly laminated, Three Forks rocks can have higher strengths than middle Bakken rocks.
- With respect to peak strength in the Bakken, sample data consistently fall in the 45,000-psi area, although the actual range was from 18,000 to 58,000 psi. Depth was not a significant factor affecting mechanical strength, although deviations from the norm appear to be tied to microstructure and/or facies.
- Examination of data from horizontal wells in which the wellbore treatments have targeted softer rocks suggests that proppant placement in the near wellbore requires critical attention to maintain a good conductivity of fluids from the formation.
Development of the BDSS has been completed and the web-based tool is now available on the EERC website[external site].
Data on production, drilling, completions, and stimulation activities from over 1000 North Dakota wells were added to the BDSS. The BDSS includes geological properties—such as thickness, depth, structure, and organic content—for the Bakken and Three Forks formations and incorporates analytical tools that allow a user to evaluate and interpret the information. Production data can be used to understand development history and identify "sweet spots" with the best oil production potential. The website also provides the latest newsfeeds about oil and gas activities in the region, and it includes educational materials about petroleum geology and oil and gas development along with supporting publications. Monthly well production data can be downloaded via the BDSS website through a subscription service with the North Dakota Department of Mineral Resources. Additional well completion data is planned for future release.
A paper entitled “Mechanical and Geochemical Assessment of Hydraulic Fracturing Proppants Exposed to CO2and H2S” based on earlier proppant laboratory work was presented at the Canadian Unconventional Resources and International Petroleum Conference.
Current Status (November 2011)
The project has been completed and the final report is available below under "Additional Information".
Project Start: May 1, 2010
Project End: October 31, 2011
DOE Contribution: $522,670
Performer Contribution: $0
NETL – John Terneus (John.Terneus@netl.doe.gov or 304-285-4254)
Energy & Environmental Research Center – James Sorensen (jsorensen@undeerc or 701-777-5181)
If you are unable to reach the above personnel, please contact the content manager.
Final Project Report [PDf-18.0 MB]
The Bakken Decision Support System (BDSS) [EERC website]