Subtask 1.2 – Evaluation of Key Factors Affecting Successful Oil Production in the Bakken Formation, North Dakota
DE-FC26-08NT43291 – 01.2
The goal of this project is to quantitatively describe and understand the Bakken Formation in the Williston Basin by collecting and analyzing a wide range of parameters, including seismic and geochemical data, that impact well productivity/oil recovery.
Energy & Environmental Research Center, Grand Forks, ND 58202-9018
The Bakken Formation is rapidly emerging as an important source of oil in the Williston Basin. The formation typically consists of three members, with the upper and lower members being shales and the middle member being dolomitic siltstone and sandstone. Total organic carbon (TOC) within the shales may be as high as 40%, with estimates of total hydrocarbon generation across the entire Bakken Formation ranging from 200 to 400 billion barrels. While the formation is productive in numerous reservoirs throughout Montana and North Dakota, with the Elm Coulee Field in Montana and the Parshall area in North Dakota being the most prolific examples of Bakken success, many Bakken wells have yielded disappointing results. While variable productivity within a play is nothing unusual to the petroleum industry, the Bakken play is noteworthy because of the wide variety of approaches and technologies that have been applied with apparently inconsistent and all too often underachieving results. This project will implement a robust, systematic, scientific, and engineering research effort to overcome these challenges and unlock the vast resource potential of the Bakken Formation in the Williston Basin.
The EERC is conducting three major activities as part of this project: 1) comparison of well file data related to drilling, completion and stimulation field activities; 2) reprocessing of historical seismic surveys and examination of geomechanical properties; and 3) geochemical studies.
It is anticipated that this project will be coordinated with complementary, but separate, ongoing research efforts being conducted by the following:
- Colorado School of Mines, DE-FC26-08NT0005672 (Golden, Colorado)—In this study, the Colorado School of Mines will conduct an initial assessment of the hydrocarbon potential of the Bakken Shale in the Williston Basin and develop an integrated reservoir geomodel for this important formation. An improved understanding of Bakken Shale producibility is expected to reduce drilling risk and provide more accurate resource estimates so that operators can significantly improve recovery by optimizing drilling and completion strategies.
- University of North Dakota, DE-FC26-08NT0005643 (Grand Forks, North Dakota)—In this project, researchers will measure geomechanical properties and determine in situ stresses within the Bakken Formation in the North Dakota Williston Basin in order to provide basic data needed to improve the success rate of horizontal drilling and hydraulic fracturing operations in this region.
The results of this study will provide a clearer understanding of how to efficiently maximize the exploitation of the vast Bakken resources in the Williston Basin. A detailed comparison of the predictive utility of various collected data sets within different geological settings of the overall Bakken play will be compiled to provide operators and stakeholders with fresh insight regarding the roles that geologic structure and geomechanics play in the design and operation of a successful Bakken well in North Dakota.
- Data has been provided to the project by the operator of one of the fields of interest. This data has been sorted and categorized with regard to the relevant geological, drilling, and completion parameters to produce a system for determining the items that are most likely to contribute to successes in the Bakken.
- Analytical work on historical production and stimulation techniques from the area has been conducted.
- Much of the current work is focused on a static petrophysical model of the Dunn County study area. This model describes the geological framework that makes up the middle member of the Bakken in Dunn County, North Dakota, and will provide the necessary background to evaluate completion and stimulation strategies to determine the correlation to “success”.
- The North Dakota Geological Survey has completed the interpretation of a seismic survey conducted in the 1980s proximal to the area of interest. The results indicate that there appear to be significant structural features that may positively affect oil production in the Parshall area of North Dakota.
- The North Dakota Geological Survey has selected samples from some of their Bakken core holdings to be used for geochemistry/mineralogy evaluations and has made them available to EERC. The EERC has used those samples to conduct a series of laboratory experiments to generate data on the mineralogical, geochemical, and geomechanical properties of the middle member of the Bakken Formation.
Current Status (May 2010)
This project consists of four tasks that analyze and describe a wide range of well data parameters in the Bakken. A collaborative relationship with a field operator currently producing oil from the Bakken has been established. This relationship has provided the project with a wide variety of data on well drilling, completion, stimulation, and production for Bakken wells in western North Dakota. The North Dakota Department of Mineral Resources (NDDMR) Oil and Gas Division has also provided field and production data.
Data was evaluated from two “type” areas of Bakken exploration and production within North Dakota so that the data could be compared, contrasted, and finally compiled into a geographic information system (GIS) database that is designed to support efficient interpretation of the data, enabling users to make comparisons between wells and/or areas of interest in a more effective manner.
EERC has 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, in an effort to better understand the key components that are critical to the efficient development of the Bakken resource, and provide technically-based guidance to stakeholders regarding future exploitation efforts. The research program focused on four topic areas: geology, geochemistry, geomechanics, and engineering. The premise of the approach for this project was that by comparing key geological and engineering attributes of the two counties, insight would be gained that could improve the productivity of Dunn County wells and/or provide guidance in exploring and exploiting new subplays. The preliminary conclusions derived from these research activities include the following:
- Horizontal drilling of wells in the middle member of the Bakken, coupled with multistage fracturing, has outperformed all previously completed Bakken wells in North Dakota.
- Geologic influences appear to be dictating the hydrocarbon production rates for given areas within North Dakota that have similar completion practices.
- Production in Mountrail County greatly exceeds production in Dunn County and has significantly higher variability, with the higher production appearing to be linked to greater total organic carbon (TOC) and shale thicknesses which, in turn, have the potential to create greater pore pressure-related fracturing.
- The presence of structural elements, although different in both Dunn and Mountrail Counties, is consistent with areas of higher production. The major contribution of these structural elements may not be as much their ability to serve as traps as their influence on the creation of both natural and operationally induced fracture systems.
- Higher production within Dunn County is associated with the Heart River Fault, which coincides with an area of high original TOC content.
- Multistage hydraulic fracturing appears to be outperforming fewer-stage hydraulic fracturing when compared in proximity.
- Multilateral wells do not appear to gain significant production advantage over single lateral wells, despite lower per-foot drilling costs.
- Lithology could potentially play a role in oil mobility, an improved understanding of which may serve to guide the design of stimulation practices and provide insight regarding future exploration efforts.
- Multistage fracture completions appear to be outperforming lesser-stage completions when compared in proximity. It appears that at least in some areas, multistage hydraulic fracturing should improve the likelihood of further oil production.
- Various multilateral wells do not appear to gain significant production advantage despite lower per-foot drilling costs.
- Well azimuth, although relevant to the direction of principal stress, does not appear to be a factor regarding oil production.
- Longer lateral wells appear to produce more oil when compared to shorter lateral wells in proximity.
More information on the results of this research may be found in the final report, which presents and discusses the activities conducted over the course of the research program (see Additional Information below).
The results of these research activities have provided a greater understanding of the natural fracture network system of the Bakken Formation, which is critical to improving production performance; however, a more detailed geologic study is required to further support the preliminary conclusions. Therefore, EERC has recently been awarded a new award to continue with a second phase of work to expand on recently completed Bakken investigations. Second-phase work will include:
- The development and expansion of a geographic information system (GIS)-based, Webdriven Bakken decision support system (BDSS). This database analysis tool will be populated with well file information and the results of UNDEERC research activities to enable investigation of various engineering and geologic parameters for the purpose of improving oil production.
- The acquisition of additional core samples for the purpose of conducting geomechanical studies of middle Bakken cores relative to fracturing. The results will provide insight regarding the development and application of effective well completion and stimulation strategies.
- The performance of geochemical studies specific to fluids and rock properties that influence the creation of pore pressure related to natural fractures and other geochemical variables that impact production.
The possible relationship between the Bakken and the Three Forks Formations with respect to oil production, and what the nature of that relationship might be, will also be explored in the upcoming research effort derived from the newly awarded financial agreement.
Project Start: October 1, 2008
Project End: March 31, 2010
DOE Contribution: $496,340
Performer Contribution: $0
NETL – John Terneus (John.Terneus@netl.doe.gov or 304-285-4254)
Energy & Environmental Research Center – James Sorensen (firstname.lastname@example.org or 701-777-5181)
Final Project Report [PDF-6.81MB]
Technology Status Assessment [PDF-38KB]