The US Department of Energy (DOE) has awarded an agreement to the University of North Dakota Energy and Environmental Research Center (UNDEERC) to extend a study that will enhance the understanding of factors affecting oil production from the Bakken and Three Forks-Sanish formations within the Williston Basin.
North Dakota is the fourth-largest oil producer in the United States, exceeded only by Texas, Alaska, and California. In December 2009, North Dakota produced 242,000 barrels of oil per day, more than doubling the 115 thousand barrels produced in December 2006. Estimated oil production for 2011 ranges from 300 to 400 thousand barrels per day and is forecast to remain at that level for 10 to 15 years. These forecasts are based on the recent production success of the Bakken and Three Forks-Sanish formation plays.
During the first phase of the research project, UNDEERC evaluated and compared key Bakken play geologic, geochemical, geomechanical, and engineering attributes in two North Dakota counties, Mountrail and Dunn. Comparison of these key attributes provided several preliminary insights to improve productivity and guide exploration and production of new subplays:
Horizontal drilling of wells in the middle Bakken member, coupled with multistage fracturing, has outperformed all previously completed North Dakota Bakken Shale wells.
Multilateral wells do not gain significant production advantage over single lateral wells, despite lower per-foot drilling costs.
Well azimuth, although relevant to the direction of principal stress, does not appear to be a factor affecting oil production.
Higher production can be linked to areas with higher total organic carbon (TOC) content.
Areas containing a higher degree of naturally occurring fractures are consistent with areas of higher oil production.
Rock type does play an important role in oil mobility, especially in the middle Bakken member.
The Bakken formation is composed of three members (upper shale, middle siltstone, and lower shale), and primary production occurs in the middle siltstone member. The Three Forks-Sanish formation is made up of sandstone and porous rock directly below the lower Bakken shale. Geologists are uncertain whether the Three Forks-Sanish is a separate oil-producing formation or acts as a “catch pan” for oil flowing from the overlying Bakken formation.
During phase two, UNDEERC plans to expand its knowledge database in order to better understand oil production mechanisms within the Bakken and Three Forks-Sanish formations. Using funds under a cooperative agreement with the DOE Office of Fossil Energy’s National Energy Technology Laboratory (NETL), UNDEERC plans to develop a geographic information system web-based Bakken decision support system to enable investigation of various engineering and geologic parameters to improve oil production.
Additionally, geomechanical studies will be conducted on middle Bakken cores to better understand fracturing mechanisms. The results will provide insight regarding the development and application of effective well completion and stimulation strategies. Fluid and rock interrelationships, especially between pore pressure and natural fracturing, will be evaluated for their correlation to oil production.
UNDEERC efforts will be coordinated with other NETL-sponsored Bakken research projects at the Colorado School of Mines and the University of North Dakota Department of Geology and Geological Engineering. These combined studies will provide a basis for increased understanding of the key components critical to the efficient development of the Bakken and Three Forks-Sanish formations resources, and provide technical guidance to stakeholders regarding future exploration efforts.