Oil & Gas, Research

Overpressured Inyan Kara Formation

A recently completed State Energy Research Center (SERC) project at the EERC has addressed the changing operations in the oil and gas industry, with the goal of determining if water extraction from the Inyan Kara (IK) Formation is technically viable for managing subsurface pressure during the drilling and construction of nearby Bakken wells.

North Dakota oil and gas operators developing the Bakken and Three Forks Formations (Bakken operators) are experiencing an increase in pore pressure when drilling through the IK Formation. To mitigate this challenge, Bakken operators have been modifying wellbore designs by installing an additional casing string (Dakota string), which increases hole size and surface casing size, to manage the overpressured formation while drilling in the target formation. Each Dakota string costs around $500,000, meaning a solution could save Bakken operators millions in additional costs in a short period of time. Many industry experts and Bakken operators agree there is a need for subsurface pressure management, which includes produced water management, to support the continued oil and gas development of the Williston Basin.

Geologic reservoir modeling and simulation techniques were used to evaluate the feasibility of using water extraction to reduce local IK Formation pressure enough to eliminate the need for the Dakota string. Existing geologic models of the IK Formation were modified to enable rapid assessment of various operation scenarios and conditions, such as the placement of the extractor well and extraction rates. Twenty-one simulations were conducted throughout this project’s duration, all generating results illustrating conditions where water extraction is a possible solution to mitigate overpressurization of the IK Formation.  

One Inyan Kara extraction well can potentially suppress the pore pressure enough to eliminate the need for the additional casing string for all the wells in the affected area. Once completed, the extraction well could then be repurposed as a saltwater disposal well to aid in the long-term management of produced water from a multiwell site. In addition, the water extracted from the formation could potentially be beneficially used for mineral extraction or source water for hydraulic fracturing of wells or be hauled and disposed of at an alternate saltwater disposal location. This early-phase research also identified critical research questions to advance the concept, improve feasibility, and provide potential avenues for continued research.

Next steps to advance this research include a detailed techno-economic assessment and, ideally, a partnership with a Bakken operator to perform a pilot demonstration field test. Another option could include gathering additional Dakota Group data such as well logs, reservoir pressures, and core data. This information could be used to develop a basin-wide geologic model to be utilized by Bakken operators and industry experts.

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