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Subtask 3.1 - Bakken Rich Gas Enhanced Oil Recovery
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The project goal is to determine the feasibility of reinjecting captured rich gas into a Bakken reservoir to enhance oil recovery. Specific research objectives related to this goal are as follows:

  • Determine the ability of various rich gas mixtures to mobilize oil in Bakken petroleum system reservoir rocks and shales.
  • Determine the changes in gas and fluid compositions over time in both the tight oil reservoir and surface infrastructure environments, and assess how those changes affect reservoir and process facility performance.
  • Optimize future commercial-scale tight oil EOR design and operations through the use of iterative modeling of surface infrastructure and reservoir performance using data generated by the field- and laboratory-based activities.
  • Establish the effectiveness of selected monitoring techniques as a means of reservoir surveillance and injection conformance monitoring in the Bakken petroleum system.
  • Determine the sorptive capacity of Bakken shales for rich gas components and the effects of sorption in the shales on gas utilization rates in samples representing areas of low, medium, and high thermal maturity.

Energy & Environmental Research Center (EERC) – University of North Dakota, Grand Forks, ND 58202-9018


North Dakota is well-situated to demonstrate the implementation of rich gas-based EOR for tight oil formations. Although flaring associated with Bakken oil production has been reduced significantly in recent years, as of March 2019, approximately 19 percent of the rich gas produced in association with Bakken oil production continues to be flared. The associated gas from Bakken oil production operations is typically a mixture dominated by methane with a significant amount of ethane and other hydrocarbons. The results of recent preliminary laboratory investigations at the EERC suggest that pure ethane and mixtures of methane and ethane may be used to mobilize oil from Bakken rocks and thus could be viable injection fluids for EOR operations. The EERC is working with Liberty Resources (LR) to design and conduct an EOR pilot test using rich gas. The project is a joint initiative between the EERC, North Dakota Industrial Commission (NDIC) through the Bakken Production Optimization Program (BPOP), LR, and the U.S. Department of Energy (DOE). Project activities will be coordinated, managed, and evaluated by the EERC. LR will be responsible for providing the wells and rich gas necessary for the test and will operate the injection, production, and monitoring activities.


Estimates for original oil in place  (OOIP) in the Bakken petroleum system range from 300 billion to 900 billion  barrels. Current resource recovery factors for Bakken wells are typically 10% or  less. If this trend continues, billions of barrels of oil will be left stranded  in the reservoir. Analysis conducted by the North Dakota Pipeline Authority  indicates that the current gas-gathering infrastructure in North Dakota  (including pipelines, compressor stations, and gas processing facilities) is  insufficient to accommodate all of the associated gas that is produced as part  of oil production from the Bakken. The geographically isolated location of the  Bakken oil play relative to large natural gas markets, combined with continued  low natural gas prices, has made it economically challenging for industry to invest  capital in expanding gas-gathering infrastructure in North Dakota. Therefore,  management of rich gas production from the Bakken is still a high priority for  government and industry stakeholders in North Dakota. This project will  demonstrate the viability of utilizing rich gas for EOR in the Bakken, which  will result in reduced flaring and an improvement in recovery factors. The  primary impacts of this project will be reductions in greenhouse gas emissions  associated with Bakken activities, and potentially the production of billions  of barrels of incremental oil.

Accomplishments (most recent listed first)

The project was initiated on September 1, 2017. A hearing of the NDIC Oil and Gas Division was held September 21, 2017, for the purpose of LR providing testimony for its application to obtain the necessary permits for the pilot injection test. Permits for injection activities in six wells have been granted to LR. LR has purchased a compression unit that is necessary for the operation of the pilot injection test. Specific accomplishments include the following:


  • Large-scale pilot tests were conducted in two wells in the Stomping Horse complex beginning on November 20, 2018, and continuing through May 2019.
  • A gas tracer was introduced to the injection well on November 21, 2018. A second tracer study — which included the injection of gas, oil, and water tracers — was initiated on January 27, 2019. Multiple sampling and analysis events for multiple wells were conducted to look for tracers as a means of identifying fast flow pathways for gas, oil, and water between the injector and various offset wells.
  • The maximum injection rate for the large-scale test is 2.0 MMscfd. For each injection cycle the pilot testing plan called for injection into each well  until one of three criteria are achieved: 1) total injection of 60 MMscf, 2) 30 days of injection, or 3) clear evidence of substantial breakthrough at an offset well.
  • As of May 1, 2019, over 130 MMscf of rich gas had been injected into four wells during six different injection periods.
  • Key observations from the pilot testing so far include:
    • The ability to effectively inject rich gas into Bakken and Three Forks reservoirs has been demonstrated.
    • Injectivity is readily established and has not been a constraint on operations.
    • Reservoir surveillance and monitoring demonstrate the injected gas can be controlled and has been contained within the drill spacing unit.
    • Pressure buildup is occurring and is showing a positive trend towards achieving minimum miscibility pressure (MMP).
    • The conceptual approach of using laboratory-based testing to inform modeling, which in turn guides injection scheme design and operations, has been effective.
  • Baseline reservoir characterization data collection has been completed for all wells within the Leon-Gohrick drill spacing units in the Stomping Horse complex. Parameters measured included analysis of produced oil, water, and gas as well as bottomhole pressure and temperature for wells permitted for injection and offset wells.
  • MMP studies have been conducted to determine the MMP of rich gas components and different rich gas mixtures in oil from the Stomping Horse complex. MMP data for methane, ethane, propane, and different relevant mixtures have shown that “richer” gas mixtures will result in lower MMP values (e.g. methane MMP > ethane MMP > propane MMP).
  • Rock extraction studies of the rich gas components on Bakken shale and nonshale samples have shown that when it comes to mobilizing hydrocarbons from Bakken rocks, methane is the least effective, propane is the most effective, and ethane has an intermediate effect. The rock extraction studies also showed that propane is effective at all pressures, ethane is effective at higher pressures, and methane is the least effective at any pressure.
  • Modeling-based studies of the potential effects of rich gas EOR operations on the surface infrastructure of the Stomping Horse complex predict that rich gas EOR will not adversely affect surface facility operations.
  • Reservoir modeling of selected injection/production scenarios predicts incremental oil recovery may exceed 25%.
  • Small-scale injectivity tests were conducted in two wells in the Stomping Horse complex during the summer of 2018. A total of 24.6 MMscf of rich gas was injected during three tests conducted in two wells between July 17 and September 10, 2018. The maximum injection rate achieved was 1.14 MMscfd. Downhole pressure and temperature data were collected before, during, and after the injection tests from six wells in the drill spacing wells, including the injection wells and the immediately adjacent offset wells. Data obtained from the small-scale injection tests were used to refine the design of the subsequent larger pilot tests.
Current Status

Monitoring activities are currently ongoing and are expected to continue into the summer of 2019. The performance of the pilot tests are being assessed using production, pressure, temperature, and operational data provided by Liberty Resources. Analytical approaches being used include production rate transient analysis, pressure transient analysis, decline curve analysis, material balance analysis, and breakthrough analysis. Shale permeability and shale sorption studies using a flow-through testing approach are ongoing. A Rubotherm Series IsoSORP SA magnetic balance for multigram determination of isotherms under reservoir temperatures and pressures is being used to quantitatively measure the sorptive capacity of Bakken shales for methane, ethane, propane, and relevant rich gas mixtures under relevant pressure and temperature conditions. Laboratory testing that includes nuclear magnetic resonance (NMR) analysis, clay separation, and separation of oil-water mixtures in core plugs is scheduled to be conducted in the summer of 2019. The NMR, in conjunction with field emission scanning electron microscopy (FESEM) techniques, will be applied to determine effects of rich gas exposure on rock properties.

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DOE Contribution


Performer Contribution


Contact Information

NETL – Gary Covatch ( or 304-285-4589)
EERC – James Sorensen ( or 701-777-5287)