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Subtask 3.1 - Bakken Rich Gas Enhanced Oil Recovery
Project Number
DE-FE0024233
Last Reviewed Dated
Goal

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 enhanced oil recovery (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.
Performer

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

Background

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 January 2017, approximately 12 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 theEERC 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.

 

Impact

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:

  • 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.
  • Minimum miscibility pressure (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.
  • Large-scale pilot tests were initated in a well in the Stomping Horse complex on November 20, 2018. A tracer was introduced to the injection well on November 21, 2018. Multiple sampling events from multiple wells were conducted in the Stomping Horse complex as a means of identifying fast flow pathways between the injector and various offset wells. The maximum injection rate for the large-scale test is 2.0 MMscfd. Injection into the first well is expected to continue 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.
Current Status

 A pilot injection test and associated monitoring activities are currently  ongoing and are expected to continue into the summer of 2019. Shale  permeability and shale sorption studies using a flow-through testing approach  have been initiated and are ongoing. A Rubotherm Series IsoSORP SA magnetic  balance for multigram determination of isotherms under reservoir temperatures  and pressures has been ordered and is expected to be delivered to the EERC in  December 2018. The magnetic balance will be 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. An Avanti  JXN-30 centrifuge to support nuclear magnetic resonance (NMR) analysis, clay  separation, and separation of oil-water mixtures in core plugs has been ordered  and is expected to be delivered in December 2018. The NMR, in conjuction with  field emission scanning electron microscopy (FESEM) techniques, will be applied  to determine effects of gas exposure on rock properties.

Project Start
Project End
DOE Contribution

$3,000,000

Performer Contribution

$1,565,891

Contact Information

NETL – Gary Covatch (gary.covatch@netl.doe.gov or 304-285-4589)
EERC – James Sorensen (jsorensen@undeerc.org or 701-777-5287)