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:
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.
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:
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 conjuction with field emission scanning electron microscopy (FESEM) techniques, will be applied to determine effects of rich gas exposure on rock properties.