The goal of this project is to inject a blend of rich hydrocarbon gas and CO₂ into an oil reservoir to reduce molecular weight selectivity, lower minimum miscibility pressure and the viscosity of the oil and improve gas solubility resulting in an overall improvement in Enhanced Oil Recovery (EOR) performance.

University of North Dakota Energy and Environmental Research Center (UNDEERC) - Grand Forks, ND 58202

Lab and field studies show that over time the injection of CO₂ into an oil reservoir will selectively mobilize lower-molecular-weight hydrocarbons, leaving higher-molecular-weight (HMW) hydrocarbons behind. The ultimate goal of the project is to determine the effect of injecting blended CO2 and rich gas into an active CO₂ enhanced oil recovery (EOR) field to improve production performance.

This project aims to inject a blend of rich hydrocarbon gas and CO₂ into an oil reservoir to reduce molecular weight selectivity, lower minimum miscibility pressure and the viscosity of the oil and improve gas solubility. This would result in an overall improvement in Enhanced Oil Recovery (EOR) performance. The EOR performance will be tested by conducting a field validation test of blended CO₂–rich gas injection and tracking changes to molecular weight selectivity and oil viscosity before, during, and after the test injection. The success criteria are a measured increase in High Molecular Weight (HMW) hydrocarbons produced from the reservoir and increased oil production during the field validation test period.

The location of the injection test will be in the Bell Creek oil field in Montana. Laboratory and simulation experiments, based on the composition of available rich gas supply, will be used to determine the quantity and blend(s) of rich gas components that will be used in the field validation test. An injection scheme will be designed incorporating preexisting wellbores installed in the field for the currently operated CO₂ EOR flood. A field validation test will be conducted to inject blended CO₂ and rich gas into a single injection well and produce oil from four nearby wells.

The field validation test will provide a unique field-based data set on co-injected CO₂–rich gas EOR, paving the way for larger-scale tests and deployment. Positive validation test results would support the development of infrastructure and a market for stranded rich gas. Results would be extrapolated to develop business cases for other potential target fields. Because of the ability to leverage existing oilfield infrastructure, commercial implementation of rich gas EOR could occur quickly.

• Verified the Denbury injection site/well
• Core and fluid laboratory evaluations of Bell Creek samples are progressing.
• The injection pattern and site were selected.
• The geologic model for the pilot pattern has been updated, and EOS modeling based on the injection gas composition is complete.
• Data collection for both Gulf Coast and Rock Mountain regions has been initiated.
• The initial geostatic models were completed in February 2022. Different huff ‘n’ puff scenarios were simulated to evaluate the EOR performance using CO₂, rich gas, and their mixtures. Simulations showed that adding rich gas to the injection stream could yield better EOR results than using pure CO₂.
• A source of rich gas has been secured for the project.

Work continues on the design of an injection scheme and installation of equipment necessary to carry out a blended CO₂–rich gas injection test optimized for the Bell Creek Field. The project team confirmed the composition, delivery, and storage of the rich gas product and is currently working on the final design of the injection/monitoring program. The preliminary piping and instrumentation diagrams (P&IDs) were finalized, with the final authorization for expenditure for purchase and installation of new equipment and equipment tie-ins for the project in progress. Quotes for storage vessels, pumps, and meters were requested and received. Initial tie-in points for rich gas product and CO₂ volumes within existing facilities were determined. Installation plans for the equipment required for the huff ‘n’ puff project at the Bell Creek well were reviewed and confirmed. Moving forward, the team will continue to coordinate to finalize the provisional injection/monitoring validation test design and options based on the results of simulations of the selected rich gas injection patterns and rich gas composition.

.Work also continues on the project laboratory studies and modeling. Laboratory analysis is being conducted on core samples from the Bell Creek Field to confirm performance with injection of rich gas–CO₂ blends and inform the design of the injection program. Concurrently, laboratory analysis is being conducted on core samples from other fields currently undergoing CO₂ EOR. Results of these analyses will support evaluations of implementing rich gas injection in existing or planned CO₂ EOR projects.

$7,973,881

$2,000,000

NETL - Robert Noll (robert.nolll@netl.doe.gov or 412-386-7597)
UNDEERC – John Hamling (jhamling@undeerc.org or 701-777-5472)