Since 2007, the Bakken Formation has been one of the most important oil-producing regions in the United States. Advances in horizontal drilling and hydraulic fracturing unlocked an enormous resource that conventional technologies could not economically reach, transforming North Dakota’s fading oil industry and generating more than $35 billion in tax revenue along the way. However, oil production will start to decline if new technologies aren’t introduced.
Unlike conventional reservoirs, where the natural porosity and permeability of the rock allow oil to move relatively easily through it, the rock layer in the Bakken’s unconventional reservoir is extremely tight. Oil is trapped in tiny pore spaces with very little room to move. Hydraulic fracturing creates pathways through the rock to allow more oil to flow to the well, but it doesn’t come close to recovering all of the oil in the rock. As production continues, the oil left behind becomes increasingly difficult to recover.
Even after nearly 20 years of production, the Bakken still contains hundreds of billions of barrels of oil trapped in the rock. The challenge is finding a practical way to mobilize that oil and move it toward existing production wells. Estimates indicate that a technique called enhanced oil recovery (EOR) could produce an additional 5–7 billion barrels of oil.
EOR works by changing the conditions within the reservoir to help that oil move. One approach is injecting certain types of gas at high pressure. Under the right conditions, the gas mixes with the oil, causing it to swell and become less viscous—in other words, making it easier to move. Think of squeezing a sponge soaked with liquid: pressure forces the liquid out, but some remains trapped in the sponge. Now imagine introducing something that loosens that liquid and maintains the pressure. In the reservoir, maintaining pressure while changing the properties of the oil helps push more of that resource toward production wells.
Cracking the Code in the Bakken
Researchers at the Energy & Environmental Research Center (EERC) have found CO₂ particularly promising for EOR because it can mix with Bakken crude oil at reservoir pressures and has a long history of use in conventional EOR. But widespread CO₂ EOR in the Bakken would require a large supply of relatively pure CO₂, along with significant investment in pipelines and other infrastructure. Securing a large supply of relatively pure CO2 and developing the infrastructure to get it to Bakken oil fields could take several years.
That’s where produced gas comes in.
Researchers are exploring whether the gas already produced alongside Bakken oil could be used to recover more of that oil through Crack the Code 2.0, a collaborative effort focused on developing and validating technologies to improve recovery from the Bakken. The idea is completely innovative yet surprisingly straightforward: use the gas we already have until long-term supplies of CO2 are readily available.
Oil production from the Bakken also produces significant volumes of natural gas. Rather than sending all of that produced gas to market, some could be redirected into the reservoir to recover additional oil. Produced gas, a mixture of hydrocarbon gases including methane, ethane, and propane, is a promising candidate for EOR because its mixture has been shown to behave very similarly to CO2 in its ability to swell Bakken oil and reduce its viscosity.
Moving from Lab to Field Demonstration
Laboratory testing has shown that, under the right conditions, produced gas can mix with Bakken crude, swell the oil, and make it easier to move through the rock. Tests using Bakken rock samples have also recovered similar amounts of oil from produced gas and CO₂ injection
EERC researchers are combining laboratory experiments and reservoir modeling to understand how produced gas behaves underground and how it can be used to recover more oil. They then compare those predictions with actual production data. Early field tests, though small and relatively short in duration, are encouraging. Oil production has increased approximately 24% in certain injection wells. Over several years, projects have recovered an estimated 4000–5000 or more additional barrels of oil per drilling area.
These projects provide more than additional oil—they show that produced gas injection can work in the Bakken and provide valuable information for planning future CO₂ EOR projects. Researchers can use field observations to understand how the reservoir responds to different injection strategies, how effectively injected gas contacts the formation, and how pressure is maintained. That information can improve reservoir models and production forecasts.
Creating a Bridge to CO2 EOR
While produced gas is a logical choice for early Bakken EOR projects because it is more readily and affordably available than CO2, the volume of produced gas available in the Bakken will never be sufficient to support commercial-scale EOR across the basin. Fully realizing the Bakken’s EOR potential will therefore require bringing large volumes of CO₂ to western North Dakota. Rather, produced gas will answer the technical and operational questions that must be solved before large-scale CO₂ EOR can become practical in the Bakken.
That knowledge can help determine whether the additional oil recovered through CO₂ EOR would justify the investment in CO₂ supply, pipelines, compression, and injection infrastructure. If it does, produced gas can serve as a bridge to CO₂ EOR—allowing researchers and industry to build confidence through progressively larger field demonstrations rather than relying solely on laboratory results and simulations.
The next phase of Cracking the Code 2.0 will build on this work by examining the infrastructure needed to deliver CO₂ from sources such as coal-fired power plants to producing oil fields. This includes evaluating CO₂ pipelines, compression and injection infrastructure, and the technical and economic considerations involved in connecting CO₂ sources with EOR opportunities.
The potential impact goes beyond recovering additional oil from individual wells. As Bakken wells mature, production declines even though substantial oil remains in the surrounding formation. If EOR can economically mobilize some of that oil, existing wells and the infrastructure supporting them can continue generating value for years to come. This could also mean an additional billions of dollars in tax revenue for the state.
The Bakken’s first transformation came from learning how to drill horizontally and hydraulically fracture an unconventional reservoir. The next transformation will come from learning how to recover the oil that was left behind initially using EOR technologies.
Through laboratory research, reservoir simulation, and field-scale produced gas demonstrations, Crack the Code 2.0 is helping establish the technical foundation for that next phase. By validating EOR performance today, researchers can reduce the uncertainty surrounding CO₂ EOR tomorrow—potentially unlocking billions of barrels of additional oil and extending the productive life of one of America’s most important oil plays.