The conventional reserves are depleting significantly on a worldwide basis. In order to meet the demand for hydrocarbon energy, it is essential to develop unconventional resources. Over the past decade, shale oil becomes an important source of oil across the North America. Bakken shale oil, one of the largest shale oils in the world, is producing near 1,000,000 barrel oil per day. The main methods exploiting Bakken oil shale are drilling horizontal wells with multi-fracturing technology. Even with the technology evolution of shale oil exploration and well stimulation in shale plays, the recovery factors in Bakken are still very low due to the nature of extremely low permeability. Original oil in place in Bakken ranges between 271 and 503 billion barrels. Primary recovery with multi-stage fracturing in horizontal wells only can produce 5 to 10%. Therefore, enhanced oil recovery (EOR) methods will play a crucial role to recover the remaining hydrocarbons. With EOR techniques such as gas injection, chemical injection, microbial injection, and thermal recovery, the recovery factor can be increased by 10–30%. In this study, different EOR methods applied in Bakken were reviewed. The mechanisms and causes that lead to the success and failure of different EOR methods were analyzed and discussed. With the lessons and experiences learned from these EOR applications in Bakken, significant cost saving on can be achieved for future Bakken oil development and production. The significances of this study are:
proposed screening criteria for different EOR applications in Bakken;
identified appropriate EOR technique to improve the recovery of specific reservoir, especially low permeability shale reservoir;
provided lessons and experiences accrued in EOR application in Bakken during last several decades to curtail learning curve and optimize EOR design in the future;
served as guidance in EOR applications in other shale oil plays.