Investigating Minimum Misciblity Pressures in the Bakken

The Bakken reservoir displays favorable initial production rates due to stimulation by hydraulic fracturing, but production rates quickly decline after few months. Experiencing extremely low permeability and low recovery factors, miscible gas injection is considered for improving the recovery of oil in the Bakken formation. Feasibility of miscible gas injection in the Bakken depends on the analysis of minimum miscibility pressure (MMP) experiments. MMP results from a Bakken crude sample show a range from 2340 to 3000 psia at reservoir temperatures using CO2 as the injection fluid. Other injection fluids such as nitrogen and hydrocarbon gases have been tested and provided MMP values from 3500 to over 5000 psia depending on the injection gas. MMP results from Bakken crude oil samples were compared to existing correlations and more correlations were found to produce unreliable MMP results. Further comparison using an equation of state phase-behavior program has shown similar results with the experimental MMP results. MMP results are influenced by the choice of injection fluids, providing valuable information for economic production and increased recovery in the Bakken formation.