Miscible gas displacement is known as one of the most efficient EOR methods throughout the world. The mechanism is seem to be promising in homogeneous sandstones but is quite challenging when it comes to heterogeneous carbonates.
The studied field is among the tight heterogeneous carbonates from southwest of Iran. The reservoir in an undersaturated high pressure oil reservoir with no active aquifer. Due to low permeability of the reservoir, a miscible gas injection was thought to be efficient in increasing the oil recovery, maintaining the reservoir pressure and increasing the production plateau. A full compositional simulation model was built taking into account reservoir heterogeneities. The simulation study includes history matching of the past reservoir performance, optimization of the gas injection well number and location, and optimization of gas injection and oil production rates. After running sensitivity analysis, the reservoir engineers came up with drilling of the 6 crestal gas injection wells.
In Addition, the water injection was thought as an alternative for EOR purpose but it didn't show up well and was given up.
The outcome of this simulation study nominates the miscible gas injection as the most promising method concerning the reservoir management purposes as it increases the recovery from 16% to around 42% through 40 years of production and could maintain the plateau of 120000 bopd up to 19 years from the production start.