Compositional simulation evaluation of eor potential in shale oil reservoirs by cyclic natural gas injection

The depletion of petroleum hydrocarbons in the world has progressively increased during the past decades. To meet the increasing demand for energy resources, improving the oil recovery of unconventional reservoirs, such as shale oil has appealed great attention. The Eagle Ford shale reservoir is one of the most active U.S. Shale plays. An article by Hart (2011) quoted one of EOG resources recent reports that recovery factor for the Eagle Ford shale play during primary drive reservoir depletion will be roughly 5%. Other articles stated that the recovery factor of these reservoirs could be between 5 to 15 %. The vast oil remaining in shale reservoir stimulates our efforts to investigate the application of enhanced oil recovery methods. The main aid of this simulation study is to examine the feasibility of cyclic natural gas injection. Cyclic natural gas injection can be applied as substitution of cyclic Co₂ injection with great advantages, such as lower corrosion levels and availability of the natural gas in some of shale oil plays such as Eagle ford shale reservoirs. In this paper, the effects of soaking period and injection pressure on oil recovery, among other parameters, were investigated. The compositional simulation study results show that cyclic natural gas injection is able to increase the recovery factor from 3 % to 5% depending on the operating conditions and number of cycles. In general, this study aided to develop a better understanding of the performance of cyclic natural gas injection in shale oil reservoirs.