Water- and Surfactant-Based Huff-n-Puff Injection into Unconventional Liquid Hydrocarbon Reservoirs: Experimental and Modeling Study

The combination of horizontal well drilling and multistagehydraulicfracturing is currently the leading method for developing shale reservoirs.However, oil recovery from these techniques does not exceed 10%, andsupporting technologies are being sought. The injection of water orsurfactant solutions in huff-n-puff mode is often considered an enhancedoil recovery option for shales, which can be used alone or in combinationwith other technologies, such as CO2 injection. This studypresents experimental and numerical investigations into the huff-n-pufftreatment of low-permeability shale cores using water-based compositions.Additionally, an attempt was made to displace oil by applying a nanofluidbooster. Computational tomography was used as one of the methods todetermine the oil recovery factor. Two core flooding tests with differentdesigns and injection fluids were conducted. The first experimentinvolved brine filtration in one direction, followed by nanofluidinjection. Second core flooding/huff-n-puff test implied injectionof a 0.5 wt % surfactant solution. The results showed that the oilrecovery factor achieved using brine was approximately 50% and decreasedafter nanofluid injection until 31%. Besides that, there was no significanteffect from the use of the surfactant. At the same time, criticalissues were observed regarding a decrease in core permeability. Anumerical simulation of the second experiment was performed to restorethe relative phase permeability (RPP) in the surfactant-oilsystem and to study the dependency of the capillary number logarithmon the miscibility coefficient. The simulation showed a good convergencein terms of the recovery factor values, with an error of & SIM;1.5%.