Experimental Evolution Of Potential Fuzzy Ball Fluids For Enhanced Oil Recovery In Sandstone Reservoirs

Conventional water injection and polymer injection drives are common methods to increase oil recovery.However,the oil-displacing agent injected into the heterogenous oil reservoir can enter the seepage channel in the high-permeability zone.Therefore,it is difficult to displace hydrocarbons in the low permeability zone.However,using agent with Plugging agents in capability operations to block high-permeability channels and promote subsequent displacement in seepage areas have become a potential optimal solution for improving heterogeneous oil reservoirs for enhanced oil recovery(EOR).This study discusses the techniques and mechanism of novel fuzzy ball fluid to enhance oil recovery from heterogeneous reservoirs.Laboratory tests were performed using 45 mm × 45 mm × 300 mm artificial cores with permeability ranging from200 to 1200 m D to simulate formation channels.Paralleling two cores with different permeability to simulate heterogeneous formations.The displacement performance of fuzzy ball fluids was compared with that of polymers and brines.Displacement of cores with fuzzy ball fluid can significantly improve the recovery of low-permeability cores.At this stage,the lowpermeability core in low recovery rate,indicating that the formation water preferentially enters the high-permeability area,and the oil displacement effect in the low-permeability area needs to be improved.During the fuzzy ball flooding phase,the recovery factors for the high permeability cores ranged from 3.29% to 10.35%,while the recovery factors for the low permeability cores ranged from 40.82% to 48.25%.At this stage,the higher recovery of the low permeability core indicates that the fuzzy ball fluid effectively seals the high permeability zone and displace it to the low permeability zone for oil displacement,it was possibly achieved“selective plugging”.The recovery factor of the high permeability core is zero,while the recovery factor of the low permeability core during the repeated flooding of formation water ranges from 4.03% to 4.87%.Subsequent injection of formation water shifted to the lowpermeability zone,indicating that the seals of the high-permeability zone remained stable.The fuzzy ball fluid may have displaced most of the movable oil in the low permeability zone,so the corresponding recovery factor in the repeated flooding stage of formation water is relatively low.The experimental results show that the injection of fuzzy ball fluid into the heterogeneous formation can effectively adjust the formation water injection profile and improve the water injection effect in the low permeability area.The permeability ratio of parallel-connected cores is on the horizontal axis,while the injection pressure at the injection port is on the vertical axis.After the first formation water injection,the pressure increased by about 30 MPa as the core was displaced by the fuzzy ball fluid.After multiple injections of formation water,the pressure dropped to 9.16-10.28 MPa,but was still 9-10 MPa higher than the first water injection.The results show that displacing the core with fuzzy ball fluid successfully enhances the flow resistance in the high permeability zone,resulting in an increase in the total flow resistance of the connected core system.