Research On The Mechanism Of Varying Reservoir Wettability To Enhance Oil Recovery

Wettability is a major factor in the phenomena of reservoir interface. Wettabilityalteration will affect relative permeability of water/oil, capillary pressure, residual oil,electrical characteristic and water-injected exploitation characteristic, so the exploitationefficiency of crude oil is depended on wettability.Reservoir wettability alterations by molecular deposition film oil displacement ragent toenhanced oil recovery were investigated in Lab. The studies include follow as:Mechanism of reservoir rock electrochemistry alteration;Compositions of film agent;Properties of film agent solutions;Absorbability of film agent on surface of silica sand;Regularity of wettability alteration of rock& sand grain;Mechanism and feasibility of film agent flood to enhanced oil recovery. Molecular film reagent is odd-molecular quaternary ammonium salt, it is a double cationorganic and with no surface activity. It transfers the medium by water, makes the deposit forma thinner unimolecular film on surface of rock, depending on static effect between ions. So thefilm can alter the reservoir wettability from oil-wet to water-wet, improve the spontaneousimbibition, reduce viscous force between crude oil and rock surface, and improve oil recovery.Results of simulative experiments in lab show that: core wettability can evidently changefrom oil-wet to water-wet by using film reagent;the recovery of water flooding is increased tomore than 4~12% by using film reagent. The increasing extent of recovery is different becauseof different rhythm cores, and the reverse rhythm is the best cores in the experiments.Mechanism of film reagent is mainly on saturation and adsorption, it is obviously differentfrom the mechanism of surfactant active reagent.