Mechanistic Study On Imbibition With Surfactant In Tight Oil Reservoir

Aiming at the existing problem of tight oil reservoir development,such as single well production declining fast(annual output decreasing rate bigger than 40%,even up to 90%),low effective reservoir production,low primary recovery efficiency(the average recovery efficiency is only 5%~10%),etc.Through laboratory experiments,it was found that spontaneous imbibition with surfactant is an effect way to further improve the recovery of tight oil reservoir.First of all,ASB was selected through spontaneous imbibition and testing of interfacial tension and wettability;Second,experimental laws were found by changing the experiment conditions,such as concentration of surfactant,length of core plugs,boundary conditions,wettability,permeability,temperature,viscosity and initial water saturation;Finally,mechanism was analyzed by investigating the change of the capillary force,wettability index and two phase percolation curve.The influence of spontaneous imbibition with surfactant on tight core plugs mainly embodies in two aspects: the influence of interfacial tension and wettability.Low interfacial tension can change the flow ability of the residual oil,but also can reduce the producing rate of spontaneous imbibition.Wettability determines the magnitude and direction of capillary force and affect the flow and distribution of fluid.It's is a sensible direction for all concerned of the influence of surfactant on interfacial tension and wettability.