Experimental Study on Spontaneous Imbibition of CO2-Rich Brine in Tight Oil Reservoirs

Abstract

This paper focuses on the CO2-EOR in fractured tight oil reservoirs after water-flooding treatment. In previous works, few studies were presented about the spontaneous imbibition experiments of CO2-rich brine at formation pressure. We investigated the influence of CO2 injection on spontaneous imbibition, which is an essential mechanism to improve oil recovery in tight reservoir. In this paper, a laboratory equipment was set up to conduct spontaneous imbibition experiments at formation temperature of 65 °C and pressures of 10–22 MPa on different low-permeability core samples from Nugget, Kentucky, Colton, and Crab-Orchard in the United States. Moreover, we proposed a saturation-based dimensionless time model to scale the spontaneous imbibition and a modified Ma model to fit the oil recovery curves of spontaneous imbibition of CO2-rich brine with double peaks of imbibition rate. The results of quantitative imbibition experiments confirm that both the oil production per unit area and the oil recovery have a ...