An Evaluation of Spontaneous Imbibition of Water into Oil-Wet Carbonate Reservoir Cores Using a Nonionic and a Cationic Surfactant

Abstract

Some surface-active chemicals are able to improve the spontaneous imbibition of water into oil-wet carbonates. In this work, the oil recovery from oil-wet reservoir cores was compared using aqueous solutions of an ethoxylated alcohol (EA) and a cationic surfactant (C12TAB). The experiments were conducted at room temperature using short (∼5 cm) and long (∼30 cm) cores with initial water saturation in the range of 17−33%. Due to wide variation in porous structure, the cores were characterized into two groups, i.e., moldic and sucrosic. The former cores had more than 25% of the pore volume (PV) related to vugs, and the latter appeared more homogeneous. The permeability of the moldic and sucrosic cores varied between 20 and 180 and 80−350 mD, respectively. In general, the efficiency of C12TAB was superior to EA regarding spontaneous oil expulsion from the cores. For the short core experiments, about 40−45% of original oil in place (OOIP) was recovered using C12TAB, while only 10% was the average recovery usin...