Experimental Investigation of Foam Flooding Performance in Bulk and Porous Media for Carbonates Under Harsh Conditions

Abstract

Foam injection has been promoted as a reliable method for improving the sweep efficiency in heterogeneous carbonate reservoirs by modifying the properties of the injected gas and hence, providing mobility control effect. However, the conditions of the Middle Eastern carbonate reservoirs are quite detrimental to foam performance, leading to unoptimized mobility control. This challenge has motivated the improvement and development of different foaming agent formulations that can withstand the harsh conditions in carbonate reservoirs of high temperature and high salinity. In this study, the effect of different amphoteric and switchable surfactants on bulk foam performance were investigated and later the optimum formulation was evaluated in carbonate porous media for EOR under high salinity and temperature conditions. For this purpose, the solutions containing different commercial amphoteric and amine-based switchable surfactants were prepared in high salinity brine (20 wt%) at high temperature conditions (80 °C). Initial screening was performed by conducting series of foamability and foam stability tests at high temperature. Foam generation and endurance were also investigated in the presence of crude oil. Foam performance was evaluated in carbonate core samples under different foam qualities and at reservoir conditions. After selecting the optimal foam quality for effective foam generation, the oil recovery experiment was then performed to recover the remaining oil after secondary N2-gas flood. The results from bulk foam experiments demonstrated the superior properties of betaine-based surfactant (B-1235), in which the highest foam generation and foam stability performance were achieved. Foam endurance of B-1235 was also found comparable to the foam produced by switchable diamine (DTTM) surfactant; however, DTTM surfactant showed poorer foamability performance. In the presence of crude oil, B-1235 surfactant was able to maintain the foam properties, compared to other tested surfactants. The optimum concentrations for B-1235 in the absence and presence of crude oil were found to be 0.25 wt% and 0.5 wt%, respectively. The injection of foam stabilized by the B-1235 was able to pronouncedly increase the mobility reduction factor (MRF) at all the tested foam qualities under high-pressure and high-temperature conditions. Coreflood investigations indicated an optimal foam quality at 70% for all tested surfactant concentrations. The cumulative oil recovery after foam injection was found to be 67%, including 25% tertiary incremental oil recovery by foam flooding. The overall performance of the tested betaine-based surfactant is promising as an effective mobility control during foam EOR process and promotes further application in difficult Middle Eastern carbonate reservoir conditions.