الملخص الإنجليزي
This study investigates the possibility to inject diluted aqueous solutions of novel surfactants into Yibal field (Sultanate of Oman). Novel surfactants selected in this work consist of a series of ether sulfonates (7-58, AES-128, AES-218, AES-208, AES-506) and an amphoteric surfactant (6-105). Ultralow transient minima were observed for all surfactants at 0.05% concentration in the range 6.7 x 104 -2.9 x 10 2 mNm-', followed by an increase in the IFT to equilibrium values in the range 1.7 102 – 3.7x 10-4 mNm? At 0.01 % concentration, transient were observed only for three surfactants, namely AES-218, AES-208, and 6-105 surfactants. Below 0.01 % concentration, no transient IFT minima were observed. Our results also demonstrated that with respect to temperature (60-80 °C), a representative surfactant (7-58) exhibited a wide range of applicability, with the transient IFT remaining below 3.7 10-2 mNm? Core flooding experiments showed an additional oil recovery by tertiary surfactant injection (surfactant following water injection) over conventional water
injection using 7-58 surfactant at 0.05 % (2 % of OOIP recovered) and 0.01 % concentrations (~ 3 % of OOP recovered). At lower surfactant concentration (0.005%), no additional oil recovery was achieved over waterflooding. On the other hand, oil recoveries generated from surfactant injection into virgin cores at all surfactant concentrations (0.05-0.001%) were 87.8 % (0.05%), 79.4% (0.01%), 87.2% (0.005%) and 81.5% (0.001%) of original oil in place (OOIP) and represents an additional increase in oil recovery of 15% (0.05%), 6.9% (0.01%), and 13% (0.005), over waterflooding. Thus, injection of surfactant as a secondary agent is preferable to its injection as a tertiary agent.
