Wettability Alteration and Foam Mobility Control in a Layered 2-D Heterogeneous System

Abstract

In a layered 2-D heterogeneous sandpack with 19:1 permeability contrast that was preferentially oil-wet, the recovery by waterflood was only 49.1% of original oil-in-place (OOIP) due to injected water flowing through high-permeability zone leaving low-permeability zone unswept. In order to enhance oil recovery, an anionic surfactant blend (NI) was injected that altered the wettability and lowered the interfacial tension (IFT) and consequently enabled gravity and capillary pressure driven vertical counter-current flow to occur and exchange fluids between high- and low-permeability zones during a 42-day system shut-in. Cumulative recovery after a subsequent foamflood was 94.6% OOIP even though foam strength was weak. Recovery with chemical flood (incremental-recovered-oil/waterflood-remaining-oil) was 89.4%. An alternative method is to apply foam mobility control as a robust viscous force dominant process with no initial surfactant injection and shut-in. The light crude oil studied in this paper was extremely detrimental for foam generation. However, the addition of lauryl betaine to NI at a weight ratio of 1:2 (NI: lauryl betaine), made the new NIB blend a good foaming agent with and without the presence of the crude oil. NIB by itself as an IFT reducing and foaming agent is shown to be effective in various secondary and tertiary alkaline/surfactant/foam (ASF) processes in water-wet 1-D homogeneous sandpacks, and in an oil-wet, heterogeneous layered system with 34:1 permeability ratio.

Foam stability in the presence and absence of hydrocarbons: From bubble- to bulk-scale

“…Their results showed a direct correlation between the critical capillary pressure and the final height of foam. It has been observed that mixing surfactants can significantly improve the stability of foams and potentially reduce the destabilizing effect of oil on foam [28,42]. For example addition of small fractions of non-ionic surfactant to an anionic surfactant enhances the foam stability as a result of the formation of a viscous surface layer which raises the interfacial viscosity of the foam thereby reducing the rate of film thinning [19].…”

“…Betaines are known for their foam enhancing properties [14]. In their 2D sand-pack experiments, Li et al [42] observed that the addition of lauryl betaine to the so called NI blend (4:1 of Neodol 67-7PO sulfate and IOS 15-18) generated a stronger and more stable foam in the presence of oil. One of the mechanisms suggested for this stabilising behavior is that betaine increases the critical capillary pressure required for droplet entry which is related to the disjoining pressure [14,43].…”

Experimental Study of Foam Generation, Sweep Efficiency and Flow in a Fracture Network

“…Foam is a proven gas mobility control method in fields (Blaker et al, 2002, Enick and Olsen, 2012 and in numerous studies (Bernard and Holm, 1964, Holm, 1968, Rossen, 1996, Schramm, 1994, Llave et al, 1990, Lawson and Reisberg, 1980. More recently, foam has been suggested as a gas diversion agent in stratified systems (Bertin et al, 1999, Tanzil et al, 2002, Nguyen et al, 2003, Siddiqui et al, 2003, Li et al, 2010, Li et al, 2011, Conn et al, 2014 and in fractures and fracture networks (Kovscek et al, 1995, Yan et al, 2006, Fjelde et al, 2008, Buchgraber et al, 2012b, Haugen et al, 2012. Nguyen et al (2003) demonstrated gas diversion in a layered system, and found that foam penetration depth in the low permeable layer increased when capillary cross-flow was allowed, even if the layers were parallel to the main flow direction.…”

Simulation Studies on the Role of Lauryl Betaine in Modulating the Stability of AOS Surfactant-Stabilized Foams Used in Enhanced Oil Recovery

“…In contrast, the NI blend (4:1 blend of Neodol 67-7PO sulfate and internal olefin sulfonate (IOS 15-18)) does not generate a strong foam. However, mixing lauryl betaine (LB) with the NI blend can generate foam that is even more stable than the one generated by AOS itself . Thus, lauryl betaine, a foam booster, can help stabilize foam even in the presence of oil .…”