Capillary Desaturation Tendency of Hybrid Engineered Water-Based Chemical Enhanced Oil Recovery Methods

Abstract

Several studies have shown the synergetic benefits of combining various chemical enhanced oil recovery (CEOR) methods with engineered waterflooding (EWF) in both sandstones and carbonate formations. This paper compares the capillary desaturation tendency of various hybrid combinations of engineered water (EW) and CEOR methods with their conventional counterparts. Several coreflood experiments were conducted, including EW-surfactant flooding (EWSF), EW-polymer flooding (EWPF), EW-alkali-surfactant flooding (EWASF), EW-surfactant-polymer flooding (EWSPF), and EW-alkali-surfactant-polymer flooding (EWASP). Capillary numbers (Nc) and corresponding residual oil saturation (Sor) for each scenario are compared with capillary desaturation curves (CDC) of conventional CEOR methods from the literature. The results indicate that hybrid EW–CEOR methods have higher capillary desaturation tendency compared to conventional methods. The capillary numbers obtained by standalone polymer flooding (PF) are usually in the range from 10−6 to 10−5, which are not sufficient to cause a significant reduction in Sor. However, the hybrid EW-polymer flooding approach considerably reduced the Sor for the same Nc values, proving the effectiveness of the investigated method. The hybrid EWASP flooding caused the highest reduction in Sor (23%) against Nc values of 8 × 10−2, while conventional ASP flooding reduced the Sor for relatively higher Nc values (3 × 10−3 to 8 × 10−1). Overall, the hybrid methods are 30–70% more efficient in terms of recovering residual oil, compared to standalone EWF and CEOR methods. This can be attributed to the combination of different mechanisms such as wettability modification by EW, ultralow interfacial tension by alkali and surfactant, reduced surfactant adsorption by alkali addition, and favorable mobility ratio by polymer. Based on the promising results, these hybrid techniques can be effectively implemented to carbonate formations with harsh reservoir conditions such as high salinity and high temperature.

Numerical approach for enhanced oil recovery with polymer flooding using CMG-STARS program

“…While the viscous finger reduces by increasing the viscosity of PAM aqueous solution [37]. These results compatible with the boundary conditions of reservoir [38]. 4 is: We can demonstrate convergence between experimental and numerical studies by comparing the two.…”

Low Salinity Water–Polymer Flooding in Carbonate Oil Reservoirs: A Critical Review

“…CDC depends on the pore structure, arrangement within the porous media, and fluid distribution inside the pores. [22] The performance of an EOR method is determined by measuring the Sor, which is the oil amount left behind in a reservoir. The CDC depicts the relationship between the residual oil saturation (Sor and the capillary number Nc (the ratio between viscous and capillary forces).…”

“…This behavior depends on the characteristics of the crude oil, the reservoir condition, and the properties of the formation brine (FB). [ 22 ]…”

“…This behavior depends on the characteristics of the crude oil, the reservoir condition, and the properties of the formation brine (FB). [22] LSW is widely used due to its high efficiency. It can produce up to 10% extra crude oil compared to simple waterflooding.…”

“…CDC depends on the pore structure, arrangement within the porous media, and fluid distribution inside the pores. [ 22 ]…”