Comparison of oil removal in surfactant alternating gas with water alternating gas, water flooding and gas flooding in secondary oil recovery process

Abstract

Growing oil prices coupled with large amounts of residual oil after operating common enhanced oil recovery methods has made using methods with higher operational cost economically feasible.Nitrogen is one of the gases used in both miscible and immiscible gas injection process in oil reservoir. In heterogeneous formations gas tends to breakthrough early in production wells due to overriding, fingering and channeling. Surfactant alternating gas (SAG) injection is one of the methods commonly used to decrease this problem. Foam which is formed on the contact of nitrogen and surfactant increases viscosity of injected gas. This increases the oil–gas contact and sweep efficiency, although adsorption of surfactant on rock surface can causes difficulties and increases costs of process. Many parameters must be considered in design of SAG process. One of the most important parameters is SAG ratio that should be in optimum value to improve the flooding efficiency.In this study, initially the concentration of surfactant was optimized due to minimization of adsorption on rock surface which results in lower cost of surfactant. So, different sodium dodecyl sulfate (SDS) concentrations of 100, 500, 1000, 2000, 3000 and 4000 ppm were used to obtain the optimum concentration at 70 °C and 144.74×105 Pa. A simple, clean and relatively fast spectrophotometric method was used for determination of surfactant which is based on the formation of an ion-pair. Then the effect of surfactant to gas volume ratio on oil recovery in secondary oil recovery process during execution of immiscible surfactant alternating gas injection was examined experimentally. The experiments were performed with sand pack under certain temperature, pressure and constant rate. Experiments were performed with surfactant to gas ratio of 1:1, 1:2, 1:3, 2:1 and 3:1 and 1.2 pore volume injected. Then, comparisons were made between obtained results (SAG) with water flooding, gas flooding and water alternating gas (WAG) processes.This study shows that using the concentration of 1500 ppm of surfactant solution is practical and economical. Results also show that the SAG ratio of 1:1 with 0.2 cm3/min at temperature and pressure of 70 °C and 144.74×105 Pa, has the maximum oil removal efficiency. In this SAG ratio, stable foam was formed and viscous fingering delayed in comparison to other ratios. Finally, the results demonstrated that SAG injection has higher oil recovery in comparison to other displacement methods (water flooding, gas flooding and WAG).

Estimation of the water–oil–gas relative permeability curve from immiscible WAG coreflood experiments using the cubic B-spline model

“…Due to the highly scattered and relatively enriched distribution of remaining oil, efficient enhanced oil recovery (EOR) techniques have become imperative. Water-alternating-gas (WAG) injection has been identified as a cost-effective EOR process yielding high recovery in some oilfields (Luo et al 2013;Salehi et al 2014;Laochamroonvorapongse et al 2014;Sheng 2015). Nevertheless, considering the complicated phase behavior and various flow characteristics in heterogeneous formations, gas tends to break through early in production wells due to overriding, fingering, and channeling, which may result in unfavorable recovery performance.…”

An Overview of the Present Stability and Performance of EOR-Foam

“…EOR-foam was first introduced by Bond and Helbrook in 1958 as a mobility control (Salehi et al 2014). Foam is generated using EOR-surfactants (Farzaneh & Sohrabi 2013;Nezhad et al 2013).…”

Synthesis and performances for treating oily wastewater of polyether copolymers based on polyethyleneimine

“…All over the world, water flooding still is a traditional and important oil recovery process, in which a large number of oily wastewater in the form of oil‐in‐water (O/W) and water‐in‐oil emulsions is generated . The more common emulsions in oil recovery process are the O/W type, which are crude oil dispersed in a continuum of droplets of water or brine.…”