Surfactant Systems for EOR in High-Temperature, High-salinity Environments

Abstract

A systematic study was made of phase behavior of alkoxyglycidylether sulfonates (AGESs). These surfactants were screened with either NaCl-only brines or NaCl-only brines and n-octane at water/ oil ratio (WOR) ~1 for temperatures between approximately 85 and 120°C. All test cases were free of alcohols and other cosolvents. Classical Winsor phase behavior was observed in most scans, with optimal salinities ranging from less than 1% NaCl to more than 20% NaCl for AGESs with suitable combinations of hydrophobe and alkoxy chain type [ethylene oxide (EO) or propylene oxide (PO)] and chain length. Oil solubilization was high, indicating that ultralow interfacial tensions existed near optimal conditions. The test results for 120°C at WOR~1 have been summarized in a map, which might provide a useful guide for initial selection of such surfactants for EOR processes. Saline solutions of AGESs separate at elevated temperatures into two liquid phases (the cloudpoint phenomenon), which may be problematic when they are injected into high-temperature reservoirs. An example is provided that indicates that this situation can be alleviated by blending suitable AGES and internal olefin sulfonate (IOS) surfactants. Synergy between the two types of surfactant resulted in transparent, single-phase aqueous solutions for some blends, but not for the individual surfactants, over a range of conditions including in synthetic seawater. Such blends are promising because both AGES and IOS surfactants have structural features that can be adjusted during manufacture to give a range of properties to suit reservoir conditions (temperature, salinity, and crude-oil type).

Complexation of Surfactant/β‐Cyclodextrin to Inhibit Surfactant Adsorption onto Sand, Kaolin, and Shale for Applications in Enhanced Oil Recovery Processes. Part I: Static Adsorption Analysis

“…brine) [13][14][15][16][17][18]. Furthermore, the use of a negative salinity gradient during surfactant flooding has been recommended because a decrease in salinity concentration reverses surfactant adsorption [19].…”

Complexation of Surfactant/β‐Cyclodextrin to Inhibit Surfactant Adsorption onto Sand, Kaolin, and Shale for Applications in Enhanced Oil Recovery Processes. Part III: Oil Displacement Evaluation

“…EOR methods include chemical flooding, thermal methods, miscible flooding, and microbial flooding, among others. Chemical EOR processes, in particular surfactant applications; have been studied and commercially applied [4][5][6][7]. The mechanism of oil recovery via surfactant flooding is the reduction of the interfacial tension (IFT) between the aqueous phase (brine) and crude oil to ultralow interfacial tension values.…”

“…Extensive research has been conducted related to the evaluation and development of highly effective surfactants for EOR chemical flooding [5,[11][12][13][14]. Nonetheless, the adsorption of surfactant onto reservoir rock is a serious problem that compromises the technical and economic success of surfactant flooding for EOR.…”

“…Other mechanisms causing the retention of surfactant within the porous media are precipitation of surfactant in the presence of divalent ions [22], diffusion of surfactant molecules into dead-end pores, and surfactant partitioning into the oil phase, among others [23]. In field applications, the adsorption of surfactant towards formation rock is somehow managed through the addition of sacrificial agents [24], alkali components such as sodium carbonate, sodium borate, and others [12,13,[25][26][27][28]; the use of surfactant systems with reduced adsorption tendency towards solid surfaces [5], and the implementation of smart injection schemes (i.e., salinity gradient) to control surfactant adsorption and retention during chemical flooding [28].…”

Study on a Novel Gelled Foam for Conformance Control in High Temperature and High Salinity Reservoirs

“…However, foam has shown in the potential for conformance control in high temperature and high salinity reservoirs. Foam is a selective conformance control agent characterized by good chemical stability in high-temperature and salinity conditions [17][18][19][20][21][22]. Foaming agents have excellent performance as surfactants [23] and are chemical stable under harsh conditions [24].…”