Controlled Hydrophobe Branching to Match Surfactant to Crude Oil Composition for Chemical EOR

Abstract

In this paper an innovative structure/property approach is used to evaluate several commercially available surfactants in tests relevant to both alkaline-surfactant-polymer (ASP) and surfactant-polymer (SP) floods, in order to gain an understanding of how hydrophobe structure is related to surfactant performance and crude oil composition. The surfactant structural elements considered here include relative branching level and carbon chain length. This has application to chemical EOR implementation in fields over a range of reservoir temperatures and salinity. Phase behavior (giving interfacial tension), and micro-emulsion viscosity tests were carried out for internal olefin sulfonates and mixtures with alcohol propoxy sulfates to identify those that perform well while minimizing or eliminating the use of costly co-solvents. Hydrophobe branching and carbon chain length, characterized by gas chromatography, were used to match surfactants to certain crude oil properties such as natural surfactants, including total acid number (TAN) and asphaltenes, and the ratio of saturates/aromatics. The paper also examines how crude oil sampling influences crude properties and surfactant performance. The approach used and associated data contribute to cost reduction of formulations through a) better matching of commercially produced surfactants to the reservoir and crude oil properties to improve oil recovery efficiency, and b) minimizing or eliminating the use of co-solvents to reduce formulation and logistics costs. In addition, the study demonstrates how binary blends from a few core surfactants can match formulations across regionally different crude oils thereby simplifying formulation selection, and reducing uncertainty and cost.

A Strategy for Low Cost, Effective Surfactant Injection

“…It should be noted at this stage that the particular surfactant used was not optimised to any specific oil or brine composition. However, as demonstrated by Barnes et al (2010Barnes et al ( , 2012, this class of surfactants can be tailored to different crude oils by changing the surfactant hydrophobe. An alcohol co-solvent was added to avoid formation of gel phases and promote formation of type III systems at reasonable salinities.…”

“…This is based on the following: (1) different anionic surfactants are known to show the same overall response to changes in salinity (see for example Salager et al (1979), and references cited therein). (2) Adapting to a given crude oil generally involves modifying the surfactant hydrophobe (Barnes et al, 2012). Changing the surfactant hydrophobe shifts the overall solubility and phase behaviour, but the response to changes in salinity remains roughly the same only shifted upwards or downwards.…”

“…The surfactant chosen was an internal olefin sulphonate (IOS). This class of surfactants is considered suitable for a range of sandstone reservoir applications, and is available in quantities for EOR pilot scale trials (Barnes et al, 2010(Barnes et al, , 2012. The main purpose is to identify a cost-efficient surfactant injection strategy, aimed at applications in sandstone fields with light to medium crude oils.…”

Review of surfactant-assisted chemical enhanced oil recovery for carbonate reservoirs: challenges and future perspectives

“…Designing and optimizing suitable surfactant flood for effective cEOR has always been very challenging and forever evolving. It is one of the robust and high-performance cEOR methods, which has been widely studied in the past decades because of its ability to alter wettability of carbonate reservoirs from the oil/mixed-wet to the waterwet surfaces, lower interfacial tension (IFT) and produce the oil entrapped in these formations (Hill et al 1973;Yang and Wadleigh 2000;Webb et al 2005;Farajzadeh et al 2010;Barnes et al 2012;Ahmadi and Shadizadeh 2013a). The idea of adding surfactants to injected water for reducing oil/water IFT and/or alter wettability thereby increasing oil recovery from reservoirs dates back to the early 1900s (Uren and Fahmy 1927).…”

Systematic Phase Behaviour Study and Foam Stability Analysis for Optimal Alkaline/Surfactant/Foam Enhanced Oil Recovery

“…The IOS surfactants used in this study were prepared by Shell Chemical Company from internal olefins with carbon chain C20-24. The synthesis steps of IOS surfactant and the chemical structures formed were described by Barnes et al (2008Barnes et al ( , 2012. These surfactants are designated by the abbreviation IOS 20-24.…”