The development of structure -property relationships are described for new commercial grade internal olefin sulfonates (marketed as the ENORDET TM O series) and laboratory scale alcohol-alkoxy-sulfate surfactants for use in chemical flooding. Surfactant structure was characterised by an in-house developed liquid chromatography mass spectrometry (LC-MS) technique and properties focused on oil/water microemulsion phase behaviour. Such relationships are important to match the surfactant formulation to particular reservoir conditions (temperature, salinity and crude oil). The relationship between IOS structure (by LC-MS) and optimal salinity (by phase tests) has been modeled by the empirical HLB number and by a semi-empirical molecular model. An IOS 24-28 based surfactant system gave excellent microemulsion performance with several, regionally different crude oils and an initial correlation of performance with the composition crude oils has been made. The IOS surfactants described have been produced on a pilot scale and with consistent quality. This commercially available family, and the commercially available alcohol-alkoxy-sulfate family, cover most of the salinity and temperature reservoir conditions expected, though for high temperature and high salinity reservoirs, alcohol based sulfonates will most likely be required. Finally, the chemistry of production of the IOS surfactants and their handling properties are summarised. Part 2 of this paper (SPE-129769-PP) describes work to formulate an IOS mixture that was subsequently used in a successful ASP field test. SPE 129766There is a body of work that describes the testing protocols and properties required to screen suitable EOR surfactants 6, 8, 9 . Reference 6 is also an excellent recent review of the surfactant EOR literature. Through the well-established relationship between the microemulsion phase behaviour and IFT it is common in the industry to screen surfactants and their formulations for low IFT through laboratory-based oil / water phase behaviour tests 8, 9 .The current paper will describe microemulsion phase behaviour for the IOS family and several alcohol-alkoxy-sulfates and discuss structure-property correlations to allow selection of surfactant(s) for specific reservoir conditions. It will also cover the chemistry of the manufacturing processes of the surfactants and the handling and flow properties of the surfactants produced. Chemistry and production of IOS surfactantsThe process chemistry and resulting products from reaction of high molecular weight internal olefins with SO 3 was first studied in Shell's laboratories in the 1990s, this work being part of a program to identify potential new detergent molecules 10,11 . The knowledge gained during that period has been of great help to identify the optimum process conditions to make IOS products for surfactant EOR application. IOS products have been produced based on four Internal Olefin (IO) carbon cuts, with nominal ranges C15-18, C19-23, C20-24 and C24-28.The production of an IOS consists of three ...

The development of structure – property relationships are described for new commercial grade internal olefin sulfonates (marketed as the ENORDET™ O series) and laboratory scale alcohol-alkoxy-sulfate surfactants for use in chemical flooding. Surfactant structure was characterised by an in-house developed liquid chromatography mass spectrometry (LC-MS) technique and properties focused on oil/water microemulsion phase behaviour. Such relationships are important to match the surfactant formulation to particular reservoir conditions (temperature, salinity and crude oil). The relationship between IOS structure (by LC-MS) and optimal salinity (by phase tests) has been modeled by the empirical HLB number and by a semi-empirical molecular model. An IOS 24-28 based surfactant system gave excellent microemulsion performance with several, regionally different crude oils and an initial correlation of performance with the composition crude oils has been made. The IOS surfactants described have been produced on a pilot scale and with consistent quality. This commercially available family, and the commercially available alcohol-alkoxy-sulfate family, cover most of the salinity and temperature reservoir conditions expected, though for high temperature and high salinity reservoirs, alcohol based sulfonates will most likely be required. Finally, the chemistry of production of the IOS surfactants and their handling properties are summarised. Part 2 of this paper (SPE-129769-PP) describes work to formulate an IOS mixture that was subsequently used in a successful ASP field test.

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.