Applying the Hydrophilic – Lipophilic Deviation (HLD) Concept to Chemical EOR Formulations

Chemical EOR surfactant use is expected to grow rapidly as this tertiary recovery method has shown improved oil production in the laboratory and the field. However, choosing an optimal surfactant formulation is still a time consuming and expensive process. Formulators need an easy-to-use tool that allows them to rapidly narrow the choices of suitable surfactant systems that match field conditions. The Hydrophilic-Lipophilic Deviation (HLD) concept has been known as a fast screening method for chemical EOR formulations based on the characteristic of the surfactant. The HLD concept can be used to determine the characteristic curvature (Cc) of the surfactant and to predict the most suitable surfactant structure for an EOR formulation. The HLD concept, therefore, indicates that surfactants of similar characteristic should have similar performance for a certain reservoir condition. To demonstrate the use of the HLD equation in selecting EOR formulations, the ASP flood in progress in the Mooney Field in north-central Alberta, Canada was used as a reference case. The surfactant currently being used in this field is a branched C1213 alcohol propoxy sulfate with Na2CO3. The characteristic curvature of this surfactant was measured, and then set as a target for synthesis of similar performing surfactants with different structures. Three other surfactant structures were synthesized (with changing alcohol structure and degree of propoxylation) to match the target Cc, and the samples were characterized using fluids from the Mooney field. It was found that these four propoxylate sulfate surfactants of different structures showed comparable behavior in terms of interfacial tension reduction and microemulsion phase behavior. The core flood tests of formulations using these four materials showed similar oil recovery efficiency under Mooney Field conditions. Therefore, this paper demonstrates that alkyl propoxylate sulfate surfactants of different molecular structures but similar characteristic show similar behavior and oil recovery performance. The finding of this work provides formulators with a guideline to not only quickly and effectively choose the most suitable surfactant in terms of performance but also in terms of feedstock availability.