Using HLD concept in enhanced oil recovery and other oilfield applications

Abstract: After the Hydrophilic-Lipophilic Deviation (HLD) concept was introduced in the 70s, it has been further developed to become a practical numerical approach to provide physico-chemical description of a surfactant-oil-water system by using 6-7 system variables. It has been widely used by formulators to screen and select suitable surfactant candidates in many different applications and helps shorten the surfactant formulation design and improvement process. This presentation provides examples of HLD applications in oilfield, especially Enhanced Oil Recovery (EOR). The focus is the process of simplifying surfactant formulation workstreams, seeking an economically viable alkali surfactant polymer (ASP) formulation for a challenging field application. It covers the initial evaluation of the promising surfactant formulation (interfacial tension and solubility), the improvement upon the formulation via HLD principles, and the evaluation of the improved surfactant formulation (coreflood studies). The final ASP formulation is composed of a 9 to 1 mixture of alkyl propoxy sulfate sodium salt (APS) to alkyl ethoxy sulfate sodium salt (AES) totaling 2000 ppm active surfactant content, 2.0 wt% Na₂CO₃, and 3000 ppm polyacrylamide polymer. All components are commercially available products. This formulation had ultra-low interfacial tension and favorable mixing behavior under reservoir conditions. This formulation reproducibly achieved target cumulative oil recovery, > 95% of original oil in place, with only 0.3 PV of ASP injection followed by alkali polymer injection. In addition to EOR application, other potential uses of HLD in oilfield application will also be discussed.