Design of Laboratory Studies to Develop the Chemical Formulation for Surfactant-Polymer Flooding

Nowadays, chemical EOR methods are becoming more and more relevant, among which the alkali-surfactant-polymer flooding is of particular interest. The efficiency of this technology largely depends on the correct choice of the components of chemical formulation, which should be based on a set of laboratory experiments carried out in a given sequence. This paper presents a methodological approach to laboratory studies in order to develop an optimal surfactant-polymer formulation, taking into account the geological and physical characteristics of the target field and the properties of reservoir fluids. The experimental part of the research work was carried out in several stages, involving the analysis of the physicochemical characteristics of reservoir oil, the screening studies of surfactant and polymer samples, as well as a series of coreflood tests with a selected chemical formulation on the terrigenous reservoir models. During screening studies, the solubility and compatibility of the chemical components, the phase behavior of surfactant solutions with oil at different salinity values and water-oil ratios, static adsorption of chemicals on the rock and their thermal stability at reservoir temperature were investigated. Optimization of the chemical formulation was based on the results of IFT measurements of the surfactant solutions and rheological studies of the polymer solutions. At the stage of coreflood tests, physical simulation of the surfactant-polymer flooding was carried out on reservoir models using natural core material in order to optimize the composition and slug size of the developed chemical formulation. The obtained results of the displacement experiment were matched by numerical 1D simulation. Based on the results of the studies performed, an effective surfactant-polymer formulation has been designed, which provides the ultra-low IFT (2.8·10−4 mN/m) values and the ability to form stable middle-phase microemulsions when interacting with oil. The findings of thermal stability and static adsorption experiments confirmed a feasibility of selected chemicals for practical application. Within the framework of the study, the key technical parameters of proposed formulation were determined, which are required for up-scaled simulation study of the chemical flooding process at pilot site.