Rheological Measurements and Core Flood Data Analysis in Support of Chemical Enhanced Oil Recovery Formulation Design

This research involved rheological measurements and the analysis of core flood test data in support of the design of a formulation for Chemical Enhanced Oil Recovery (cEOR) at the Pioneer Rock Hill reservoir, a site characterized by relatively low formation brine salinity and temperature. Extensive and systematic rheological measurements identified viscosity values and rheological behaviors of different polymers, surfactants and polymer-surfactant solutions over a range of concentrations, salinities, and temperatures relevant to the targeted field conditions. The results were used to support formulation design in combination with phase behavior studies and interfacial tension measurements, provide information relevant to in-tank mixing/pumping operations, and maximize sweep efficiency and mobility control in the core flood tests. Further rheological measurements were conducted on the primary surfactant, Petrostep® S13D, over a broad range of concentrations in both deionized water and two synthetic brines, up to neat solution. The results of these tests indicate that different structures (micellar solution, hexagonal liquid crystal, and lamellar liquid crystal) form at different concentrations, supporting SAXS observations performed by another research group. In a separate effort, data obtained from core flood tests conducted in the Purdue EOR laboratory to evaluate and optimize formulations, were collected and organized. Five performance parameters: recovery factor in terms of %ROIP, oil saturation after chemical flood (Sorc), maximum injection pressure during chemical flood, surfactant sorption, and total injectant cost, were selected to evaluate test efficiency, based on technical and economic feasibility. Performance analysis of the core flood data and comparison with data from the literature show average to very good performance of the Purdue core flood tests