Solution Property Investigation of Combination Flooding Systems Consisting of Gemini-Non-ionic Mixed Surfactant and Hydrophobically Associating Polyacrylamide for Enhanced Oil Recovery

The aim of this work was to investigate the solution properties of a new polymer surfactant (SP) flooding system, including hydrophobically associating polyacrylamide (HAPAM) and mixed surfactant [mixture of fatty acid disulfonate anionic gemini surfactant (DMES) and non-ionic surfactant Triton X-100 (TX-100)]. The critical micelle concentrations (cmc's) of four gemini surfactants were smaller than 100 mg L-1. Furthermore, their interfacial tensions (IFTs) could reach an ultralow value with Bohai oil at lower concentrations. Through optimized formulation, we found that DMES-14 had better properties and was selected as the major component of the surfactant. We designed an optimal formulation of the SP system with 1750 mg L-1 HAPAM and 3000 mg L-1 mixed surfactant (the mass ratios of DMES-14 and TX-100 are from 4:1 to 5:1). The SP system (ratio of 4:1) with a very small surfactant concentration could reach ultralow IFT with different crude oils, which proved that the simpler component surfactant had better reservoir compatibility. TX-100 could widen the window of increasing viscosity and weaken the disadvantage of the interaction between HAPAM and the surfactant. The stability of this SP system was evaluated by the temperature, mineralized degree, shearing, aging time, adsorption, and chromatographic separation. All of experiments showed that it still keeps higher viscosity and ultralow IFT with different evaluation conditions; therefore, it is feasible to use as a SP combination flooding system for enhanced oil recovery (EOR).