(59d) Displacement Efficiency and Production Characteristics of in-House Developed Surfactants for Enhanced Oil Recovery

Enhanced oil recovery (EOR) is a technique in which chemicals are injected into the formation to recover over 60% of the remaining oil after waterflooding. Surfactants are the main components used for chemical-enhanced oil recovery (cEOR). However, surfactant adsorption as well as precipitation due to elevated temperature and salinity reservoir environments are the significant challenges the industry facing today. The current research intends to systematically experiment with the influence of elevated temperature and high salinity on surfactant adsorption and provides a guideline for controlling their retention and precipitation due to harsh conditions.

In the first step, the zwitterionic surfactants were prepared using green or no solvents and characterized by NMR, FTIR, and ESI-MS tests to verify the structure of the surfactant and validate the synthetic method. The heat tolerance capacity of the surfactant was measured by Thermal Gravimetric Analysis (TGA) as well as the aging technique. The surface/interfacial tension was studied using a force tensiometer and spinning drop method, respectively. The adsorption tests were conducted on calcite, dolomite, and quartz. The morphology of the rocks was characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) methods.

The in-house prepared surfactants displayed high solubility in high and low-salinity water without any precipitation over a long period. The TGA curves revealed a sharp decline above 250 ^oC which was greater than the reservoir temperature (≥90^oC). In addition, the aging technique showed no phase separation or milkiness of the aqueous solution of surfactants after keeping the samples in the oven for up to three months at 90 ^oC. The surface/interfacial tension of the prepared surfactants was similar to or larger than the commercial surfactants. Experimental data indicates that the surfactant adsorption varies by varying the clay minerals due to intercalation of surfactant on the carbonates.

The results revealed that the generated surfactants exhibited high heat stability, clear aqueous solutions, low surface/interfacial tension, and less adsorption onto carbonates. All these advances are important in cEOR that will help to develop a suitable material to enhance production with reduced cost and time.