Jichao Fang

Study on the reutilization of clear fracturing flowback fluids in surfactant flooding with additives for Enhanced Oil Recovery (EOR).

An investigation was conducted to study the reutilization of clear fracturing flowback fluids composed of viscoelastic surfactants (VES) with additives in surfactant flooding, making the process more efficient and cost-effective. The clear fracturing flowback fluids were used as surfactant flooding system with the addition of α-olefin sulfonate (AOS) for enhanced oil recovery (EOR). The interfacial activity, emulsification activity and oil recovery capability of the recycling system were studied. The interfacial tension (IFT) between recycling system and oil can be reduced by 2 orders of magnitude to 10−3 mN/m, which satisfies the basic demand of surfactant flooding. The oil can be emulsified and dispersed more easily due to the synergetic effect of VES and AOS. The oil-wet surface of quartz can be easily converted to water-wet through adsorption of surfactants (VES/AOS) on the surface. Thirteen core plug flooding tests were conducted to investigate the effects of AOS concentrations, slug sizes and slug types of the recycling system on the incremental oil recovery. The investigations prove that reclaiming clear fracturing flowback fluids after fracturing operation and reuse it in surfactant flooding might have less impact on environment and be more economical.

Construction and performance evaluation of a highly efficient mixed foaming system

To develop a highly efficient foaming agent, the fluorocarbon surfactant (4-hydroxyethylether) (pentadecafluoroalkyl) amide was designed and synthesized and the surface activity and foaming performance were investigated through surface tension, surface viscosity and foaming performance measurements. The results show that the fluorocarbon surfactant has superior surface activity and can reduce the surface tension of water to 15.3 mN m−1. When used as a foaming agent, it also shows great advantages over conventional hydrocarbon surfactants. For the sake of cost reduction, sodium dodecyl sulfate (SDS) was added to construct a highly efficient foaming agent. The results show that the mixture has superior surface activity and great foaming ability. Surface viscosity measurements show that surface viscosity of the mixture is much higher than that of single SDS. The foam integrated value of the mixture is enhanced by about 67% compared to SDS. The optimized formula of the foaming system is 0.03–0.08% HPA4 + 0.20–0.40% SDS.

Study on adsorption characteristic of novel nonionic fluorocarbon surfactant (4-hydroxyethyl ether) (pentadecafluoro-alkyl) amide at coal-water interface

Experimental investigations were carried out to examine the adsorption equilibrium, isotherm, kinetic behaviors of adsorption, and effect on adsorption-desorption of coal-bed methane (CBM) of the nonionic fluorocarbon surfactant (4-hydroxyethyl ether) (pentadecafluoro-alkyl) in the development process of CBM. The results show that the surfactant adsorption pattern is consistent with the Langmuir adsorption law for different rank coals, and the adsorption capacity is increasing from low-rank coal to high-rank coal. The surfactant adsorption process is spontaneous and endothermic, indicating that augmentation of temperature facilitates the adsorption of surfactant. The adsorption densities over electrolytes concentration on the surface of low-rank and medium-rank coal show the same trend; while for high-rank coal, it gives some details about the different trends. Adsorption densities decrease with pH value increasing of bulk solution for all coal samples. Adsorption behavior of surfactant is conducive to accelerating CBM desorption through wettability alteration of a coal surface.