Abstract
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.
Highlights
Hydraulic fracturing [1] is the most effective technique to enhanced oil recovery (EOR), which plays an important role in ultra-low permeable oilfield development all over the world [2,3,4]
The reduction of interfacial tension (IFT) as low as possible is very important to the final oil recovery, which is generally a decisive factor in the surfactant flooding
The lowest IFT is only about 1021 mN/m, which can not satisfy the demand of surfactant flooding
Summary
Hydraulic fracturing [1] is the most effective technique to enhanced oil recovery (EOR), which plays an important role in ultra-low permeable oilfield development all over the world [2,3,4]. The development of fracturing fluids has been separated into three stages: active water, gelled hydrocarbons and transition metal cross-linked guarbased fluids [5]. These fracturing fluids are used most widely, their disadvantages seriously limit their extensive applications, such as poor sand carrying capability and great damage to the formation [6]. Cristian Fontana et al performed rheological and conductivity test of viscoelastic surfactant (VES) and polymeric fluid respectively [10]. The results showed that their rheological properties were similar, the retained conductivity of VES was 77% and that of polymeric fluid was 44%, indicating its lower formation damage.
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