Abstract
Surfactant polymer (SP) flooding has become an important enhanced oil recovery (EOR) technique for the high-water cut mature oilfield. Emulsification in the SP flooding process is regarded as a powerful mark for the successful application of SP flooding in the filed scale. People believe emulsification plays a positive role in EOR. This paper uses one-dimensional homogenous core flooding experiments and parallel core flooding experiments to examine the effect of emulsification on the oil recoveries in the SP flooding process. 0.3 pore volume (PV) of emulsions which are prepared using ultralow interface intension (IFT) SP solution and crude oil with stirring method was injected into core models to mimic the emulsification process in SP flooding, followed by 0.35 PV of SP flooding to flood emulsions and remaining oil. The other experiment was preformed 0.65 PV of SP flooding as a contrast. We found SP flooding can obviously enhance oil recovery factor by 25% after water flooding in both homogeneous and heterogeneous cores. Compared to SP flooding, emulsification can contribute an additional recovery factor of 3.8% in parallel core flooding experiments. But there is no difference on recoveries in homogenous core flooding experiments. It indicates that the role of emulsification during SP flooding will be more significant for oil recoveries in a heterogeneous reservoir rather than a homogeneous reservoir.
Highlights
Most of the continental sedimentary reservoirs are feathered with severe heterogeneity
It means that compared to SP flooding, more oil were dispersed in the aqueous phase, which indicated that combining emulsion flooding and SP flooding can reflect the influence of emulsification on the ultimate oil recovery in the process of SP flooding
The recovery factors of water flooding in two experiments were similar, which indicated that they had a good repeatability
Summary
Most of the continental sedimentary reservoirs are feathered with severe heterogeneity. SP solution can increase the viscosity of displacing phase and control mobility by adding water-soluble polymer and effectively mobilize trapped oil with the ultralow oil-water interfacial tension (IFT) surfactant [6, 7]. Guo et al [20] and Luan et al [21] used surfactants with different emulsifying capacities for core flooding experiments and found that emulsification was more important than the reduction of IFT in some cases. There is no clear conclusion whether the emulsification during SP flooding with ultralow IFT surfactant can further enhance oil recoveries To clarify these problems, this paper selects the industrially applied SP system with corresponding crude oil to generate emulsions and compare the effect of emulsification on oil displacement efficiency in the SP system on homogeneous cores and dual cores after water flooding. Our work shows that the emulsions in the ultralow IFT SP system can enhance oil recoveries in the heterogeneous dual cores rather than the homogeneous cores
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