Application of the Marangoni Effect in Nanoemulsion on Improving Waterflooding Technology for Heavy-Oil Reservoirs

Summary Waterflooding is considered an important cold-production method because it is economically advantageous for heavy-oil-reservoir development; however, its efficiency is not remarkable because of the adverse oil/water-mobility ratio and cold damage from solid-state adsorption. To address this problem, oil/water emulsion is critical for improving the recovery by significantly altering oil mobility. Previous research is mainly focused on the effect of surfactants, salinity, and water/oil ratio on emulsion formation, rather than on the effect of kinetic energy under low or no shear stress on emulsification. In this study, experiments are conducted using a microscope to observe oil/water interfacial turbulence (Marangoni effect) when oil is dropped into a nanoemulsion. The purpose of this study is to form an emulsion using the interfacial turbulence under low or no shear stress, to improve heavy-oil recovery under waterflooding. The interfacial movement between a nanoemulsion and oil and the mechanism of formation of the emulsion are investigated. The Marangoni effect and mass transfer are observed by use of a microscope and low field nuclear magnetic resonance (NMR), respectively. Nanoemulsion, along with other methods of chemical enhanced oil recovery (EOR), is compared by conducting coreflooding and sandpack-flooding experiments after waterflooding. The results show that the Marangoni effect can help to emulsify and remove the oil from oil sand by converting interfacial energy into kinetic energy. On the basis of flooding-experiment results, we conclude that slug injection with a combination of nanoemulsion flooding and polymer flooding is an effective method for improving heavy-oil recovery.

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Synergistic effects of Janus graphene oxide and surfactants on the heavy oil/water interfacial tension and their application to enhance heavy oil recovery

Journal of Molecular Liquids ◽

10.1016/j.molliq.2020.113791 ◽

2020 ◽

Vol 314 ◽

pp. 113791 ◽

Cited By ~ 1

Author(s):

Han Jia ◽

Pan Huang ◽

Yugui Han ◽

Qiuxia Wang ◽

Xin Wei ◽

...

Keyword(s):

Graphene Oxide ◽

Interfacial Tension ◽

Oil Recovery ◽

Heavy Oil ◽

Synergistic Effects ◽

Heavy Oil Recovery ◽

Oil Water

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Water-Based Nanofluid-Alternating-CO2 Injection for Enhancing Heavy Oil Recovery: Underlying Mechanisms that Influence its Efficiency

10.2118/204331-ms ◽

2021 ◽

Author(s):

Changxiao Cao ◽

Zhaojie Song ◽

Shan Su ◽

Zihan Tang ◽

Zehui Xie ◽

...

Keyword(s):

Crude Oil ◽

Oil Recovery ◽

Heavy Oil ◽

Phase Inversion ◽

Core Flooding ◽

Heavy Component ◽

Water Emulsion ◽

Heavy Oil Reservoirs ◽

Oil Water ◽

Underlying Mechanisms

Abstract The efficiency of CO2 water-alternating-gas (WAG) flooding is highly limited in low-permeability heavy oil reservoirs due to the viscosifying action of W/O emulsification and high mobility contrast between oil and CO2. Here we propose a new enhanced oil recovery (EOR) process which involves water-based nanofluid-alternating-CO2 (NWAG) injection, and investigate the synergistic effect of nanofluid and CO2 for enhancing heavy oil recovery. Firstly, the oil-nanofluid and oil-water emulsions were prepared, and the bulk rheology and interfacial properties of emulsion fluid were tested. Then, core flooding tests were conducted to examine the NWAG flooding efficiency and its underlying mechanisms. The results showed that the bulk viscosity and viscoelasticity of oil-nanofluid emulsion reported much lower than those of oil-water emulsion, and nanofluid presented a positive contribution to the phase inversion from W/O to O/W emulsification. Compared with oil-water emulsion, the interfacial storage modulus of oil-nanofluid emulsion was obviously increased, which confirmed that more of crude oil heavy components with surface activity (e.g., resin and asphaltene) were adsorbed on interfacial film with the addition of silica nanoparticles (NPs). However, the interfacial viscosity of oil-nanofluid emulsion was much lower than that of oil-water emulsion, showing the irregularity of interfacial adsorption. This implied that the self-assembly structure of crude oil heavy component of the oil-water interface was destroyed due to the surface activity of silica NPs. During the core flooding experiments, NWAG injection could reduce the displacement pressure by 57.14% and increase oil recovery by 23.31% compared to WAG injection. By comparing produced-oil components after WAG and NWAG injection, we found that more of crude oil light components were extracted by CO2 during NWAG flooding, showing that the interaction between CO2 and crude oil was improved after oil-nanofluid emulsification. These findings clearly indicated two main EOR mechanisms of NWAG injection. One was the phase inversion during the nanofluid flooding process. The addition of silica NPs promoted phase-inversion emulsification and thus improved the displacement efficiency. The other was the enhanced interaction between CO2 and crude oil after oil-nanofluid emulsification. Because of the enhanced adsorption of crude oil heavy component on the oil-water interface, the proportion of light hydrocarbon increased in the bulk phase, and so the interaction between CO2 and oil phase was improved. This work could provide a new insight into the high-efficiency exploitation of low-permeability heavy oil reservoirs.

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