InterPore2022

Surface-Active Compounds Induced Time-Dependency and Non-Monotonicity in Fluid-Fluid Displacement in Porous Media

2 Jun 2022, 14:00

15m

Oral Presentation (MS06-A) Physics of multiphase flow in diverse porous media MS06-A

Speaker

Dr YUJING DU (Harvard University)

Description

Low salinity waterflood (LSWF) has proven to be an economic, environmentally friendly IOR method which leads to more oil recovery without adding additional chemicals into water [1-3]. However, the efficacy and the underlying mechanisms are still under debate and many mechanisms are proposed in literature. Many factors are believed to attribute to the additional oil recovery by low salinity water injection, which can be categorized into fluid-solid interactions and water-oil interactions. The lack of agreement is partially due to the complex composition of the crude oil used in previous studies. Surface-active compounds in the crude oil can render the naturally hydrophilic rock surface hydrophobic by adsorbing on fluid/solid interfaces [4-6]. Similarly, their desorption from the interfaces at low salinity can alter the surface back to hydrophilic [7]. The surfactant’s redistribution and reactions with oil/water can potentially impact the macroscale water-oil two-phase flow dynamics in porous media.

In this paper, we investigate the impacts of surfactant concentration on the fluid-fluid displacement dynamics in porous media at both the macroscale and the microscale. We design the pseudo dual-component oils by mixing a non-polar mineral oil with different concentration of a non-ionic surfactant (sorbitan monooleate). This way, we mimic the crude oil that contains natural, surfactant-like polar components. Deionized water (DI water) and a high salinity brine (8.6 wt% NaCl, 1.2 wt% KCl, 2.0 wt% CaCl2) are used as the high salinity and low salinity in the displacement experiments. We visualize the macroscale water-oil displacements in inch-long micromodels and the oil droplet swelling processes in a dead-end pore. Interfacial tension between different oils and high and low salinity waters are measured. The oil swelling rates versus time at different surfactant concentrations are analyzed.

We observe that, at low salinity, the surfactant in the oil phase causes the water-in-oil emulsion and the droplet swelling and de-wetting, leading to the wettability alteration to a more water-wet state. Significant incremental oil displacement is obtained from the low salinity waterflood when the oil has high surfactant concentration. However, the impact of the surfactant on the incremental displacement efficiency is non-monotonic. This is caused by the two opposing effects of the increased surfactant concentration: stronger initial hydrophobicity which adversely affects the displacement and oil swelling which is beneficial for displacement. Two modes, gradual invasion and sudden collapse, are identified during the incremental displacements. They are explained by the evolution of local capillary force and global force imbalance, respectively. Both the microscale droplet geometry change and the macroscale two-phase displacement dynamics show time-dependency; the latter is characterized by a delay time of ~10^1 hours. The microscale droplet geometry change is over an order of magnitude faster than the macroscale displacement dynamics.

References

[1] Tang, G. Q.; Morrow, N. R. Salinity, Temperature, Oil Composition and Oil Recovery by Waterflooding. SPE Reserv. Eng. 1997, 12, 269–276.

[2] Lager, A.K., Webb, K.J., Black, C.J.J., Singleton, M. and Sorbie, K.S. Low Salinity Oil Recovery-An Experimental Investigation1. Petrophysics 2008, 49, 28–35.

[3] Yousef, A.; Al-Saleh, S.; Al-Kaabi, A.; Al-Jawfi, M. Laboratory Investigation of the Impact of Injection-Water Salinity and Ionic Content on Oil Recovery from Carbonate Reservoirs. SPE Reserv. Evaluation Eng. 2011, 14, 578–593.

[4] Standal, S.; Haavik, J.; Blokhus, A.; Skauge, A. Effect of Polar Organic Components on Wettability as Studied by Adsorption and Contact Angles. J. Pet. Sci. Eng. 1999, 24, 131−144.

[5] Mohammadi, S.; Mahani H.; Ayatollahi, S.; Niasar, A. Impact of Oil Polarity on the Mixing Time at the Pore Scale in Low Salinity Waterflooding. Energy Fuels 2020, 34, 12247−12259.

[6] Chen, Q.; Otaibi, M.; Ayirala, S.; Yousef, A. The Prospects and Potential Opportunities of Low Salinity Water Flooding for Offshore Applications in Sandstones. J. Pet. Sci. Eng. 2021, 199, 108260.

[7] Du, Y.; Xu, K.; Mejia, L.; Zhu, P.; Balhoff, M. T. Microfluidic Investigation of Low-Salinity Effects during Oil Recovery: A No-Clay and Time-Dependent Mechanism. SPE J. 2019, 24, 2841–2858.

Presentation materials

Interpore2022_YujingDu_#135_05_19_2022.pptx