Review of the litterature available outside the petroleum industry concerning wettability. This litterature discusses surface forces and their effects on wettability, including van der Waal and electrostatic forces. Hydrogen bonding and ion/water interactions, are also discussed. Advancing and receding contact angles for oil/water/mineral systems in terms of these surface forces are described.

Wettability : fundamentals and surface forces

Electrokinetics of Carbonate/Brine Interface in Low-Salinity Waterflooding: Effect of Brine Salinity, Composition, Rock Type, and pH on ζ-Potential and a Surface-Complexation Model

A comprehensive review of low salinity/engineered water injections and their applications in sandstone and carbonate rocks

Literature review of low salinity waterflooding from a length and time scale perspective

Advances in improved/enhanced oil recovery technologies for tight and shale reservoirs

Numerous studies indicate that the pressure/volume/temperature (PVT) phase behavior of fluids in large pores (designated “unconfined” space) deviates from phase behavior in nanopores (designated “confined” space). The deviation in confined space has been attributed to the increase in capillary force, electrostatic interactions, van der Waals forces, and fluid structural changes. In this paper, conventional vapor/liquid equilibrium (VLE) calculations are modified to account for the capillary pressure and the critical-pressure and -temperature shifts in nanopores. The modified VLE is used to study the phase behavior of reservoir fluids in unconventional reservoirs. The multiple-mixing-cell (MMC) algorithm and the modified VLE procedure were used to determine the minimal miscibility pressure (MMP) of a synthetic oil and Bakken oil with carbon dioxide (CO2) and mixtures of CO2 and methane gas. We show that the bubblepoint pressure, gas/oil interfacial tension (IFT), and MMP are decreased with confinement (nanopores), whereas the upper dewpoint pressure increases and the lower dewpoint pressure decreases.

Phase Behavior and Minimum Miscibility Pressure in Nanopores

A Laboratory Study of Ionic Effect of Smart Water for Enhancing Oil Recovery in Carbonate Reservoirs

Carbonate reservoirs are considered to be in the range of mixed to oil wetting state. Their present wetting state seems unfavorable to recover more oil via conventional waterflooding especially as the water cut increases with huge residual oil saturation. In recent years, studies have shown that tuning the injected brine chemistry can help decrease the oil-wetness, resulting in additional oil recovery and reduction in residual oil saturation. Thus, rock wettability is being dictated by the surface chemistry associated with the water-film stability between crude oil and the rock surface. This study presents series of experiments conducted on Middle Eastern carbonate core plugs at high pressure and high temperature in order to determine the impact of sulfate ions in smart brine on oil recovery. Each experiment was initially conducted using the formation brine, and subsequently, various versions of seawater with varying sulfate concentrations were used. Coreflooding experiments showed an additional recovery of about 7–9 % oil originally in core when sulfate concentration was increased while none when decreased. Decrease in rock oil-wetness was observed to be responsible for the improved recovery as demonstrated by the contact angle analysis. Similar trend was observed with the zeta potential analysis which further proved that the magnitude of surface charge alteration contributes immensely to wettability modification toward more water-wetness.

Ali M. AlSumaiti

Papers

Phase Behavior and Minimum Miscibility Pressure in Nanopores

A Laboratory Study of Ionic Effect of Smart Water for Enhancing Oil Recovery in Carbonate Reservoirs

An Experimental Investigation into the Impact of Sulfate Ions in Smart Water to Improve Oil Recovery in Carbonate Reservoirs

Wettability Alteration during Low-Salinity Waterflooding in Carbonate Reservoir Cores

Low-salinity water-alternating-CO2 EOR