Measurement of Non-Wetting Phase Trapping in Sand Packs

Abstract

We measure the trapped non-wetting phase saturation as a function of initial saturation in sand packs. The application of the work is for carbon dioxide (CO 2) storage in aquifers, where capillary trapping is a rapid and effective mechanism to render the injected fluid immobile: the CO 2 is injected into the formation followed by chase brine injection or natural groundwater flow that displaces and traps it. Current models to predict the amount of trapping are based on experiments in consolidated media; while CO 2 is likely to be injected at depths greater than around 800 m to render it super-critical, it may be injected into formations that tend to have a higher porosity and permeability than deep oilfield rocks. We use analogue fluids-water and refined oil-at ambient conditions. The initial conditions are established by injecting oil into vertical or horizontal sand packs 1 m long at different flow rates and then allowing the oil to migrate due to buoyancy forces. The packs are then flooded with water. The columns are sliced and the residual saturation measured with great accuracy and sensitivity by gas chromatography. This method allows low saturations to be measured reliably. The trapped saturation initially rises linearly with initial saturation to a value of around 0.11, followed by a constant residual as the initial saturation increases further. This behavior is not predicted by the traditional Land (1968) model, but is physically consistent with poorly consolidated media where most of the larger pores can easily be invaded at relatively low saturation and there is, overall, relatively little trapping. The best match to our experimental data was achieved with the Aissaoui (1983) trapping model.

Three Phase Measurements of Nonwetting Phase Trapping in Unconsolidated Sand Packs

“…We also find that the amount of oil trapped is insensitive to either the initial gas saturation or the amount of gas that is trapped. More oil is trapped than would be predicted from an equivalent two-phase system, although the trapped saturation is never larger than the maximum reached in two-phase flow (around 11%) (Pentland et al 2008). These initially surprising results are explained in the context of oil layer stability and the competition between snap-off and piston-like advance.…”

Injectivity and quantification of capillary trapping for CO 2 storage: A review of influencing parameters

“…A number of parameters have been highlighted with impacts on capillary trapping of residual CO 2 including pore aspect ratio (Pentland, 2011;Tanino and Blunt, 2012), initial gas-phase saturation (Al-Menhali et al, 2014;Pentland et al, 2011b;Suekane and Nguyen, 2013), initial oil saturation (Al Pentland et al, 2008), interfacial tension (Bennion and Bachu, 2006) and CO 2 viscosity (Harper, 2013). Pore geometry (Holtz, 2003;Iglauer et al, 2009;Pentland et al, 2012;Suekane et al, 2010;Tanino and Blunt, 2012), wettability (Chalbaud et al, 2007(Chalbaud et al, , 2009Farokhpoor et al, 2013;Iglauer et al, 2015;Soroush et al, 2013), rock type (Andrew et al, 2014), presence of impurities in CO 2 gas stream (Metz et al, 2005;Wang et al, 2011) and hysteresis (Jalil et al, 2012;Juanes et al, 2006) may also contribute into changes in capillary trapping.…”

Evaluation of relative permeability functions as inputs to multiphase flow models simulating supercritical CO2 behavior in deep geologic formations

“…To experimentally mimic flow and capillary trapping of scCO 2 in saline aquifers, Soltrol 220 (hereafter referred to as Soltrol) and an 80% by weight solution of glycerol in water (hereafter referred to as 80% glycerol) were used as surrogates for scCO 2 and brine, respectively. These fluids were chosen as to be within the range of dimensionless groups such as capillary num- Table 2 Density ( ) and viscosity ( ) of 80% and 50% by weight solutions of glycerol in water (Cheng, 2008 ber, bond number, viscosity ratio, and density ratio, relevant to that of scCO 2 and brine (Cinar et al, 2009;Pentland et al, 2010;Aminzadeh-goharrizi et al, 2012;Trevisan et al, 2014;Mori et al, 2015). These dimensionless numbers are defined in Mori et al (2015).…”