Contamination of silica surfaces: Impact on water–CO2–quartz and glass contact angle measurements

Abstract

CO 2-wettability of sandstones is a key variable which determines structural and residual trapping capacities and strongly influences multi-phase fluid dynamics in the rock. An increasing number of researchers has now estimated this wettability by conducting contact angle measurements on quartz, however, there is a large uncertainty associated with the reported data. We demonstrate clearly that the main factor which leads to this broad data spread is due to surface contamination. It is clear that typically inappropriate cleaning methods were used which resulted in artificially high contact angle measurements. We used surface cleaning methods typically prescribed in the surface chemistry community and found that the water contact angle θ on a clean quartz substrate is low, 0-30°, and that θ increases with pressure. We conclude that quartz is strongly water-wet at high pressure conditions.

Potential applications of cyclodextrins in enhanced oil recovery

“…In spite of the great dispersion found in the literature for the oil-water-quartz system (the reported data vary broadly from 7 to 92 • , according to Ref. [30]), the value we found for this system was approximately in the center of the dispersed data. The reason for such dispersion is related to the cleaning method.…”

“…The cleaning procedure was repeated three times. We opted for solvent cleaning instead of other cleaning procedures given in the literature [30,31] involving strongly oxidizing agents (such as piranha solution) because these methods are known to render the surface too hydrophilic (high density of silanols and  ow close to zero), and the effect of the CD would not be detected. Moreover, these oxidizing agents could cause etching of the cuvette, which would not be optically clear any longer, making it difficult to register the drop pictures.…”

“…The reason for such dispersion is related to the cleaning method. It is known that strongly oxidizing agents increase silanol density to a maximum [30,31,46], leading to highly hydrophilic surfaces, not suitable for our purposes. We decided then to use a milder cleaning procedure (sonication with solvents), in order to keep the natural silanol density of airequilibrated quartz, for which the value of  ow = 36 • is consistent.…”

Contact angle measurement ambiguity in supercritical CO2–water–mineral systems: Mica as an example

“…For examples, NOCROMIX [(NH4) 2 S 2 O 8 ] (Saraji et al, 2013), Piranha solution (H 2 SO 4 :H 2 O 2 in a 5:1 volume ratio) and air plasma (Iglauer et al, 2014) can chemically increase surface charge density to artificially make the substrate more hydrophilic, as pointed by Saraji et al (2014). All of these aforementioned differences in surface preparation methods may contribute to the variation in measured CAs, pinning and hysteresis.…”

A Realistic Look at Nanostructured Material as an Innovative Approach for Enhanced Oil Recovery Process Upgrading

“…Carbon capture and storage (CCS) [123][124][125][126][127][128] is considered the most direct carbon management strategy for long-term reduction of such greenhouse gases. However, the capturing and storage process of CO 2 in geological formations such as deep saline aquifers or depleted reservoirs pose potential leakage threats, which has raised several concerns about the feasibility and long-term storage fate of such CO 2 .…”