Influence of Rock Firing on the Wettability of Clay-Rich Sandstones

Abstract

Rock firing is a conventional technique of core preparation to prevent clay swelling and fines migration in clay-rich rock; however, the influence of rock firing on the wetting behaviors and alterations of mineralogical compositions of clay-rich sandstones is not yet explicit. Thus, we assessed and compared the impacts of rock burning at two different temperatures (700 and 1100 °C) on the changes in wetting states of Bentheimer (BN) and clay-rich Bandera Gray (BG) sandstones through contact angle measurement, Amott wettability index determination, and thermogravimetric analysis (TGA). Results showed that rock firing makes the rocks more water-wet, but the clay-rich BG sandstone becomes significantly more water-wet than the quartz-dominated BN rock with increasing temperature. There was no change in rock porosity due to firing, but some clay remained, whereas some clays were transformed into other minerals after rock firing. Particularly, there were thermal transformations of clay to quartz and the disappearance of dolomite, chlorite, and clinochlore. Such transformation of these minerals into alkali metal oxide silicates dispersed on the rock matrix makes the surface more polar and enhances the interactions with water molecules, resulting in more water wettability for the BG sandstone. The study suggests that rock firing could change the clay-rich rock-wetting state into a more water-wet condition than the clay-poor or zero-clay sandstone samples; thus, the influence of rock burning on rock-wetting behavior should be considered to ensure an accurate prediction of the rock-wetting state due to rock burning. Moreover, burning at 1100 °C is recommended to achieve effective clay transformation and removal in clay-rich rock to prevent swelling, fines migration, and clay–fluid interactions.

Molecular Dynamics Perspective of Illite Wettability in Induced Acidic Conditions during Supercritical and Subcritical Carbon Dioxide Sequestration in Deep Saline Aquifers

“…In addition, Chen et al, 2023, further stated that strong interactions between clay minerals and water are a consequence of the polar nature of both clay minerals and water molecules. Al-Yaseri et al, 2023, obtained a comparable result from their experiments, stating that rocks with a higher content of clay had a stronger attraction to water compared to rocks with lesser clay minerals.…”

Role of Wettability Alteration in Enhanced Oil Recovery by In Situ Combustion: A Comprehensive Experimental and Modeling Study

“…Although Al-Yaseri et al studied the changes in wettability of different rock minerals under calcination processes and further analyzed their effects on recovery rates. Anthony Kerunwa et al find that the permeability and wettability of the calcined core will be improved to enhance oil recovery.…”

“…20 However, there is currently no research from the perspective of changes in wettability at the oil−water interface during in situ combustion (ISC) to study their contributions to improving recovery. Although Al-Yaseri et al 21 studied the changes in wettability of different rock minerals under calcination processes and further analyzed their effects on recovery rates. Anthony Kerunwa et al 22 find that the permeability and wettability of the calcined core will be improved to enhance oil recovery.…”