Influence of rock firing on the wettability of clay-rich sandstones

Document Type

Journal Article

Publication Title

Energy & Fuels

Volume

37

Issue

13

First Page

9329

Last Page

9338

Publisher

ACS

School

School of Engineering

RAS ID

60132

Comments

Al-Yaseri, A., Yekeen, N., Isah, A., Abdel-Azeim, S., Bello, A. M., & Sakthivel, S. (2023). Influence of rock firing on the wettability of clay-rich sandstones. Energy & Fuels, 37(13), 9329-9338. https://doi.org/10.1021/acs.energyfuels.3c01251

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.

DOI

10.1021/acs.energyfuels.3c01251

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