Experimental investigations of the wettability of clays and shales

Abstract

[1] Wettability in argillaceous materials is poorly understood, yet it is critical to hydrocarbon recovery in clay-rich reservoirs and capillary seal capacity in both caprocks and fault gouges. The hydrophobic or hydrophilic nature of clay-bearing soils and sediments also controls to a large degree the movement of spilled nonaqueous phase liquids in the subsurface and the options available for remediation of these pollutants. In this paper the wettability of hydrocarbons contacting shales in their natural state and the tendencies for wettability alteration were examined. Water-wet, oil-wet, and mixed-wet shales from wells in Australia were investigated and were compared with simplified model shales (single and mixed minerals) artificially treated in crude oil. The intact natural shale samples (preserved with their original water content) were characterized petrophysically by dielectric spectroscopy and nuclear magnetic resonance, plus scanning electron, optical and fluorescence microscopy. Wettability alteration was studied using spontaneous imbibition, pigment extraction, and the sessile drop method for contact angle measurement. The mineralogy and chemical compositions of the shales were determined by standard methods. By studying pure minerals and natural shales in parallel, a correlation between the petrophysical properties, and wetting behavior was observed. These correlations may potentially be used to assess wettability in downhole measurements.

Experimental study on crack propagation in shale formations considering hydration and wettability

“…The presence of organic matter affects and complicates the LF shale wettability (Borysenko et al, 2009;Larsen and Aida, 2004;Elijah et al, 2011;Liu et al, 2014). The clay minerals were rich in Illite and did not contain swelling minerals, which indicates the LF shale hydration by spontaneous imbibition was different from the stronger swelling mudstone and shale (Qiu et al, 1989;Xiong et al, 2015a).…”

“…Additionally, the contact angle measurement liquid included water, white oil and diesel. We also used an LLE method (Borysenko et al, 2009) to evaluate the shale particle hydrophobicity. During this test, 1 g of powered shale (grain size below 10 mm) was placed inside a container with 20 mL of water and 20 mL diesel oil.…”

Study of the Effect of Clay Particles on Low Salinity Water Injection in Sandstone Reservoirs

“…Higher contact angle values of samples with kaolinite clays are due to the fact that kaolinite clay is hydrophobic in nature and shows more attraction towards asphaltenes and resins than montmorillonite clays [14]. Montmorillonite, on the other hand, is hydrophilic in nature and hence samples with montmorillonite have lower contact angle values when compared to samples with kaolinite content as shown in Figure 3 below.…”

Clay interaction with liquid and supercritical CO2: The relevance of electrical and capillary forces

“…The measurement of contact angle on fine-grained sediments is not straight forward due to heterogeneities, particle orientation and the development of suction. The film flotation and spontaneous/forced imbibition techniques can help characterize wettability in fine-grained sediments (Borysenko et al, 2009). Together, interfacial tension T s and contact angle  determine the magnitude of capillary phenomena (T s ·cos Â).…”