Effect of carbonate microfacies on contact angle: Study from middle jurassic Tuwaiq Mountain formation

Tuwaiq Mountain Limestone Formation (TMLF) is an important Middle Jurassic formation in Saudi Arabia as it encompasses two reservoir rocks, one source rock, and unconventional reservoir in Jafura basin. It is important to characterize the rock fluid interaction properties of the different microfacies of TMLF. Different samples were taken from different microfacies; spiculitic wackstone, coral floatstone, coral rudstone, and foraminiferal wack/pack-stone. The selected samples have four different facies with variable mineral composition, mud ratio, sorting, roundness, different types of porosities. Because of that, the petrophysical properties of different facies are different and this was governed by the different depositional and diagenetic controls on each microfacies. These differences affect the rock fluid interaction in terms of contact angle and adhesion forces between surface of rock plate and oil. The study showed that the difference in concentration of major and trace elements (especially Al⁺³, Mn⁺³ and Fe) in different microfacies controlled the difference in contact angle measurements. This difference is governed by the effect of the binding energy of Al⁺³, Mn⁺³ and Fe with polar substances in oil which in turn affect the oil adhesion on the rock surface. Also, it should be noted that the composition of oil has an interaction with microfacies as in case that the oil doesn't have polar substance (Resins and Asphaltenes), the differences in the concentration of major and trace elements in different microfacies might not have any effect adhesion and thus wettability and contact angle measurements.