Titania minerals of Upper Jurassic - lower cretaceous sandstones of the Scotian Basin

Abstract

A study of titania (TiO₂) minerals was performed to test the hypothesis that precipitation of late diagenetic titania minerals in reservoir sandstones of the Scotian Basin is related to the migration of hydrocarbons. Reservoir sandstones of Upper Jurassic- Lower Cretaceous from the Scotian Basin showed all three polymorphs of titania to be present as authigenic minerals indicating Titanium (Ti) was mobile. Diagenetic anatase and brookite are more prominent than diagenetic rutile. Anatase is mostly early diagenetic, whereas brookite is usually late diagenetic and is abundant in reservoir sandstones above the free-water level. The availability and mobility of Ti is attributed to the dissolution of Ti-containing minerals (ilmenite, pseudorutile, biotite) enhanced by Ti complexes formed from hydrocarbon-rich and highly saline fluids. This study suggests that the precipitation of diagenetic brookite may be due to the incorporation of Fe and V during hydrocarbon charge and the presence of Clin the circulating fluids, which favour brookite polymorph formation.