Diagenesis, Burial history, and Reservoir Characterization of the Scollard sequence sandstones in Alberta

A detailed laboratory study of sandstone samples from outcrops and conventional core samples from the Maastrichtian-Paleocene Scollard-age fluvial strata in the Western Canada foredeep was undertaken to investigate the reservoir characteristics, burial depth history, and sandstone diagenesis.;It has been observed that kaolin mineral content increases in sandstones lying below subaerial unconformities, which mark the most significant stratigraphic hiatuses and hence the sequence boundaries in fully fluvial successions.;This study demonstrates the effects of burial depth and paleoclimate on pore-water chemistry, which in turn, influenced the mineralogy and the distributions of authigenic minerals in the sandstones. The delta 13C and delta18O compositions of pedogenic carbonate nodules from the Willow Creek Formation associated with the red shale host sediments have been used as a paleoclimate and paleoenvironmental proxy. The isotopic composition of nodules suggests that these formed during drier conditions when C3 vegetation prevailed at the site. The predominance of smectite and illite in fines and the poor floral content point to a low seasonal rainfall in a semi-arid climatic environment.;The sandstones are predominantly litharenites and sublitharenites, which accumulated in a variety of fluvial environments. The porosity of the sandstones is both syn-depositional and diagenetic in origin. The potential of a sandstone to serve as a reservoir for producible hydrocarbons is strongly related to the sandstone's diagenetic history. Detailed study of the distribution of authigenic minerals of the Scollard sequence suggests that the diversities in the pattern distribution of authigenic clay minerals in the regions are not random but they coincide with the burial depth of these strata and has a well-defined relation to the sequence stratigraphic framework The general absence of dickite, coupled with limited conversion of smectite into illite in the Scollard sandstones, suggests crystallization at a depth less than 1.5 km. In contrast, the occurrence of blocky dickite, fibrous illite and chlorite in the Coalspur and Willow Creek sandstones, coupled with albitized feldspars and quartz cement, suggests that sandstones there underwent a maximum burial depth greater than 3 km.