High resolution sequence stratigraphy, sedimentology, petrology and reservoir potentials of the Glauconitic member in Westerose and adjacent fields, Alberta, Canada
The Glauconitic member hosts significant gas reserves in an extensive northeastsouthwest trending marine complex informally known as the Hoadley barrier. The unit is studied in order to develop a high resolution sequence stratigraphic model and understand facies architecture, petrology and diagenetic pathways of this strata within a sequence stratigraphic framework. Six high frequency sequences are recognized (G 1, G2, G3, G4, G5 and G6) within the Glauconitic member in the study. These sequences are separated from one another by surfaces of incision or subaerial exposure which in locations are coincident with a flooding surface or transgressive surface of erosion. The sandstones of the G 1 sequence are very fine grained quartzarenites deposited in a storm-dominated shoreface. A transgressive systems tract (TST) as well as a highstand systems (HST) are recognizable in the G2 sequence. Within the HST, two parasequences (G2A and G2B) are recognized separated by a flooding surface. The G2A sandstones are very fine to fine-grained dolomite-rich litharenites deposited in a stormdominated shoreface. They are characterized by abundant dolomite cement and rarely develop reservoir quality porosity and permeability. The G2B sandstones are very to fine grained chert litharenites deposited in a strandplain storm-dominated system. These sandstones develop reservoir quality within the relatively quartz-rich foreshore facies. The G3 sequence is characterized by a TST consisting of estuarine and shoreface depositional systems. The overlying HST is a wave-dominated delta fed by shoreface coeval delta distributaries. G3 sandstones are fine to medium grained chert litharenites (shoreface) to sublitharenites (foreshore) and are excellent gas producers as a result of their coarser grain size and abundance of secondary porosity. Volcanic arenites and feldspar-rich litharenites are typical of the G4 sequence. Pluvial and estuarine incised valleys of the TST and coastal plain sediments of the HST characterize the G4. The sandstones are plugged with carbonate and clay cement and matrix and do not develop reservoir quality. The G5 and G6 sequences are recognized and mapped on the basis of the recognition of regional correlatable G4, G5 and G6 coals. These coals cap the various sequences and amalgamate, split and contain crevasse splays and channels in between them. The 06 channel is interpreted as being deposited in a large bedload channel with a tendency to erode its banks.
Bibliography: p. 264-280.
Okaro, P. I. (2001). High resolution sequence stratigraphy, sedimentology, petrology and reservoir potentials of the Glauconitic member in Westerose and adjacent fields, Alberta, Canada (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/11545