Quantitative facies discrimination and the application of sequence stratigraphy to bed length modelling of shallow marine heterolithic facies

Quantitative studies of reservoir units at the facies and particularly the bed scale are rare though such data are essential to the modelling of connectivity and effective reservoir volumes in heterolithic facies. This paper describes a study of heterolithic shallow-marine, storm-dominated sediments in upward bed-thickening and coarsening cycles. Data were collected from two sequences: 1) the Cretaceous, Blackhawk Formation at Book Cliffs, Utah; 2) the Ordovician, Beach Formation, on Bell Islands, Newfoundland. Data from the two areas show that there is a consistent organisation of facies upward through a cycle. Detailed measurements of lateral bed continuity (bed length), show a difference of up to two orders of magnitude in bed length between different facies. Length is not necessarily strongly correlated with bed thickness or with height within a cycle. Although there is a consistent facies sequence in the cycles studied, it has been found that one facies is repeatedly reduced in thickness throughout a number of cycles. Analysis in terms of sequence stratigraphy suggests that this repetition reflects the position of the cycles within a lower order, lower frequency cycle and should help to constrain models of the facies architecture. -from Authors