Sedimentology and seuence stratigraphy of the late cretaceous lowe Ferron Sandstone: Application of 3-D geocellular modelling to the drunkards wash CBM-field in central Utha, USA

Abstract

Deposition of the Ferron Sandstone Member occurred during a widespread regression of the Western Interior Seaway during the Turonian. The Ferron is informally subdivided into two units. The Upper Ferron, ferronensis sequence is well exposed as a shallow marine and coastal plain clastic wedge along the edge of the Wasatch Plateau in central Utah. In contrast the Lower Ferron, hyatti sequence, has previously only been documented in the outcrop and as a basal sandstone in the subsurface Drunkards Wash, Buzzard Bench and Helper fields around the town of Price, where the Upper Ferron is interpreted to form a major coal bed methane accumulation in non-marine deposits overlying the Lower Ferron sandstone. The aim of this study is to improve the current understanding of the stratigraphy and sedimentology of the Lower Ferron unit. Correlation of 55 borehole logs coupled with outcrop studies have resulted in a new depositional model for the system. The correlations suggest that the Lower Ferron is comprised of a series of progradational to aggradational shoreface parasequences which prograded in an east to south-easterly direction. Modelling also suggests that a series of outcrops, previously interpreted as long shore bars, are in fact the downdip expression of these shorefaces. This model is supported by extrapolation of the facies tracts mapped in the subsurface, geometric reconstruction of the large scale structures and correlation of bentonite horizons. The final model suggests a more prominent Lower Ferron depositional system than previous studies and suggests a dynamic transition between the informally named Upper and Lower Ferron Sandstone.