Outcrop characterization of architecture and permeability structure in fluvial-deltaic sandstones, Cretaceous Ferron Sandstone, Utah

This dissertation discusses the control of sedimentary architecture on permeability structure within a Cretaceous fluvial-deltaic system. Research concentrated on quantifying reservoir heterogeneity within distributary and delta front sandstones from outcrops of the Ferron Sandstone by detailed analysis of facies architecture and use of a Mechanical Field Permeameter.; The deltaic Ferron Sandstone, deposited during a regressive maximum of the Cretaceous Western Interior Seaway, is composed of discrete deltaic units bounded by time significant surfaces. Deltaic units are arranged into a succession of two strongly progradational units overlain by five retrogradational units. This sequence stratigraphic framework was utilized to compare styles of heterogeneity between a strongly progradational and retrogradational deltaic unit.; Textural and detrital characteristics of sandstones correlate predictably to permeability. On the basis of lithofacies relationships, discrete permeability groups can be established that describe permeability variation at multiple scales of stratal organization and are related to processes active at the time of deposition. In turn, permeability patterns and correlation ranges as estimated by the semivariogram are scale-dependent and related to the arrangement of beds, bedsets, and groups of bedsets. Horizontal correlation ranges exceed vertical by a factor of five to ten and range from several ft for beds, tens of ft for bedsets, and hundreds of ft for groups of bedsets.; Stratal architecture displays systematic changes as a function of stratigraphic position within the Ferron clastic wedge. The principal reservoir facies within strongly progradational and retrogradational deltaic units are delta front and distributary channel sandstones, respectively. Within each reservoir facies, autocyclic processes related to delta lobe switching and distributary channel avulsion are the primary controls reservoir heterogeneity. Within strongly progradational deltaic sequences, homogeneous, wave-dominated shoreline sand bodies alternate with heterolithic, fluvial-dominated delta front strata. Internally, mudstones deposited along abandonment surfaces attributed to distributary channel avulsion further compartmentalize the interval both laterally and vertically. Within the retrogradational deltaic unit distributary channel deposits form a complex network of broad tabular sand bodies compartmentalized both laterally and vertically by abandoned channel fill and low permeability lithologies deposited along channel base bounding surfaces.