Abstract: Facies Architecture and Its Effect on Permeability; Gypsy Sandstone, Northeast Oklahoma

Fluvial sandstones are not homogenous bodies of rock. They can be divided into facies architecture elements, and each of these packages have different characteristics. This study will examine directional permeability of facies architecture elements in the Gypsy Sandstone (lower Vamoosa), a Pennsylvanian meandering fluvial system.

The Gypsy outcrops expose several channels. These outcrops are being studied using photomosaics and high-precision surveying. Oriented samples of selected architectural elements are being collected. The samples will be serially sliced parallel and perpendicular to the bedding surfaces. The permeability will be measured on these surfaces using a pressure-decay profile permeameter. Thin sections will be cut to examine the microscopic characteristics such as grain size, packing, sorting and pore characteristics that may affect permeability. In this way, the directions of lesser and greater permeability within a facies architecture element will be explained by the microscopic characteristics of the rock.

Preliminary results indicate a hierarchy of architectural elements based on discrete genetic intervals (DGIs) each of which include facies such as channel fill and the associated levee, crevasse splay, and flood plain mudstones. Each of the facies can be divided into subfacies. Channel fill facies can be divided into lower, middle, and upper channel subfacies. Although results are consistent with recently published studies of others, this study suggests that exposures reveal transverse to highly oblique views of channel fill facies. 

AAPG Search and Discovery Article #90940©1997 AAPG Foundation Grants-in-Aid