Combining field description, in situ minipermeameter measurements, geostatistical analysis, and ground penetrating radar (GPR) analysis permits development of an interwell-scale 3D characterization of sandstone deposits. In the Tonganoxie Sandstone incised-valley-fill (IVF) system in the Pennsylvanian of eastern Kansas, outcrop analogs were examined in order to determine the types of macroforms that exist in the system, describe architectural elements and their orientation, and provide estimates of the variations in permeability values in these elements. In the Tonganoxie Sandstone, fluvial and fluvially-influenced, estuarine (FIE) sandstones are present that are potential reservoir analogs for numerous IVF oil and gas reservoirs in the Pennsylvanian of the midcontinent. Two outcrop sites were studied, one of fluvial sandstone and the other of FIE sandstone. The sites were analyzed in terms of their flow unit characteristics by combining geological descriptions utilizing architectural element analysis with geostatistical descriptions of their permeability structure. Conventional statistical analyses and semivariograms were used to determine the permeability structures and the horizontal continuity of permeability values within flow units identified at the sites. The results of the analysis of permeability measurements taken along the two exposures are discussed and the sites are compared in order to highlight differences in their permeability structures. In addition, the fluvial study site was investigated using a combination of information from outcrop description and three-dimensional GPR analysis. A grid of high-resolution GPR profiles showed the three-dimensional (3D) geometry of component elements in one of the flow units identified at the fluvial site and was used to establish the size, spatial continuity, and general transport directions for several of these elements. This study provides geological descriptions, geometric information, and geostatistical descriptions of macroform types that are thought to commonly occur in subsurface IVF reservoirs.

Abstract The best exposure of the Spillway fault system is in the northwest wall of the northwest-trending spillway of Tuttle Creek reservoir (SW¼, SE¼SW¼, Sec.18, T.9S., R.8E.) in westernmost Pottawatomie County, immediately northwest of the point where Kansas 13 crosses the spillway (Fig. 1). From Manhattan, Kansas, drive north-northwest on Tuttle Creek Boulevard (also US 24, Kansas 13 and 177) 3.6 mi (5.7 km) from its intersection with Kimball Avenue to the point where Kansas 13 turns right (northeast). Drive 1.8 mi (2.9 km) across the dam to the parking areas on both sides of the road that overlook the spillway to the northeast.

Abstract Seismic reflection profiling in northeastern Kansas by COCORP was initiated to investigate several prominent features of the midcontinent, including the Midcontinent Geophysical Anomaly (MGA), which has been associated with a buried extension of the Keweenawan rift, and the Nemaha Uplift, part of a crystalline basement block uplifted in Pennsylvanian time (Figure 1). The MGA is characterized by gravity and aeromagnetic highs extending from the Lake Superior region to near the Kansas-Oklahoma border (Figure 1, 2, 3; see Yarger, 1981). Surface exposures in the north, as well as samples drilled along the trend of the anomalies, indicate that mafic volcanic rock and associated clastic sediments were deposited in a narrow trough formed by continental rifting of Keweenawan age (1.1 b.y. ago; see also King and Zietz, 1971; Chase and Gilmer, 1973). The Nemaha Uplift is a north-south trending feature extending from Omaha, Nebraska to northern Oklahoma (Figure 1). in northeastern Kansas the Nemaha separates the Forest City basin from the Salina basin to the west (Steeples, in press). The origin of the Nemaha Uplift and associated Humboldt border fault (Figure 4) is enigmatic, but their lateral proximity and subparallelism to the MGA suggests that they may represent reactivated rift structures (Yarger, 1981).