Facies examined during the Clastic Reservoir Facies Field Seminar include: channelbelt, alluvial valley fill, shoreface, wave- and river-dominated deltas, distributary channel and mouth bar, tidal inlet and tidal channel, transgressive lag, and shelf sand. Outcrops visited are in the Book Cliffs, Castle Valley, the Henry Mountains Basin, and the Kaiparowits and Markagunt Plateaus.
The seminar focuses on the lithologic variations that characterize clastic reservoir facies and on development of models that can be used to predict these variations in the subsurface. Participants will learn about clastic reservoir facies through a series of case studies. Case studies initially focus on the vertical facies successions that characterize particular paleoenvironments and the criteria that can be used to recognize them on wireline logs and in cores. The main emphasis of the case studies, however, is on lateral relationships. The scales of lateral variations examined range from reservoir heterogeneities at inter-well spacing up to the more regional facies variations that are the basis for exploration models.
Lateral relationships that characterize clastic reservoir facies are demonstrated by walking representative units out in areas of continuous exposure. To cite one example: on outcrops of the Ferron Sandstone, participants examine the sandstone grain size and the sedimentary and biogenic structures that occur at the landward edge of a sandstone body that accumulated on a prograding shoreface. They then walk across the landward pinch-out of the sandstone body into deposits of the lagoon and swamp that lay behind the shoreline. Sections from the outcrops and from a large number of nearby drillholes reveal the facies relationships. The emphasis in this field seminar is on practical applications: if, for instance, a discovery well penetrated a hydrocarbon bearing shoreface unit consisting of 8 m of upper shoreface and foreshore strata lying directly on a marine flooding surface, what is the likelihood that an appraisal well drilled one km landward would also encounter shoreface strata, rather than non-reservoir lagoonal beds? The Ferron example mentioned above serves as an analog and provides an answer.
Larger-scale variations are examined by driving between localities. By this means, architectures of river-dominated deltas and of the channel belts that fed them are demonstrated in the Ferron Sandstone in Castle Valley. The effects of subsidence patterns on the architectures of channel belts and shoreline sandstone bodies of the Dakota Sandstone are examined in the Henry Mountains Basin and on the margins of Kaiparowits Plateau.
Class size is kept small for mobility and to promote group and individual discussions with the instructor on the outcrop. A considerable amount of hiking is involved. Participants should be in good physical condition.
The field trip route passes through Capitol Reef, Bryce Canyon and Zion National Parks and the Grand Staircase-Escalante National Monument, which contain some of the most beautiful country in the Colorado Plateau region.