ABSTRACT: Using Well-Cutting and Wireline Log Analysis to Better Understand the Tectonic and Eustatic Controls of Reservoir Development in the Subsurface Appalachian Basin, West Virginia, USA
WYNN, THOMAS C., and READ, J. FRED, Dept. of Geological Sciences, Virginia Tech, Blacksburg, VA
High resolution sequence stratigraphy of the 50 to 500 m thick mixed carbonate-siliciclastic Mississippian Greenbrier Group is being done in the subsurface Appalachian Basin, West Virginia, using well-cuttings and wireline logs to better understand the tectonic and eustatic controls on reservoir development. Using this data set, a series of detailed regional cross-sections and isopachs are being prepared.
Subsurface analysis shows five major sequences composed of two to five regionally mappable high frequency sequences (HFS's). Major- and high frequency sequences are composed of lowstand red beds up-dip and shallow marine sands along the ramp margin, semi-transgressive shale's, and high-stand quartz peloidal grainstone (dominantly eolian), peritidal lime mudstone, peloid grainstone, ooid grainstone, skeletal grainstone, open marine skeletal wackestone/mudstone, and shaly slope mudstone. Sequence boundaries underlie lowstand sands along the ramp margin, and up-dip they underlie red beds, caliches and/or eolianites.
A subtle regional linear tectonic high is evident along the ramp margin in the vicinity of the basinal hinge line. This hinge separates the relatively stable up-dip sections from the faster subsiding basin. Thickness trends strongly reflect tectonically induced basinal subsidence. Even though subsidence rates in the up-dip and downdip areas differ by an order of magnitude it was the eustatic signal, which is traceable from the Appalachian Basin into the Illinois Basin, that generated the HFS's. Three to five of these HFS's are bundled to make up the four third-order sequences, which can be matched with the sea level curve of Ross and Ross (1987).
Search and Discovery Article #90907©2000 AAPG Eastern Section Meeting, London, Ontario, Canada