Abstract: Subsurface Structure of the North Summit Gas Field, Chestnut Ridge Anticline of the Appalachian Basin

Guojun Zhou, Robert C. Shumaker, William K. Staub

The Chestnut Ridge anticline is the westernmost of the High Plateau folds in southwestern Pennsylvania and north-central West Virginia that are detached primarily in the Marcellus Shale, and the Martinsburg, Salina, and Rome Formations. The primary, basal detachment at the Summit field occurs in the Salina salt. Production from fracture porosity in the Devonian Oriskany Sandstone commenced in 1936. During the late 1980s and early 1990s, 14 wells were drilled preparatory to conversion of the reservoir to gas storage. Schlumberger's Formation MicroScanner (FMS) logs were run in each of these wells to provide information on the structural configuration and fracture patterns of the reservoir. These data indicate that two inward-facing, tight folds at the Oriskany level form t e upper flanks and core of the anticline at the northern end of the field, whereas the main part of the field to the south is a comparatively simple, broad closure at the Oriskany level. The structure is a broad, slightly asymmetric open fold in the Mississippian Greenbrier Formation at the surface.

Fracture patterns mapped using FMS logs indicate a complex fracture system which varies slightly along the trend of the fold and among the units analyzed, including the Helderberg Formation, Huntersville Chert, Oriskany Sandstone, and Onondaga Formation. An orthogonal joint system strikes toward the northwest and northeast slightly askew to the trend of the fold's crestal trace. A similar, but more complex fracture pattern is found in an oriented core of these units.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas