Structural Geology of Delsignore 1: A Central Eastern Overthrust Well: ABSTRACT

Abstract

Located along the Appalachian structural frontal zone of the central Eastern Overthrust, the Robert Delsignore 1 was drilled in early 1984 to a total depth of 9,965 ft after 77 days. The well was spudded within the lower Upper Devonian Chemung Group, and at total depth, the well was in the Lower Devonian Helderberg Group. The well is located less than 1 mi from the nearest Lower Devonian outcrop and approximately 1 mi across strike from the Mastellar discovery wells by Columbia Gas in Mineral County, West Virginia. The well penetrated only Upper Devonian through Upper Silurian strata and showed the existence of the following: repeated and overturned strata, numerous southeast-dipping thrust faults, a northwest-dipping backthrust, nearly recumbent folds, and a folded, overturned thrust fault. From this geologic discombobulation, a nearly true stratigraphic penetration of 3,150 ft was made within a 9,965-ft well. Several good hydrocarbon shows were found in the lower portion of the well while drilling. Data obtained from this well, coupled with local and regional studies, have several implications relevant to development of size, geometry, timing, and emplacement of frontal-zone structures involving Silurian-Devonian rocks. Structural development involving Silurian-Devonian strata near a major decollement step-up can be shown to have generally progressed from east to west, resulting in a frontal-zone pile-up. The well data also provide insight into the stratigraphy, potential reservoirs, and relative timing of migration and entrapment of hydrocarbons along structurally complex frontal zones. End_of_Article - Last_Page 1447------------