Architecture and Rock Typing of Coal-Bearing Successions in Late Carboniferous Fluvio-Deltaic Deposits (Southeast Kentucky, USA)

Abstract

The exploration of coal-bearing reservoirs for both conventional and unconventional hydrocarbon resources, has increased the interest in similar fluvial/estuarine successions worldwide. In this context, Eastern Kentucky offers excellent outcrop analogues for Carboniferous fluvial-dominated deltaic where facies associations, depositional environments and sequence-stratigraphic patterns can be observed in detail. Extensive roadcuts and a vast database of well/core data (coal and gas exploration), available at the KGS (Kentucky Geological Survey) make the Eastern Kentucky an great field laboratory for studying sedimentology and stratigraphy in coal-bearing successions. The middle Pennsylvanian Pikeville and Hyden Formations are very well exposed along the US highways 23 and 119 in Pike County (SE Kentucky). The local stratigraphy is well known thanks to numerous studies focused on very extensive Pennsylvanian coal beds, used as stratigraphic markers for outcrop correlation. Both formations were deposited in a foredeep basin during the building of the Appalachian orogeny located ot the East. Fluvio-deltaic systems prograded toward west and northwest across the basin, subject to periodic transgressions driven by high-amplitude glacio-eustatic base-level changes during the Late Palaeozoic Gondwanan glaciation. In this paper we present the observations from several outcrops in the Pikeville Formation. They were logged at 1:20 scale and densely sampled for rock-typing analysis including automated petrography with QEMSCAN. In the Pikeville Formation, successions are generally formed by vertically stacked, erosively based transgressive depositional sequences with thickness varying from a few meters to a few tens of meters. The studied sedimentary interval consists mostly of three main architectural elements: (1) river-dominated valley fills with frequent tidally-influenced deposition; (2) transitional sediments of coastal to marginal-marine environments, including coalbeds; (3) extensive marine shales, locally intercalated with prograding mouth-bar deposits. The vertical stacking of this facies form fourth-order sequences, which are grouped into third-order sequences bounded by the extensive marine shales. A series of closely spaced logs, integrated with the available subsurface datasets, will be used to derive detailed geo-cellular 3D facies and architectural models of coal-bearing succession, with the aim to link rock properties to sequence-stratigraphic system tracts.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015