Hibernia formation sequences and Breathitt Group (Kentucky) analogue

Bidgood, Michael John (2003) Hibernia formation sequences and Breathitt Group (Kentucky) analogue. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (36MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

The Hibernia oilfield is located 315 km offshore and east-southeast of St. John's Newfoundland. An estimated 620 million barrels of recoverable oil are located in the Hibernia oilfield within a basal Cretaceous, fluvial-dominated delta system known as the lower Hibernia zone of the Hibernia Formation. Informal lithostratigraphic units assigned to the lower Hibernia zone include a non-reservoir, finer grained Layer 1 and sandstone- dominated Layers 2 and 3 separated by the field-wide marine Medial Shale. During deposition of the Hibernia Formation, braided rivers draining the Avalon uplift, located to the south, deposited sands in incised valleys. The Hibernia reservoir sandstones of Layers 2 and 3 represent late lowstand to early transgressive systems tracts and are separated by finer grained lower delta plain, lagoonal and open marine facies which represent late transgressive to highstand systems tracts. The entire lower Hibernia zone is interpreted as a third-order composite sequence; it can be further subdivided into higher frequency fourth- and fifth-ordered cycles. -- The Pikeville, Hyden and Four Comers formations of the Pennsylvanian Breathitt Group, eastern Kentucky, constitute a facies and sequence-stratigraphic analogue for the Hibernia Formation. The Breathitt Group is interpreted as a fluvially dominated, shallow- water deltaic succession punctuated by the deposits of a number of marine incursions. The high net sandstone intervals of the Breathitt Group were deposited by a west- or west-northwest-flowing fluvial system characterized by braid bars in distributary channels and incised valley systems. The high net sandstone intervals represent late lowstand to early transgressive systems tracts and are separated by finer grained, lower delta plain, lagoonal and open marine facies, which represent late transgressive to highstand systems tracts. The stacking patterns and sequence stratigraphy of this part of the Breathitt Group strongly resemble those of the Hibernia Formation, and therefore can be used to refine existing models at Hibernia. Despite the differences in age, tectonic setting, and likely scales and frequency of relative sea level change, the Breathitt Group is shown in this thesis to be a suitable stratigraphic and sedimentological analogue for the Hibernia Formation. -- Based on excellent outcrop exposure and well data, permeability pathways through the Breathitt Group are postulated. Marine shales and abundant coals are identified as candidates for intraformational seals and pressure barriers, respectively. Vertical sealing attributes are recognized for similar marine shales at Hibernia. This thesis provides a justification for a more detailed field and laboratory study needed to quantify reservoir properties of the Breathitt Group, so that numerical data can be incorporated into reservoir models for the Hibernia field.

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