High Resolution Stratigraphy, Avalon Reservoir Development, Hibernia Field, Jeanne d'Arc Rift Basin

Osama M. Soliman, John D. Harper

The Avalon reservoir sandstones are synrift sediments, which were deposited over the rollover anticline of a growth fault. An integrated facies and event correlation approach was used to investigate the depositional history and to delineate various sandstone bodies in this reservoir.

The cored sections were subdivided into facies successions, 0.5-26.0 meters thick. Each succession consists of a group of genetically related facies and was deposited in a specific depositional environment. Facies successions are bounded by near-isochronous transgressive, erosional or subaerial exposure surfaces. These bounding surfaces were delineated in the cored and non-cored wells. A soil zone and early marine calcite cements can also be correlated throughout most of the field. Spatial relationships of laterally equivalent facies successions were used to construct a series of paleogeographic maps for successively younger intervals.

Paleogeographic maps reflect deposition of the Avalon sandstones in a structurally-controlled valley. The valley was incised into older offshore shales, during emergence of the rollover anticline. Subsequently, a river and wave-dominated estuary occupied the valley. Filling of the estuary and local subaerial exposure of the estuarine sediments were followed by submergence of the rollover anticline. This submergence resulted in deposition of laterally-extensive transgressive barrier island sandstones. The latter are cut by younger estuarine sediments which were deposited due to renewed movements of the rollover anticline.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995