Floyd 'Bo' Henk¹, Gavin S. Ward²

(1) University of Alberta,Edmonton, The Pachiron Group Consultants, McKinney, TX
(2) BP Exploration, Wytch Farm, UK, Wytch Farm, England

ABSTRACT: The Bridport Sandstone of the Wytch Farm Oil Field, a Shelf Sandbody or Shoreface? : An Ichnological and 3-D Seismic Sequence Stratigraphic Investigation Into the Shallow Marine. Origin

Conventional Core from seven wells within the Wytch Farm field and the Winterbourne Kingston BGS borehole, outside of the field, were described for Ichnology and Sedimentolgy. Large format thin-sections were made and examined for all lithofacies and the core, where oil-stained, was treated with solvents/cutting agents to better expose the trace fossil assemblages. The results of the core interpretation suggest there are several west to east prograding shorefaces separated by flooding surfaces and deeper water deposits within the upper 200 feet of the Bridport. Deeper water deposits, which are 5-10' thick, shale-rich and contain Chondrites and Helminthopsis are the vertical pressure barriers within the compartmentalized structure. The upper part of the Bridport is characterized by a shallow marine Skolithos suite and Macaronichnus sp. is present suggesting high energy shoreface conditions. A west to east progradational shallowing upward from inner shelf to shoreface environment is interpreted from the core and the 3-D seismic data also reveals the presence of several large west to east progradational packages capped by the Bridport Sand. Overlying the Bridport is the Inferior Oolite historically interpreted as a low stand system. Our work indicates the Inferior Oolite, primarily composed of ooids near the basal marine trangressive surface, marks a major transgressive event for the trace fossil assemblage is deepening upward to shelf depths.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado