Floyd 'Bo' Henk¹, S George Pemberton², Scott Shaver³

(1) University of Alberta, Edmonton/ Pachiron Group Consultants, McKinney, Texas, McKinney, TX
(2) University of Alberta, Edmonton, AB
(3) Barrow Shaver Resources, Tyler, TX

ABSTRACT: Reservoir Ichnology of the Subclarksville 'A' Sandstone, BSR Field, East Texas, through an Integrated Ichnology, Petrology and Reservoir Properties Data Set

Examination of conventional core from 24 wells in the BSR field, a 20 MMBOIP 1994 discovery in Madison County, East Texas, has revealed two different sandstone bodies separated by a regional Glossifungites assemblage within the Subclarksville 'A'Sandstone. The lower sandstone is the upper part of a northwestward prograding shoreface sandbody and at the BSR location only the inner shelf and distal lower shoreface facies are preserved. High intensity burrowing with Teichichnus sp. and Paleophycus sp. has modified the substrate to the point that the oil is found only within the burrow fill. UV photographs, thin-sections and minipermeameter data confirm that the organism burrows are the hydrocarbon storage with the burrows having much better reservoir properties than the burrow linings and matrix. Above the lower sands a transgression ensued and the resultant TSE deposit is a vertical flow barrier of low permeability represented by glauconite and iron-bearing ooids, pellets and coarser grained bioclastic lag material and in several locations a Thalassinoides colony representing a firmground Glossifungites assemblage is present. Above the TSE deposits a second sandstone member comes into play with a distinctive suite of iron-bearing Asterosomas and Paleophycus grading upward into Diplocraterion and Ophiomorpha-rich sand intervals. This sand is interpreted as a prograding lower shoreface but distinctly different in reservoir properties and ichnoassemblage compared to the lower sand. This study has lead to a better understanding of the mechanism for sand emplacement and preservation as well as higher quality reservoir distribution and will impact future secondary recovery and horizontal drilling plans.

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