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Brooks, James M.1, Bernie B. Bernard2, Neil S. Summer2, Gary A. Cole1
(1) TDI-Brooks Int'l Inc, College Station, TX
(2) TDI-Brooks, College Station, TX

ABSTRACT: Deep Water Surface Geochemical Exploration Coring: Hit Rates, USBL-Positioning and Target Size

The authors have been involved in the collection of nearly 15,000 piston cores over the last twenty years are part of mostly deepwater surface geochemical exploration (SGE) studies in frontier regions. This poster will address the following issues related to the design and hit rate expectations from deep water SGE coring programs:
Comparison of worldwide gas and oil seepage hit rates; Targeting deep water cores using USBL positioning; and The expected size of seepage features.
We will provide comparison of seepage hit rates from deep water coring programs in the northern and southern Gulf of Mexico, Trinidad, Angola, Nigeria, NW Africa/Nile Delta, NE Canada and SE Asia. The authors will show the increase in seepage hit rates as more recent coring studies have benefited from the increased use of 3-D seismic data over previous 2-D based site selection.
The question often arises in SGE coring studies whether positioning of cores to ±5-meters of pre-selected positions with USBL instrumentation is advantageous. USBL positioned cores in benign and robust metocean regions are generally within ±10 and ±20-25 meter offset from true vertical, respectively. If the size of the deep water seep features are smaller than ±20-25 meters than USBL core positioning becomes critical. The authors will show from coring programs in the more prolific macroseep regions in the Gulf of Mexico, Trinidad and West Africa that is most cases where multi-cores are acquired over targets that seepage features are significantly larger than the 25-meters in size.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.