Kaiser, David¹, Alan H. Silliman¹, Wayne Wells¹ 
(1) W. L. Gore & Associates, Inc, Elkton, MD

ABSTRACT: Three "G's" are better than Two: Integration of Surface Geochemical Data in Petroleum Exploration Efforts for the Woodbine Prospect, Polk County, Texas

The integration of geological, geophysical and geochemical data (“3G’s”), is an effective exploration strategy. Passive surface geochemical data can differentiate petroleum phases from background. Integration of geochemical and other information allows greater certainty in evaluating potential drilling locations, and deciding where to focus future exploration efforts. This is illustrated by work in Polk County, Texas, targeting the Cretaceous Woodbine and accumulations in the Jurassic. This is the site of significant Woodbine gas discovery, including the recent Comstock Resources Hamman-1 (averaging 19 MMcfed). 
Although an adequate seal may exist, reservoir hydrocarbons will permeate the seal in nanogram quantities, and migrate to the surface (“microseepage”). Microseepage has been detected from many reservoirs around the world, with different geological and stratigraphic conditions. This surface geochemical technique, with sensitive analytical and multivariate data processing capability, provides a means to map petroleum accumulations. Geochemical models of petroleum emanation are constructed by sampling known production and background areas. Geochemical models are applied to survey sample data, allowing the classification of samples into either “production-like” or “background-like” groups. 
Geochemical model data from the Woodbine Prospect show logical chemical distinctions between gas production and dry well sites. Gas production sites exhibited higher hydrocarbon response levels than those of dry wells. Regions of enhanced light hydrocarbon response are defined, showing prospective locations for further investigation. Carbon isotope data for light hydrocarbons from selected survey locations fit within thermogenic limits. Combined with structural information, optimal locations for hydrocarbon entrapment can be determined.

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