Title: Use of a Powerful Geochemical Risk Reduction Method for Oil and Gas Exploration
Speakers: Andre Brown and Paul Harrington, W.L. Gore & Associates, Inc.
Publication: The Outcrop, February 2004, p. 6, 8
Surface geochemical exploration methods that identify the presence of petroleum hydrocarbons are an effective means of lowering oil and gas exploration risk and finding costs. Previous efforts to characterize trapped subsurface accumulations using surface methods have relied on measuring and interpreting gaseous flux (continued rate of flow) or concentration. These measurements are short term (often only C1-C6 saturated compounds) and transitory in nature and subject to considerable unaccounted variability affecting quantification and interpretation.
This presentation describes a drill-bit supported (~90% success rates) methodology which delineates the time-integrated geochemical signature (up to iC20 phytane) through the stratigraphic column and measured over a survey area. Geochemical survey signatures are correlated with known geochemical signatures of the stratigraphic column at selected productive and dry wells, which respectively characterize reservoir geochemistry and background geochemical signal (fingerprint). Chemical signatures composed of ~90 organic compounds provide compound-rich data, which surmounts the variability of flux/concentration measurements. A dataset is obtained that allows differentiation between the productive geochemical signature and background hydrocarbon signature (source rock and other organics). Adequate well information allows delineation of a target horizon in situations where multiple productive horizons are possibly present.
This methodology, which is not subject to weather or climatic variations, is in worldwide use in permafrost, desert, temperate, and tropical conditions. Data acquisition and interpretation are not limited by difficult lithology (e.g., massive salt and fracture sequence stratigraphy). Costs are at least an order of magnitude lower than traditional geophysical data collection and interpretation techniques, allowing the affordable addition of this risk reduction technique to the exploration tools portfolio.
Survey results are typically incorporated with geophysical data to locate prospective areas within a concession, high grade prospects, identify basin-centered “sweet-spots,” and define accumulation margins. Risk reduction case studies highlighting surface geochemical integration with traditional geophysical results are presented. A variety of geochemical survey objectives will be presented, including frontier and reconnaissance, production field infill, and offshore applications. A brief geological overview of a recent Rocky Mountain survey will be presented.