Relationship Between Reservoir Quality and Hydrocarbon Signatures Measured at the Surface

Harrington, Paul; Silliman, Alan
W.L. Gore & Associates, Inc., Elkton, MD.

Amplified Geochemical Imaging(SM) technology has been used to image reservoirs over 7000 meters in depth. A relationship is noted between reservoir quality, as measured by the net pay thickness - porosity product, and strength of surface geochemical signature, as measured by pattern and mass of hydrocarbon compounds. A relationship is also noted between strength of surface signature and current production volume at numerous well sites. Reservoir pressure is correlated positively with the strength of surface geochemical signature.

Adsorbent-based surface geochemical samplers are used to detect volatile organic hydrocarbon compounds at the surface. Many of these compounds are of thermogenic origin, from underlying petroleum reservoirs. Heavy saturated compounds as heavy as phytane (C20) are detectable in minute amounts (10-9 grams).

Examples of the correlation between reservoir character and surface hydrocarbon signature are presented from geochemical surveys in the Anadarko Basin of Oklahoma, Oriente Basin of Ecuador, the Pietu Siupariai Field of Lithuania, the East Texas Salt Basin, the Green River Basin of Wyoming, and the Western Canadian Sedimentary Basin.

Practical applications of this relationship are shown by results from the Banff B Pool reservoir, where a map of geochemical signature over the reservoir matches closely a map of (Øh) product for the Banff Formation. Another example of the correlation between production strength and geochemical signature strength is provided by work over the Woodbine sand trend in eastern Texas. Interpreted well log cross-sections through the Double A Wells gas field show sand thickening with consequent increase in surface geochemical signature quality.

In concept, the measurement of local surface geochemical signal may be used to reveal bypass pay sections in existing wells and compartmentalization in existing fields. For exploration regions and proposed well locations, the strength of geochemical signature would allow priority assignment and ranking of sites and prospects. The application has been used in unconventional hydrocarbon plays to define regions of higher pressure and may also be used to screen broad areas to define regions that may be more liquid rich. When properly integrated with other geological and geophysical information, this surface geochemical technology can significantly reduced exploration risk.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012