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New Techniques for Recognizing and Understanding High-Maturity Petroleum Systems in California

Zinniker, David A.*1; Mesdakom, Monporn 3; Lorenson, Tom D.2; Lillis, Paul G.4; Magoon, Leslie B.2; Moldowan, J. Michael 1; Dahl, Jeremy E.1; He, Meng 1
(1) Department of Geological and Environmental Sciences, Stanford University, Stanford, CA.
(2) Pacific Coastal & Marine Science Center, USGS, Menlo Park, CA.
(3) PTTEP, Bangkok, Thailand.
(4) Energy Resource Program, USGS, Denver, CO.

Deep petroleum systems are little understood components of California’s sedimentary basins. Condensates, high API gravity admixtures to black oils, and thermogenic gas represent new and difficult plays for exploration. Our work is aimed at recognizing these systems, their source rocks, their thermal history and migration. It involves surveying extensive sample libraries for the occurrence of ultra-stable markers (diamondoids, simple aromatics, triaromatic steroids, etc.) in cracked or mixed oil and mapping out their contributions to known reservoirs. Previous work in California focused on less stable molecular markers (i.e. biomarkers) and was blind to these high maturity contributions.

Ultra-stable components can be fingerprinted and correlated with petroleum source rocks using higher diamondoid distributions, diamondoid isotopes, aromatic isotopes, and light hydrocarbon isotopes. Newly defined petroleum systems can be modeled and potential hydrocarbon contributions considered during exploration.

A growing database of more than 100 petroleum samples from the San Joaquin, Salinas, Santa Barbara, Los Angeles, and the Eel River basin is being collected. High maturity contributions have already been recognized in many San Joaquin, Santa Barbara, and Eel River fields as part of this work. Preliminary fingerprinting of ultra-stable markers indicates deep highly-cracked sources from the Cretaceous, Eocene, and Miocene in California's sedimentary basins. Most deep contributions are found as mixes with black oils where they dominate the distribution of ultra-stable markers but contribute little to the distribution of biomarkers. Unique fingerprints for both biomarkers and ultra-stable markers helps point toward the source rock for these independent components and provide a fuller view of petroleum systems.

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California