An isotopic and sedimentological study of deepwater carbonates Lobburi, Central Thailand
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Abstract
The present study is concerned with the application of sedimentological and geochemical isotope analysis approaches in order to predict the depositional environment, fluid evolution history and reservoir rock
property alteration, tied to burial and uplift of Permian basinal and platform margin sediments in outcrops in central Thailand (UTM: X:705100;707000 and Y:168600;1627400).Three representative measured
section were constructed, two in a mixed carbonate-siliciclastic interval and one in a sequence of intercalated hemipelagic mud-volcaniclastics. A combination of field observation and laboratory analysis established three distinct lithofacies, namely: a) mud-wackestone, b) wacke-packstone and C) grainstone (rudstone). Multiple diagenetic features were observed microscopically and most are related to a progressive burial (mesogenetic) evolution. Stylolite dissolution seams and penetrative grain-to-grain
contact features account for significant losses in reservoir rock porosity with complete matrix permeability once the succession under study attained deeper burial domains. Related to this evolution the stable isotopic signatures shows two distinct field behaviors in a C-O covariant crossplot that defines two separate plot fields for the sampled matrix and calcite veins. Two different timings/stages of calcite veins were also identified based related to calcite stabilization in earlier versus later burial and likely indicate mesogenetic calcite formed from earlier somewhat (cooler) and somewhat later (warmer) burial fluids.
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Copyright © 2008 Department of Geology, Faculty of Science, Chulalongkorn University. Parts of an article can be photocopied or reproduced without prior written permission from the author(s), but due acknowledgments should be stated or cited accordingly.
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