The use of inversion volumes for reservoir imaging, CU field, Gulf of Thailand
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Abstract
The study area lies in the southern part of Pattani Basin, Gulf of Thailand. The studied reservoirs are Late Oligocene fluvial sandstones. Imaging of these reservoirs by using full-stacked seismic data is known to be challenging due to rapid lateral, and vertical lithological variation. Rock physics analysis was examined, and post-stack seismic inversion of full-stack and partial-stack seismic data was applied to improve reservoir imaging and to better identify hydrocarbon-bearing zones. According to rock physics analysis, P-impedance, 10⁰-, 20⁰-, and 30⁰-elastic impedance crossplots show a significant impedance contrast between oil-bearing sands and shales in the studied interval. These oil-bearing sands have lower impedance value than shales and tight sands. The impedances of tight sands and shale fall in the same range, so they cannot be differentiated in inverted volumes. To determine quality of the inverted volumes, inverted seismic sections were displayed with impedance logs at well locations, and they show a reasonable match. There are 13 out of 14 blind test wells that show a good match between oil-bearing sands and other lithologies. The 2 main reservoirs, Sand A and Sand B, were observed by using horizon slices; Sand A shows a large and broad channel belt, and Sand B shows a narrow belt with separated bars. This study indicates that P-impedance, 10⁰-, 20⁰-, and 30⁰-elastic impedance can be used to predict and identify oil-bearing sands.
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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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