Reservoir Characterization of Pagasa and Lower Matinloc Formations by Using AVO and Multi-Attribute Analysis, Southwest Palawan Basin, Philippines
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Abstract
Several distinct high amplitude anomalies occur in both the Lower Matinloc Formation and Pagasa Formation equivalent in the Southwest Palawan Basin, Philippines. The main objective of this study is to conduct a thorough investigation on the nature, occurrence, extent and reservoir potential of these high amplitude anomalies. This study explores the possibility that either these high amplitudes are associated with reservoir sands. On a regional scale, the cross plot analysis for all the wells revealed that no generalized P-Impedance and Gamma Ray (GR) relationship could be established for the whole area. However, P-Impedance can be an effective lithology indicator when the cross plot analysis is applied in small intervals and over small regions. Similarly, density was able to discriminate sands from shales in the Lower Matinloc Formation (Upper Miocene Section). But it is not a good lithology discriminator for other formations. Due to great variations of rock physics parameters, it is required to establish local relationship before computing multi-attributes or applying inversion techniques. Fluid replacement modeling and AVO analysis indicate that water wet and gas saturated sands have same AVO response. The sands can be classified as Type 2 and Type -4, per Young et. al., (2003) AVO response classification. Multi-attribute analysis and GR prediction showed that the high amplitude anomalies are associated with shale to shaley sands. The bright amplitudes in the area correspond to shales. Therefore, these bright amplitudes are not associated with reservoir or 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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