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Depth conversion in geologically complex structures: Case study in offshore southwest Palawan

Authors
Journal
Journal of Asian Earth Sciences
0743-9547
Publisher
Elsevier
Publication Date
Volume
15
Identifiers
DOI: 10.1016/s0743-9547(97)00010-x

Abstract

Abstract Time-to-depth conversion in complex structures such as those found in thrust fault systemsrequires further considerations than those usually assumed conversion procedures adopting a “layer-cake” in routine depth geological model. Most of the assumptions inherent in this model are inadequate in deriving a plausible geologic depth model for the complex case. This paper presents another scheme for depth converting time maps of complex structures interpreted in southwest Palawan. A key seismic line over a structure is used in seismic modeling and eventually converted to depth after ray tracing. This line provides the well-constrained source of depth data. The other lines in the grid are tied to this key line and their interval velocity profiles derived from the migration velocities. The low-frequency component of the interval velocity curves of each reflecting layer is extracted and subsequently used in generating the velocity map for each horizon overlying the structure. The series of velocity maps so produced provide the link to depth converting the various geologic intervals. After the depth conversion process, a hypothetical time-depth curve over a possible drilling location was constructed and compared to actual curves of some wells drilled earlier in the area. The hypothetical curve resembles the behavior of the actual curves, implying that the approach adopted may have reasonably described the velocity behavior to the prospect area.

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