--> ABSTRACT: Synthetic Seismic Modeling of the Guánica Bay Outcrop, Southwest Puerto Rico, by Ruidiaz-Santiago, Cyd M.; Bandyopadhyay, Kaushik; Baechle, Gregor; Fullmer, Shawn ; Guidry, Sean A.; Harris, Christopher; Hasiuk, Franek ; Kaczmarek, Stephen E.; Ramirez, Wilson; Santos, Hernan ; Simo, Toni; #90142 (2012)

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Synthetic Seismic Modeling of the Guánica Bay Outcrop, Southwest Puerto Rico

Ruidiaz-Santiago, Cyd M.*1; Bandyopadhyay, Kaushik 2; Baechle, Gregor 3; Fullmer, Shawn 2; Guidry, Sean A.2; Harris, Christopher 2; Hasiuk, Franek 2; Kaczmarek, Stephen E.4; Ramirez, Wilson 1; Santos, Hernan 1; Simo, Toni 2
(1) Geology, University of Puerto Rico, Mayaguez, Mayaguez, Puerto Rico.
(2) ExxonMobil Upstream Research Company, Houston, TX.
(3) ExxonMobil Production Company, Houston, TX.
(4) Geological Sciences, Bridgewater State University, Bridgewater, MA.

A broadly applicable workflow was developed to create synthetic seismograms directly from digital images with the goal of helping seismic interpreters visualize stratal geometries in mixed carbonate-siliciclastic depositional systems, and to test the effects of different rock and fluid properties on seismic response. The workflow was applied to Cenozoic outcrops along Guánica Bay in southwestern Puerto Rico. Guánica Bay offers an opportunity to understand the stratal architecture of an Oligocene-Miocene, land-attached carbonate system. The Oligocene succession is distinguished by high-frequency sequences that change from a mixed carbonate-siliciclastic ramp to a rimmed prograding margin. The Miocene exposure in this area is characterized by onlapping, cross-bedded coastal to platform interior deposits. It is separated from the subjacent Oligocene deposits by a tectonically enhanced unconformity (~15-20 Ma). This sequence stratigraphic interpretation is based on measured sections, petrographic analysis, field gamma ray logs, biostratigraphy, age dating ( 87Sr/86Sr), and isotope stratigraphy (δ13C, δ18O).

Key events were digitized from the reconstructed sequence stratigraphic cross section. The Vp, Vs and density values were taken from published, field, and modeled data. These different datasets were used to populate synthetic seismograms at varying frequencies. The effects of lateral facies transitions and the implication of velocity distribution were explored. AVO analysis and fluid substitution was also performed. The synthetic seismograms showed dimming amplitudes due to sharp lateral facies transitions, “pull ups” and “sags” due to Vp stacking patterns and the detection of facies geometries at frequencies greater than 40Hz. The log response did not change significantly when initial fluid (water) was replaced with gas. The AVO analysis showed no significant change in amplitude. This study takes outcrop-based sequence stratigraphic analysis the next step by modeling its seismic response.

 

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