Interpretation of the a” and B” Reflectors in the Eastern Part of the Colombian Caribbean Offshore. from Approach to the Seismic Stratigraphy of the Southern Caribbean

Torres, Emilio J.²; Rodriguez, Heidy L.^1
1 Geology Department, Universidad Industrial de Santander, Bucaramanga, Colombia.
² Group of Research in Hydrocarbon and Coal Geology GIGHC, Universidad Industrial de Santander, Bucaramanga, Colombia.

Geologic interpretation of Caribbean Offshore seismic data can be achieved using seismic analysis techniques as spectral decomposition. This tool is for detecting low and high frequency shadows that are associated with different types of bedrock in the frequency domain. Spectral decomposition provides a novel means of using seismic data and the Discrete Fourier Transform (DFT). By transforming the seismic data into the frequency domain via the DFT, the amplitude spectra delineate temporal bed thickness variability while the phase spectra indicate lateral and vertical geologic discontinuities. This seismic attribute show rock properties as density, representing the different sedimentary units in the seismic sections. The study area is South Caribbean, offshore of Colombia, and the dataset used includes well information of DSP Site153 and a 2D seismic sections. In Time Domain B” reflector was identified as an inter basement layer. This reflector is continuous, tectonically affected with reverse faulting associated to a regional strike-slip tectonics that generates negative flower structures, indicating a transtensive tectonic system. A bent fold is recognized, this is due to a horary strata rotation, denoting over the faulted zone an anticline Fold, just to the right with more amplitude and to the left a syncline Fold. The sediments near A” reflector, wedge over it, with onlap truncations. Also the sediments under A” wedge over the basement highs. Interpretation were aided with the seismic response of the amplitudes and frequencies where this properties suffer attenuation, reduction the signal level, because near to the crystalline basement, to B”, a reduction occurs in the energy levels. Interpretations were adjusted to the seismic section according to the attribute processing. The top of the crystalline basement is clearly exposed; this wedges over the basement uplift, but is continuous on the sides of the section. The seismic reflectors that were identified correspond to: E0) Oceanic Floor; E1) Top of the Pliocene-Pleistocene Sequence; E2) Top of the Late Miocene Carbonate sequence, this sediments are thin beds of sands and clays rich in carbonate, that conform the Early Eocene - Middle Miocene sequence; E3) top of the Cretaceous sediments, principally limestones and carbonate rich cherts. The E0, E1, E2, E3, A”, B” reflectors were correlated with the seismic units of Bowlad(1993), of the Western part of the South Caribbean CB1, CB2, CB3, CB4, CB5.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009