Characterization of the Magdalena Fan Beginning from the Seismofacies Analysis in a Pseudo-Impedance Volume

Vargas, M. L.; Mosquera, J. C.; and Porto, Plauto^1
1[email protected]

In the last few years several companies have acquired exploration blocks into the Magdalena Fan in the Caribbean Colombian offshore. In the fan area three exploratory wells have been drilled in the 70's decade and one more recently in 2012. This area is partially covered by 3900 sq km of 3D seismic and more than 4,600 km of 2D seismic data. In recent years, several authors have conducted studies focused on characterizing the Magdalena Fan considering seismic data and also data provided by wells, but these wells are limited in depth and sediments age. The oldest part of the fan, possibly early-middle Miocene has not been drilled and its characterization has been done basically with available seismic data, but the question is: When did commence the sedimentation in the Magdalena Fan? How can we characterize the depositional environment in this initial period?

Seismic data from the fan base generally presents very continuous reflections with no clear evidences of seismofacies that could allow to characterize precisely the beginning of the event.

A study was then performed focused on a small portion of the fan in order to improve the quality of the seismic data from its basal portion. A pos-stack series of filters were applied to the data that allowed to create a pseudo-impedance seismic volume. The pseudo-impedance data generated suggests for both seismic sections and amplitude maps the presence of lower slope channels and frontal lobes that could indicate the lower part and the first entrance of sedimentation in the Magdalena Fan which in general is a prograding sequence until recent age sediments. This lobes and channels slope sequence overlies erosively a sequence of shales which probably could be Oligocene (correlatable with data obtained on land) and corresponds to a maximum flooding event.

These seismofacies indicative of lobes and lower slope channels evidenced with the improved seismic data from the pseudo-impedance volume suggest the beginning of the Magdalena Fan sedimentation, generating in a exploratory level, a more promising possibility of good quality reservoirs within the Magdalena fan area.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013