Abstract: Seismic Stratigraphy of the Guajira Basin Cuiza Platform, Offshore Colombia
John D. Pigott, Rita Rongiao Wang, Alfredo Hosie
The Chuchupa and Ballena are two of northern Colombia's largest gas fields which produce from Paleogene carbonates and clastics of the Guajira Basin. In order to define the three dimensional architecture and temporal interplay between these Cenozoic carbonates and siliciclastic depositional systems as well as the relationships between these units and relative changes in sea level, a seismic stratigraphic analysis was conducted for the Cuiza Platform of the offshore Guajira Basin. The data for analysis included paleontology and petrophysics from two boreholes and approximately 600 km of reflection seismic provided by the Texas Petroleum Company Colombian Division.
Fourteen major seismic sequences were defined from seismic and geologically constrained with well synthetics. Most of the sequence boundaries coincide with global sea level falls, while the remainder suggest instead local basinal depositional events. Through time the shelf edge has prograded from the southeast to the northwest, commencing with the drowning of Paleogene shallow water mixed clastics and carbonates by turbidite deposition which slowly gave way to Neogene deltaic sedimentation. Carbonate influence began once more to dominate by the Pliocene.
Seismic facies analysis was conducted upon both the carbonates and clastics. According to a seismic classification of the Miocene widespread deltaics, these sediments are medium amplitude, long wavelength, high gradient, acute dipping clinoform reflectors of alternating progradational medial to distal shelf highstand wave dominated clastic wedges. Hydrocarbon reservoir quality in these ancestral highstand Rio Ranchera deltaic sands is considered to be optimal, however, the stratigraphic sealing potential is questionable. However, direct hydrocarbon indicators from seismic attribute analysis of truncated reflectors imply the existence of seals from the fines of the subsequent offlapping deltaics. Similar dramatic progradational wedge geometries are generated by the overlying Pliocene c rbonate shelf-edge reefal buildups.
Future hydrocarbon exploration strategies based upon seismic stratigraphic analysis on the Cuiza platform in the Guajira basin should include determining the spatial and temporal distributions of both reservoir and stratigraphic seal quality.
AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994