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Abstract: Stratigraphic and Structural Reinterpretation of the Tello Field, Upper Magdalena Valley, Colombia

The Tello field reservoir section was interpreted from 3-D seismic and biostratigraphic analysis from cuttings as an Early Miocene blanket-like fluvial sandstone overlying an Oligocene unconformity. Reservoir stratigraphy was "layer cake."Absence of sandstone in wells was interpreted as a lateral facies change to mudstone. Unexpected results from a recent infill drilling and water injection led to a review of the geological model.

Data from over 800 feet of outcrop, 928 feet of cores from five wells, 21 new biostratigraphic analyses from cores, dipmeter and wireline logs from 35 wells, 5 check-shot and a 36 sq km seismic cube were interpreted and integrated to define a new reservoir model. Sedimentological studies indicate that the reservoir section was deposited in a well oxygenated, current-swept, shallow-marine shelf as aggradational tidally influenced cycles, as progradational shorefaces and as tidal bars and channels. High-resolution sequence stratigraphic subdivision of the reservoir allows identification of repeated sections in several wells. Dipmeter data shows low to very high dip angles within the oil-bearing reservoir and confirms the location of low-angle thrust faults, interpreted from well log data. Siliceous siltstones in the Lower Monserrate act as detachment surfaces for these thrusts.

The integration of multiple data sets lead to a reinterpretation of the stratigraphic and structural models that results in better reservoir modeling and planning and recognition of undrilled potential of the Tello field.

AAPG Search and Discovery Article #[email protected] International Conference and Exhibition, Birmingham, England