RAMON, JUAN CARLOS, and GLORIA VIDAL*, HOCOL S.A., Bogotá, Colombia
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 #90923@1999 International Conference and Exhibition, Birmingham, England