- Copyright © 2002 Society of Exploration Geophysicists
The complex sedimentary architecture of various offshore turbidite systems within the Tertiary formations of Gulf of Guinea, offshore West Africa, can be explained by using 3D seismic interpretation to define sedimentary and stratigraphically units which then become input for reservoir models and simulations. The geologic model is composed of sedimentary units of different scales whose width, thickness and lateral continuity, composition, facies partitions, and lateral/vertical succession are determined from analysis of 3D seismic and well data.
The study discussed in this article integrates different seismic attributes, calibrated with well logs and core data. Our integrated geoscience team developed a methodology, based on 3D seismic interpretation, to build a sedimentary model honoring the stratigraphical architecture of turbidite deposits. The main constraints were the absence of an existing facies model and very limited dynamic data available before the start of field production. The limited geologic data available consisted of a few calibration wells.
However, many problems were solved by integrating conventional 3D seismic with new high-resolution 3D seismic and by using a few innovative interpretation tools, such as “sismage” peeling. Aiding the study were excellent core recoveries on key wells and complete sedimentological, biostratigraphical, and structural studies.
This turbidite system is defined as occurring between two major third order stratigraphic surfaces—a submarine unconformity and a maximum flooding surface made up of shale deposited during phases of fan deactivation. In the following example, the interval limited by the third-order sequence boundaries corresponds to the Upper Oligocene interval. The turbidite system is composed of channel complexes limited by fourth-order stratigraphic surfaces. A channel complex is formed by “channel stories” defined at the fifth-order scale. An assemblage of channel phases (sixth-order scale) defines a channel story. Each channel phase is characterized by a facies that can be calibrated by well log data.
Biostratigraphic analysis indicates …