Geological Heterogeneities Characterization through 4D Seismic Interpretation

Brechet, Emmanuelle; Prat, Philippe; Cailly, Frédéric
TOTAL SA, Pau, France.

Time lapse seismic (4D) is now a common reservoir monitoring tool to monitor field reservoir changes (injection fronts, depletion, geomechanical effects, fluid communications, fault barriers) that could occur during field production. 4D is also a tool to characterize geological heterogeneities that are not always or easily detected on 3D seismic images and can contribute to make reservoir models more predictive.

Several examples encountered through the monitoring of different oil fields in different geological contexts will be shown on this paper:

First example: Characterization of fine laminated sands using 4D on Turbidites fields. Laminated facies are present on Turbidites fields and often contribute to field production but are very difficult to detect and to model.

Second example: Understanding of channel lateral accretions dynamic behavior on Turbidites fields. Lateral accretions are sometimes seen on seismic but their dynamic behavior is not obvious. Some channel bases can act as fluid transmissivity barrier and reduce injectivity/production of a channel.

Third example: Detecting dense zones on Carbonates fields, which act as permeability barriers.

Fourth example: Reservoir facies characterization on Turbidites and carbonates fields.

The 4D seismic has a 4D resolution that is linked to the variance of signal and is smaller than 3D resolution, which make us access to smaller geological features. Modern interpretation methodologies and workflows have been developed to help this geological characterization such as: 4D volumetric attributes obtained after 4D inversion, 3D volumetric propagation in consistency with 3D geological lithoseismic cubes, Comparison of 4D anomalies to cores and logs data, Integration of 4D anomalies inside geological model by using relevant upscaling techniques.

Understanding which geological heterogeneity plays a role in the dynamic behavior of a production field is one key of field development success. 4D is now a tool that must be used not only for understanding the dynamic behavior but also geology.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012