Reservoir Characterization and Estimating EOR Potential with a Sector Model Simulation of Señal Picada, a Large Mature Field in Argentina

Abstract

A number of fields in the Neuquén Basin are currently mature waterfloods. To obtain significant incremental volumes of additional oil, EOR technologies need to be screened and then implemented. Señal Picada is one of Argentina's largest fields with nearly 500 wells in 2013. These wells have exploited all the oil bearing areas of the field and have identified all of the oil water contacts in the various reservoir that make up this field. In 2013 the field was producing with a 96% water cut. Therefore for this field to have a long term future, post waterflood opportunities need to be identified. To accelerate the characterization of such a large field, it was decided to study a sector of the field which was thought to be suitable for an EOR pilot and where an excellent quality core has been acquired. By focusing on a sector, the construction and data QC of both the static and dynamic models was faster than if an attempt was made to construct a full field model. Additionally more iterations between static and dynamic models were possible in less time to identify which variables had the greatest impact on the history matching process and forecasts. With the main reservoir layers characterized, it was possible to both extrapolate the learning to the whole field and to evaluate EOR processes in more detail. The sector modeling demonstrated that 3–4 stratigraphic cycles had the highest potential for EOR. However within these cycles two very different facies were identified by the study, a high permeability sandstone suitable for EOR and a low permeability carbonate which would negatively impact any chemical injection program. The dynamic modeling of the field combined with analysis of the logs of infill wells surprisingly demonstrated that there was significant attic oil potential. This was interpreted as being due to the high vertical permeability in the field resulting in a waterflood which was more affected by gravity forces than viscous forces. In conclusion the sector modeling study characterized the reservoir, identified the key sands with potential for exploitation by EOR and that there was remaining oil to be recovered both by the reduction of the residual oil saturation to water or by improving the vertical sweep efficiency.