Connecting Seismic Derived Attributes with Production Performance at Tambaú Gas Field, Santos Basin, Offshore Brazil

Porosities, permeabilities and production performance from Upper Albian reservoir sands vary widely throughout Tambau gas field, offshore Brazil. Seismic attributes such as far-angle stacks, IP-IS and Poisson's ratio, here referred as hydrocarbon friendly attributes guided well positioning in discovery, delineation and development. At the end of the nine wells, it became clear that these attributes work well to detect gas saturation, but not necessarily reservoir quality. Due to the lack of clear connection between those attributes and good reservoirs, a multi-scaled study, integrating data from lab, logs and seismic, was conducted to define better seismic tools for field sweet spots identification and mapping. The link between better reservoir facies from well core and log analysis was only achieved by using a Petrobras in-house attribute Seismic Class, where seismic band pseudo P-impedance traces are separated in 9 classes based on the value and standard deviation. Log derived Seismic Class show a strong connection between class 7, (high negative value and high standard deviation) and better reservoir zones. The validation in seismic scale was very positive, since in all wells with good production performance class 7 is present and where the performance was considered poor class 7 does not occur.