Ultra-Thin Bed Reservoir Interpretation Using Seismic Attributes

The great value that seismic attributes added to geosciences lies in the fact they link various seismic data properties to subsurface rock properties. In this work, we show how a simple attribute, once best integrated with other data, can help in extracting vital information about complex formations in subsurface. We focus on F39 Frio reservoir from South Texas. The target reservoir is one of ultra-thin beds, Oligocene aged gas sand reservoirs. Due to the interference of closely separated reservoirs, reflectivity over F39 changes significantly making horizons difficult to interpret through the seismic data. After performing tuning analysis, seismic broadband was decomposed into its constituent bands. The workflow was first examined on shallower interval and then implemented at the reservoir interval. Interestingly, the decomposition could successfully image the reservoir and confirmed its compartmentalization occurrence suggested in previous work. It revealed also a meandering channel reservoir that was buried in the seismic band. Furthermore, the frequency images revealed an explanation for well pressure changes between two wells only 60 m apart where seismic showed no appreciable change.