Abstract: Seismic Character Analysis of a Mixed Siliciclastic-Carbonate Reservoir

Hannes E. Leetaru

Detailed reservoir characterization at King field, Jefferson County, Illinois, indicated that Mississippian Aux Vases Sandstone is part of a nearshore mixed siliciclastic-carbonate system. The intercalated sequence of reservoir sandstone and non-reservoir shales and calcareous facies form a compartmentalized reservoir. High-resolution seismic can be used to predict some of the lithologic changes that contribute to reservoir compartmentalization.

The principal data at King field are old wireline electric logs. Pseudovelocity logs were created from these old electric wireline logs and subsequently used to create synthetic seismogram models of the facies changes. Synthetic seismogram modeling compared with actual seismic data from King field suggests that amplitude variations of the seismic reflectors can be used to differentiate reservoir from non-reservoir calcareous facies. This amplitude variation is due to destructive interference of the seismic wavelet created by the non-reservoir calcareous facies with high impedance reflectors beneath the reservoir interval. Seismic character analysis can be successfully applied to King field because most of the compartmentalization in this field was due to the interrelationship of the c lcareous facies with reservoir sandstones.

The application of seismic character analysis may be used to reduce the risk during reservoir development in mixed siliciclastic-carbonate systems. Seismic character analysis may also be used as an exploration tool in searching for new stratigraphic traps within the Aux Vases Sandstone.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994