Abstract

The transgressive Carrizo Sand is a shallow reservoir sand (∼1600 ft) in central-northern Louisiana that is poorly imaged in industry standard seismic data. Exploration of the sand has relied upon mapping from well-logs. To investigate this problem, a 2D high-resolution surface-sourced seismic survey was performed in LaSalle Parish by students from the University of Louisiana at Lafayette and the University of Houston. The survey consisted of a line of 144 geophones, each spaced 16.5 ft apart and a truck-mounted A 200 (nitrogen accelerated weight drop) source. The survey was designed to utilize the high frequency from the source (∼60 Hz useable) and the high sampling frequency from the layout to map the shallow horizons better. In the stacked data image, the Cane River Shale/Carrizo Sand contact is a continuous high amplitude reflector. To investigate the ability of the high-resolution data to yield fluid content and lithologic information in the Carrizo, we have performed pre-stack analyses of the data. Amplitude variation with offset (AVO) analyses along the horizon indicate changes which we are investigating. If this study proves successful, high-resolution surface-sourced seismic surveys may be applied to other areas in northern Louisiana in exploration for reservoirs in the Carrizo Sand. Through pre-stack analyses and by generating AVO gathers along the horizon of interest, observations can be made that there is a change in fluid or lithology along this horizon by a large increase in amplitude with offset.