Will the Coals in the Cooper Basin Preclude Wuccess for 3D VSPs?
Black, Richard A.
Geoscience Honours Degree, 2010
University of Adelaide
The success of a Vertical Seismic Profile survey depends upon the preservation of the high frequencies in the data. These frequencies give the increased resolution which is the benefit of a VSP survey over a conventional surface seismic survey. In the Cooper Basin, the Patchawarra Formation has the potential for gas sand discoveries that are smaller than what is resolvable with conventional seismic data. The formation includes many coal beds, and the multiple reflections from these coal beds were thought to pose a threat to the success of a VSP survey due to attenuation of the high frequencies in the VSP data.
Seismic modelling with Hampson Russell software, using simple geological models and a code for generating multiples, has shown that the multiples do in fact dominate the signal. The impedance models used were simplified to study the interaction of the coal multiples with the signal response from sand beds. A series of models containing a sand wedge, a series containing a constant thickness sand with variations in impedance, and a model with an anticlinal sand show that the multiples generated by the coal beds are dominating the signal and overwriting the response from the sand beds.
There is room for further investigation into the success of processing the data to remove the multiples, to see if the high VSP frequencies can be preserved to maintain the resolution level.