Design Aspects in Reflection Seismology Aiming at Rock Properties Detection

Abstract

ABSTRACT The geological complexity of many hydrocarbon traps and the related seismic anomalies often give rise to serious difficulties in inferring geological characteristics from seismic signals. Optimum seismic processing sequence can be carefully designed only after an accurate analysis of the available seismic and geological data in order to single out the geophysical problems to be solved in the particular exploration site. Stratigraphic processing architecture requires the use of the residual propagating wavelet in order to transform the reflectivity section into a profile of calibrated seismic logs which represent a quantitative datum bearing structural and stratigraphic information. Seismic logs obtained from surface seismics integrated with borehole data and correlated to studies of reservoir-rocks allow to detect the reservoir internal structure in terms of geometries and lateral variations of petrophysical properties. Combining seismic-petrophysical profiles with the depositional model enables to move within possible solution ranges, through sensitivity analyses and confidence limits of the observational data, towards the unique and most proved solution of the sedimentary features of the investigated layers. This methodology was tested with a pilot project in an oil bearing pre-Miocene limestone of a field in Central Italy. Thickness and porosity variations were determined from absolute seismic logs obtained from land seismic data recorded during different years (77–84) and processed optimizing: signal amplitude and phase, field and residual statics, wave velocity propagation. The resulting distribution of reservoir heterogeneity will technically and economically affect the techniques related to enhanced oil recovery.