Physical Reservoir Models: from Pictures to Properties

Petrophysics and geophysics have not always worked together as closely as one might expect. This paper discusses current advances and sketches future developments. The major objective of geophysical research is to obtain sharper pictures. With the advent of 3D seismic, there is a strong trend to make displays both in time and depth and to convert seismic attributes into rock properties. Conversions based on seismic data alone give non-unique results due to limited resolution. Further progress hinges on calibration of acoustic attributes with parameters measured on core. For time-lapse seismic, the situation is even more complex, due to changing effects of temperature, pressure and compaction. All these effects have to be properly quantified if 4D seismic interpretation is to be integrated with dynamic reservoir models to realize the situation where all geoscientists work on one ‘unified’ 3D earth model. Biot–Gassman fluid substitution algorithms were successfully applied for decades, but suffer, like all mixing laws, from non-uniqueness. Recent investigations demonstrate that dispersion in the low frequency band could have strong implications for seismic attribute analysis. It is important to find out which relations measured on core at high frequencies can be used at seismic frequencies and which require additional laboratory work. The shock-tube is well suited to this task, because it handles large rock samples, and obtains responses below 1 kHz.