Seismic physical modelling of reservoirs, its past, present and future

Abstract

In the early 1970s, conventional two dimensional (2D) seismic methods were used to understand subsurface geological structure. Three dimensional (3D) surveying had not yet arrived as a method for delineating oil fields. Gulf Oil Research Laboratories was working on the problem of how to convince geologists that to delineate complex structure, seismic data should be recorded more closely spaced than was accepted practice. A physical modelling system was constructed utilizing a metre square water tank. Scaled models of geologic structures were suspended in the tank and an ultrasonic source and receiver pair was moved over the models to mimic both conventional 2D and experimental 3D seismic reflection surveys. 3D seismic migration algorithms were developed using the digitally recorded model data. The results clearly demonstrated the pitfalls of using widely spaced 2D seismic lines in the interpretation process ? 3D acquisition and processing was required for accurate imaging. Exxon was next to build a physical modelling system. When Gulf was taken over by Chevron, the Gulf modelling system was donated to and installed at the University of Houston, where a new laboratory housed a larger tank. Subsequently, other physical modelling systems were built in China, Japan, Australia, Saudi Arabia and Holland. State-of-the-art recording has changed from single shot to single receiver, to multi-shots into 48 receivers, with further channel expansion soon. From simple impulsive shot recording simulating explosives, the technology has moved to simulation of any form of vibroseis sweep or frequency required. From simple plastic models, the technology has moved into the realm of injecting fluids into real sand reservoirs in pressure vessels. This paper will discuss the changing face of seismic physical modelling.