Computer representation of complex 3-D geological structures using a new “solid modeling” technique

During our recent work with 3-D dynamic ray-tracing and velocity inversion problems, a new 3-D model generation system has been developed using a so-called “solid modeling” technique. The term “solid modeling” refers to the fact that the logical system governing the internal geometrical properties of the model describes the model as a combination of “solids” or “volumes” in 3-D space. In each of these volumes the physical parameters (such as seismic velocity, density) vary continuously. Discontinuous changes occur only across the model interfaces separating the volumes. The model is constructed by firstly forming a number of “simple volumes” from the given interfaces and then combining these simple volumes into more complex volumes which represent the physical volumes of the model. It is easy to make changes to the model, by adding volumes or subtracting volumes and perform more composite operations, all by simple use of Boolean expressions. Every time a model has been specified (or changed), the internal logic automatically carries out a check of physical consistency of the 3-D model space (no overlapping volumes, no holes). By including various types of coordinate transformations, different kinds of complex structures can be handled, such as salt domes and vertical and near vertical faulting.