Study On 3-D Geological Modeling And Seismic Ray Tracing Methods

Nowadays the development trend of exploration seismology is the integration of seismicdata acquisition, processing and interpretation. 3-D geological models are the key of this process.Along with the development of exploration and exploitation, it is possible to buildmulti-resolution geological models with different attributes from regional to local scale, based onthe previous geological and geophysical studies. Geological modeling provids necessaryguarantee for building different kind of models. The combination of geological modeling andgeophysical applications can prompt the development of related disciplines. In this article, thejoint study of 3-D geological modeling and ray tracing methods is carded out. The geologicalmodeling results are successfully introduced into seismic ray tracing studies. Two researchcontentses are completed respectively: 3D fast two-point ray tracing in block models andwavefront construction with triangulated surface in ray coordinates. The results of this paper areas follows:(1) The modeling elements and related core technology are analysised and concluded. TheCharacteristics and disadvantages of current fault modeling methods are discussed. Two real datamodeling examples are shown with geological modeling modules.(2) Based on model data from modeling process, a fast two point ray tracing algorithm inblock models is developed for geometry optimization in seismic data acquisition. The forwardmodel consists of serveral blocks, whose physical parameters are constant in it. The surface ofeach block is represented by TIN, which is suitable for complex geological models. Ray pathcode is used to discribe different types of rays and rays in different parts of the model. Wholepath iteration method is used for ray path calculations. Redundancy check is used to check thelegitimacy of traced rays in complex structrues. A ray tracing code is developed with C++.Examples of VSP ray tracing in different models are shown.(3) The topology of Tin structure is introduced into wavefront construction ray tracingstudies. Each wavefront is represented by triangle network in ray coordinates. Initiated fromsource, the wavefront can expand to the whole region of the model.The ray density on thewavefront is controlled by dynamic checking of triangle qualities. New rays are introduced bydirect ray tracing from source, which provides a higher accuracy. Kenematic and dynamicproperties of rays are interpolated on fine migration grids in ray tubes. A wavefront construction ray tracing code in C++ is developed and a low velocity model is tested.(4) Model space searching efficiency is improved in specific ray tracing applications. On raytracing for block models, regularly partition index of surface triangles and rectangle of eachtriangle are built for fast point positioning on surface. Collision detection is used for pointpositioning in block. The upon methods greatly improve ray tracing efficiency in models withlarge data sets. On wavefront construction ray tracing, rectangular box is used for fast excludingpoints from ray tubes. Tetrahedron is used for point positioning, and a linear method is used forfast interpolation of different kind of attributes in each tetrahedron.