The Study Of Seismic Acquisition Method Based On Modeling Of 2D And 3D Complex Geologic Structure

There are more and more requests for petroleum energy as the continuous development of our national economy. At present, we are facing a great shortage of oil and nature gas and have to depend on the import from abroad. So speed up the development of ours petroleum industry and find more and more petroleum mothball resource are a great national policy for insuring the rapid development of ours national economy and the safety of our country. In our country, the petroleum mothball resources are mainly distributed in mountain area, Loess Plateau, desert, Gobi etc. furthermore, these areas are very complicated not only on surface but also under ground. There are exquisite elevation variation and huge thick gravels or low velocity sand or loessial layer on surface, the excitation and receiving both are difficult, operating in field is not easy and the statics correction problem is seriously existed; meanwhile under ground, the faults are developed widely and the dip angle of the stratum is big, the velocity variation is exquisite, all these make it is difficult to obtain the primary reflection and to get the correct image of structure. The study in this paper aimed at the survey in complex area and proposed the optimization method for geometry design and determining the reasonable acquisition parameters based on the built complex model, ray tracing and the analysis of the distribution of reflection point and ray path, thereby improving the seismic acquisition effect, the quality of seismic data and the ability of finding oil and gas.Traditionally, the geology structure is described by samdwich model, which can't meet the needs in complex prospecting area obviously. In this paper I proposed a method, which describes 2D complex structure with closed curved plane and for 3D complex structure with 3D closed block. During building 2D model, I use the concepts of point, segment, line and plane, the segment can be formed from points, then line can be formed from segments, the closed curved plane can be obtained by around lines, and finally the 2D model can be built by closed curved plane; I express the un-smooth stratum or fault by linear fitting and express the smooth stratum or default by cubic spline fitting segmentally, in this way I can describe the variation feature of 2D interface properly. During building the 3D mode, I use the concepts of point, triangle, plane and block, that is from point to triangle to stratum surface or fault to closed block, and finally all the closed block will form a 3D model. Especially the auto-adaption triangle grid method for interface fitting and the 3D visualization technique for building 3D model are the feature of our method. In addition, using the concept of graphics, the automatic tracing for 2D closed plane and for 3D closed block creates the conditions for building the 3D or 2D model interactively. The actual examples indicate that using the 2D closed model and 3D closed block to describe the complex structure is very practical andeffective.Based on the model built with 2D closed plane and 3D closed block, I proposed three types of ray tracing methods, which are suitable for complex structure: they are "test-fire" ray tracing method, "iterative" ray tracing method and "test-fire plus iterative" ray tracing method. The "test-fire" ray tracing method is based on the Snell theorem; it calculates the ray path from source to receivers. Its most advantage is: it is suitable for any complex geology structure, the "iterative" ray tracing method is based on Fermat "minimum travel time principle", it uses Taylor expansion and finds the solution segmentally and iterativelyi then modifies the initial ray path. Its most advantage is: the calculation speed is fast and the efficiency is higher. The "test-fire plus iterative" ray tracing method is the combination of "test-fire" and "iterative", it gathers the advantages of two methods in one body, it can meet the requests both complex structure and fast calculation.Based on the built complex model and ray tracing, I proposed a method for...