The Analysis And Application Of FVO Technology With Prestack Seismic Data

With the rapid development of economic construction in China, the position of oil and gas resources has been significantly improved in national economy. Domestic oil and gas exploration and development is also becoming more and more difficult. Therefore, the exploration and development of oil and gas have a higher level of requirement for explorating technology.In the downward propagating process of seismic waves, they are affected by the absorption attenuation effects of many factors, resulting in a large extent absorption of high-frequency components and the significant reduction of frequency. Among these factors, oil and gas fluids in the subterranean formation play an important role and are major study objects in seismic exploration. However, due to the strong lateral heterogeneity of the underground medium, sometimes single AVO inversion can not be used to exactly predict the hydrocarbon bearing property of the subsurface strata. And, the traditional frequency attenuation attribute analysis is conduct after stack. But, the sensitivity of frequency attenuation attribute to fluid will be reduced after prestack. It will make against to the prediction of fluid.In order to solve the above problems, this thesis studies the theoretical formulas of AVO, selects the AVO parabola calculation formula of Zheng Xiaodong as the prototype, derives and improves the approximate theoretical formul a the FVO(frequency attenuation with offset variation) combining frequency attenuating theory and proves that FVO attributes can be used to predict the storage of underground oil and gas and other fluids from a theoretical point of view. Then under the guidance of the theory, two different two-dimensional geological models are designed for prestack forward modeling test, obtaining the result that when there are fluid bodies in the underground strata, frequency of seismic waves will actually sufer severe attenuation. Therefore, it is found that it is feasible to predict the spatial distribution of underground fluid through prestack FVO attributes. Then, with a combination of actual raw prestack seismic data set, the prestack inversion work of the underground storage layer is completed through data analysis and processing. I extract the prestack AVO attributes and the prestack FVO attributes, and a n analysis is carried out for the corresponding attribute graph. Combined with the field drilling data, it can be found that the prestack FVO attributes also achieve good results in practical application. It is proved that the prestack FVO attributes can reflect the spatial distribution of the underground fluid accurately.According to the derivation of the theoretical formulas, the model forward tests and the verifying effect of the real seismic data, it can be found that the prestack FVO attributes are very sensitive to fluids in the underground. When the seismic waves propagate in the subsurface formations, the prestack FVO attributes will change with offset, the formation containing fluid or not and the thickness of fluid saturated storage layer. There are some specific performances: frequency attenuation will increase with offset; after the underground storage layer is filled with oil and gas fluids, the frequency attenuation will also increase accordingly; when the thickness of fluid saturated storage layer increases, same attenuation happens for the frequency, while for a small thickness, frequency attenuation may be very weak and even unable to identify. Overall, the FVO attributes can predict the subsurface fluid with a strong feasibility.