Study On AVO Forward Modeling In Lower Shaximiao Reservoir Of Guandu Structure Belt Of The Southeast Margin Of Sichuan Basinthe

Guandu district is located in the eastern part of chishui area which is located in the southern edge of low plait belt of the southern sichuan basin, in the composite superimposition area between the facing south broom shape extensions of the eastern sichuan high and steep fold belt and the constant dam in southern sichuan east-west structural belt. Since the start of oil and gas exploration in the early 1970s, many wells already have industrial airflow and oil & gas display.At present, a few achievements about AVO have been acquired in the region, including the forward modeling in AVO angle trace gathers, and the gradient analysis on the modeling results of angle gather data, and angle trace gathers sorting and AVO fitting analysis in the CMP trace gathers obtained by conventional seismic data processing. Although many scholars have done a lot of work about AVO aimed at the target area, by now, there has yet to form a set of special technical methods on the effective reservoir prediction and identification, due to the complexity of reservoir and the restriction of technology. And AVO techniques have not been used successfully in this region, so now needs to establish the AVO curve characteristics atlas and the AVO section characteristies atlas, which apply to the sandstone in this region.The main method of searching for gas and oil is seismic exploration around the world. Making use of amplitude versus offset to search for gas and oil is a new seismic exploration technology, which developed in recent ten years, it mainly analysed the amplitude versus offset rule in pre-stack trace gathers, in order to seek the elastic parameters of rock,distinguish lithology and pore fillings, and that was a new method of finding useful mineral deposits (gas reservoir, underlying salt, etc.). The technology of AVO is based on Zoeppritz precise equation and its approximate formulas. According to the Zoeppritz precise equation and its approximate formula, we could get the reflection coefficient curve which can reflect the AVO characteristic of particular geological model, and the curve would be the important object in the study of AVO modeling. Modeling study played a very important role in AVO technology. According to the research on AVO modeling, we could bulid the AVO atlas of characteristics about the regional stratigraphic combination and typical petroleum formation, which is in favor of the AVO data processing and interpretation; the extraction of formation parameters also used AVO modeling technique, generating atlas of characteristics quickly and effectively according to geological model would help the whole research and exploration.This paper firstly introduced the current research status and research significance of AVO technology, then introduced the basic physical theory of AVO technology, rock physical basis, Zoeppritz precise equation and the approximate formulas. On the basis of above-mentioned, building a suitable model to study how different differences of different parameters can affect the accuracy of the Zoeppritz approximation equations, and then studied the effect of variation of different parameters on the reflection coefficient curve. Based on this study, building a suitable horizontal layer model and generated seismic record using ray tracing and apply NMO, sorting CDP gather etc, in the above after work, selected a suitable approximation equation to do AVO property parameters inversion and obtained P section, G section, PG section, P+G section, P-G section, sgn(P)G profile, etc. Then, using the actual logging data to construct the two-dimensional model, generated seismic record using ray tracing and completed AVO property parameters inversion, contrasted and analysed the results, and according to the area seismic geological conditions, analyzed on AVO data acquisition, processing, interpretation and the feasibility of application AVO in this area, and put forward some suggestions.After researched the AVO forward modeling, on the basis of generated seismic record using ray tracing, combined with the practical seismic profile, completed the extraction of property parameters, obtained the main amplitude, the main frequency, three transient parameters, and so on, and the parameters of the above verify the results of AVO forward modeling. And the feasibility of AVO application are analyzed and discussed.