AVO Response Analysis Of Gas Hydrate Reservoir

Gas hydrates, as a kind of clean energy, which has great development prospects,often exists in permanent permafrost and the bottom of the sea at continental marginarea. The formation of gas hydrate need special external environment and subtlevariations in temperature and pressure will pose a threat to the stability of the hydrate,so the hydrate reservoir tends to be thinner and its distribution changing withtemperature and pressure gradient, which provides a certain basis method for theexploration of gas hydrates, but at the same time, to a great extent, increased thedifficulty of exploration. According to the hydrate forming mechanism and itsdistribution rule, this paper establishes a series of hydrate reservoir models withdetailed divisions. Through the forward modeling and AVO processing, it discussesthe AVO response characteristics of different layers with different contact relationsunder various kinds of patterns and analyzes the AVO response of the BSR in actualdata, then, it summarizes the AVO response characteristics for finding and identifyingthe gas hydrate reservoir, which has certain reference significance for the gas hydratereservoir interpretation and prediction.The formation and distribution characteristics of hydrate are the geological basisof hydrate reservoir research. It mainly discusses the formation mechanism,occurrence mode and reservoiring pattern of gas hydrate, and the responsecharacteristics of hydrate reservoir on seismic profile. In the second chapter,combining with the equivalent medium theory and the G’assmanns equation, itanalyzed relations between the lithological parameters and velocity. Finally, on thebasis of the above content, the hydrate reservoir model and velocity-density model areestablished.By studying the change in reflection amplitude versus offset or angle ofincidence, AVO technology can directly estimate the reservoir lithology parameter,which has a good effect in practical application and has been widely applied to oil and gas exploration. The theory is based on Zoeppritz equations and its various simplifiedstyle. In third chapter, it analyzes the applicability for all the approximation forms ofZoeppritz equation to the hydrate reservoir. Then, it analyzes the influence of rockporosity, hydrate saturation and free gas saturation on the reflection amplitudecalculation of hydrate reservoir reflection interface.In the fourth chapter classified and stratified detailed modeling and AVOprocessing are done using ray tracing method on the reservoir models, by change ofcontrol of rock porosity, saturation of hydrate and free gas saturation, and discuss theinterface reflection characteristics and AVO characteristics in detail, focusing on theexistence and characteristics of different situations BSR, and then analyze theresponse of different BSR in the AVO attribute section, and finally the method offinding BSR via AVO attribute and the method of distinguishing true and falserecognition of BSR through the AVO property are found.The AVO technology requires seismic data can reflect the relationship betweenreflection amplitude variation with offset truly, so the AVO seismic data processing isthe key technology of AVO. The fifth chapter discusses the basic procedures by AVOdata processing to obtain attribute profile and problems. Taking advantage of theconclusion mentioned above, AVO processing is done in the actual data of one seaarea, comprehensive BSR analysis and evaluation is made combined with loggingdata in the area.