Analysis Of AVO Forward Modeling

AVO (Amplitude versus offset), a new method in searching for oil and gasseismic exploration using the relationship between the use of seismic reflectionamplitude and offset, has been developed and widely used in the world in recentyears.AVO forward modeling study is an important part of AVO technology and playsan important role in it. As with other methods of seismic model, AVO forward modelfacilitates the design objective field observation system for the right selection ofacquisition parameters, and according to the forward curve type which is based on thesynthesis of the actual area objective layer AVO response model is able to judge thefeasibility of objective layer of oil and gas, at the same time using AVO technology toretrieve formation parameters can also be used with AVO forward modelingtechnique.As everyone knows that model’s choice and the parameters is the key to thesuccess of the analysis. This article starts from the Zoeppritz equation, first introducedto the equation for the development and current situation of theoretical foundationestablished by the AVO technology, and the development trend and applicationpractice which is helpful to the study of AVO technology. In theory, with theZoeppritz equation deducing, the article reveals the plane wave in the incident plane,and analyzes using Zoeppritz equation of longitudinal wave which is widely used inseismic exploration. Being based on the theoretical model, the article analysis of therelationship between reflection coefficient and the wave incident angle, therebysubstantially the principle of AVO technology.The classical Zoeppritz equation can fully reflect the energy distribution ofvarious conversion interface on both sides of the wave, but the equation itself is toocomplex. At the same time, in seismic exploration based on P-wave source, in order to reduce the amount of computation and unnecessary parameters influence on theforward simulation, the article, based on the former research, comparison and analysisof the approximation equation of Zoeppritz equation, through the modeling of allsolutions of the equation were fitted. Results show that, because the focus in thesimplification of each equation is different, so that the degree of fitting parameters inthe different models are also different. The approximate equation of different havedifferent applicable scope, while the equations in the model parameters change fittingdegree will change too. This shows that in the forward modeling for AVO, in theequations and parameters selection is very important, also the AVO forward basis andkey simulation. For the choice of model parameters, the article discussed the rockphysics for AVO, and focus on comparing the characteristics of three kinds of gasreservoir, so that the theoretical research and practical work is carried out incombination with AVO forward modeling.In this paper, the forward modeling is based on ray tracing as the main method.Starting from the theoretical model constructing, model data to obtain the reflectioncoefficient curve and AVO response gathers by programming calculation, then carrieson the research analysis. In this study model, the forward model is extended to theabove layered model close to the actual formation, construction of layered mediummodel different, further analysis. For a layered medium model, change the mainphysical parameters of rock, and highlights the main features of the model. At thesame time with the reflection coefficient curve and AVO response to gather areanalyzed, reflecting the forward model in the actual formation conditions. Analyzedand summarized according to the map of model stratum, the feasibility analysis ofAVO technology.