The Analysis Of The AVO Effect Factors

ThetechniqueofAVO(AmplitudeVersus Offset) is a method which use the relationship of seismic reflection amplitude and offset(or angle of incidence) to research oil and gas. This technique is established on elastic wave theory. AVO technique has been emerged for more than twenty years,with the continuous development of computer technology, A lot of geophysicists have done more research and analysis for it. On this basis, we use it in petroleum geophysical exploration,and has achieved very good results.On the basis of a large number of domestic and foreign literature, I have neaten the principle and the development process of AVO technology in this paper. I have carried on the induction summary in Zoeppritz equation and its simplified formula. And, I have studied the rock physical parameter and the qualitatively classified of gas-bearing sand on AVO attribute analysis. Set the stage for the behind AVO influence factoranalysis.On the basis of Zoeppritz equation, I have combined with the actual seismic data to do AVO forward modeling in this text. The AVO curve offorward modeling consistent with the actual AVO curve of each well, so the established model is reasonable and the forward modeling method has higher precision. For summarize the actual seismic data in detail, I combined withreservoir stratum in the well, Respectively to analyzed the AVO characteristics of reservoir is located in the horizon of the top or inside.Respectively analyzed the porosity, water saturation, depth of stratum effects on AVO curve.In this paper, I have introduced layered medium,thick-layer and thin-layer. Zoeppritz equation is formula which is only used to compute the reflection coefficient of the interface between two semi-infinitemedium. But, it cannot reflect the internal properties of thin-layer for layered media. In this paper, using Berkhovski equation get the thin-layer’s reflection coefficient and transmission coefficient of the three layers ofmedium. I established the relevantthin-layer model, and used the formula to analyze the reflection coefficientcurve. Then analyzed the influence of the thickness of middle layer and the incident wave frequency onreflection coefficientcurve.Due to the effect ofstratum’s absorptive action, with the increase of the thickness, the shock of reflection coefficient curve is more and more serious. Considering the effect of the stratum’s absorption, quality factor is introduced. In 1978, the complex wave velocity using quality factor to showwas proposed. Replace the wave velocity of Brekhovski with complex wave velocity, get the reflection coefficient formula with absorptive action.Using this formula analysis the influence of absorptive action to reflection coefficient curve.