Research On The Prediction Method Of Poisson's Ratio And Reservoir Thickness Based On The AVO Effect

The Amplitude versus Offset (AVO) analysis is that the reflection coefficient of waves varies with the incident angle, its theoretical foundation is the Zoeppritz equation and its approximate equations. It has been confirmed that AVO anomaly are of importance to the identification of natural gas, and it has AVO anomaly in gas-sand reservoir. Its Poisson's ratio significantly decreases and the slope of AVO is negative generally. Therefore in AVO study the Poisson's ratio is an extremely important parameter which be used to examine oil and gas directly. The variety of Poisson's ratio not only reflect the circumstance of oil and gas in geologic strata, but also reflect the variety of rock properties, and it has important value in the research of oil and gas examination. The Poisson's ratio can be get from laboratory measurements,a calculator analysis of full wavetrain acoustic logging,seismic prospecting methods of multiwave,the data of VSP logging and the theoretical formula calculation, etc. AVO processing is to detect hydrocarbon by using amplitude information of seismic reflection.First, AVO forward modeling and analysis were carried out by using drilling data, then AVO processing of field seismic data were performed with optima processing flow chart and preserved amplitude processing technology,and finally favorable zones for exploration were delineated based on AVO processing results and comprehensive analysis of various seismic and geologic data. In this paper we invert Poisson's ratio and reservoir thickness, it based on the study of AVO forward modeling. In the text, elaborated the technical theories foundation of AVO first, tallied up various simplification form of Zoeppritz equation systematically, and analyzed AVO characteristic curves of the each simplification form, and then chose a simple form which is advantageous to the Poisson's ratio invertion to research AVO forward modeling. In forward modeling, firstly, we set up typical two-layer and three-layer theoretical geologic model, researched vary characters of AVO effect in various parameters composing conditions, analyzed the relationships of AVO effect (intercept and slope) with Poisson's ratio,formation velocity and reservoir thickness; then we set up multi-layer theoretical geologic model and further discussed how the Poisson's ratio and reservoir thickness affect AVO effect, find out the relationships of reservoir parameters (Poisson's ratio and reservoir thickness) with AVO effect, and put forward the method of inverting Poisson's ratio and deduced the experiential equation, we can predict Poisson's ratio and reservoir thickness by means of this method. Theoretical model data and raw data were computed to bring quite good result, this method proved to be effective.