The Study Of Petrophysical-Properties Inversion Base On Pre-stack Seismic Data

Petrophysical parameters include reservoir porosity, fluid saturation, shale content, reservoir pressure, reservoir permeability and so on, these parameters are important to reservoir comprehensive evaluation and reservoir fine description. Currently these parameters are mainly acquired from the core and logging data. The research of petrophysical parameters inversion method based on the seismic data is becoming a very promising research subject of the application research of seismic data. In this paper, All of the research is conducted around petrophysical parameters. The relationship between seismic attributes and petrophysical parameters is fully studied based on rock physics and pre-stack seismic forward modeling. On the other hand, The petrophysical parameters inversion method is studied based on pre-stack seismic data.This paper studies the petrophysical parameters joint inversion method based on bayesian classification theory. This method comprehensively applies some various theories such as statistical rock physical model, monte carlo simulation technology and bayes classification method. The inversion objective function is established based on bayesian inversion framework and the final result is the maximum posteriori probability of petrophysical parameters. Firstly, the prior distribution of petrophysical parameters is acquired by means of logging data analysis. Meanwhile, the relationship between elastic parameters and petrophysical parameters is established based on statistical rock physical model. Secondly, the fully sampling to prior relationship is obtained by means of monte carlo simulation technology, so as to realize the petrophysical parameters transverse extrapolation. According to the sample data, the bayes classifier whose classification target is petrophysical parameters is constructed. Finally, the petrophysical parameters can be joint inversed according to pre-stack elastic impedance inversion results.Based on the theory research, to solve the problems and difficulties which exist in a complex gas reservoir prediction, an integrated reservoir fluid recognition method is proposed based on pre-stack seismic inversion. In view of the problems of the actual project, this following technical ideas are established. First, the reservoir and fluid sensitive elastic parameters is determined by means of rock physics crossplotting technology. Base on elastic impedance inversion, then the elastic parameters which are favorable to reservoir recognition can be acquired. Then the lithology and favorable containing gas reservoir can be recognized through petrophysical parameters inversion method. Finally, the space distribution of high gas saturation sandstone is successfully distinguished based on the elastic parameters which is sensitive to gas saturation. For such a set of technical ideas, we can realize saturation prediction of complex gas reservoir.