Petrophysical Reservoir Characterization and Uncertainty Analysis

A methodology of petrophysical reservoir characterization is presented. The goal of this methodology is to provide a complete solution for reservoir properties determination, including estimation and uncertainty analysis. The strengths of this reservoir characterization methodology are: i) uncertainty analysis and ii) integration of multiple geophysical data-sets, rock physics analysis and prior information in a straightforward way provided by the Bayesian framework. The inference problem reported on in this paper is formulated to solve the problem of porosity estimation. The sources of information are pre-stack seismic data, well log data and core samples. The waveform elastic pre-stack inversion is incorporated in this methodology to access the porous medium physical property information from pre-stack seismic data. Geostatistical modeling is incorporated to access the porous medium spatial variability information from well-log data. The methodology is implemented considering a reservoir composed of block cells. One posterior pdf is computed for each reservoir cell. Two cell volumes contain the final result. One is constructed with the modes of the posterior pdfs related to each cell and represents the estimated porosity model, and the other is constructed with the confidence interval of the posteriors pdfs and represents a measure of the related uncertainties. This paper is going to describe the general theory of the methodology, the practical implementation and results of tests with a 3-D pre-stack seismic data set (1995 3-D Blackfoot data)