GEOLITH: An Interactive Geostatistical Modeling Application

A menu-driven workstation application program designed to analyze reservoir data and construct reservoir simulation models with a geostatistical approach is presented. The program analyzes reservoir data in the form of well logs and interpreted bed markers and allows interactive fitting of variogram models to data. These models then are used to construct gridded models of reservoir flow properties by kriging and conditional simulations and the use of flow-property transforms of well log values. The interpolation of data to the interwell region is done in a stratigraphic framework that honors the geologic interpretations provided by the bed markers. Small-scale variations are added through a number of methods (matrix, fractal, sequential, simulated annealing) to produce conditional simulations that reproduce the measured variability of properties at unsampled locations. The program also integrates indirect information, such as acoustic impedance derived from seismic data, with well-log data by several different methods. The program has an intuitive and accessible data interface, a structured sequence of user prompts and error checks, and striking graphical presentations of modeling results. With it, the complex task of converting geological data into quantitative reservoir models for flow simulation and reservoir performance prediction is greatly streamlined.