Application of Self-Organizing Feature Maps to Reservoir Characterization

Abstract

Neural networks are becoming an increasingly popular analysis tool in a wide variety of applications. One application of considerable interest is reservoir characterization. Calculating reservoir properties has typically been a process of extrapolation or interpolation from a sparse number of locations using geostatistical methods. A neural networks approach allows estimation of reservoir parameters from not only the sparse set of well locations, but also an auxiliary data set such as a complete grid of 3-D seismic data.

This chapter discusses the novel application of unsupervised neural networks for reservoir characterization. The unsupervised approach is compared to conventional supervised neural network approaches to illustrate the fundamental differences. Two examples of supervised neural network parameter estimation are presented followed by an introduction and application of unsupervised neural networks. The three cases can be summarized as: 1) estimation based on spatial information only, 2) estimation guided by seismic data, and 3) analysis using an unsupervised neural network approach.

A numerical study described in the first approach shows that it compares reasonably well with conventional geostatistical approaches. The second or guided approach is a practical way to associate seismic data with well data over the entire area of a prospect. Validation results for this method are also good, and the example shown emphasizes that results are highly data dependent. The third or unsupervised approach comprises a novel method for analyzing a 3-D seismic data volume in a relatively unbiased manner. This technique gives two useful results: first, class or correlation maps showing similarities of data traces over the prospect area and second, output or weight vectors that represent prototype seismic traces associated with a particular output class. These prototype traces have proved to be very useful for further analysis of the data volume. An example of the application of the unsupervised approach to a producing oil field in Montana is described in which a prediction for a well location based on the neural network analysis proved successful on drilling.