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An Expert System for Well-to-Well Log Correlationby Submitted to the Department of Earth, Atmospheric, and Planetary Sciences on December 10, 1986 in partial fulfillment of the requirements for the degree of Doctor of Master of Science in Geophysics ABSTRACT
This thesis presents a robust method for correlation of geologic sequences
known as "Dynamic Depth Warping" (DDW). This method uses dynamic
programming to find an optimal depth matching between two sets of log data.
The advantage of dynamic programming over conventional spectral correlation
methods is the ease at which local geologic knowledge can guide the matching
process both before and during the correlation. The Dynamic Depth Warping algorithm is implemented in a LISP program called
COREX. This program uses a knowledge-based system to integrate all of the information
usually available to geologists for log correlation. For this thesis the data
includes digitized wireline logs, simple lithologic information, seismic lines,
interpreted dipmeter logs, and local geologic knowledge. The system uses rules
stored in the knowledge base to analyze these data and impose geologic constraints
on the correlation algorithm. We use the knowledge base of COREX for two purposes. First, the program performs
an initial match of the wells based on the lothologies present, the scale of
the correlation, and the depositional environment under consideration. Second,
using the initial match to establish tie lines, the knowledge base analyzes
the local geologic structure and log quality, and translates this information
into constraints on the DDW algorithm. This guidance allows meaningful correlations
in areas that were previously too complex because of geologic structure or large
data volume. We demonstrate the method with synthetic examples in which the program successfully
correlates across geologic structure and pinch-outs. We also apply the program
to field examples from West Africa and Turkey. In both cases, the automated
correlation agrees very well with hand correlations provided by geologists. Return to Theses Return to ERL Home Updated: {Date2}
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