Interpreting formation tops

Abstract

Formation tops correlation is interpreted between sampled log curves by a weighted combination of covariance, the ratio of standard deviation, and the ratio of summed amplitude. This covariance function is computed and evaluated appropriately for the geologic environment over a sliding analysis window. Correlations are determined for any number of wells and any number of events in each well. Geologic rules are used to establish a parameter for the algorithm operation and for the analysis of the resulting function. The geologic rules include bounding guide horizons, sequence rules, and a covariance cutoff parameter. Bounding horizons are picked from pre-existing seismic or geologic interpretations and from map grids. The rule set includes onlap, truncated, conformable, and unstructured sequence definitions. Additional geologic complexity such as crossover, repeat sections, and inverted sections are accommodated by the rule set. Back-correlation for cross over sections and loop-tying for map interpretation are performed for validation.