Application of Walsh Filter in Geophysical Well-Log Data Interpretation for Automated Lithological Bed Boundary Detection

Lithofacies extraction is an essential step for mapping the earth's subsurface, which is crucial for effective hydrocarbon extraction. The identification of lithofacies in borehole location is frequently handled as a part of the core data analysis. The exact knowledge of the various lithological units is also provided by the downhole well log data. In our present work, we use the Walsh low pass filter to the wire-line log signal responses and the bed boundary identification algorithm to spot the bed boundaries at their corresponding depth with an automated approach. Initially, we construct a stepped version of the well log data using the Walsh domain filter with a fixed step width. Afterwards, each version of the well log data is given a different weight according to their influence on lithological change. The fluctuation at a particular location is compared with a reference value to generate an automatic set of lithological boundaries. Within a complicated environment of sedimentary strata, the Walsh low pass filtering can correctly locate the thin lithological units. Further, the proposed work is an efficient way of understanding the subsurface inhomogeneity and identification of the lithofacies boundaries. The approach is tested successfully on the well log data obtained from the Krishna-Godavari basin.