Bed boundary identification from well log data using Walsh transform technique: A case study from NGHP Expedition-02 in the Krishna–Godavari basin, India

Abstract

Identification of thin stratigraphic beds is often dealt with using the scale of core data analysis. The downhole wireline log data also provide accurate information on the characteristics of lithological boundaries. In the present study, we have used a Walsh low pass filter and bed boundary detection algorithm to develop an automated bed boundary identification approach. Initially, we ran a Walsh low pass filter against the wireline log responses. Afterwards, a bed boundary detection algorithm has been applied to the Walsh low pass filtered version of the wireline log data. The Walsh domain filter creates a stepped version of the well log data having a constant step width over the entire low pass version of the log signal. As the Walsh function basically represents the binary waveforms, the Walsh low pass filtering can appropriately identify the thin lithological units within a complex succession of sedimentary strata. Further, the proposed approach is an efficient way of resolving and understanding subsurface inhomogeneity from wireline log data. The feasibility of the technique is successfully tested on the downhole wireline log data acquired from the Krishna–Godavari basin during the Expedition 02 of Indian National Gas Hydrate Program (MGHP).