Abstract

Low-resistivity pay zones present a unique challenge in hydrocarbon exploration due to their ambiguous log signatures, which often resemble water-bearing intervals. This study investigates one such zone encountered in the Daman Formation within the Tapti-Daman sector of India’s Western Offshore Basin. A well (Well W) was observed to produce significant quantities of gas from a sand interval exhibiting anomalously low resistivity (2–3 ohm-m), considerably lower than the typical 8–10 ohm-m resistivity seen in gas-bearing Daman sands. Despite conventional petrophysical logs suggesting water saturation, well control events, gas shows, and testing confirmed hydrocarbon presence. A multidisciplinary approach—integrating CMR, ECS, XRD, and resistivity-independent saturationheight modeling—was applied to decode the anomalous behavior. The analysis revealed that high formation water salinity, elevated clay content, and the presence of pyrite contributed to the reduced resistivity. Additionally, clay-bound and capillarybound water further complicated interpretation. The case underscores the limitations of conventional resistivity-based evaluation techniques in shaly, lowresistivity formations and the necessity of integrating advanced logging tools for accurate reservoir characterization. This work highlights the importance of careful assessment of low-resistivity intervals, which are often overlooked yet can be productive. Understanding their petrophysical behavior is vital for optimizing field development strategies, especially in mature or complex basins like Mumbai Offshore