Abstract

The Tipam pay sands of the Changmaigaon field in Northern Assam Shelf have posed a significant challenge for petrophysicists due to their Low Resistivity Low Contrast (LRLC) characteristics. In some areas, the resistivity in the upper oilbearing sections is even lower than that of the underlying water-bearing zones, complicating the identification of the Oil Water Contact (OWC) and the hydrocarbon-bearing nature of the reservoir. Additionally, conventional log data processing fails to accurately quantify water saturation in established oil-bearing sections. To address the complexities of the reservoir and obtain realistic estimates of its parameters, this study integrates all available geological and geophysical data along with production testing & reservoir pressure data collected throughout the field's operational history. An integrated petrophysical analysis was conducted using a resistivity-independent workflow that included reservoir rock typing, permeability modeling, and saturation height modeling (SHM). The results were validated against observed production behaviour and also with conventional petrophysical processed outputs from few nonLRLC reservoirs within Tipams. This study clarifies the unusual production testing results like water production from structurally shallower wells, ambiguity in OWC values inferred from log data and the uncertainties surrounding the reservoir's structural configuration & water saturation computation. The findings have been applied to create a realistic three-dimensional reservoir model, aiding in realistic estimation of in-place volumes and devising further development plan for the field.