Abstract

The Rudrasagar Field in the Upper Assam North Shelf of the Assam and Assam-Arakan (A&AA) Basin is a mature hydrocarbon producing area from Barail sands of Oligocene age. Tipam reservoirs of Miocene age also have commercial success particularly in TS-4 sand and showcase the potential of reservoirs but are relatively underexplored. The TS-4 sand is characterized by thin, laterally heterogeneous fluvial sands, encased within the Lower Clay Marker (LCM). This study adopts an integrated geoscientific workflow to assess the reservoir potential, depositional architecture, and hydrocarbon charge behavior of the TS-4 sand. In the present study 3D Wide-Azimuth (WAZ) seismic data, integrated with 200 well datasets is used to characterize the TS-4 sand. Through seismic modeling, the response of TS-4 sand is calibrated with seismic signature which indicates that high-impedance thin TS-4 sands, sandwiched between low impedance shale are expressed as low-amplitude features, aiding in their sub-seismic detection. The results delineate a meandering fluvial system with point bar geometries and lateral accretion surfaces, mapped through seismic attribute anomalies and spectral decomposition followed by CMYblending. Analysis of the results suggests that hydrocarbon distribution in TS-4 is found to be controlled by starti-structural entrapment, facies connectivity, and fault-assisted vertical and lateral migration. Dry wells lacked the effective charge either due to poor facies or strati-structural alignment. Based on the study, stratigraphic features were identified for future exploration and development strategy. The model was tested in a nearby well through workover operation which successfully encountered hydrocarbon-bearing sand, validating the methodology. The study offers a predictive framework for identifying subtle stratigraphic traps in similar setups.