Abstract

Assam Shelf originated as a passive margin pericratonic basin that suffered multiple phases of tectonism leading to a varied phases of structural deformation of its sediments. The most dominat phase of deformation that shaped the basin configuration as well as most of its structural entrapments are thrusting along Main Boundary Thrust (MBT) that defines its northern boundary and the Naga-Disang Thrust defining its southern extent. This deformation was followed by an across basin strike slip Kopili Fault that led to clockwise rotation of the eastern shelfal block. The present study attempts to study the effect of strike slip faults on the basin and its implication on hydrocarbon distribution and basement exploration. . The strike slip faults resulting from rotation associated with Kopili fault are broadly E-W and affect the entire width of the Assam Shelf cutting across the Bramhaputra arch. These faults are found to affect the entire south and north bank of of Bramhaputra River forming a regional wrench couple with a dextral shear system. Since these faults cut across the Bramhaputra Arch and are repeatedly reactivated these can be instrumental in re-migration of hydrocarbon from the south bank to the north bank acting as a conduit. Additionally since these faults are associated with multiple fracture sets, they lead to an increased fracture porosity within basement resulting in basement reservoir conditions.