Estimating basal friction and fluid pressure from the geometry and spacing of frontal faults in Naga fold thrust belt, India

Naga fold thrust belt is an emerging destination for petroleum exploration in eastern India. It is a thin skinned FTB where new initiatives are being taken after a long gap of initial discoveries. In absence of sufficient drilling or quality seismic data in the southern part of the fold thrust belt, fluid pressure regimes remain largely speculative. Using the concept and the formulation for efficient coefficient of basal friction, we have revisited the method and concept of pressure-dependent Coulomb wedge theory for thin skinned thrust belts for deriving the fluid pressure ratio in Naga fold thrust belt. The efficient coefficient of basal friction on the decollement and the fluid ratio of Naga fold thrust belt are estimated to be 0.22 and 0.85 respectively. This indicates an overpressure situation in the wedge. This method of estimating basal friction and fluid pressure is more case-specific and can be obtained from the data of thrust initiation angle and thrust spacing. ► Efficient coefficient of basal friction in NFTB is found to be 0.22. ► The fluid pressure ratio in Naga fold thrust wedge is found to be 0.85. ► Geometry of FTB used to calculate basal friction & fluid pressure.