Reservoir characterization for Lower-Cretaceous fluid system in Southwest Pakistan based on seismic spectrum decomposition and static wedge modelling

Abstract

This is an innovative study that deals with the application of continuous wavelet transform (CWT)-based seismic spectrum decomposition (SD) and static wedge modelling (SWM) to characterize the fluvial system of Indus Basin, Pakistan. The CWT better discriminates the thin and thick-bedded hydrocarbon-bearing reservoir pore-fluids compared to band-limited seismic characteristics. The hydrocarbon-bearing point bar shows higher amplitudes compared to the water-filled channel, which indicates lower amplitudes A static amalgamation of CWT attributes within the sandstone reservoirs indicates that 28 Hz can resolve the thick-bedded sandstone-filled point bar facies. The mapping of reservoir facies within the 27 Hz to 40 Hz CWT-based frequencies predicts the lateral distribution of channel sandstone, fluvial point bars, regional faults, and three-dimensional seal of shale-bearing levee deposits. The 48 Hz amplitudes can be used for predicting the regional seal for petroleum system. The SWM resolves a 25 m thick gas-bearing fluvial point bar, which is laterally distributed by head-to-head continuity of 29 km. The SWM can be used to predict the quantitative aspects of fluvial systems. The paleo-flow direction of the river was predicted in NNE-SSW orientations. The low-velocity of ∼3500 m/s of river flow eroded the coarse-grained sandstone facies from the eastern flanks and deposited in the western regions of the Basin. The angle of stratigraphic trap and thickness of point bar petroleum system was 20° and 25 m in the west of Basin. These observations can serve as an analogue for the development of stratigraphic plays within the Indus Basins of Pakistan and fluvial systems with similar geological settings.