Seismic sedimentological-based quantifications of late-Cretaceous hydrocarbon-bearing late-aggradational lowstands prograding wedges in the Indus basin: Frequency-controlled porosity-constrained dynamic simulations

Abstract

Seismic quantitative reservoir simulations and characterizations have played a vital role in exploring stratigraphic traps, such as late-aggradational lowstands prograding wedge systems (LPWS) within lowstands systems tracts (LST). However, seismic data acquisition operations are always dominated by exceptional seismic coherent noise events, e.g., multiples, which reduce the signal strengths of the source-generated incident seismic waves within vertically and laterally heterogeneous earth systems. Hence, these noise events create hurdles in predicting paleo-depositional impedance (PDI), paleo-thickness (PTS), paleo-dense fractured networks, erosional and depositional zones, fault-controlled migrations, and types of seismic reflection configurations (SRFC), which are key elements in developing stratigraphic pinch-out traps. This research utilizes the state-of-the-art technologies of spectral wavelet-based instantaneous time-frequency analysis and seismic waveform frequency-controlled porosity-constrained static reservoir simulation (FDPVS) tools to quantify the LPWS inside the Onshore Basin, Pakistan. The use of conventional amplitude-based seismic attributes, such as the average energy, remained a better tool for deciphering the overall geological architecture of the LPWS. Conventional FDPVS realizations resolved a PDI of −1.391 gm./c.c.∗m/s to −0.97 gm./c.c.∗m/s for LPWS with PTS of 12 and 20 m, respectively. A 0.9 km lateral extent of paleo-dense fractured networks (PDFN) with a strong linear regression R² = 0.93 was also resolved. Average energy attribute-based instantaneous frequency FDPVS realizations enabled the imaging of parallel-to-prograding SRFC with resolved magnitudes of −0.259 gm./c.c.∗m/s for PDI, 20 m for PTS, and 0.73 km for PDFN with linear regression transforms at R² = 0.92, which indicates the deposition of onlap fill facies inside the LPWS during extensive sea-level fall. These realizations have also resolved frequency-controlled fault migrations on 27-Hz spectral waveform-based amplitude plots with 2.174 gm./c.c.∗m/s PDI for conduit fault systems and 27-Hz with 0.585 gm./c.c.∗m/s PDI for sealing fault systems. All these structural configurations are completely sealed up by transgressive seals of transgressive systems tracts and, hence, developed into pure stratigraphic-based oil and gas plays. This research has strong implications for side-tracking drilling locations and provides an analogue for basins with similar geology and stratigraphy worldwide.