Delineating the fluvial sedimentary reservoirs of Cretaceous sedimentation using seismic attributes and seismic‐petrophysical simulations, Southwest Pakistan

• Published in: Geological journal (Chichester, England) Vol. 58; no. 3; pp. 1192 - 1203
• Main Authors: Naseer, Muhammad Tayyab, Naseem, Shazia, Naseer, Adil, Ameen, Hawzhen Fateh M.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.03.2023; Wiley Subscription Services, Inc
• Subjects: Amplitude; Amplitudes; channel‐levee system; Continuous wavelet transform; continuous wavelet transforms; Cretaceous; Density; density and velocity profiles; Dimensions; Levees; Porosity; Reservoir sedimentation; Reservoirs; Sandstone; Sedimentary facies; Sedimentary rocks; seismic attributes; Shale; Stratigraphic traps; Stratigraphy; System effectiveness; Velocity; Velocity distribution; Velocity profiles; Wavelet transforms; Pakistan
• ISSN: 0072-1050; 1099-1034
• DOI: 10.1002/gj.4651

Channels filled with coarse‐grained sands are one of the hot issues in stratigraphic explorations. However, the sub‐surface uncertainty restricts the prediction of porous channel sandstones using the conventional seismic attributes, which is a concern for the demarcation of stratigraphic plays. The amplitude‐based frequency attributes and seismic‐petrophysical simulation tools were applied to characterize the fluvial channel system from the Indus Basin, Pakistan. The conventional amplitude of the Basal Sand Formation shows limited imaging ability to detect the dimensions of channel‐levee and point bars. The continuous wavelet transforms (CWT) tool distinguishes the whole channel‐levee reservoir system at tuning frequencies of 21, 25, 29, and 34 Hz. The amplitudes extracted along the pseudo‐porosity wells depict the low‐density and low‐velocity profiles within the gas‐bearing zones. The zone between 20% and 30% porosity displays low‐density and low‐velocity compartments within the point bars. Hence, it implicates the zone of deposition for hydrocarbon‐bearing fluvial facies. Based on the porosity constraint, the gas‐bearing fluvial reservoirs have high (>25%) porosity, which implicates the development of aggradational parasequences. The oil‐dominated sandstone facies experience relatively low‐porosity of <12% and negligibly high density and high velocity, which implicates the development of transgressive parasequences. The reservoir system shows an eastward shale‐out zone, where the high‐density and high‐velocity shales mask the channel‐levee systems. Consequently, these stratigraphic configurations are developing into a cost‐effective stratigraphic trap, and hence, this exploration scheme serves as an analogue for global fluvial depositional systems. The zone between 20% and 30% porosity displays low‐density and low‐velocity compartments within the point bars, and hereafter, authorizes the occurrence of porous fluvial facies. The gas‐bearing fluvial reservoirs have high (>25%) porosity, which implicates the development of aggradational parasequences. The oil‐dominated sandstone facies experience relatively low‐porosity of <12% and negligibly high density and high velocity, which implicates the development of transgressive parasequences.