Imaging Lowstand prograding stratigraphic pinch-out traps of a Lower Cretaceous clastic system using inverted seismic-based porosity simulation of SE-Asian Basin: Implications for petroleum exploration
Abstract
Prograding sandstone-filled incised valleys of the Lowstand System tract (LST) form stratigraphic plays. The band-limited seismic data interpretation techniques constrain the prediction of porous and gas-bearing reservoir facies. Therefore, the development of a cost-economic petroleum-bearing reservoir system is a challenge for reservoir geophysicists. This research is intended to predict the porosity and thickness of incised valleys by executing the continuous wavelet transforms (CWT)-based spectrum decomposition (SD), seismic static inverted simulation (SWM), and inverted seismic-based porosity simulation (IVPS) on a Lower Cretaceous LST system of Pakistan. The seismic, root-mean-square (RMS), and absolute average seismic attributes have provided a limited capability to image the gas-bearing sandstones.The 24-Hz tuning frequency has imaged the progradational sandstone-filled incised valley and retrogradational fluvial point bars. The 37-Hz has imaged the aggradational barrier bars. The amalgamation of multiple attributes has accurately demarcated the reservoir sandstone and sealing shale. The SWS has resolved a 32-m-thick prograding incised valley, 30-m-thick aggrading barrier bars, and 23-m-thick retrograding point bars within the complete fluvial hierarchy. The well correlation has provided evidence for the distribution of point bars, barrier bars, and shallow-marine incised valley reservoir facies. The 24-Hz CWT waveform-based conventional IVPS has predicted 94 and 42 m-thick valleys and \"point bars\" between 25 and 13% pseudo-porosity wells. The 24-Hz waveforms-based treatment of conventional IVPS has predicted enhanced thicknesses of 75 and 29 m for valley and point bar deposits with porosities between 25 and 13%. The 24-Hz IVPS has resolved two valleys compared to the conventional IVPS during the rapid fall of sea level and negligible rise, which have accumulated the coarse-grained point bar deposits of a fluvial meandering stream. The integration of IVPS and GR (API) has provided strong implications for the exploration of a pure stratigraphic trap within a shallow marine sedimentary system of Pakistan. A NE to SW oriented regional change was observed in the lithology, thickness, and depositional environments of the petroleum system. The dominant lithology in the eastern zones was point bar sandstones. The dominant lithology in the central zones was barrier bar sandstones. The dominant lithology in the western zone was incised valley sandstone. The thickness of the reservoir was 18 m thick in the west, which was reduced to 8 m in the eastern flanks of this gas field. The depositional environment in the northeast was fluvial, which changed to shallow-marine in the southwestern zones of the Indus basin. These lateral fluctuations have proved that a pure stratigraphic fairway was present within the LST of the Indus Basin of the sedimentary system of Pakistan. The porous incised valley stratigraphic reservoirs are embedded inside the non-porous shales, which validates the presence of a pure stratigraphic petroleum play inside the Indus Basin, Pakistan.
Author
Dyana Aziz Bayz
DOI
https://doi.org/10.1016/j.marpetgeo.2022.106060
Publisher
Marine and petroleum Geology
ISSN
1873-4073
Publish Date: