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Controls on Reservoir Heterogeneity of a Shallow-Marine Reservoir in Sawan Gas Field, SE Pakistan: Implications for Reservoir Quality Prediction Using Acoustic Impedance Inversion

1
Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming 650500, China
2
Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074, China
3
Department of Earth and Environmental Sciences, Bahria University, Islamabad 44000, Pakistan
4
School of XingFa Mining Engineering, Wuhan Institute of Technology, Wuhan 430074, China
5
Geological Survey of Pakistan, Ministry of Energy, Karachi 75290, Sindh, Pakistan
*
Authors to whom correspondence should be addressed.
Water 2020, 12(11), 2972; https://doi.org/10.3390/w12112972
Received: 16 September 2020 / Revised: 15 October 2020 / Accepted: 19 October 2020 / Published: 23 October 2020
The precise characterization of reservoir parameters is vital for future development and prospect evaluation of oil and gas fields. C-sand and B-sand intervals of the Lower Goru Formation (LGF) within the Lower Indus Basin (LIB) are proven reservoirs. Conventional seismic amplitude interpretation fails to delineate the heterogeneity of the sand-shale facies distribution due to limited seismic resolution in the Sawan gas field (SGF). The high heterogeneity and low resolution make it challenging to characterize the reservoir thickness, reservoir porosity, and the factors controlling the heterogeneity. Constrained sparse spike inversion (CSSI) is employed using 3D seismic and well log data to characterize and discriminate the lithofacies, impedance, porosity, and thickness (sand-ratio) of the C- and B-sand intervals of the LGF. The achieved results disclose that the CSSI delineated the extent of lithofacies, heterogeneity, and precise characterization of reservoir parameters within the zone of interest (ZOI). The sand facies of C- and B-sand intervals are characterized by low acoustic impedance (AI) values (8 × 106 kg/m2s to 1 × 107 kg/m2s), maximum sand-ratio (0.6 to 0.9), and maximum porosity (10% to 24%). The primary reservoir (C-sand) has an excellent ability to produce the maximum yield of gas due to low AI (8 × 106 kg/m2s), maximum reservoir thickness (0.9), and porosity (24%). However, the secondary reservoir (B-sand) also has a good capacity for gas production due to low AI (1 × 107 kg/m2s), decent sand-ratio (0.6), and average porosity (14%), if properly evaluated. The time-slices of porosity and sand-ratio maps have revealed the location of low-impedance, maximum porosity, and maximum sand-ratio that can be exploited for future drillings. Rock physics analysis using AI through inverse and direct relationships successfully discriminated against the heterogeneity between the sand facies and shale facies. In the corollary, we proposed that pre-conditioning through comprehensive petrophysical, inversion, and rock physics analysis are imperative tools to calibrate the factors controlling the reservoir heterogeneity and for better reservoir quality measurement in the fluvial shallow-marine deltaic basins. View Full-Text
Keywords: reservoir characterization; constrained sparse spike inversion; sand-ratio estimation; shallow-marine reservoir; Lower Goru Formation reservoir characterization; constrained sparse spike inversion; sand-ratio estimation; shallow-marine reservoir; Lower Goru Formation
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MDPI and ACS Style

Ashraf, U.; Zhang, H.; Anees, A.; Ali, M.; Zhang, X.; Shakeel Abbasi, S.; Nasir Mangi, H. Controls on Reservoir Heterogeneity of a Shallow-Marine Reservoir in Sawan Gas Field, SE Pakistan: Implications for Reservoir Quality Prediction Using Acoustic Impedance Inversion. Water 2020, 12, 2972. https://doi.org/10.3390/w12112972

AMA Style

Ashraf U, Zhang H, Anees A, Ali M, Zhang X, Shakeel Abbasi S, Nasir Mangi H. Controls on Reservoir Heterogeneity of a Shallow-Marine Reservoir in Sawan Gas Field, SE Pakistan: Implications for Reservoir Quality Prediction Using Acoustic Impedance Inversion. Water. 2020; 12(11):2972. https://doi.org/10.3390/w12112972

Chicago/Turabian Style

Ashraf, Umar; Zhang, Hucai; Anees, Aqsa; Ali, Muhammad; Zhang, Xiaonan; Shakeel Abbasi, Saiq; Nasir Mangi, Hassan. 2020. "Controls on Reservoir Heterogeneity of a Shallow-Marine Reservoir in Sawan Gas Field, SE Pakistan: Implications for Reservoir Quality Prediction Using Acoustic Impedance Inversion" Water 12, no. 11: 2972. https://doi.org/10.3390/w12112972

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