Seismic based characterization of total organic content from the marine Sembar shale, Lower Indus Basin, Pakistan
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ORIGINAL RESEARCH PAPER
Seismic based characterization of total organic content from the marine Sembar shale, Lower Indus Basin, Pakistan Omer Aziz1 · Tahir Hussain1,2 · Matee Ullah1,2 · Asher Samuel Bhatti1,2 · Aamir Ali1 Received: 9 December 2016 / Accepted: 8 February 2018 © Springer Science+Business Media B.V., part of Springer Nature 2018
Abstract The exploration and production of unconventional resources has increased significantly over the past few years around the globe to fulfill growing energy demands. Hydrocarbon potential of these unconventional petroleum systems depends on the presence of significant organic matter; their thermal maturity and the quality of present hydrocarbons i.e. gas or oil shale. In this work, we present a workflow for estimating Total Organic Content (TOC) from seismic reflection data. To achieve the objective of this study, we have chosen a classic potential candidate for exploration of unconventional reserves, the shale of the Sembar Formation, Lower Indus Basin, Pakistan. Our method includes the estimation of TOC from the well data using the Passey’s ΔlogR and Schwarzkofp’s methods. From seismic data, maps of Relative Acoustic Impedance (RAI) are extracted at maximum and minimum TOC zones within the Sembar Formation. A geostatistical trend with good correlation coefficient (R2) for cross-plots between TOC and RAI at well locations is used for estimation of seismic based TOC at the reservoir scale. Our results suggest a good calibration of TOC values from seismic at well locations. The estimated TOC values range from 1 to 4% showing that the shale of the Sembar Formation lies in the range of good to excellent unconventional oil/gas play within the context of TOC. This methodology of source rock evaluation provides a spatial distribution of TOC at the reservoir scale as compared to the conventional distribution generated from samples collected over sparse wells. The approach presented in this work has wider applications for source rock evaluation in other similar petroliferous basins worldwide. Keywords Shale gas · TOC · Passey’s ΔlogR method · Schwarzkopf’s method · Relative acoustic impedance · Correlation coefficient
Introduction The ever-increasing demand of energy requires a deep insight into all possible ways of fulfilling it. One of the major components of the global energy mix comes from the exploitation of conventional resources (Bocora 2012; Zou et al. 2016). The increasing rate of the hydrocarbon production from conventional resources show continuous depleting trend for over 50 years (Miller and Sorrell 2014). Hence, there is a strong impetus to explore the hydrocarbon potential of unconventional resources i.e. oil/gas shales. Furthermore, the rise of unconventional resource exploitation * Aamir Ali [email protected] 1
Department of Earth Sciences, Quaid-i-Azam University, Islamabad, Pakistan
Department of Geology, Bacha Khan University, Charsadda, Pakistan
2
could present a new era in the overall global energy mix (Kefferpütz 2010; Sunjay 2011; Boc
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