Total organic carbon content and total porosity estimation in unconventional resource play using integrated approach through seismic inversion and well logs analysis within the Talhar Shale, Pakistan

Around the globe, the organic rich shale has become an increasingly important hydrocarbon resource due to the rapid depletion of conventional hydrocarbon reservoirs. The successful exploration and production schemes for organic rich shale are based on reliable identification of major organic components and total porosity. Therefore it is mandatory to identify the organic content in terms of total organic carbon (TOC) content and total porosity in promising shale formations through indirect seismic data, which is usually the only available source of information in most exploration phases. This research paper is focused on quantifying the Talhar Shale (member of Lower Goru Formation) as an unconventional reservoir using model based inversion in Badin concession area located near Karachi, Pakistan. Model based inversion is applied for computation of total porosity and total organic carbon (TOC) content because it provide a greater bandwidth and detail of variation of the acoustic impedance over the study area. The empirical relation for Total Organic Carbon (TOC) content has been derived through Passey et al. (1990) technique using data from Zaur-Deep 01, while for porosity a simple relation between impedance and porosity is used. The TOC and porosity models indicate that the unconventional reservoir potential is significantly greater over the northern region while it tends to decrease towards the south-eastern area.