Search

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. [ABSTRACT FROM AUTHOR]

Rock wettability is a key parameter determining fluids distributions and migrations in hydrocarbon reservoirs. In shale rocks, the widespread existence of organic matter and the significant variation of total organic carbon (TOC) content lead to huge uncertainty on shale wettability. Therefore, this work systematically examines the dependence of shale wettability on TOC content (ranging from 1.2 wt% to 20.05 wt%). Multiple relations were probed experimentally, namely: 1) the effect of TOC content on n-dodecane (n-C 12) contact angles for shale-methane (CH 4)-n-C 12 systems at 5 MPa and 50 °C; 2) the effect of TOC content on n-C 12 contact angles for shale-carbon dioxide (CO 2)-n-C 12 systems at 5 MPa and 50 °C; 3) the effect of TOC content on brine contact angles for shale-brine-n-C 12 systems at 0.1 MPa and 50 °C; 4) the effect of pressure (0.1 MPa–25 MPa), temperature (25 °C and 50 °C) and TOC content on brine contact angles for shale-CH 4 -brine systems. The results demonstrate that for shale-CH 4 -n-C 12 , shale-CO 2 -n-C 12 and shale-brine-n-C 12 systems, the affinity of n-C 12 to shale increases with increasing TOC content. However, for shale-CH 4 -brine systems, the affinity of CH 4 to shale increases firstly, then flatten out and afterwards increases again; while shale wettability shifted from water-wet to CH 4 -wet with TOC content increase. In addition, a larger pressure renders shale less hydrophilic while a higher temperature causes shale more hydrophilic. The temperature influence is reduced with TOC content increase. The results can aid in better understanding of shale wettability at reservoir conditions. • Effect of TOC on shale wettability is systematically investigated. • Wettability shift from hydrophilic to hydrophobic with increasing TOC. • At reservoir condition (e.g., 20 MPa and 50 °C), a CH 4 -wet behaviour was found for 20.05 wt% TOC shale. [ABSTRACT FROM AUTHOR]