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Journal of Chemistry
Volume 2013 (2013), Article ID 636845, 10 pages
Research Article

Diamondoid Hydrocarbons as Maturity Indicators for Condensates from Southern Indus Basin, Pakistan

Department of Chemistry, University of Engineering & Technology, G.T. Road, Lahore-54890, Pakistan

Received 13 May 2013; Accepted 5 September 2013

Academic Editor: Alexander Tatarinov

Copyright © 2013 Shagufta Nasir and Tahira Fazeelat. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Diamondoid hydrocarbons have been examined in condensates reservoired in the Southern Indus Basin using GC-MS. Bulk properties reveal that samples are waxy and low sulfur with the exception of Pakhro and Gopang which are nonwaxy. TIC show bimodal distribution of n-alkanes along with high abundance of C20+ n-alkanes indicating substantial contribution of terrigeneous OM in these samples. CPI close to one is consistent with mature nature of oils. The samples show two ranges of Pr/Ph ratios. Those within the range of 2.2–2.7 reflect marine depositional settings for OM while others with Pr/Ph >3 may have originated from terrestrial OM deposited under marine oxic conditions. The cross plot of Pr/n-C17 versus Ph/n-C18 indicate type III kerogen as main source of OM deposited under marine to marine oxic conditions. The values of diamondoid based maturity parameters, like methyladamantane index 54.1–75.8% and methyldiamantane index 34.9–56.3% indicate high level of thermal maturity corresponding to vitrinite reflectance 1.1–1.6%. No biodegradation is observed in any of these samples as shown by methyladamantanes/adamantane 3.99–5.52 and methyldiamantanes/diamantane 2.16–2.99 and supported by high values of API gravity (45.13°–60.02°) and absence of UCM.