25th International Meeting on Organic Geochemistry IMOG 2011

P-296
Geochemical record of ancient sediments from the Potwar Basin
Pakistan, inferred by biomarker and stable isotopic signatures
Shahid Nadeem 1,2 , Kliti Grice 1 , Fazeelat Tahira 2
1 WA-OIGC, Department of Applied Chemistry, Curtin University, Perth, Australia, 2 Department of Chemistry,
University of Engineering and Technology, Lahore, Pakistan (corresponding author:snk777@gmail.com)
Cambrian and Infra-Cambrian source potential has
been universally recognised. A major portion of the
petroleum systems in the Potwar Basin of Pakistan
comprises of Permian or Cambrian and infra-
Cambrian aged-oils. The source potential of early
Permian and Cambrian sequences has been
recognised in the Potwar Basin. The present study
deals with the organic geochemical characterisation
of Cambrian sequences from the Eastern Potwar
Basin. A total of 24 sediment samples from 150m
thick organic-rich Cambrian and ~200m early-Permian
shales comprising of 6 geological formations have
been selected at 10m depth of intervals. These
sequences contain types I/II Kerogens based on the
Rock Eval data. n-Alkane profiles of the bitumens of
the sediments show a variation in the algal to
terrestrial source inputs. Very low Pr/Ph ratios 0.1-0.7
are indicative of strong anoxic conditions in the
original depositional environment. High
hopane/sterane ratios are consistent with a high
bacterial input.
Pyrolysis mainly by MSSV and HyPy has been
performed on the source rock kerogens and the
asphaltenes of the related oils. Biomarkers and
carbon isotopic profiles of individual aromatic
hydrocarbons such as 1,6-DMN, 1,2,5-TMN, 1,MP,
1,9-DMP have been used and cross plots have been
constructed along with Pr/Ph and P/DBT to establish
source and age of organic matter. Thermal history
has been evaluated using hopanes, steranes, alkylnaphthalenes
and alkyl-phenanthrene isomerisation
ratios. An oil to source correlation has been made
based on CSIA approach.
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