Abstract:
Understanding source rock and its related petroleum system is of critical
importance in hydrocarbon prospecting. Organic matter quantity, quality and maturity
studies have been carried out on shales of Ranikot Formation in Sawan-01, located in
Middle Indus Basin. The formation was investigated using total organic carbon (TOC)
and Rock-Eval pyrolysis analyses measurements. Analyses were performed on five
well cutting samples from well, having TOC 0.16-2.28 wt. % representing poor to
very good source rock potential. The Genetic potential (GP) values of the samples lies
between 0.12 to 2.81mg HC/g rock, depicting poor to fair source rock potential. HI
values are in between 65-112 mg HC/g indicating presence of type III kerogen with
gas generation phase. Type of organic Matter evaluation using hydrogen and oxygen
indices also show that samples are predominantly of kerogen type III (gas prone) in
origin. Tmax values ranges from 446 to 452oC which indicate that samples
predominantly lie in peak to onset of late thermally mature region.
Weathering/oxidation effect is greater in lower part of formation represented by high
oxidation index values. Organic matter supply was good at the time of deposition of
Ranikot Formation but lower part of this formation was deposited in oxic environment
and lead to poor preservation which is confirmed by decreasing trend of organic
richness against depth. Hence, it can be concluded that upper shales of Ranikot
Formation got enough organic matter richness and maturity to produce gas in study
area.
