Geochemical study of Dalan and Kangan gas-condensate reservoirs in the south of Iran

According to the geochemical study done on the 23 gas samples taken from 12 gas fields in the coastal Fars and central part of the Persian Gulf, Dalan and Kangan reservoirs consist of thermogenic gases, which were generated from the cracking of oil in temperature between 150°C and 180°C. Gas fields in the southern part of the studied area have lower maturity in comparison to the other parts. Recent oil exploration studies show that the light crude oil in Eastern Assaluyeh and Khayyam fields could be an indicative of original oil remaining in these fields which is converted into gas in other fields, due to temperature increment. Using the stable isotope maturity for methane and ethane suggested a source rock with maturity level of about 1.0% to 1.8% vitrinite reflectance for the field gas under study. According to the TOC content and similarity between the isotope curve of organic matter of rock samples and those of the condensate – oil reservoir of Dalan and Kangan, the lower silurian Sarchahan organic-rich shale could be the main source for hydrocarbons in Permian and Triassic reservoirs in this area.