Significance of petroleum seepages in hydrocarbon exploration-case study of Khourian Desert, Central Iran

Abstract Hydrocarbon exploration has long been based on such costly and time-intensive methods as geophysical surveys, geological studies, drilling. In recent years, however, researchers have started to consider inexpensive alternatives surface geochemistry for hydrocarbon exploration. Some 100 years ago, the leakage of hydrocarbons onto in form micro- macro-seepages motivated toward drilling a well Khourian Desert south Semnan Province, Iran. Upon well, found evidences non-released (free) hydrocarbons. These findings drove further study area using while considering nearby accumulation Qom Formation. Conventional indirect geochemical provide an insight into relationship between subsurface present work, results Rock–Eval pyrolysis showed total organic carbon (TOC) values range 0.31–4.13 wt.% S 1 peaks 0.07 27.35. Sulfur isotope analysis sulfur isotopic value −0.4. The hydrocarbon-oxidizing bacteria presence bacterial colonies MSM at 1.22 × 10 6 cfu/g soil sample. We investigated changes due free pH variations (4.9–8) resulted from concentrations calcium carbonate iron. According given samples, occurrence Gach-i-turush alike phenomena was proposed this area. geo-microbial prospecting method, secondary changes, studies were agreement with characteristics existing reserves Surface surveys can precede other identify anomalies hence focus more probable locales Desert, central