Investigation of geochemical characteristics of Sarvak Formation in Block D, Persian Gulf

Sarvak Formation (Cretaceous) is considered as one of the most prominent oil reservoirs in the south of Iran and hosts significant volume of oil accumulation in the Persian Gulf basin. In the present research plan, in order to evaluate the hydrocarbon generation capacity of this formation, cores, cuttings and oil samples collected producing oil and gas wells located in block D underwent detailed geochemical investigations which were in the Iranian sector of the Persian Gulf. Correlation is defined as the geochemical comparison between hydrocarbons themselves, or also hydrocarbons with source rocks, and furthermore defining the quality of the genetic relation between them. In order to achieve this goal a variety of gadgets and parameters are used, some of them being biomarkers and stable isotopes. The results obtained geochemical analyses including primary analyses (pyrolysis rock-eval), bitumen extraction and separation, complementary analyses (gas chromatography), gas chromatography-mass spectrometry and stable isotope studies on samples indicate that kerogen of studied samples is a combination of types II and III and it implies that most organic matter generating hydrocarbon wereformed in a marine environment along with a little entering land. The hydrocarbons existing in Sarvak Formation were generated a semi carbonated clastic source rock and were deposited under a reducing or semi-reducing environment. The saturate fractions analyzed using GC and GCMS techniques indicate the lack of environmental biodegradation in the studied samples. The inter bed shaly-marl samples of the Sarvak Formation show a fair to good hydrocarbon potential. The set of under study samples are located in the beginning of the oil generation window (late diagenesis) and early catagenesis in terms of their maturity degree. Furthermore, hydrocarbons show a paraffinic-naphthenic characteristic. It seems the shaly-marl layers existing in some parts of the Sarvak Formation (Ahmadi member), in Block D, in the Persian Gulf, have been the cause for the generation of hydrocarbons available in the Sarvak reservoir.