Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Generation Mechanism of H₂S and CO₂ in Petroleum Reservoirs and the

Effect of Bacterial Activity to the Chemical Composition of Petroleum
This following study is prepared at Istanbul Üniversity Institute of Science Geology Department as a master graduation thesis. The aim of the study is to determine the aspects of biodegredation process (limiting parameters, optimum conditions, effects to petroleum chemistry) as well as to find out the generation mechanisms of hydrocarbon gases, hydrogen sulphur and carbon dioxide gases generated in oil reservoirs.
Gas and oil samples are collected from 2 different fields (Silivanka, Dodan) in Southewestern Anatolia. The samples are analized with GC, GC-MS and GC-IRMS equipments. After the results are evaluated with the help of different classification charts, comments have been made about origin of the gases, possible source rock sedimentation environment and mixture of gases.
The hydrocarbon gas samples from the Dodan field are derived from a source rock which its organic matter is rich in type III and with a maturity value of %1,5 Ro according to methan-ethan isotope modelling and type II with a maturity value of %1-1,5 Ro according to ethan-propane isotope modelling. The maturity value of the source rock in Silivanka field is between%1,2-1,4 Ro and the organic matter is mostly marine.
The sulphur isotope ratio of gas samples collected from the Dodan field are 11.9‰ ve 13.4‰. Considering the isotope values and reservoir characteristics, the origin of hydrogen sulphur is thermochemical sulphat reduction and a small part is derived with a bacterial process. The carbon isotope ratio of carbon dioxide gas samples from the Dodan field are between -1,59 and -8,13‰ showing that they have an inorganic origin. The carbon isotope ratio of carbon dioxide gas samples from the Silivanka field are between -7,69 and-10,75 ‰ showing that they have an organic origin.