Formation Conditions of Hydrocarbon Systems on the Sakhalin Shelf of the Sea of Okhotsk Based on the Geochemical Studies and Modeling

Abstract

The article is a study of the conditions and distribution patterns of generation and accumulation hydrocarbon systems (GAHS) on the Sakhalin shelf of the sea of Okhotsk. A complex of geochemical studies was conducted for the evaluation of oil and gas source rocks generative capabilities and for the study of the organic matter geochemical parameters. The study included the determination of total organic carbon (TOC) in rocks, pyrolysis by Rock-Eval method, parameters (S1, S2, Tmax, HI, PI); bitumoid extraction from rock with subsequent determination of its group composition. Analysis of oil geochemical parameters by hydrocarbons-biomarkers for the purpose of determination genetic unity and maturity level of oil and gas source sequences was conducted. Using the method of capillary gas-liquid chromatography (GZhC), the analysis of n-alkanes and isoprenanes in paraffin-cycloparaffin (PCP) oil fractions was conducted. Method of chromato-mass spectrometry (ChMS) was utilized for a study of high-molecular hydrocarbons -biomarkers (steranes and terpanes). It was implemented using computer data processing under SIM regime with the recording ions m/z 217, 218 for steranes and diasteranes, m/z 191, 177 for terpanes. The separation of hydrocarbon organic matter was conducted in a capillary column with silicone phase HP-1ms. Chromatographing was implemented under temperature linear programming regime between 70 and 290 ο C at the rate of temperature increase 4ο/minutes. The carrier gas was helium. The study of geochemical parameters in the Paleogene-Neogene sediment complex indicates a sufficiently high corg content and its concentration increases down the section. Organic matter type in the sedimentary section often changes from humic to humic-sapropelic, the dominating type is humic (III). GAHS, elements and processes of these natural systems were modeled for the study of the formation environment and distribution patterns of generative-accumulative hydrocarbon systems and HC generation foci and their energy resources on the Sakhalin shelf in the Sea of Okhotsk utilizing techniques of basin modeling and Petro Mod (Schlumberger) software. Based on modeling results, 6 independent generation foci of oil and gas were identified on the Sakhalin shelf. Each of them could have independently generated hydrocarbon fluids for saturating nearby traps.

Cretaceous-Cenozoic Hydrocarbon Systems of the Eastern Arctic Seas

“…The depression mode, which is indirectly proving the mode of stable submersions both under the continental conditions and during the epochs of the sea ingressions and transgressions from the part of the Arctic Ocean, was typical for only two regions within the Russian part of the Eastern Arctic shelves -the Central Laptev Sea and the East Novosibirsk [8], [9].…”

Origin of hydrocarbons in the Bach Ho field (The Vietnamese shelf)

“…The electric fields were caused by the piezoelectric effect and electrization of the crystalline rocks in the process of fracturing. This mechanism of oil and gas accumulation provides a reason to believe that the oil and gas hydrocarbon accumulations are in the secondary occurrence in the basement and that the source of their formation is the organic matter of overlying sedimentary complexes [18][19][20][21][22][23][24][25][26].…”

Hydrocarbon Systems and Estimation of the Probability of Discovery of Oil and Gas Accumulations in the Bering Sea

“…In the offshore part of the region, the analogs of the Eocene-Oligocene Mainitsky horizon existing in the continental mainland can be represented as the regional fluid traps within the Paleogene section. Distribution of the fluid traps of different quality possessing the opal-cristobalite composition is typical for the Miocene section within the offshore part of the region [10].…”