Concerning the petroleum hydrocarbons migration in the permafrost zone

Abstract:

In order to understand the mechanisms controlling methane emissions in the Laptev Sea it is extremely important to know the distribution patterns of subsea permafrost in the coastal zone. One possible solution to this problem is to analyze the hydrocarbon fluids in the bottom sediments. The object of our study was the core sample from Ivashkinskaya lagoon (Lena Delta, Sakha Republic). Pyrolytic studies were performed for this core sample (ROCK- EVAL 6 TURBO). According to the pyrolysis results there were 5 samples from the upper section in the range 0.36-5.58m selected for the further studies. The common feature of these samples is high content level of the pelitic component. They contain more than 1.0% of TOC and are composed of volatile organic compounds. Extracts obtained from the core sample were analyzed by GC-MS («Hewlett Packard» 6890/5973). Analyzed extracts demonstrated different classes of organic compounds in their composition with saturated and unsaturated hydrocarbons and acids dominating. Here are the histograms of n-alkanes in function of the carbon atoms number in the molecule (Figure). Considering our work experience with the Black Sea sediments we suggest that the samples with a high degree of even n-alkanes are confined to zones of petroleum hydrocarbons migration coming from the deep oil deposits.

Figure. Typical n-alkanes distribution in the extracts (horizontal axis - the number of carbon atoms in the molecule, vertical axis - relative abundance)