Paragenesis of fluids under evaporates in the Volga-Ural Basin |
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| Institution: | 1. Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX 77204, USA;2. Hydrate Energy International, 612 Petit Berdot Drive, Kenner, LA 70065, USA;1. ConocoPhillips, Indonesia;2. University of Stavanger, Department of Petroleum Engineering, 4036, Stavanger, Norway;1. Computer Science Department, Science College, Basrah University, Basrah, Iraq;2. Mathematic Department, Science College, Basrah University, Basrah, Iraq;3. School of Computer Science, Bangor University, Bangor, Gwynedd, UK;4. School of Computer Science, University of Chester, Chester, UK;1. Molecular Biotechnology and Health Sciences Department, Università degli Studi di Torino, via Quarello 15, 10135 Torino, Italy;2. Chemistry Department, Università degli Studi di Torino, Via Giuria 5, 10125 Torino, Italy |
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| Abstract: | To unravel the mystery of the relationship between evaporates, Ca–Cl brines and accumulations of oil and N2 in the basins of ancient cratons, their N2, CH4 and He concentration ratios, as well as the isotopic composition (δ15N, δ13C and 3He/4He) were compared within the Volga-Ural basin. The study allowed subsalt fluids from Volga-Ural Basin to divide into two genetic groups. The first one is found within the basin's platform area. It includes Ca–Cl brines, high-viscosity heavy oil, bitumen and N2, which has concentrations higher than that of CH4 and positive values of δ15N. The second one is tied to the edge of the platform, the Ural Foredeep and Peri-Caspian Depression. In this group, only the oil and gas reservoirs, which have more CH4 than N2, and possibly negative values of δ15N, were discovered. Interaction of gas components in compared fluids indicates great role of degassing in the formation of their composition. It is suggested that the fluids of the first group (N2 > CH4) is what remains, and the second group (N2 < CH4) is what is disappears from the rocks during their metamorphism and degassing. |
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| Keywords: | Reservoir oil and gas Ca-Cl brines Fluids Isotopes Molecular nitrogen Methane Helium Degassing |
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