THE FIRST DATA ON THE ISOTOPIC COMPOSITION OF STRATAL WATERS OF THE DEVELOPED OIL FIELDS IN NOVOSIBIRSK REGION

• Main Authors: Dmitry A. Novikov, Aleksandr N. Pyrayev, Anatoliy V. Chernykh, Fedor F. Dultsev, Svetlana V. Ryzhkova
• Format: Article
• Language: Russian
• Published: Tomsk Polytechnic University 2021-02-01
• Series: Известия Томского политехнического университета: Инжиниринг георесурсов
• Subjects: groundwater; δ18o; δd; δ13с; isotopic ratios of 87sr86/sr и 87rb/86sr; interaction in «water–rock» system; developed pool; oil field; novosibirsk region; western siberia
• Online Access: http://izvestiya.tpu.ru/archive/article/view/3043/2402

The relevance of the research lies in solving the issues of isotope geochemistry of groundwater in oil and gas deposits of large artesian basins. The waters of oil and gas bearing sediments of the region under consideration are practically not studied from the point of view of the distribution of stable isotopes δD, δ18O, δ13С and isotopic ratios 87Sr86/Sr and 87Rb/86Sr. The aim of the research is to identify the features of the genesis of groundwater and the interaction in the «water–rock» system from the standpoint of isotopic geochemistry. Methods. The analysis of the complex of δD, δ18O, δ13СDIC of waters and dissolved inorganic carbon was carried out at the Center for Collective Use of the IGM SB RAS using the Isotope Ratio Mass Spectrometer FinniganTM MAT 253. The 87Sr86/Sr и 87Rb/86Sr isotopic ratios were studied on an MI 1201T mass spectrometer in a two-tape mode with registration on one collector. Results. The authors have studied the stable isotope composition (δD, δ18O, δ13СDIC) and isotopic ratios of 87Sr86/Sr and 87Rb/86Sr of the waters of the developed oil fields of the Novosibirsk region. The hydrogeological section shows the presence of two main genetic types of groundwater: ancient infiltrogenic and sedimentogenic. For most of the studied samples, the δD-δ18О indicates a combination of two determining factors: initial depletion of water in the light isotope 16O as a result of climatic impact during the period «before disposal» up to 4–5 ‰; further saturation of waters with the heavy isotope 18O during a long WRI, which led to additional 2–3 ‰ of heavier isotopic composition. The δ13CDIC values for a number of samples suggested bacterial origin of dissolved inorganic carbon. There is a clear increase in the δ13CDIC in waters which temperature exceeds 90 °С, to the values corresponding to the «normal» ones in thermal waters: from –8 up to +4 ‰ VPDB. The waters are characterized by low 87Sr86/Sr ratios relative to ocean waters. A significant contribution of mantle sources of strontium is assumed, which manifests itself to different degrees for the waters of various deposits.