Modern Hydrogeochemical Regime of Mesozoic Sediments Influenced by Oil and Gas Production in Western Siberia

In Western Siberia, the modern hydrogeochemical conditions of Mesozoic sediments form under the influence of longstanding multidirectional processes associated with oil and gas production. On the one hand, this is the extraction of groundwater to maintain formation pressure in productive horizons, on the other hand, the injection of excess formation water into absorbing horizons. The accumulated volume of extracted groundwater for use in formation pressure maintenance systems exceeded 7.4 bln m³. The total volume of liquid injected into the absorbing horizon is 671 mln m³. The relevance of the study is justified by the need to understand the changes in the hydrogeochemical conditions of the Mesozoic hydrogeological basin due to significant man-made impact according to monitoring data.

The article discusses the results of long-term studies of the groundwater composition of the Apt-Albian-Cenomanian hydrogeological complex (AAC HC) of the West Siberian megabasin in oil fields (a total of 27 water intake sites and 19 injection sites). During the observation period (2011-2024), a significant amount of information was accumulated on the composition of formation waters of the Aptian-Albian-Cenomanian sediments at monitoring sites (more than 4,700 samples).

Monitoring of AAC HC groundwater quality consists in sampling to determine the density of water, the content of the main macro- and micro components, and other parameters. Research methods include: quality analysis of laboratory measurements of groundwater chemical composition; rejection of data that do not meet the criteria of reliability; characterization of the groundwater type according to existing genetic classifications.

The research found that the typical natural affiliation and chemical composition of the AAC HC waters remain close to the natural background, despite the significant man-made load.