Technogenic impact on groundwater of deep aquifers and oil bearing complexes of the West Siberian megabasin

Groundwater in the West Siberian megabasin (WSMB) has been exposed to long-term technogenic loads due to the exploitation of hydrocarbon deposits. The objective of the study was to systematize the types of technogenic impacts on deep horizons to the use of a reservoir pressure maintenance system (RPMS). Over the past 10 years alone, the volume of water selected from the Aptian-Albian-Cenomanian complex (AAC GC) for RPMS has amounted 380 million m³.

Data on the key fields in the central part of the WSMB (17 fields) were systematized. The research methods included: collecting data on the start time of the use of the RPMS, analyzing water sources and sampling volumes for use in the RPMS and analyzing hydrogeochemical transformation.

We have identified 6 types of fields. The first type includes fields where only oil is produced without RPMS. The second type is associated with forced RPMS at fields where AAS GC waters are used as a flooding agent. The third type: fields where fresh water from the upper horizons is used in the RPMS. The environmental consequences here are associated with a drop in the level of the freshwater horizon and a slight increase in mineralization. The fourth type pertains to areas for the associated water in AAC GC. The fifth and sixth types are associated with the most loaded fields, where the RPMS operates with fresh or salt water from AAC GC, and associated and waste water is utilized (Fedorovskoye, etc.). Long-term exploitation has led to the appearance of elevated petroleum products, bromides, chromium, lead, chlorides and boron in the freshwater horizons . But the appearances are not widespread. Currently, monitoring is standard for all deposits. We propose the introduction of new hydrogeochemical criteria as indicators of transformation (for example, Cl/Br) taking into account the established type of technogenesis.