Methodology for geodynamic assessing the damage to the territory of the mining complex by exogenous geological processes and hydrogeological phenomena

Abstract

Introduction: the activity of exogenous geological processes (EGP) and hydrological phenomena (HP) shapes the modern appearance of the terrain, and also determines the geodynamic ecological function of the lithosphere, which was quantitatively expressed through an assessment of the degree of infestation of the surveyed territory by EGP and HP. Geodynamic assessment plays an important role in determining approaches to rational economic development of territories.

Methodology: the object of this research is the development sites of the Urengoy oil and gas condensate field, located within the boundaries of the Purovsky and Nadymsky districts of the Yamal-Nenets Autonomous Okrug. As initial data, the results of engineering and environmental surveys carried out at the Urengoy oil and gas condensate field development sites in the period 2015–2021 were analyzed. The methodology for assessing the extent of the territory affected by EGP and HP was based, firstly, on calculating the percentage of the area of territories exposed to the influence of EGP and HP to the area of hexagonal sections into which the study area was automatically divided using the tiling function in the ArcGIS program; secondly, on further ranking of all selected hexagons according to a four-rank classification of damage.

Results and discussion: analysis of the available materials from engineering and environmental surveys made it possible to compile a register of the main types of EGP and HP recorded at the sites of the UNOGCF development, among which slope processes were noted (talus processes on anthropogenically untransformed slopes in river valleys and on the slopes of technogenic sand embankments, landslides on slopes river valleys, solifluction occurring in the layer of seasonal thawing of soils on slopes steeper than 2–3 degrees); fluvial processes (erosive activity of watercourses and reservoirs, reworking of banks, thermal abrasion); cryogenic processes (thermokarst, traces of cryogenic heaving observed everywhere); aeolian processes activated on leveled surfaces devoid of vegetation and not classified as hazardous according to the requirements of the current legislation of the Russian Federation; hydrological phenomena, expressed primarily in technogenic flooding, swamping with the formation of various types of swamps, flooding of the territory during periods of high water, when the processing of the banks is most intense.

A significant area of the surveyed territory of the UNОGCF (62 % of hexagons) is characterized by the percentage of EGP and HP infestation in the range of 5–25, which correlates with the category of environmental risk.

Conclusion: a comparative analysis of the research area within the boundaries of the deposit showed that the northern area is characterized by a relatively homogeneous structure in terms of the degree of infestation

of EGP and HP with a total predominance of territories with a percentage of infestation of 5–25 %, while within the southern area a certain anomalous zone can be traced with the highest percentages of infestation – more 50 %. Such differentiation of the study area may be due to differences in ecological and geological conditions, as well as the degree of anthropogenic transformation, which in turn determines the nature and intensity of the manifestation of certain EGP and HP.

The proposed methodology for geodynamic assessment of the territory through determining the degree of infestation of EGP and HP can be used for the purpose of rational management of economic activities in 2 main areas: for making design decisions on the engineering protection of buildings and structures under construction (mainly for areas with a percentage of infestation of more than 25); to maintain the sustainability of natural Arctic ecosystems by leveling anthropogenic activation of processes (for areas with damage up to 25 %).