Genetic classification of subsurface waters and brines of Arctic regions of Siberia

Abstract

Specificity of hydrogeological aspects of the Siberian sedimentary basins is most pronounced in their Arctic part where the saltless type the cross section grades into saline type in the direction from the Yamal Peninsula (as part of the West Siberian sedimentary basin), passing through the Yenisei-Khatanga basin as far as the Anabar-Khatanga basin with salt domes in its structure. It has been established that the modern chemistry of groundwaters and brines of petroleum-bearing deposits is a product of long-term geological evolution affected by many geological and hydrogeological factors. Slightly metamorphosed groundwaters and weak brines of sodium chloride, chloride-bicarbonate sodium and sodium bicarbonate-chloride composition, with the TDS value varying from 2 to 63.3 g/dm3 (after S. A. Shchukarev) are widely developed within the West Siberian and the Yenisei-Khatanga basins. Subsurface brines from the areas adjacent to the Anabar-Khatanga basin are found to be dominantly sodium chloride in composition, with TDS value varying from 52.3 to 312.3 g/dm3, while those identified in the adjacent areas of the Siberian platform are strongly metamorphosed, of sodium chloride, sodium-calcium and calcium composition, with the TDS value up to 480 g/dm3. Results of the detailed hydrogeochemistry analysis of petroleum reservoirs and paleohydrological history of Arctic parts of the Siberian sedimentary basins have prompted the presence of three genetic groups of subsurface waters in their section: infiltrogenic, sedimentogenic and condensatogenic. The first group includes modern and ancient infiltrogenic waters and brines resulting from salt domes leaching; the second group is composed of sedimentogenic waters (including brines), lithogenic waters and cryopegs. Comprising condensatogenic waters formed syngenetically with the hydrocarbon pools, the third group represents a special type, since the “water-rock-gas-organic matter” system has largely affected the processes of formation of their chemical composition.