Chemical equilibrium of groundwater with minerals of the host rocks in Upper Jurassic sediments (Arctic regions of Western Siberia)

Dmitry A Novikov,O Chudaev,R Millot,Y Kharaka,O Shouakar-Stash,R Harmon

doi:10.1051/e3sconf/20199801037

Abstract

The results of thermodynamic calculations for a water-rock system in the Upper Jurassic deposits of the Arctic regions of Western Siberia are presented. In the area under investigation the groundwaters have been identified with mineralization up to 63.3 g/L and various chemical composition and genesis. Despite the long interaction with the rock (150-160 ma) equilibrium with endogenous minerals (albite, microcline and anorthite) is practically not observed. At the same time, groundwaters are in equilibrium with clay minerals and micas, such as: Caand Na-montmorillonites, kaolinite, paragonite, margarite, illite, muscovite and Mg-chlorite. The establishment of a balance of groundwater with primary aluminosilicate minerals is also affected by interactions with carbonate minerals. The differences in composition of groundwater in equilibrium with certain aluminosilicates and carbonates indicate that the mineral changes are formed from a solution of a strictly defined chemical composition in an appropriate geochemical environment.

Highlights

Understanding the hydrogeochemical mechanisms of diagenesis of sedimentary rocks of oil- and gas-bearing deposits in sedimentary basins, using comprehensive studies of groundwater and host rocks, is one of the most urgent fundamental problems of modern geochemistry
Goundwaters of different compositions occur in the various geological formations in the Arctic regions of Western Siberia
Our results demonstrate: 1) Groundwaters developed within the Upper Jurassic sediments in Arctic regions of Western Siberia are mainly of sodium chloride, sodium chloride – bicarbonate composition, varying from almost fresh to weak brines (TDS up to 63.3 g/L)

Summary

Introduction

Understanding the hydrogeochemical mechanisms of diagenesis of sedimentary rocks of oil- and gas-bearing deposits in sedimentary basins, using comprehensive studies of groundwater and host rocks, is one of the most urgent fundamental problems of modern geochemistry. The hydrogeochemical data analysis has revealed a decrease in the groundwaters diversity (with respect to their chemical composition) associated with an increase in TDS levels (according to S.A. Shchukarev’s classification), as follows: several water types for mineralization 2-5 g/L, five types for 10-15 g/L, two types for 20-25 g/L, and only one type – sodium chloride – for mineralization more than 25 g/L.

Results

Conclusion