Origin and evolution of formation water in North China Plain based on hydrochemistry and stable isotopes (~2H, ~(18)O,~(37)Cl and ~(81)Br)

摘要

Origin and evolution of formation water are of great hydrogeochemical interest, the research on which can provide indicator for genesis and production of oilfield. Although many studies were carried out to investigate the origin and evolution of formation water in North China Plain (NCP), the research is still insufficient because of its Complicated history. Considering these, based on hydrogeochemistry and stable isotopes (~2H, ~(18)O,~(37)Cl and ~(81)Br), the origin and evolution of formation waters in North China Plain were further discussed. Results indicate that formation waters both in Jizhong Depression and Huanghua Depression in NCP are derived from meteoric water (river water and/or lake water) and the primary evolution processes are evaporation and mixing with seawater. The difference between two tectonic units is that the evolution of formation waters in Jizhong Depression is similar to that of salt lake in arid area, which underwent more evaporation, while formation waters in Huanghua Depression show more trace affected by seawater. This geochemical difference reflects the tectonic difference between two depressions. It can also be concluded that ~(81)Br behaves more conservatively than ~(37)Cl in the evolution of groundwater under certain circumstances.