Abstract:

The formation water chemical characteristics in the pre-Tertiary had good response to the sedimentary conditions in Dongying Depression. The contents of total salinity and chloride ion increased from the Archean to the Cambrian in the Lower Paleozoic for the invasion of sea water, and decreased from the Ordovician to the Mesozoic with the stronger tectonic movement and the worsen conservation environment.The vertical distributions of the formation water chemical and dynamical belts have obvious zoning features. According to the vertical characteristics of the formation water, three hydrological environments can be divided: formation water frequency alternation belt(0-1.1 km), formation water alternate blocking belt(1.1-1.75km)and formation water alternate tardy belt(>1.75km).In every belt,the total salinities, ions and ion composition ratios have different responses to strata, and the blocking belt and the tardy belt were favorable for hydrocarbon accumulation. There mainly developed CaCl₂ type water and NaHCO₃type water, and the NaHCO₃ type water was substituted by the CaCl₂ type water with the content of total salinity increasing.The hydrodynamic field of the pre-Tertiary in Dongying Depression had characteristics of symmetry, and from the Archean to the Mesozoic the center of the hydrodynamic field and the symmetrical axial line changed. The hydrodynamic field in the central depression was controlled by centrifugal flow, and the hydrodynamic field in the boundary of the basin was mainly dominated by endocentric flow, and in the sluicing positions of the centrifugal flow in contacting region by the centrifugal flow and endocentric flow were the favorable targets for hydrocarbon accumulation.

Key words: formation water chemical field, hydrodynamic field, hydrocarbon accumulation, the pre-Tertiary, Dongying Depression