Faults and salts are widely developed in Wenliu region in Dongpu sag

Bohai Bay Basin.And hydrocarbon migration processes and the contacts between water-

oil and gas are complex.Based on analysis of the current vertical and horizontal hydrochemical distribution of the Paleogene formation water

this paper determined the origin of formation water by using isotopes of hydrogen and oxygen.Combined with the features of regional tectonics and hydrodynamics

we also studied the relationship between the hydrochemical property and the accumulation and distribution of hydrocarbon in Wenliu region.Besides

by means of dissecting the typical profiles of Well Wen 218 to Well Wen 245

the coupling relation between hydrochemical characteristic and hydrocarbon migration and accumulation was further analyzed.The analysis of isotopes of hydrogen and oxygen show that the formation water of this region is primarily composed of the connate water

with paleo-meteoric water permeating only in some local areas.This indicates that the sealing conditions area good in the Wenliu region

favorable for hydrocarbon accumulation and preservation.Moreover

the hydrochemistry of this region can be divided into five zones in vertical

namely diluting zones due to permeating of(paleo-)meteoric water

released water of mudstone compaction and fault communication

concentration zones due to cross-formational flow and end over flow.In the plane

the Wendong rolling anticline belt and graben belt are the common areas for the gathering of released water from mudstone compaction and meteoric water.The concentrations of salinity and chloridion gradually increase as a result of the condensation process of cross-formational flow of formation water.The areas with high concentration of salinity and chloridion correlate well to hydrocarbon enrichment areas.In addition

the Wenliu region displays good connectivity of faults

resulting in the vertical hydrocarbon migration being dominant while the lateral migration being subsidiary.