Oil field water is coexist with oil and gas in tin-subsurface mineral porosity, and it is an absolutely necessarily composition in each of the reservoir systems. All the time its forming and laws of movement has a close relationship with petroleum generation, migration, acxu mulation and pool forming, preservation, even destruction. Whether distribution of total salinity or Cl ion. there is a good corresponding telween petroleum accumu lalion section and abnormal high values, in particular, as a response pointer indicates petroleum accumulation sec tion. distribution of Cl- ion has a higher resolation Therefore, the study of hydrochemistry field plays a very significant role in petroleum exploration and development.