Abstract: Qiongdongnan basin is an offshore petroliferous basin with several hydrocarbon generating sags,but there is no great breakthrough except fro the YC13-1 gas field after years of exploration. One of the challenges met in the exploration if the overpressure closely related with hydrocarbon migration and accumulation. No doubt that understanding the overpressure clearly is very helpful to the exploration. Based on years of research results in this area,this paper gave out a systematic description of the pressure field of Qiongdongnan basin. Beginning with the well alone characteristics of the pressure, the paper sum up the characteristics into four types (normal pressure, one segment overpressure, overpressure compartment, cycling overpressure), and further, described the distribution characteristics of present pressure, and zoned the pressure field of the whole basin. At last this paper presented the palaeopressure modeling result, and reappeared the evolution process of the pressure field in the geological history.

Key words: Qiongdongnan basin, sag, pressure field, overpressure, mathematical simulation