Features Of Formation Pressure And Their Relationship With The Oil And Gas Distribution In The Northern Liaodong Bay

Overpressure phenomena are very common in the E3d and E2s formation of the Liaodong Bay which is located in the northeast of Bohai Bay Basin. The overpressure developed in the northern Liaodong Bay the most widely which is the main production region of the Bohai Bay.The existing exploration practice showed that the Northern Liaodong Bay has high oil and gas exploration potential. Based on the Equivalent depth method, Eaton method and Bowers method as long as the measured formation pressure as calibration, the single well formation pressures are calculated and the applicabilities of these methods in different areas are also analyzed. Combined with the lithology and the organic matter maturity, the single well formation pressure longitudinal section figures are made and the overpressure causes of the wells are also analyzed. According to all these work above, the formation pressure transverse and plane distribution characteristics are obtained. Combined with the oil, gas and water distribution and reservoir types, the relationships between formation pressure and oil and gas distribution in the northern Liaodong Bay and the favorable hydrocarbon enrichment and exploration direction in the study area are also discussed.(l)The Equivalent depth method is more suitable for the calculation of shallow formation pressure. For the deeper formation pressure, however, it is noneffective, especially for the E2s formation pressure in the Liaoxi low salient. For the pressure calculations in these areas, the Eaton method is the most useful one with the Eaton exponent of1.8-2.4which is roughly the same in the same area.(2) The normal pressure mainly develop in the central part of the salient and the overpressure pressure mainly develop in the the depression and slpoe with the pressure coefficients changes quickly in the slope zone which shows good hydrocarbon migration and accumulation conditions. From E3d2to E2S3; the overpressure area is more widespread and the E3d3developed the most greatly overpressure in the study area; the extent of overpressure become smaller from north to south. (3) The reservoirs in Liaozhong depression are predominantly oil or oil and gas saturated which are mainly distributed in E3d2with normal pressure. Liaoxi depression are predominantly oil saturated whose reservoirs are mainly distributed in E3d2L.. Its gas layers are mainly in E3d2L and E2S2. The hydrocarbon reservoirs in Liaoxi depression are normal pressure. Liaoxi low salient are predominantly oil or condensate gas saturated which are distributed from E3d2L to buried hill formation with the oil and gas layers mainly in E3d2U,E2s1and E2S2. Its condensate gas layers are mainly in E2S1,E2s2and E2s3with overpressure.(4) There are at least three kinds of oil and gas layer of deep formation in northern Liaodong Bay:overpressure type with good sealing ability(ⅠA type); normal pressure type with good sealing ability (Ⅰ B type; normal pressure type with relatively weak sealing ability (ⅡA type)..ⅠA type is distributed in northern subsag of Liaozhong depression and Liaoxi low salient. ⅠB type is mainly distributed in slope zone. ⅡA type is distributed in shallow formation of depression zone. The main accumulation models are "buried hill+draped reservoirs with ⅠA type" in Liaoxi low salient,"fault block reservoirs with ⅠA type" in gentle slope of Liaozhong dpression and "buried hill+draped reservoirs with ⅠB type" in actic region of Liaoxi depression, These areas are the favorable zone of oil and gas accumulation.