南堡凹陷异常压力分布与油气聚集

以实测地层压力为限定,利用声波测井、波阻抗反演数据对南堡凹陷的地层压力进行了分析。结果显示,南堡凹陷在2.8 km以下开始出现较明显的异常压力现象;3 km以下,超压明显,最大压力系数可达1.6。压力异常现象主要出现在古近系东营组中下段以及沙河街组。纵向上,南堡凹陷存在常压带、第一超压带和第二超压带3层结构,中间由致密的岩性段分隔。平面上,剩余压力具有继承性分布特点,古近系剩余压力中心位于林雀次凹和曹妃甸次凹一带,由凹陷中心向周缘的南堡1、2号构造以及老爷庙构造剩余压力逐渐降低。异常压力分布与油气储量分布有明显关系,南堡凹陷已发现的石油储量主要分布于超压带顶部,超压对油气成藏控制作用明显。

Characteristics of Abnormal Pressure and Its Relationship with Hydrocarbon Accumulation in Nanpu Sag, Bohai Bay Basin

Characteristics of abnormal pressure were investigated in Cenozoic,Nanpu sag by means of geophysical data and DST/RFT data.The top of overpressure occurs under 2.8 km,more overpressure under 3 km.Overpressured formation is always comprised of Ed and Es.Overpressured section could be divided into 3 segments vertically,which are hydrostatic segment,top overpressured segment and bottom overpressured segment.Excess pressure is horizontally charactered by successive distribution in different Cenozoic formations: Linque sub-sag and Caofeidian sub-sag are located in the central overpressured part,and from center of Nanpu sag to south shelving region,western Beipu structural belt and Laoyemiao structural belt the excess pressure decreases.The distribution of abnormal pressure is mainly controlled by the burial depth.Most hydrocarbons are distributed beyond the top overpressured segment.Overpressure is a significant controlling factor of hydrocarbon accumulation.