黄骅坳陷歧口凹陷深层异常压力特征

歧口凹陷是黄骅坳陷中一个主要的第三系富油气凹陷，沉积了厚逾万米的下第三系，上第三系 第四系，歧口凹陷深层的主体指3500米以深的沙一段，沙二段，沙三段和部分东营组。该套地层是目前歧口凹陷的主要生油层系和油气勘探的主要领域，油气资源潜力巨大。前人研究表明，歧口凹陷深层异常高压十分发育。异常高压与油气运移，聚集和油气分布有十分密切的关系，如马西油田的沙一下亚段压力系数高达1．5米，长芦油田沙三段压力系数为1．44－1．55。因此，异常压力的分布特征对于研究歧口凹陷油气运移和油气分布有重要意义，本文主要利用平衡深度法研究歧口凹陷深层的异常压力特征及其分布，有关异常 压力 对油气运移的影响已另文发表。

The characteristics of abnormal pressure in deep formations in Qikou sag, Huanghua depression, Bohai Bay basin

Three pressure zones were identified by pressure data derived from sonic log in Qikou sag, Huanghua depression. These three pressure zones were the hydrostatic zone, the upper overpressured zone and lower overpressured zone. The bottom depth of the hydrostatic zone is approximately 2,000m. The upper overpressured zone mainly occurred in the central part of the sag, while the lower overpressured zone developed all over the sag. The thickness of the upper overpressured zone is only several hundred meters and the pressure coefficient is 1.3-1.4. The top depth of lower overpressured zone is 2,000-2,500m in marginal area and 3,000m in the central part. With the value of 1.5-1.6, the pressure coefficient is higher in the lower overpressured zone than in the upper one. The pressure coefficient is vertically higher in the first member of Shahejie Formation, as compared with that in the second and the third members of Shahejie Formation, and is horizontally higher in the central part of the sag, as compared with that in the marginal area. The distribution of abnormal pressure is mainly controlled by the burial depth and strata, and is also closely related to diagenesis.