歧口凹陷新生代宏观构造解释及勘探前景分析

Macrostructure interpretation and exploration potential analysis of Neozoic in Qikou depression

（东方地球物理公司研究院大港分院,天津300280）

Dagang Branch of Geophysical Research Institute, BGP, Tianjin 300280, China

歧口凹陷三维地震资料分年度采集区块小，为此进行了连片三维地震宏观构造解释研究。提出“点—线—面—体”的解释方法，即井震结合层位标定、区域结构剖面建立、构造层序划分、井层控制变速成图等方法。将歧口凹陷连片三维地震区新生代划分为7个构造层序进行对比解释，获得了井震结合全区统层、宏观构造格局、断裂平面和剖面组合特征、火山岩发育与分布情况等成果。分析认为，该区宏观构造格局为“三横三竖”：受北西—南东向拉张应力场控制形成的北北东—北东东向构造带和同沉积断层组成“三横”，由南西—北东侧向挤压应力控制和同沉积断层分段活动差异形成的褶皱组成“三竖”。受中生界残留盆地的控制，在近南北向大区域拉张应力场作用下经历了古近纪扩张深陷、稳定发展和衰减3个阶段。新生代断裂类型主要有正断层和张扭断层，均为伸展断层，其分布具有明显的方向性。火山岩发育与湖盆拉张期构造活动关系密切，主要分布在主断层交汇或弯折处。根据新成果提出北大港潜山带东翼围斜构造和南翼同沉积构造为近期勘探重点目标，张东歧东断裂构造带为近期重点勘探区带，预期具有较大的勘探前景。

The 3-D seismic data in Qikou depression was collected in different years with small acquisition area. This is not beneficial to the study of the macrostructure pattern and macro-depositional sequence. Therefore, a merged 3-D macrostructure interpretation was carried out in this area. The‘point-line-plane-body’ interpretation method was proposed, including well seismic connected calibration, regional structural profile establishment, structural sequence division and well-layer controlling variable-speed mapping. Using this method, the 3-D area of Neozoic in Qikou depression was divided into seven structural sequences. obtaining the uniformity of formations, the macrostructure framework, the configuration characteristics of faults on plane and section, the development and distribution of volcanic rock. The analysis indicates that the macrostructure is‘three-in latitudinal and three-in-longtitudinal’. The NNE-NEE structural belt and contemporaneous fault controlled by the NW-SE tension stress field form the ‘three-in-latitudinal’. The fold controlled by the SW-NE lateral compression stress and the activity difference of contemporaneous fault in different section form the ‘three in-longtitudinal’. Controlled by the residual basin of Mesozoic and affected by the nearly N-S regional tension stress field, the macrostructure of Palaeogene system has experienced three stages: expansion and depression, stable development and depletion. The fracture types of Cenozoic mainly include normal fault and transtensional fault, both of them are extensional faults and have apparent directivity. The development of volcanic rock is intimately related with the structural activity of the basin extension period. The volcanic rock mainly distributes in the joint or bending point of major faults. According to the new achievements, the pericline belt of eastern Beidagang buried hill and the syndeposit structure of southern part were thought to be the main exploration target. Meanwhile, Zhangdong-Qidong faulted structural belt was the major exploration belt in the near future.