歧口凹陷馆陶组底界是一个区域上可对比的不整合界面,将盆地演化划分为古近纪裂陷期和新近纪一第四纪后裂陷期,后裂陷期构造样式主要为断层以及断层相关褶皱、火成岩构造.本文基于高精度三维地震资料精细解释,揭示了歧口凹陷后裂陷期的构造特征,通过计算断层活动速率了解了歧口凹陷的构造活动规律,得出以下认识:①断层构造包括继承性活动的主干断层及在后裂陷期构造应力场下发育的大量近东西向新生断层,在平面上两类断层成小角度相交,整体构成帚状构造,表现出明显的右旋张扭特征;②褶皱构造包括逆牵引褶皱、正形负花状构造、披覆背斜,在平面上披覆背斜、逆牵引褶皱和正形负花状构造基本上依次向东排列,但在局部地区也有相互共存的现象;③火成岩构造表现为一个火山通道发育多个帽型构造,火山顶部表现为强反射层,后裂陷期地层超覆其上,在火成岩构造旁侧断层发育;④断层活动速率计算结果表明,后裂陷期主干断层活动趋势主要分为断层活动速率由逐渐增大到逐渐变小、逐渐增大、混合型三种,其中前两种类型断层对油气的运聚最为有利,控制的油田分布最多.综合分析后认为,歧口凹陷内最有利的浅层油气藏类型是断层相关褶皱型油气藏和潜山披覆背斜型油气藏,火成岩活动对油气的生成和运聚也具有重要意义.%The bottom surface of the Guantao Formation, in Qikou sag,is an important unconformity interface which can be traced in the region. This surface divides the basin evolution into the rifting stage in Paleogene and post-rifting stage in Neo-gene-Quaternary. The most post-rifting structure styles include faults, faulted-folds and the igneous structures in the Qikou sag. Through detailed interpretation on high quality 3D seismic data, we summarize the post-rifting structure characteristics and calculate fault active rate to determine the tectonic activity law in Qikou sag. Then we get the following observations; ① The active faults includes continued growing main faults and numerous EW trended new faults,and these two kinds of faults intersects to each other with low angle which show as the broom shape on the plane, associated with the regional dextral tensile shearing stress field. ② The fold structure includes drape anticline, reservoir drag fold and normal shaped negative flower structure which distributes orderly from west to east on the plane,but they coexist together in some place. ③Igneous structures usually show as a long volcanic channel with several hat shape structures. The top of volcano characterizes as strong reflections because of the onlap of the o-verlaying strata, and several faults formed beside these volcano channels. ④ The main fault active rates show that the activity of the post-rifting faults can be divided into three types in Qikou sag:continuous decrease after continuous increase, continuous increase and mixed pattern. The first and second types of the faults are most beneficial to hydrocarbon accumulations and distributed in the oil fields. The most valuable shallow reservoirs in Qikou sag are the faulted-fold type and the buried-hill drape anticline type. Active igneous rocks are also very valuable to the generation and migration of the hydrocarbon.
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