歧口凹陷滨海地区断裂特征及其对油气成藏的控制作用

Fault characteristics in Binhai area of Qikou sag and its control on hydrocarbon accumulation

渤海湾盆地歧口凹陷滨海地区新生代断裂发育,构造特征复杂。为了探究该地区断裂特征及其与油气成藏间内在联系,基于测井、录井及全区三维地震资料对断裂的几何学、运动学规律进行系统分析,并在此基础上揭示了断裂特征对油气成藏的控制作用。研究结果表明,滨海地区新生代经历了初始裂陷期、强烈裂陷期和拗陷沉降期三期构造运动,发育了NE向、EW向两组走向的断裂系,决定了研究区东西分带的构造特征。沙三段至沙二段时期,主要形成NE向断裂;沙一段至东营组时期,受右旋走滑应力场叠加控制,EW向断裂开始发育;馆陶组至明化镇组时期,裂陷作用持续减弱,盆地进入拗陷期。滨海地区的断裂活动对油气成藏具有重要的控制作用,断裂的强烈伸展控制了烃源岩及优势储层的分布,伸展构造变形与走滑构造变形的叠加改造,形成了不同的圈闭类型,加之断裂对油气的垂向疏导作用,在该区域构成了油气富集成藏的优越条件。

Binhai area of Qikou sag in the Bohai Bay Basin has developed Cenozoic faults with complex structural characteristics. In order to explore the inherent relationship between fault characteristics and hydrocarbon accumulation in this area,the geometry and kinematic laws of faults were systematically analyzed based on well logging,mud logging and 3D seismic data of the whole area,and the controlling effect of fault characteristics on hydrocarbon accumulation was revealed. We found that the Cenozoic in Binhai area progressed through three tectonic movements of the initial rifting stage,the strong rifting stage and depression subsidence stage,and developed two sets of NE and EW trending rift systems,determining the structural characteristics of the east⁃west zoning in the study area. From Sha 3 Member to Sha 2 Member,the NE trending faults were mainly formed. From Sha 1 Member to Dongying Formation,controlled by the superposition of dextral strike⁃slip stress fields,EW trending faults began to develop. From Guantao Formation to Minghuazhen Formation,the rifting activity continued to weaken and the basin entered the depression period. The fault activity in Binhai area plays an important role in controlling hydrocarbon accumulation. The intense extension of faults controls the distribution of source rocks and favorable reservoirs. The superimposition and reformation of deformation of extensional tectonics and deformation of strike ⁃ slip structures have formed different trap types,combined with the vertical drainage effect of faults on oil and gas,forming favorable conditions hydrocarbon enrichment and accumulation in this area.