渤南洼陷北带埕南断裂带构造特征及形成演化

Structural Characteristics, Formation and Evolution of Chengnan Fault Zone in the Northern Belt of Bonan Subsag

摘要: 利用三维地震、测井、岩心等资料，从渤南洼陷北部埕南断裂构造几何学、运动学及动力学特征入手，对埕南断裂西部、中部及东部不同段的地震剖面进行精细解释，精细划分出埕南断裂带不同段之间断裂结构特征及差异性，分析得到埕南断裂特征、断层活动特征，剖析得到埕南断裂成因机制，恢复得到构造演化过程。对该区油气勘探、成藏规律具有重要的意义。研究发现：埕南断裂是多期多段式活动断层的组合，剖面差异特征明显，由西段至东段依次呈上陡下缓的坡坪式、铲式同生正断层及板状正断层，一系列NW、NE、近EW优势方向断层相互切割，伴生、派生次级断层呈旋扭构造体系，表现为“网格化”的断裂系统。不同构造样式的断层在活动期次及活动强度的差异造就了现今渤南洼陷北部沿埕东凸起自西向东断层活动强度逐渐增强，活动期次逐渐变晚的特点，板式断裂发育在活动强度大区域，铲式断裂发育在活动强度中等区域，活动弱的地区则以坐椅式断裂为主，这与埕南断裂带剖面分段形态差异变化相吻合。不同时期的区域构造环境，控制着埕南断裂带构造特征及多阶段演化规律。新生代以来，郯庐断裂带具有明显的张扭特征，时而左旋，时而右旋；郯庐断裂带左旋走滑挤压到右旋走滑拉张应力场的根本性变革，是研究区复杂断裂形成的控制性因素。

Abstract: Based on the data of 3D seismic, well logging, core data and other data, starting from the structural geometry, kinematics and dynamics characteristics of the Chengnan fault in the northern zone of the Bonan subsag, fine interpretation of the seismic sections of the western, central and eastern sections of the Chengnan fault, the fracture structural features and differences between different sections of the Chengnan fracture zone are delineated, analysing the fracture structural features and fault activity features of the Chengnan fault. The genetic mechanism of the Chengnan fault is analyzed and tectonic evolution process is recovered. It is of great significance to the law of oil and gas exploration and accumulation in this area. The study found: The Chengnan fault is a combination of multi-stage and multi-segment active faults, with obvious profile differences. From the west section to the east section, there are successively steep slopes, shovel syngenetic normal faults, and plate-shaped normal faults. The faults in the dominant directions of, NE, and near EW cut each other, and the associated and derived secondary faults are a twisted structural system, which is represented as a “grid” fault system. The difference in the active periods and active intensity of faults with different structural styles has resulted in the gradual increase in the active intensity of faults from west to east along the Chengdong bulge in the northern Bonan subsag, and the gradual late active period. Plate-type faults are developing. In areas with high strength, shovel type faults develop in areas with medium activity intensity, and areas with weak activity are dominated by chair-type faults, which is consistent with the change in section morphology of the Chengnan fault zone. The regional tectonic environment in different periods controls the tectonic characteristics and multi-stage evolution of the Chengnan fault zone. Since the Cenozoic, the Tan-Lu fault zone has obvious characteristics of tension and torsion, sometimes left-handed and sometimes right-handed; the Tan-Lu fault zone is a fundamental change in the tensile stress field from left-handed strike-slip extrusion to right-handed strike-slip. It is a complex fault in the study area. It is a controlling factor of Tanlu fault zone sinistral strike-slip extrusion dextral strike-slip extensional stress field of radical change for the formation of the complex fracture in the study area.