冀中坳陷南部中—新生代构造转换及其油气地质意义

Mesozoic Cenozoic Tectonic Transition and Its Significances for Petroleum Exploration in the Southern Jizhong Depression

为了分析冀中坳陷南部中—新生代构造转换机制及其与油气分布的关系,基于地震解释资料,对该区地质结构特征、构造演化及构造转换过程进行研究,并对其油气地质意义进行了探讨。结果表明:冀中坳陷南部衡水调节带两侧地质结构存在明显差异,北部为“双断-双向滑脱-背倾半地堑”结构,南部为“多断-单向滑脱-复式半地堑”结构;冀中坳陷南部地区中—新生代构造演化大致分为基底演化(中生代)、初始裂陷演化(孔店组—沙四段沉积时期)、强裂陷演化(沙三段—沙二段沉积时期)、弱裂陷演化(沙一段—东营组沉积时期)及后裂陷演化(馆陶组沉积时期以来)5个阶段;冀中坳陷南部经历了基底NNE向构造体系向新生代NE向构造体系的转换,区域中—新生代以来应力场变化是冀中坳陷多方位复杂构造形成的原因;冀中坳陷南部构造转换作用通过影响洼槽迁移进而影响有效烃源岩分布,通过控制砂体入盆通道影响储层砂体展布,构造变换过程中主干断层位移梯度变化导致横向背斜形成指示油气富集的有利部位。构造体制转换形成的不同规模变换构造具有一定勘探潜力。

In order to analyze the Mesozoic-Cenozoic tectonic transition and its significance for oil and gas distribution in the southern Jizhong depression,based on seismic data,geological structure characteristics,structure evolution and tectonic transfer of the southern Jizhong depression are analyzed,at the same time,the geological significance for petroleum exploration are discussed.The study shows the differences in the geological structure and evolution on the two sides of the Hengshui accommodation zone(HAZ).The northern part of the HAZ is characterized by a half-graben controlled by double detachment faults with opposite dips,and the southern part of the HAZ is characterized by a compound half-graben controlled by a single detachment fault with multiple faults.The Mesozoic-Cenozoic evolution of the southern Jizhong depression can be divided into the following five periods:basement evolution stage(Mesozoic),initial rift evolution stage(Ek-Es^(4)),strong rift evolution stage(Es^(3)-Es^(2)),weak rift evolution stage(Es^(1)-Ed)and post-rift evolution stage(after Ng).The southern Jizhong depression has experienced a tectonic transition from basement NNE structural systems to Cenozoic NE systems,and the change of the stress field during the Mesozoic to Cenozoic is the dynamic reason for the formation of multi-directional complex structures.The Cenozoic transition affects the distribution of effective source rocks by affecting the migration of troughs,and influences reservoir sand distribution by controlling sand entry channels.The gradient change of displacement of main faults during structural transformation results in transverse anticline forming a favorable position indicating oil and gas enrichment.The transform structures formed by the tectonic transfer in different scales have a certain exploration potential.