克拉通盆地内部走滑断裂发育、演化特征及其石油地质意义:以塔里木盆地顺北地区为例

Structural Styles and Evolution Models of Intracratonic Strike-slip Faults and the Implications for Reservoir Exploration and Appraisal:A Case Study of the Shunbei Area,Tarim Basin

在详细刻画与定量分析顺北地区走滑断裂几何学特征的基础上,解剖了走滑断裂典型构造样式,建立了主干断裂演化模式,并结合生产动态资料探讨了走滑断裂差异演化对规模储集体发育部位、油气沿断裂带差异分布的控制作用:(1)顺北地区普遍具有“纵向分层变形、主滑移带平面分段”的空间结构特征,纵向分层变形分界面多为岩性界面,平面分段主要发育于中下奥陶统碳酸盐岩(勘探目的层)。平面分段中叠接变形段长宽比相似,均值为3.2。(2)顺北地区走滑断裂在目的层同时发育有“压脊‒地堑”复合构造样式,上覆地堑构造是下伏压脊构造在后期活动时拖曳上覆地层形成的伴生构造。(3)顺北地区走滑断裂演化受控于盆地南、北不同区域应力场的叠加作用,演化早期最大主应力方向从南到北发生了NNE向到NNW向的逆时针偏转,为顺北5断裂弧形构造行迹的发育奠定了基础。(4)压脊构造与压隆段边界断面类似,根部沟通烃源,具有“控储、控藏”特征。地堑构造自上而下发育至目的层,不直接沟通烃源,暂未钻遇规模性储集体。研究区走滑断裂晚期活动强度可控制晚期高成熟油气充注程度。

Based on detailed structural characterization and geometric analysis,the structural styles of the strike-slip faults in the Shunbei area are determined and the evolution models are proposed.Incorporated with analysis of production data,the controls of strike-slip fault evolution on the formation of reservoir space as well as the heterogeneous distribution of hydrocarbon along the faults are discussed.The new findings include the following:(1)The strike-slip faults in the Shunbei area are characterized by“layered deformation”in profiles,which display subvertical segments as“principal displacement zone”at depth and en echelon normal fault zones at relatively shallow parts.The interfaces between the“layered deformations”are commonly lithological boundaries,and the fault segmentations are usually developed in the carbonate rocks(i.e.,target layers for exploration).The length to width ratios of the step-over structures between segments are around 3.2;(2)“Pressure ridges and graben”composite structures are also developed in the strike-slip faults in the Shunbei area.The formation of the overlying graben structure is associated with the movement of the underlying pressure ridges;(3)The evolution of the strike-slip faults in the Shunbei area is controlled by the superposition of stress fields in the northern and southern regions.Such a superposition caused a counterclockwise rotation of the maximum compressive stress from NNE-orientation in the south to the NNW-orientation in north,which shaped the curved trace of the Shunbei 5 at the early stage of evolution;and(4)Pressure ridges and push-up step-overs cut through the source rocks at depth,and they both can control the hydrocarbon accumulation in the carbonate rocks developed above the source rocks.In contrast,the graben structures are not directly connected with the source rocks due to their nature of downward propagation into the carbonate rocks,and no reservoirs associated with the graben faults have been discovered so far.In the study area,the intensity of fault movements at the later stages can control the charge amount of hydrocarbons at higher maturity levels.