乌石凹陷断-坡-凹耦合控制下的三角洲沉积模式及其构型特征

Sedimentary Model and Its Architectural Characteristics of Delta under the Control of Fault-Rupture-Sag Coupling in Wushi Sag

针对乌石油田群流沙港组二段油藏断裂构造复杂、薄层砂岩分布及连通性认识不清等问题,通过岩心、测井、地震资料的综合解释与应用,深化了对乌石凹陷三角洲沉积模式及构型特征等认识。研究表明:研究区沉积发育受基准面变化、断裂发育、古地貌等多重因素影响,主要发育基准面调控下的断裂-坡折-凹陷耦合控制形成的三角洲沉积模式;以沉积模式为约束,识别典型沉积微相特征,明确了基准面在先下降再上升的变化过程中经历了湖相—三角洲前缘—三角洲萎缩的沉积;厘清了流二段三角洲砂体以多条水下分流河道的侧向叠置为特征,具有侧叠型、对接型和孤立型等叠置样式,最终建立适宜研究区的构型模式,明确各项环境因素对砂体展布的影响,有效指导砂体连通性分析。研究成果为乌石油田群高效开发奠定了基础,同时对类似复杂断块油气田的沉积模式及内部结构研究具有重要的借鉴意义。

In view of the problems of complex fault structure and unclear understanding of flagstone distribution and connectivity of the reservoirs in Member 2,Liushagang Formation,Wushi Oilfield Cluster,the deposition patterns and architecture characteristics of delta in Wushi Sag were more understood on basis of comprehensive interpretation and application of core,well logging and seismic data.It was found in the study that the sedimentary development in the study area was affected by multiple factors such as base level change,fault development,and paleo-geomorphology,and mainly develops the delta sediment was mainly formed by fault-rupture-sag coupling under the control of base level;constrained by the sedimentary model,the characteristics of typical sedimentary microfacies were identified,and it was determined that the base level has experienced the lacustrine-delta front-delta shrinking sediment in the process of first falling and then rising;it was clarified that the delta sand body in Member 2 of Liushagang Formation was characterized by the lateral superposition of multiple underwater distributary channels,with such superposition styles as lateral,docking and isolated superposition;finally an architecture model suitable for the study area was established,and the influence of various environmental factors on sandbody distribution was determined.The results can effectively guide the analysis of sandbody connectivity.The results of the study lay a foundation for the efficient development of Wushi Oilfield Cluster,and can be used as a reference for the study of sedimentary models and internal structures of similar complex block-faulted oil and gas fields.