坡折带砂体成因及分布规律——以准噶尔盆地车排子地区下白垩统清水河组为例

Origin and distribution of sandbody in slope break zone:a case study of the Lower Cretaceous Qingshuihe Formation in Chepaizi area,Junggar Basin

富烃凹陷坡折带是地层-岩性油气藏勘探的一个重要领域。准噶尔盆地车排子地区清水河组富烃凹陷共发育4级坡折带和6期坡折带控制下的地层超覆带,为了研究清水河组坡折带砂体的成因与分布,利用钻井、岩心、地震属性等资料刻画出目的层沉积相,并结合层序地层学、古地貌恢复等技术,探讨车排子地区清水河组规模砂体发育成因与主控因素,落实砂体富集区带及勘探有利区。结果表明,清水河组主要发育曲流河三角洲和滨浅湖2种沉积相,总体表现出"贫砂富泥"的沉积特征;有利储集砂体分布局限,主要受4个因素控制,即幕式挤压形成的"二元"(冲断挤压—应力释放)体系域、沉积相带、沟谷地貌、坡折带。坡折带之下沟谷地貌中低位体系域发育的三角洲前缘亚相是有利砂体富集带,也是规模油气发现的主要领域。

The slope break zone in hydrocarbon-abundant depression is an important exploration area for stratigraphic reservoirs. Stratigraphic overlap controlled by four different levels of slope break zone in six stages is developed in Qingshuihe Formation in Chepaizi area, Junggar Basin. In order to investigate the controlling factors of petroleum accumulation and distribution, the sedimentary facies was studied by the data of drilling, core and seismic attributes, combined with the technologies of stratigraphy and paleogeomorphology restoration, the ori- gin and controlling factors of reservoir were discussed, and the favorable reservoir and potential exploration pros- pects were defined. The results show that Qingshuihe Formation developed meandering river delta and shore-shal- low lacustrine sedimentary facies, and can be characterized by ＂mud-rich and sand-poor＂ and limited high quality reservoir distributions. The favorable reservoir distribution was controlled by the ＂dual＂ （thrust squeeze-stress relief） systems tract formed by episodic squeeze, sedimentary facies, valley topography and slope break zone. The delta front facies developed at the under-part of the slope break zone is favorable for high-quality reservoir enrich- ment and potential for petroleum prospecting.