准噶尔盆地特低渗油藏岩相划分与沉积成因——以百口泉油田三叠系储层为例

Lithofacies Classification and Sedimentary Genesis of Ultra-Low Permeability Oil Reservoirs in Junggar Basin—Taking the Triassic Reservoirs of Baikouquan Oilfield as an Example

摘要: 本文以准噶尔盆地百口泉油田三叠系储层为例，系统分析了特低渗油藏的岩相划分与沉积成因。研究首先提出了岩相划分的基本依据，包括颜色、砾石排列方式、支撑结构、粒度、岩性、磨圆度及分选特征。在此基础上，对百口泉组、克下组及克上组的岩相类型进行了详细划分，分别识别出17种、若干种以及35种岩相类型。研究区岩性以砾岩为主，砂岩和泥岩次之，整体表现为分选差、磨圆度低和结构成熟度低的特征。从沉积动力学角度出发，研究将不同岩相的成因归纳为四类：重力流成因、高流态牵引流成因、低流态牵引流成因和静水沉积成因。结果表明，砾岩和砂岩主要形成于重力流及高流态牵引流环境，而粉砂岩和泥岩则多与低流态牵引流及静水沉积相关。综合分析显示，研究区的沉积体系主要为干旱环境下的冲积扇沉积体系，其内部发育复杂多样的岩相组合和沉积构造。本研究不仅明确了不同岩相的类型及沉积特征，还揭示了其成因机制，为特低渗油藏储层预测与沉积学研究提供了参考方向。

Abstract: This study systematically analyzes the lithofacies classification and sedimentary genesis of ultra-low permeability oil reservoirs using the Triassic reservoirs of the Baikouquan Oilfield in the Junggar Basin as a case study. The research first establishes the basic criteria for lithofacies classification, including color, gravel arrangement, support structures, grain size, lithology, roundness, and sorting characteristics. Based on these criteria, the lithofacies types of the Baikouquan Formation, Kexia Formation, and Keshang Formation were carefully classified, identifying 17, several, and 35 lithofacies types, respectively. The dominant lithology in the study area is conglomerate, followed by sandstone and mudstone, with overall characteristics of poor sorting, low roundness, and low structural maturity. From the perspective of sedimentary dynamics, the study categorizes the genesis of different lithofacies into four types: gravity flow, high-flow regime traction flow, low-flow regime traction flow, and standing water sedimentation. The results show that conglomerates and sandstones primarily are formed in gravity flow and high-flow regime traction flow environments, while siltstones and mudstones are more commonly associated with low-flow regime traction flow and standing water sedimentation. A comprehensive analysis reveals that the sedimentary system in the study area is primarily an alluvial fan system in an arid environment, with complex and diverse lithofacies associations and sedimentary structures developed within it. This study not only clarifies the types and sedimentary characteristics of different lithofacies but also reveals their genetic mechanisms, providing valuable insights for reservoir prediction and sedimentological research in ultra-low permeability oil fields.