准噶尔盆地腹部西侧侏罗系三工河组储层成岩作用及控制因素

准噶尔盆地现今的地温梯度低（约为2.3℃/hm），其腹部西侧侏罗系三工河组辫状河三角洲砂体的埋深差异极大（约为2100 m）、成岩作用复杂，影响油气勘探开发部署。通过岩石薄片、阴极发光、扫描电镜和包裹体荧光显微鉴定，结合黏土矿物的演化特征，深入分析了准噶尔盆地腹部西侧沙窝地、莫西庄及征沙村3个小区三工河组储层的成岩作用、成岩阶段及其差异性的控制因素。准噶尔盆地腹部西侧三工河组储层的成岩作用主要受埋深、砂岩碎屑组分、地温梯度及油气充注等多因素控制。喜马拉雅期的构造运动使得不同小区之间呈现出极大的埋深差异，是制约其差异成岩作用的主要因素。沙窝地小区和莫西庄小区的三工河组因埋深相对较浅，砂岩的压实作用相对较弱，胶结作用以方解石胶结和高岭石胶结为主，处于早成岩阶段B期—中成岩阶段A期，储集空间主要为原生孔隙；征沙村小区的三工河组埋藏较深，砂岩的压实作用显著，胶结物以白云石和铁白云石为主，伊利石含量高，可见长石等溶蚀形成的大量次生孔隙，达到中成岩阶段B期，原生孔隙极不发育，储集空间以次生溶蚀孔隙为主。砂岩碎屑的组分是成岩作用的物质基础，塑性岩屑含量越高，砂岩的抗压实能力越弱。准噶尔盆地的低地温梯度延缓了三工河组压实作用和有机质成熟的进程，是盆地腹部三工河组储层在深埋条件下仍处于中成岩阶段的重要原因。埋藏史分析表明，地层超压的存在有效延缓了准噶尔盆地腹部三工河组储层的压实作用强度。白垩纪晚期以来的3次油气充注在不同程度上抑制了胶结作用的发生，促进了三工河组储层中钙质胶结物、钾长石及岩屑等的溶蚀。

Diageneses and controlling factors of Jurassic Sangonghe Formation reservoirs on the west side of the hinterland of Junggar Basin

In Junggar Basin, the present geothermal gradient is low (ca. 2.3℃/hm), and the braided river delta sandbody of Jurassic Sangonghe Formation on the west side of its hinterland has a great difference in burial depth (ca. 2 100 m); the complicated diagenesis has influences on hydrocarbon exploration and development deployment. Using rock thin sections, cathode luminescence, scanning electron microscopy and fluorescent microscopic identification of fluid inclusions, in combination with the evolution characteristics of clay minerals, the paper analyzes the differential diageneses, diagenetic stages and the controlling factors of the Sangonghe Formation reservoirs in Shawodi, Moxizhuang, and Zhengshacun areas on the west side of the hinterland of Junggar Basin. The diagenesis of the Sangonghe Formation reservoirs on the west side of the hinterland of Junggar Basin is mainly controlled by multiple factors such as burial depth, detrital component of sandstone, geothermal gradient, and hydrocarbon charging. The tectonic movement during Himalayan epoch caused great differences in burial depth between various small blocks, which is the main factor restricting their differential diagenesis. In Sangonghe Formation of Shawodi and Moxizhuang areas, the weak compaction of sandstones is caused by shallow burial depth, and calcite cementation and kaolinite cementation are the dominant diagenesis types, which is in the periond between the Stage B of early diagenesis and Stage A of middle diagenesis. The reservoir space is dominated by primary pores. Sangonghe Formation in Zhengshacun area has a larger burial depth, showing the significant compaction of sandstones; dolomite and ferrodolomite are the main cements, and the content of illite is high. It can be observed that plenty of secondary pores are formed by the dissolution of feldspar; when reaching the Stage B of middle diagenesis, primary pores are extremely undeveloped, and the reservoir space is dominated by secondary dissolved pores. The composition of sandstone debris is the material basis of diagenesis. The higher the content of plastic debris, the weaker the ability of sandstone to resist compaction is. The low geothermal gradient in Junggar Basin delays the compaction and maturation of organic matter in Sangonghe Formation, which is an important reason for the middle diagenetic stage of the Sangonghe Formation reservoirs in the hinterland of Junggar Basin under deep buried conditions. Analysis of burial history shows that overpressure effectively delays the compaction intensity of the Sangonghe Formation reservoirs in the hinterland of Junggar Basin. Three stages of oil and gas charging since Late Cretaceous have inhibited the occurrence of cementation to varying degrees, and promoted the dissolution of calcareous cements, potassium feldspar and rock debris in the Sangonghe Formation reservoirs.