库车坳陷依奇克里克地区下侏罗统阿合组致密砂岩储层的成岩差异性特征研究

塔里木盆地库车坳陷依奇克里克地区深层致密砂岩储层的非均质性强，成岩成藏过程复杂。根据岩心观察、薄片鉴定、流体包裹体、荧光特征及碳氧同位素等分析，对下侏罗统阿合组致密砂岩的岩石类型、成岩演化及其差异性特征进行了研究。研究表明，阿合组致密砂岩分为强钙质胶结砂岩(C类)、富刚性颗粒岩屑砂岩(A类)、含塑性颗粒岩屑砂岩(D类)、富塑性颗粒岩屑砂岩(B类)4类，经历了两期油气充注，不同类型砂岩的成岩、致密化及成藏过程差异明显。A类砂岩的构造缝及溶蚀孔隙均较发育，渗透率较高、孔隙度分布范围广，代表第二期油气充注的蓝色荧光强。D类砂岩的长石及软岩屑含量稍高，晚期溶蚀作用发育，孔隙度较高、渗透率低，黄色和蓝色荧光共存。A、D两类为有效的致密气藏储层，成岩、成藏过程有差异，D类砂岩早期与晚期油气充注共存，早期油气充注减缓后期压实和碳酸盐胶结作用的发生，有利于晚期酸性溶蚀及油气充注。A类砂岩裂缝发育，对储集性能的影响大，渗透性好，晚期油气充注受早期油气充注的影响小。

Diagenetic differences of tight sandstone of the Lower Jurassic Ahe Formation in the Yiqikelike Area of the Kuqa Depression,Tarim Basin

The deep tight sandstone in the Yiqikelike Area of the Kuqa Depression presents both great exploration potential and challenge due to its complex reservoir densification & accumulation process, and strong heterogeneity. Here, the differential diagenetic evolution processes of this tight sandstone were studied through core observation, thin section identification, porosity and permeability measurements, and analyzes of fluid inclusions, fluorescence, carbon and oxygen isotopes, sandstone types and reservoir quality characteristics. Applying the modified Dickinson's triangle principle, the sandstone of the Ahe Formation are divided into four types based on the contents of calcium cement, ductile debris and rigid particles: type C, the calcareous cementitious sandstone; type A, the lithic sandstone with high rigid particle content; type D, the lithic sandstone containing medium level ductile debris (10%25%); and type B, the ductile rich lithic sandstone with more than 25% ductile debris. Types A and D are effective tight gas reservoirs where the blue fluorescence, representing the second oil (gas) filling, is strong as a result of high emposieu and structural fractures. The feldspar and ductile debris contents are somewhat high in type D, in which the porosity is high but permeability is low due to late dissolution. Most type D oil layer samples have yellow and blue fluorescence, and the average porosity of type D is higher at early oil filling but slightly declines after second oil and gas filling start. In comparison, types B and C have stronger compaction and cementation but poor physical properties; only a few samples emit yellow but no blue fluorescence; and they are all effective reservoirs. Notably, there are differences in diagenesis and accumulation between types A and D: the early oil filling of type D slowed the occurrence of structural compaction and carbonate cementation, conducive to the late acid dissolution and oil (gas) filling; whereas the structural fractures affecting the performance of type A was developed by the second rather than the early oil (gas) fillings.