银额盆地拐子湖凹陷深层优质储层特征及形成机理

银额盆地拐子湖凹陷巴音戈壁组发育一套深水重力流沉积，虽然埋深超过3 400 m，但储层物性较好。为了阐明该优质储层的特征，综合应用薄片、扫描电镜、压汞和物性分析等资料，结合埋藏史特征，对储层的岩石学特征、储层物性与孔隙结构特征进行分析，进而探讨该套深层优质储层的形成机理。结果表明:储层的岩石类型以长石岩屑砂岩为主，成分成熟度较低，总体属于低孔、特低渗型储层（平均孔隙度11.4%，平均渗透率6.093×10-3 μm2），储集空间类型以残余粒间孔隙为主，其次为粒间溶孔和粒内溶孔，发育少量微裂缝，储层的喉道总体偏细、孔喉比较大，属于中高孔、中细喉储层。沉积组构条件是形成拐子湖凹陷巴音戈壁组深层优质储层的重要基础，由于沉积水动力强、沉积物粒度粗、分选中等、杂基含量低，使得储层初始物性好；同时，较高的刚性颗粒含量增加了储层的抗压性，而一定含量的长石和岩屑为后期的溶蚀提供了物质基础。早期快速深埋、后期构造抬升以及有机质生烃等对于超压的形成和溶蚀作用的发生具有重要意义，异常高压、有机酸溶蚀和油气充注等综合作用是形成巴音戈壁组深层优质储层的关键因素。

Characteristics and Formation Mechanism of a High-quality Reservoir in the Deep Strata of the Guaizihu Depression,Yin-E Basin

A set of deep-water gravity flow deposits was developed in the Bayingebi Formation in the Guaizihu Depres-sion. Although the buried depth is more than 3 400 m, the reservoir exhibits good physical properties. In order to illus-trate the characteristics of this high-quality reservoir, petrological features, reservoir properties, and pore structure characteristic were analyzed based on the integrated application of thin section observations, scanning electron micros-copy (SEM), mercury penetration, and petrophysical properties, combined with the burial history features. We then discuss the formation mechanism. The results show that the sand bodies are mainly composed of feldspathic litharen-ite with low compositional maturity, low porosity, and extra-low permeability (the average porosity is 11.4%; the aver-age permeability is 6.093×10-3 μm2). The types of reservoir space are dominated by residual intergranular pores, fol-lowed by dissolved intergranular and intragranular pores, and a small amount of microfractures. The throat of the reser-voir is small, and the pore/throat ratio is relatively large. This reservoir is mainly characterized by medium-large pores and a medium-thin throat. The primary textural and mineralogical compositions of the sediments were the fundamental conditions for the formation of the high-quality reservoir in the Bayingebi Formation. Good initial physical properties developed due to strong hydrodynamic conditions, coarse-grained sediments, medium-sorting, and low matrix content. In addition, high hard particle contents gives the reservoir a stronger ability to resist compaction, and some feldspar and rock debris provide material basis for later dissolution. Early rapid burial, the later stage of tectonic uplift, and the hydrocarbon generation of organic matter played an important role in the formation of overpressure and dissolution. The combination of abnormal high pressure, dissolution by organic acid, and hydrocarbon filling were the key factors in forming the high-quality reservoir in the deep-burial Bayingebi Formation.