深部优质储层成因机理——以准噶尔盆地阜东斜坡区侏罗系三工河组碎屑岩储层为例

阜东斜坡区侏罗系三工河组3 600~4 300m内存在平均孔隙度12.7%、平均渗透率12.2mD的优质碎屑岩储层。为了探明其成因机理，通过岩心观察和扫描电镜等技术手段分析了1 232个储层样品，确定了其沉积环境特征、岩石和孔隙类型，并通过GC-MS分析了13个烃源岩样品的地球化学特征。结果表明，研究区地层发育于辫状河三角洲-湖相体系，岩性主要包括中砂岩、粗砂岩和细砂岩，砂岩以长石砂岩和长石岩屑砂岩为主，结构和成分成熟度低；孔隙以原生粒间孔、粒内溶孔和粒间溶孔为主。烃源岩中有机质属于Ⅱ2-Ⅲ型，处于低成熟-成熟阶段，正在大量生成乙酸和乙二酸。溶蚀作用是深部优质储层发育的根本原因，烃源岩中有机质热解排出的有机酸溶蚀了长石颗粒，形成了大量的次生孔隙，从而改善了储层物性；其溶蚀产物高岭石在深部优质储层段的大量发育，为溶蚀机理提供了有利的证据。

Formation Mechanism of Deeply Buried High-quality Reservoir: Example from Clastic Reservoir of Sangonghe Formation in Fudong Slope Zone,Junggar Basin

A high-quality clastic reservoir exists at the depth range of 3 600~4 300m in Sangonghe Formation of Fudong slope zone, Junggar Basin, having an average porosity of 12.7% and average permeability of 12.2mD. In order to explore its formation mechanism, 1 232 reservoir samples have been tested and analyzed through core observation, thin identification, X-ray diffraction and scanning electron microscope, and then their sedimentary environment, rock and pore types have been determined. And the geochemical characteristics, organic matter types and maturity of 13 source rock samples have been analyzed by GC-MS method. The results reveal that the reservoir of the research area is developed in the braided river delta-lake sedimentary system, which mainly consists of braided river delta frontier and shore-shallow lake subfacies. The lithology is mainly composed of medium sandstone, coarse sandstone and fine sandstone, which mostly belong to feldspar sandstone and feldspar lithic sandstone with low texture maturity and component maturity. Pore types primarily contain intergranular pore, intergranular solution pore and solution pore in grains. The kerogen of source rocks belongs to type Ⅱ2-Ⅲ and has a wide range of maturity, which produces abundance of acetic acid and oxalic acid. Dissolution is the main cause for the development of deep high-quality reservoirs the pyrolysis. The organic matter in source rock released organic acid to corrode feldspar particles through fractures and unconformities into reservoir, and then the secondary pores was formed, which improves the reservoir properties. The kaolinite, served as the dissolution product, was developed mostly in deep high-quality reservoirs, providing a favorable evidence for the mechanism of dissolution.