准噶尔盆地中央坳陷莫索湾地区侏罗系三工河组深层致密砂岩气储集层特征及成因*

综合利用岩心、薄片、扫描电镜以及测井资料,对准噶尔盆地中央坳陷莫索湾地区侏罗系三工河组一段致密砂岩气储集层特征及致密化成因进行研究。结果表明: (1)三工河组一段储集层平均埋深超过4500 m,具低—特低孔、低—特低渗特征,属于典型深层致密砂岩气储集层;(2)沉积类型为浅水三角洲—湖泊相沉积,三角洲前缘水下分流河道砂岩为主要储集层;(3)岩石类型以细砂岩、粉—细砂岩为主,主要为低成分成熟度的岩屑砂岩,具有岩屑和塑性岩屑含量高及胶结物含量低的“两高一低”特征;(4)储集层孔隙类型以混合孔为主,孔隙-孔喉组合类型以中细孔-细喉型为主,孔喉分选性、连通性和渗流能力相对较差,微观孔隙结构总体较差;物质成分、压实作用及胶结物充填是3个导致储集层致密化的因素,从而形成三工河组一段深层致密砂岩气储集层。

Characteristics and origin of deep tight sandstone gas reservoirs of the Jurassic Sangonghe Formation,Mosuowan area,Central Depression,Junggar Basin

The characteristics and origin of densification of the tight gas reservoirs from the Member 1 of Jurassic Sagonghe Formation,Junggar Basin were investigated through analyses of cores,thin sections and scanning electron microscope images,and well logging data. The results show that: (1)The studied reservoirs can be categorized as typical deep tight sandstone gas reservoirs that show ultra-low porosity and permeability with average burial depth lower than 4500 m. (2)The reservoir sandstones are interpreted to be subaqueous distributary channel sandstones that were formed in a shallow-water deltaic to lacustrine environment. (3)The lithology of the reservoir rocks is dominated by fine- to silty-fine-grained sandstones with high components of lithic grain and ductile lithic grain and low components of cement. (4)The pore space of the reservoir is mainly characterized by a mixture of pore types with middle to fine pores and fine throats. The throats and pores are highly heterogeneous with poor connectivity and percolation. Finally,lithological composition,compaction and cementation are considered to be the main controls of the formation of the studied tight gas reservoirs.