库车坳陷依南地区阿合组致密砂岩气储层特征与有利区带预测

库车坳陷依南地区下侏罗统阿合组具有形成致密砂岩气的有利地质条件,并已获勘探证实。通过对岩心、录井、测井资料、普通薄片及铸体薄片的观察鉴定以及扫描电镜、黏土矿物X射线衍射分析,认为研究区致密砂岩储层的成因类型主要为辫状分流河道和水下分流河道;岩石类型以岩屑砂岩为主,岩石成分成熟度低,结构成熟度中等,裂缝发育,孔隙度集中分布在4%~12%,平均为7.53%,渗透率集中在(0.1~100)×10-3 μm2,平均为12.33×10-3 μm2,其中小于1×10-3 μm2的样品占到75%,属于典型的致密砂岩储层。储层形成与沉积背景、成岩作用和构造作用等因素相关。综合有利相带、特征曲线重构反演砂岩厚度、裂缝发育程度,结合构造背景对有利区进行了综合预测,指出有利区主要发育在依南2、依南5和吐孜2井一线南侧,其中依南2井南侧和西南侧潜力最大,是下一步勘探的重点。 

Reservoir characteristics and favorable zone prediction of tight sandstone gas of the Ahe Formation in Yinan area,Kuqa Depression

The Lower Jurassic Ahe Formation in Yinan area of the Kuqa Depression has favorable geologic conditions for the formation of tight sandstone gas reservoirs. Core, logging, drilling data, thin section observation, cast thin section identification, scanning electron microscope and the X-ray diffraction analysis of clay minerals showed that the tight sandstone reservoirs in the study area mainly originated from braided distributary channels and underwater distributary channels.Lithic sandstones are dominant with low compositional maturity and medium textural maturity. Fractures were well developed. The porosity is 4%-12%, averages 7.53%. The permeability is (0.1-100)×10-3 μm2, average 12.33×10-3 μm2. The samples with a permeability less than 1×10-3 μm2 account for 75%, consistent with typical tight sandstone reservoirs. Reservoir formation is related to sedimentation, diagenesis and tectonism. Favorable facies belts and characteristic curves were applied to reconstruct sandstone thickness and fracture distribution, and to predict favorable exploration targets combined with tectonic background. The study showed that the area to the south of wells Yinan2, Yinan5 and Tuzi2 is a potential play for tight sandstone gas exploration, especially the area to the south and southwest of well Yinan2.