准噶尔盆地深层致密油储层特征及致密化成因——以莫索湾—莫北地区侏罗系八道湾组为例

综合利用岩心、岩石薄片、扫描电镜及测井等资料,对准噶尔盆地莫索湾—莫北地区侏罗系八道湾组致密油储层特征及其致密化成因进行研究。结果表明:八道湾组储层为低—特低孔、低—特低渗储层,属典型的深层致密砂岩储层;储层砂体主要为三角洲前缘水下分流河道细砂岩、中—细砂岩,成分成熟度低,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;垂向上以4 100和4 500m为界,可划分为减小原生孔、稳定混合孔及增加次生孔3个孔隙演化带;孔隙主要为中—小孔,孔喉类型以分选较差的中-细孔—细喉型为主,连通性和渗流能力相对较差,结构相对较差。储层致密化主要受控于沉积环境相对稳定性、岩石主要成分、储层埋藏深度及胶结物赋存状态4个因素,构成了致密化的背景、内因和外因;相对稳定的沉积环境、低成分成熟度、高岩屑和塑性岩屑含量、储层埋深大、压溶作用大量减孔,以及不同类型胶结物以4种状态充填孔喉,形成了八道湾组致密储层。

Deep Tight Oil Reservoir Characteristics and Densification Causes in Junggar Basin:A Case from Jurassic Badaowan Formation in Mosuowan-Mobei Area

The tight oil reservoir characteristics and densification causes of Jurassic Badaowan Formation in Mosuowan-mobei area of Junggar basin were studied by using integrated analysis of cores,thin section identification,scan election microscope and well logging data.The results show that reservoir has a low and ultra-low porosity and permeability in general,is a typical deep tight sandstone reservoir.Reservoir sand body is mainly delta front subaqueous distributary channel fine and middle-fine sandstone,maturity is low,with high debris content,high content of plastic lithic and low content of cement,that is,"two high and one low".It can be divided into three porosity evolution zones in vertical which taking 4 100 m and 4 500 m as the boundary,they are reducing-primary,stable-mixing,and increasing-secondary pore.The pore size is mainlymiddle-small,and the pore throat is middle-fine porefine throat with poor sorting,connectivity,percolation ability and structure are relatively poor.Tight sand reservoir is controlled by relative stability of sedimentary environment,main component of reservoir rock,burial depth and cements occurrence state,and so on,which constitute the background,internal and external densification.The densification reservoir of Badaowan Formation formed mainly due to relatively stable deposition environment,low compositional maturity,high debris and plastic debris content,deeply buried reservoir make pressolution largely reducing pore space,and different types of cements in four states filling pore throat.