准噶尔盆地阜康凹陷二叠系上乌尔禾组砂砾岩储层特征及发育模式

Glutenite reservoir characteristics and development model of Permian Upper Wuerhe Formation in Fukang Sag,Junggar Basin

准噶尔盆地阜康凹陷二叠系上乌尔禾组砂砾岩具有较大的油气勘探潜力,目前存在的砂砾岩储层特征以及成储机制不清晰等问题,严重制约了对该类储层的勘探。利用显微薄片、扫描电镜、X射线衍射等对准噶尔盆地阜康凹陷上乌尔禾组砂砾岩储层特征、主控因素以及成储模式进行了系统研究。结果表明:上乌尔禾组砂砾岩具有“双填隙物”特征,砾石间主要被较粗的砂质组分填隙,胶结作用主要发生于砂质组分之间;砂砾岩孔隙度低,砾石中基本不发育孔隙,砂质填隙物中孔隙较发育,储集空间主要为晶间孔和次生溶孔;与储层形成有关的成岩演化现象主要发生在砾石之间的粗填隙物砂质组分中,主要为铝硅酸盐矿物的溶蚀作用,形成较多的溶蚀孔隙;河口坝、水下分流河道等高能沉积微相中储层更发育,储集空间主要与长石溶蚀有关,裂缝、不整合面是酸性流体运移的主要通道;早成岩期酸性流体主要为沿不整合面下渗的大气水,尤其是靠近北三台凸起的区域大气淡水溶蚀更为显著,中成岩期主要为有机酸溶蚀;砂砾岩中发育大气酸溶蚀型、有机酸溶蚀型和双源酸叠加溶蚀型等3类储层,不同类型储层分布决定了阜康凹陷上乌尔禾组砂砾岩油气藏的勘探方向,斜坡区、凹陷区的砂砾岩+断裂发育叠合区是阜康凹陷上乌尔禾组砂砾岩油气勘探的重点方向。

The glutenites in the Permian Upper Wuerhe Formation in the Fukang Sag of the Junggar Basin possess great potential for oil and gas exploration.However,uncertainties in the reservoir characteristics and formation mechanisms of these glutenites seriously restrict their effective exploration.The study provides a comprehensive analysis on the characteristics,main controlling factors,and development models of glutenite reservoirs of the Upper Wuerhe Formation in the Fukang Sag of the Junggar Basin using microscopic thin sections,scanning electron microscopy(SEM),and X⁃ray diffraction(XRD).The results show that:(1)Two types of interstitial mate⁃rials are observed in the glutenites of the Upper Wuerhe Formation,where the spaces between gravels are primarily interstitially filled with coarser sandy components,and the cementation mainly occurs between these sandy compo⁃nents.(2)The glutenites generally exhibit low porosity,with minimal pore development within gravels,while the pores in sandy interstitial materials are more developed.The reservoir space is mainly composed of intercrystalline and secondary dissolution pores.(3)Diagenetic processes related to reservoir formation mainly occur within the coarse sandy interstitial materials between gravels,mainly involving aluminosilicate dissolution,which results in abundant dissolution pores.(4)In high⁃energy sedimentary microfacies,such as estuary bars and underwater distributary channels,reservoirs are more favorably developed,where the reservoir space is mainly associated with feldspar dissolution.Fractures and unconformities are the main channels for acidic fluid migration.(5)During the eodiagenesis,acidic fluids,mainly atmospheric water,infiltrated along unconformities,with more significant dissolution near the Beisantai arch.During the middle diagenetic period,dissolution was mainly attributed to organic acid.(6)Three types of reservoirs are developed in the glutenites:atmospheric acid dissolution reservoirs,organic acid dissolution reservoirs,and dual⁃source acid superimposed dissolution reservoirs.The distribution of these reservoir types determines the exploration strategies for oil and gas reservoirs of glutenites of the Upper Wuerhe Formation in the Fukang Sag of the Junggar Basin.Glutenites in the slope and sag areas and zones of superim⁃posed fault development are the key objectives for oil and gas exploration of glutenite reservoirs of the Upper Wuerhe Formation in Fukang Sag.