准噶尔西北缘风城组云质碎屑岩类储层特征及控制因素

Reservoir Characteristics and Controlling Factors in the Dolomitic Clastic Rocks of Fengcheng Formation in Northwestern Juggar Basin

随着准噶尔西北缘石油勘探开发与地质综合研究,在二叠系储层非均质性强、岩石类型复杂多样的风城组发现云质碎屑岩类储层。通过岩心观察、薄片鉴定、X-射线衍射、扫描电镜和物性资料的统计分析,表明云质碎屑岩类储层以云质泥岩、云质粉砂岩、云质凝灰岩及含白云凝灰质泥岩为主;储集空间主要为裂缝和溶孔,具有裂缝—溶孔双重介质结构;储层平均孔隙度为4.42%,平均渗透率为0.19×10-3μm2,孔隙结构较差,微孔细喉,为典型低孔低渗储层。通过沉积环境、白云岩化作用、构造作用和热流体作用对储层物性及分布的影响,认为研究区沉积环境与沉积相制约储层发育规模和早期孔隙的发育,白云岩化作用与溶蚀作用决定次生孔隙的形成,构造作用控制储层的改造效应。

With the petroleum exploration and development and comprehensive geological research in northwestern Juggar Basin,high-quality dolomite reservoirs were found in Permian Fengcheng Formation which are characterized by strong heterogeneity,complex and various types of rocks.Through core observation,thin section identification,X-ray,scanning electron microscopy（SEM）,physical property data statistics and analysis,the result indicates that high quality dolomitic clastic reservoir mainly include argillaceous silty dolomite,dolomitized mudstone,tuffaceous dolomite and dolomitic tufffaceous shale.Reservoir type is complicated,and characterized by fracture-pore dual medium,with an average porosity of 4.42% and the average permeability is 0.19×10-3μm^2.The pore geometry is poor and its throat is tiny,and the reservoir belongs to low porosity and low permeability reservoir.Due to sedimentary environment,dolomitization,tectonism and hydrothermalism have influences on the reservoir physical property and distribution.The reservoir controlling factors was proposed.It is thought generally that depositional environment and sedimentary facies controlled the scale of high quality reservoir and early porosities,while dolomitization,acidic dissolution and hydrothermal fluids influenced secondary pore formation,and the effect of tectonism activity controls the modification effect of reservoir.