中国低渗透砂岩储层类型及地质特征

TYPES AND CHARACTERISTICS OF LOW PERMEABILITY SANDSTONE PESERVOIRS IN CHINA

低渗透砂岩储层系指空气渗透率小于５０ｍｄ的含油砂岩储层，按其渗透率大小及开采方式可细分为三类；另根据地质成因，我国低渗透砂岩储层分为三种类型，即原生低渗透储层、次生低渗透储层和裂缝性低渗透储层。不同成因类型的低渗透砂岩储层，其储层描述与评价方法各异。我国低渗透砂岩储层的地质特点：沉积物成熟度低，成岩成熟度高；孔喉半径小，毛管压力高；原始含油饱和度低；粘土矿物含量高，在钻井、完井和开采过程中极易造成伤害。大多数低透储层测井反映为低电阻率，以岩性圈闭及岩性一构造圈闭油藏为主，天然裂缝比较发育。因此，认识和开采此类油藏难度较大。

Low permeability sandstone reservoirs generally are defined as oil reservoirs with gaspermeability of less than 50md,in China. They can be further graded into three types basedon values of permeability and development scheme. Accroding to their geological occurrence,low permeability sandstone reservoirs in Chinacan be classified into three categories:primary low permeability reservoirs,secondary lowpermeability reservoirs and fractured low permeability reservoirs. Reservoir description andevaluation would be different in different types of low permeability sandstone reservoirs.The characteristics of low permeability sanstone reservoirs in China are small diameterof pore throats,high capillary pressure,low oil saturation,high clay content,and easily sub-jecting formation damage to reduce producibility. The maturity of sediments of reservoirs islow,and their diagenetic maturity is high.Many low permeability sandstone reseroirs are lowresistance oil reservoirs,lithologic trap reservoirs,and have natural fractures. As discribedabove,they will result in some of difficulty for reservoir study and development.