低电阻率油层的成因类型与测井响应

低电阻率油层根据其成因影响因素可划分5种类型：岩石骨架导电型、高束缚水饱和度型、高矿化度地层水型、双孔隙度结构与裂缝并存型、咸水泥浆侵入型。导致油层电阻率降低的主要内在因素包括：储层岩石骨架中含有导电物质如含黄铁矿等金属矿物时,是导致低电阻油层形成原因之一;岩石中黏土矿物阳离子交换性与平衡阳离子的附加导电作用可以造成油层电阻率的明显降低,形成低电阻率油层;岩性细、泥质含量高、储层孔隙结构复杂化,孔隙吼道变小,微孔隙增多为束缚水提供了储存空间,形成高束缚水饱和度储层,导电能力增强,使油层电阻率变低。咸水泥浆侵入是油层电阻率变低的外在因素。

The Types of Low-resistivity Reservoirs and Well Log Response

According to the factors,the low-resistivity reservoirs can be divided into 5 types：rock matrix conducting,high irreducible water saturation,high salinity of formation water,double pores system together with fracture and salt mud invasion.The main factors that make the oil reservoir resistivity lower are rock matrix containing conductive material especially pyrite and other metal elements of heavy minerals;clay minerals cation exchange and additional conductivity of balance of cationic in rock can make the resistivity of reservoirs apparently decrease;it provides storage space for irreducible water,which is fine lithology,high shale content,the complication of pore structure in reservoirs,the small pore and throat,and increase of microporosity.It is formed of high irreducible water saturation of reservoirs,which can enhance the conductive capacity and make resistivity of reservoirs lower.Saltwater mud invasion is the extrinsic factor to make the reservoir resistivity lower.