板桥油田低电阻率油层成因机制分析

板桥油田东营组—馆陶组低电阻率油层在测井曲线上的响应特征与正常油层有明显的差别，通过对板桥油田地质、粘土矿物分析等，综合研究其低电阻率油层的成因，认为粒度细、泥质含量高、岩石的亲水性是形成低电阻率油层的主要原因。研究区低阻油层岩性以粉砂岩、细砂岩为主，泥质含量较高，较高含量的泥质充填了颗粒的孔隙空间；以孔喉为主的孔隙类型，使自由水在较细的孔喉中无法自由流动产生束缚水；由于粘土矿物的存在，油层的粒间孔隙受到改造，引起孔隙直径变小及微孔隙发育，加之蒙脱石强烈的吸水能力，导致大量水被吸附于颗粒及粘土表面，同时由于较疏松的高岭石的迁移而堵塞孔喉，使部分自由水成为束缚水，造成油层束缚水含量较高。导致低阻油层形成的次要原因是粘土矿物的附加导电作用、较薄的油层厚度及泥浆侵入。

GENETIC MECHANISM OF LOW RESISTIVITY RESERVOIR IN BANQIAO OIL FIELD

The low resistivity oil reservoirs in Banqiao Oilfield have apparent different response features in logging curses from normal oil reservoir.Through the analysis of geology and clay minerals of Banqiao Oilfield,an integrated study on the causes of the low resistivity reservoir is made.From the study,it can be concluded that the hydrophilicity of rocks which have thinner sizes and higher clay contents is the main cause of low resistivity reservoir.The stratum in Ban-qiao oil field mainly consists of siltstones and fine sandstones which have a high shale content.The high shale content clays fill the pore of grain.The pore type which is mainly pore-throat makes free water incapable of flowing freely in the finer pore-throat.As a result,the upper content bound water is formed.On account of clay mineral，the intergranular pore of oil formation is rebuilt and it makes the pore diameter lessening and tiny pore developed.Additionally，because of the violent absorption ability of montmorillonite，a great deal of water is absorbed into the surface of particles and clays.At the same time，the migration of looser kaolinites leads to the jam of pore-throat which makes part of free water bound water.This makes the bound water content even higher in the oil formation.The secondary causes which lead to the formation of low resistivity reservoir are the additional conductive function of clay mineral,the thinner thickness of reservoir and mud invasion .