南堡地区火山岩蚀变特征及储层测井评价

蚀变作用是火山岩储层中常见现象,蚀变对火山岩储层评价影响较大。通过对研究区A、B、C3口井的测井资料和黏土矿物资料等分析,选出对蚀变敏感的测井曲线,定义蚀变指数I_A,利用I_A对蚀变火山岩的蚀变程度进行定量评价。在测井系列分析的基础上,根据自然伽马、深侧向电阻率、声波、密度和中子5条测井曲线,回归预测火山岩储层蚀变后的黏土矿物含量,结果表明I_A越大,火山岩储层蚀变程度越高,黏土含量越高。由岩电实验数据拟合得到蚀变后的饱和度指数n,根据阿尔奇公式计算评价储层蚀变后的饱和度,发现蚀变后储层的n值>未蚀变时n值,这是由于蚀变产物绿泥石和伊利石等为油湿矿物,导致饱和度指数n增大。

Alteration characteristics of volcanic rocks and reservoir logging evaluation in Nanpu area

Alteration is a common phenomenon in volcanic reservoir,which has great influence on the evaluation of the reservoir.Through the analysis of logging data and clay mineral data of wells A,B,and C in the study area,the logging curves sensitive to alteration are selected and the alteration index I A is defined,and the degree of alteration is quantitatively evaluated using I A.Based on the analysis of logging series,according to five logging curves including gamma ray,deep dual resistivity,sonic,density and neutron,the clay mineral content of volcanic reservoir after alteration is predicted by regression.The results show that the higher I A,the higher the alteration degree and clay content.By fitting the experimental data of core-electrical,the saturation index n after alteration is obtained,and is evaluated according to Archie formula.The results show that the value of n after alteration is bigger than the value of n when it is not altered,because the alteration products chlorite and illite are oil-wet minerals,which increase the saturation index n.