地层元素测井确定矿物含量的新方法

A method for determining mineral content by formation element logging

地层中矿物的种类及含量对地层矿物识别、岩性划分、确定地层黏土含量与类型、计算骨架参数以及研究沉积环境等方面,均有着非常重要的意义。地壳中化学元素的丰度与矿物的形成及其化学成分有着密切的关系,通过确定元素含量和矿物含量之间的转换关系,可以把元素含量转换成矿物含量。根据不同的岩性选择,建立从元素含量向矿物含量转换的模型,通过相应的转换关系,借助最小二乘方法和广义逆矩阵求解线性方程组的方法,采用地层元素测井得到的元素含量,从而计算出地层中的矿物含量。通过对实际井资料的处理,将其计算结果与实验室结果和斯伦贝谢计算结果进行对比,其结果表明:①转换系数是病态矩阵时,最小二乘方法计算出的矿物含量不准确;②通过广义逆矩阵计算得到的矿物含量的精确度较高,计算结果与实验室结果误差较小,且优于斯伦贝谢计算结果,可以用于地层评价求取储层参数。

It is very important that the species and content of strata minerals can be used for identifying minerals, differentiating li thology, determining the clay content and species, calculating effective matrix parameters, and researching sedimentary environ- ment. In addition, the abundance of chemical elements has a close relationship with the formation of minerals and their chemical composition in the crust. The elemental concentration can be converted into mineral content by determining the relationship between elemental concentration and mineral content, the model of which was then chosen and established on the basis of different lithologies. Then we calculated the mineral content in the formation based on ECS （Element Capture Spectroscopy） logging with the least squares method and generalized the inverse matrix method of solving the linear system of equations. The processing of some practical data was used to illustrate the effect of this method, and results were compared with the laboratory-measured results and results computed by Schlumberger. On one hand, the result of the least squares method is imprecise when conversion factor is the ill condi tioned matrix. On the other hand, the accuracy of the mineral content calculated by generalized inverse computation is higher than the results computed by Sehlumberger, and also compared with the laboratory-measured results, the error is smaller. This shows that this method can be used for obtaining reservoir parameters in formation evaluation.