元素测井产额计算及影响因素分析

Yield calculation of elemental logging and analysis of influencing factors

元素测井是非常规储层测井评价的主要测井方法之一.元素测井是以元素测量为基础,从矿物成分的角度提供地层信息,有效地将测井资料与地质信息结合起来.元素产额获取会受地层矿物和井眼环境的影响.为了提高元素产额计算的准确性,有必要对影响元素产额计算的因素进行分析.本文利用蒙特卡罗方法分析加权最小二乘逆矩阵法在地层矿物相对复杂的情况下求取元素产额时,地层减速作用、地层俘获作用、地层密度与井眼尺寸对元素产额计算精度的影响.研究结果表明,地层密度对元素产额计算的精度影响较大,地层密度越低,地层元素之间的相互影响越大,使得元素产额计算的误差变大,而元素产额计算受地层减速作用与地层俘获作用的影响较小,仅在地层减速能力较弱或地层俘获作用较强时对元素产额计算有一定影响,井眼尺寸对元素产额计算的精度影响取决于井内介质.

Element logging is one of the main logging methods used in unconventional reservoir logging evaluation.Element logging is based on element measurement,which provides formation information from the perspective of mineral composition and effectively combines logging data with geological information.The calculation of elemental yield would be affected by formation minerals and borehole environment.In order to improve the accuracy of elemental yield calculation,it is necessary to analyze the factors affecting the accuracy of elemental yield calculation.In this paper,Monte Carlo method is used to analyze the influence of formation deceleration,formation absorption,formation density and borehole size on the accuracy of element yield calculation when weighted least squares inverse matrix method is used to calculate elemental yield in the formation with relatively complex minerals.The results show that the formation density has a great influence on the accuracy of elemental yield calculation.The lower the formation density,the greater the interaction between the elements,which makes the error of elemental yield calculation larger.The calculation of elemental yield is less affected by formation deceleration and formation absorption.Only when the formation deceleration is weak or the formation absorption is strong,it has a certain influence on the calculation of elemental yield.The influence of borehole size on the accuracy of elemental yield calculation depends on the medium in the borehole.