利用元素成分准确评价海相页岩脆性的方法

Method of accurately evaluating the brittleness of marine shale by elementary composition

页岩气水平井通常不进行钻井取心且测井资料少或不测井,难以为精细分段压裂提供可靠的脆性评价数据,故利用页岩气井广泛采用的元素录井技术连续、实时评价页岩的脆性具有重要的现实意义。在厘定脆性评价标准的基础上,通过对比常用脆性评价模型的精度,分析Si、Ca、Mg等元素成分的分布特征,提出了以过量硅表征石英、以Ca元素表征碳酸盐岩矿物的新思路,建立了以(Si过量+Ca)含量评价页岩脆性的新方法与评价标准,其与脆性矿物含量的相关系数达到0.81,超过基于弹性参数的脆性评价模型及已有的基于元素成分的脆性评价模型,实现了页岩气水平井地层脆性的高精度评价。

Shale gas horizontal wells are usually not drilled for coring,with little or no log data,it is difficult to provide reliable brittle evaluation data for fine staged fracturing.Therefore,it is of great practical significance to continuously and real-time evaluate shale brittleness by element logging technology widely used in shale gas wells.Based on the determination of brittleness evaluation criteria,by comparing the accuracy of the commonly used brittleness evaluation models and analyzing the distribution characteristics of elements Si,Ca and Mg,a new idea of characterizing quartz with excessive silicon and carbonate minerals with element Ca is proposed.The new method and criteria for evaluating shale brittleness with(Si excess+Ca)content are established.Its correlation coefficient with the content of brittle minerals reaches 0.81,which is higher than the brittleness evaluation model based on elastic parameters and the existing brittleness evaluation model based on elementary composition,and realizes the high precision evaluation of formation brittleness in shale gas horizontal wells.