基于核磁共振技术的古龙页岩含油饱和度评价新方法

New evaluating method of oil saturation in Gulong shale based on NMR technique

古龙页岩具有黏土含量高、气油比高、页理和微纳米孔隙发育、孔隙结构和岩电关系复杂的特征,传统饱和度实验分析和测井饱和度评价面临挑战。实验分析表明古龙页岩具有大孔隙含可动油、孔隙中不含可动水、微纳米孔隙中也含油的特点。通过分析现有保压密闭取心含油饱和度实验技术方法的不足,提出以现场一维核磁实验分析饱和度为依据,建立适合古龙页岩油的二维核磁测井(特指斯伦贝谢公司的CMR-NG)饱和度解释模版,采用聚类分析数学算法对二维核磁测井数据进行处理与解释,实现了可动油和总含油饱和度的定量计算,经与现场一维核磁实验含油饱和度对比,平均绝对误差为4%,极大提高了含油饱和度解释精度,为储量计算和开发方案的编制与实施提供了技术保障。研究形成的技术流程与方法,对类似页岩油含油饱和度评价同样具有指导意义。

Gulong shale is characterized by high clay content,high oil-gas ratio,developed lamellation and micro-nano pores,complex pore structure and rock-electricity relationship,causing challenges for conventional saturation experimental analysis and logging calculated saturation.The experimental analysis shows that Gulong shale has characteristics of movable oil in macropores,no movable water in pores and oil in micro-nano pores.By means of analyzing shortcomings of existing experimental techniques and methods of oil saturation in pressure maintaining sealed coring,a 2 D NMR(CMR-NG)saturation interpretation template suitable for Gulong shale oil is established by using 1 D NMR experiment to analyze the oil saturation.Clustering analysis algorithm is used to process and interpret 2 D NMR logging data,thus quantitative calculations of movable oil and total oil saturations are realized.Compared with 1 D NMR field experiment,the average absolute errors of oil saturations are 4%,which greatly improve interpretation accuracy of oil saturations and provide technical support for reserves calculation and development plan compilation and implementation.Technical workflow and methods achieved in the study have guiding significance for oil saturation evaluation of similar shale oil.