自由烃差值法评价页岩含油性的思想、方法及应用

Idea,Method and Application of Evaluating Shale Oil Potential by Free Hydrocarbon Difference

如何准确判断页岩含油性是页岩油勘探甜点预测的关键.根据陆相泥页岩非均质性特点,提出用自由烃差值(即原始生烃量减去现存残留量)评价页岩含油性的方法,并对泌阳凹陷深凹区重点井进行采样分析,刻画自由烃差值在剖面上与平面上的分布特征.结果表明:剖面上,泌页1井5号页岩层的底部含油性较好,程2井5号页岩层的顶部含油性较好;平面上,含油性较好的主要分布在程2井区一带,而最先获得工业油流的泌页1井区并非含油性最好的区域.结合地层压力系数、脆性矿物含量及其他地质因素,在大甜点区内进一步划分出3个不同级别的小甜点区.由此可见,用自由烃差值法评价和预测页岩含油性是可行的,后期的勘探实践也证明了该甜点预测的正确性.

Assessment of shale oil potential is an important issue for predicting the sweet spots of shale oil exploration.Here,we suggest a new free hydrocarbon index to assess the oil content considering the characteristics of heterogeneity,and we present a case study of the Paleogene Hetaoyuan Formation in the Biyang Depression by this method to analyze the key wells of shale oil in the deep sag,Biyang Depression.First,the section characteristics of free hydrocarbon difference for the No.5 shale layer in Well Biye1 and Well Cheng2 are depicted.The results show that the oil potential for the No.5 shale layer is good for the bottom of Well Biye1 and the top of Well Cheng2.Then,the above-mentioned process is appled to the whole deep sag to predict the horizontal distribution of shale oil.It is found that the area of good shale oil potential is located in the area of Well Cheng2,while the area of Biye1 is not the best shale oil area though the industrial shale oil has been found there.Combined with the formation pressure coefficient and the content of brittle mineral,we overlap the thickness of non-mudstone interlayer,the development area of micro-cracks and the distribution of micro-structures,and three different grades of small sweet spots have been proposed based on the previous one big sweet spots.This prediction has been partly proved by the recent exploration.