岩石热解方法应用于页岩油气研究需注意的几个问题

Remarkable issues of Rock-Eval pyrolysis in the assessment of shale oil/gas

张谦 金之钧 朱如凯 刘全有 张瑞 王冠平 陈万利 Littke Ralf

Qian ZHANG Zhijun JIN Rukai ZHU Quanyou LIU Rui ZHANG Guanping WANG Wanli CHEN Ralf Littke

岩石热解方法自问世以来被广泛地应用于烃源岩的研究，其可以简便、快捷地评价岩石的含油特性、干酪根的生烃特征以及有机质的丰度、类型和成熟度，但该方法有其适用的范围，且岩石热解数据不合理的解释会增加页岩油气勘探的风险。基于近年来发表的大量实验测试数据，总结了在岩石热解分析数据解释中经常出现的3个问题。①对于高-过成熟的样品，其应用性受到限制；利用氢指数（）、氧指数（）、岩石最高热解峰温（）以及热解过程中产生的烃类（）与二氧化碳（）数量的比值（/）来划分有机质的类型，应尽量针对有机质成熟度（镜质体反射率，）低于1.35 %的烃源岩。② 的有效性取决于峰的大小及其是否对称，的准确性依赖于有机质的类型和；残余烃与黄铁矿含量会对的准确性造成一定的影响。对于Ⅰ，Ⅱ和Ⅲ型有机质，为确保测试获得的准确、有效，烃源岩的应不高于1.70 %。③含油饱和度指数（）被用来表征页岩油的可动潜力，大于100 mg/g指示页岩油甜点。值得注意的是，并不能直接指示页岩中的含油饱和度，对于有机质含量较高的层段，通常低于100 mg/g，而较低的总有机碳含量也能导致大于100 mg/g。目前，大多数论文所报道的极具潜力的页岩油储层，只有极少数高于100 mg/g。因此，将大于100 mg/g作为一个评价页岩油可动性和甜点的参数值是否合适值得进一步思考。建议针对不同类型的沉积盆地和不同的页岩地层建立各自的评价标准。此外，不同岩性的样品在存储和制备过程中轻烃损失量差异较大，应对多岩相共生页岩油储层采用分岩相评价方法。

Rock-Eval pyrolysis has been widely used in assessing source rocks from the very beginning. Although this approach can evaluate oil content， hydrocarbon generation， as well as the abundance， type， and thermal maturity of organic matter in a simple and rapid way， it is noteworthy that this technique has some limitations in application， and improper interpretation of pyrolytic data may bring more risks to shale oil/gas exploration. This study summarizes three main pitfalls commonly seen in previous publications based on massive experimental results. First， the use of hydrogen index （）， oxygen index （）， the temperature of maximum pyrolysis yields （）， and the ratio of / to discriminate kerogen of diverse types should target source rocks with maturity less than 1.35 % ； the feasibility of the technique to highly-to-over-mature source rock samples is limited. Second， the validity of depends on the area of and whether it is in normal distribution， and the accuracy of relies on kerogen type and thermal maturity； moreover， residual hydrocarbon and pyrite content have some effects on the accuracy of . To obtain accurate values， the maturity of source rocks of types Ⅰ， Ⅱ， and Ⅲ should not be larger than 1.70 % . Third， the oil saturation index （） has been used to indicate the mobility of shale oil， and a value larger than 100 mg/g suggests sweet spots of shale oil. However， it should be noted that could not directly provide information on the saturation of oil in shale. values are generally smaller than 100 if the rocks are very organic-rich， and a small value could also lead to a large value （more than 100 mg HC/g ）. Besides， only a few shales bear higher than 100 mg HC/g ， although many of the shales have been proven commercially successful. Therefore， the applicability of larger than 100 mg HC/g as a parameter for shale oil mobility merits further consideration. We suggest using individual criteria for different types of sedimentary basins and shale formations. Moreover， the loss of light hydrocarbons during the storage and preparation of rock samples is strongly dependent on rock lithofacies， and thus， classified assessment should be adopted for shale oil reservoirs of multiple lithofacies.

10.11743/ogg20230417