Abstract: The shale in the bottom of Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formationin in Sichuan Basin has been proven to be rich in biogenic siliceous minerals. To quantitatively calculate the biogenic silicon content in reservoirs, and study its role in the fracture evaluation of reservoir, the biogenic silicon content of the target reservoir interval was quantitatively determined using the improved element standard ratio method, which can account for more than 70% of the total silicon content. The traditional fracture calculation method was improved; silicon minerals were divided into biogenic and non-biogenic minerals, and the impact of biogenic and non-biogenic silicon minerals on reservoir fracture was investigated, thus making up for the deficienciesbrought by traditional method without distinguishing the silicon source. The results show that the high organic matter content does not necessarily indicatethe best reservoir interval for fracturing; the fracture index calculated without taking into account biogenic silicon turns to be small, which may lead to a wrong understandingof the fracturing ability of reservoir during the actual exploitation. Further, according to the actual tracing fracturing construction on site and the cumulative gas production proportion, the fracture levels of reservoirdivided when considering biogenic silicon are more in line with the actual fracturing conditions, which is of certain guiding significance for fracturing construction in fields.

Key words: shale gas reservoir, biogenic silicon, element standard ratio method, quantitative analysis, fracturing ability evaluation

摘要： 四川盆地上奥陶统五峰组—下志留统龙马溪组底部页岩被证实富含大量生物成因硅质矿物。为了定量计算储层生物成因硅的含量，研究其在储层可压裂性评价中的作用，利用改进后的元素标准比值法定量确定了目的层段生物成因硅含量，其最高可占总硅含量的70%以上。通过改进传统的可压裂性计算方法，将硅质矿物分为生物成因和非生物成因，研究不同成因硅质矿物对储层可压裂性的影响，弥补了传统方法不区分硅质成因带来的不足。研究结果表明，有机质含量高的储层段并不一定是最好的可压裂层段；在不考虑生物成因硅时计算的可压裂指数偏小，在实际压裂过程中容易错误认识储层可压裂情况。结合现场实际压裂示踪施工情况与累积产气占比，在考虑生物成因硅时划分的储层可压裂级别更加符合现场压裂情况，对现场压裂施工具有一定的指导意义。

关键词: 页岩气储层, 生物成因硅, 元素标准比值法, 定量分析, 可压裂性评价