论文详情
基于笔石表皮体反射率和拉曼光谱评价海相页岩热成熟度的方法
石油与天然气地质
2022年 43卷 第No.6期
阅读:113
查看详情
Title
A method for evaluating the thermal maturity of marine shale based on graptolite reflectance and Raman spectroscopy: A case from the Lower Palaeozoic Wufeng‒Longmaxi Formations, southern Sichuan Basin, SW China
Authors
Jianghui Meng
Peixi Lyu
Wei Wu
Renfang Pan
Yiqing Zhu
摘要
五峰组(O)-龙马溪组(S)海相页岩是川南下古生界页岩气勘探的主力层系之一,热成熟度是烃源岩和页岩气评价的一项重要指标。由于缺乏镜质体,一直难以建立准确评价下古生界海相页岩热成熟度的方法。共采集33块川南五峰组-龙马溪组岩心样品,用于观察源内固体沥青及笔石表皮体的光学特征,并测试其随机反射率。同时,利用样品中干酪根的拉曼光谱参数分析热成熟度的演化趋势。研究结果表明,相较于源内固体沥青,笔石表皮体来源单一、颗粒较大、特征明显,且垂直层理切面上非粒状笔石表皮体随机反射率()数值分布更集中,更适合作为反射率测试对象。干酪根的拉曼光谱参数特征表明,热演化过程中与等效镜质体反射率()并非单一的线性关系。利用干酪根的拉曼光谱参数为中间变量,建立了通过计算的方法。计算结果表明,五峰组-龙马溪组页岩在长宁、泸州-大足和威远地区的热成熟度依次降低,分布范围分别为2.99 %~3.91 %,2.87 %~3.54 %和2.46 %~3.03 %,平均值分别为3.44 %,3.22 %和2.77 %。长宁西部出现了异常高成熟度区域,需要评价其对页岩气勘探的影响。
Abstract
The marine shale of Wufeng-Longmaxi Formations is one of the main targets of the Lower Palaeozoic shale gas exploration in southern Sichuan Basin. The thermal maturity is a vital indicator for source rock and shale gas evaluation. Due to the lack of vitrinite, it has been difficult to establish a method to accurately evaluate the thermal maturity of Lower Palaeozoic marine shale. In total, 33 core samples were selected from the Wufeng-Longmaxi Formations in southern Sichuan Basin to observe the optical characteristics of solid bitumen and graptolites and measure random reflectance. Simultaneously, Raman spectroscopic parameters of kerogen were also used to quantitatively analyze the change of thermal maturity. The results show that compared with solid bitumen, non-granular graptolites are more suitable for reflectance measuring because they have a single source, larger particle size and obvious characteristics, and the random reflectance () values of non-granular graptolites on sections perpendicular to bedding are more concentrated. The characteristics of Raman spectroscopic parameters of kerogen show that the relationship between and the equivalent vitrinite reflectance () is not a single linear relationship in the whole process of thermal evolution. By using Raman spectroscopic parameters of kerogen as mediators, a method for calculating by was established. The calculation results show that the maturity of Wufeng-Longmaxi Formations in Changning, Luzhou-Dazu and Weiyuan areas decreases successively, their falls in the range of 2.99 %-3.91 %, 2.87 %-3.54 % and 2.46 %-3.03 %, and the average is 3.44 %, 3.22 % and 2.77 % respectively. There is an abnormally high maturity area in the western Changning that calls for evaluation of its impact on shale gas exploration.
关键词:
固体沥青;
笔石表皮体;
拉曼光谱;
热成熟度;
海相页岩;
五峰组-龙马溪组;
下古生界;
四川盆地;
Keywords:
solid bitumen;
graptolite;
Raman spectroscopy;
thermal maturity;
marine shale;
Wufeng?Longmaxi Formations;
Lower Palaeozoic;
Sichuan Basin;