川南地区下志留统龙马溪组有机质热演化及其主控因素

Thermal evolution of organic matter in the Lower Silurian Longmaxi Formation， southern Sichuan Basin and its main controlling factors

蒋前前 吴娟 王恒 匡龙伟 周志鹏 杨雨然 李彦佑 罗超 邓宾 焦堃

Qianqian JIANG Juan WU Heng WANG Longwei KUANG Zhipeng ZHOU Yuran YANG Yanyou LI Chao LUO Bin DENG Kun JIAO

为研究川南地区下志留统龙马溪组有机质热演化特征，根据钻井、岩性和温度实验数据，研究了现今地温场特征，利用激光拉曼光谱测定计算了龙马溪组页岩有机质镜质体反射率，以镜质体反射率（）为约束，用BasinMod盆地数值模拟技术重建了该区热流史及龙马溪组有机质热演化史。研究结果表明，川南地区龙马溪组储层沥青激光拉曼镜质体反射率（）为2.7 % ~ 3.9 %，有机质现均已到过成熟阶段，平面上从威远—泸州—长宁区块成熟度逐渐增加。加里东期大部分有机质尚未进入生烃门限。东吴期—印支期威远北部及渝西北部有机质处于低成熟-成熟阶段，同期长宁—宁西及泸州南部有机质分别进入高成熟和过成熟阶段。燕山期川南龙马溪组有机质普遍达到过成熟阶段。川南地区龙马溪组有机质热演化受古地貌、古埋深、峨眉山玄武岩喷发及构造隆升等地质因素的共同影响，其中古埋深及峨眉山玄武岩喷发是有机质热演化最主要的控制因素。

This study aims to investigate the thermal evolution characteristics of organic matter in the Lower Silurian Longmaxi Formation， southern Sichuan Basin. Data from wells， lithology， and temperature experiments is applied to examine the present-day geothermal field characteristics； Laser-excited Raman spectroscopy is employed to measure and calculate the vitrinite reflectance （） of organic matter in shales in the Longmaxi Formation. Using as a constraint and the BasinMod technique for numerical simulations of basins， we reconstruct both the heat flow history in the southern Sichuan Basin and the thermal evolution history of organic matter in the Longmaxi Formation within the basin. The results show that the bitumen in the reservoirs of the Longmaxi Formation in the southern Sichuan Basin exhibits values varying from 2.7 % to 3.9 %， indicating the presence of overmature organic matter， with the maturity increasing gradually from the Weiyuan to Luzhou and then to Changning blocks. During the Caledonian， most organic matter was yet to reach the hydrocarbon generation threshold. From the Dongwu to the Indosinian orogenies， the organic matter in the northern Weiyuan and northwestern Chongqing areas featured low to medium maturity， while that in the Changning-Ningxi blocks and the southern Luzhou block was highly mature and overmature， respectively. During the Yanshanian movement， the organic matter in the Longmaxi Formation in the southern Sichuan Basin was generally overmature. The thermal evolution of organic matter in the Longmaxi Formation in the southern Sichuan Basin is jointly affected by several geological factors such as paleogeomorphology， paleo-burial depth， eruption of the Emeishan Basalt， and tectonic uplifting. Of these， the paleo-burial depth and eruption of the Emeishan Basalt are identified as the primary factors.

10.11743/ogg20240509