岩石热声发射和盆模技术研究中扬子区西部下古生界海相页岩最高古地温和热成熟史

中扬子地区西部下古生界海相页岩热演化程度高，有机显微组分中无镜质组，沥青反射率具有不确定性，故热成熟度较难确定。综合运用岩石热声发射实验与干酪根红外光谱，并结合盆地模拟技术对中扬子地区西部典型井下古生界海相页岩经历的最高古温度及热演化成熟史进行了恢复。样品的热声发射信号随温度的升高变化显著，热凯瑟尔（Kaiser）效应明显；下寒武统水井沱组经历的最高古温度范围为293~324℃，上奥陶统五峰组-下志留统龙马溪组为210~256℃。同时利用二次加温验证热Kaiser效应敏感，表明热声发射技术可用于岩石经历的最高古地温的测定。在对典型井的下古生界海相页岩热演化成熟史模拟中结合最高古温度作为约束条件所得结果表明，模拟计算的下寒武统水井沱组和上奥陶统五峰组-下志留统龙马溪组镜质体反射率分别为4.0% ~4.5% 和2.6% ~3.2% ，处于高演化过成熟阶段，与干酪根红外光谱分析得出的有机质成熟度结果一致。

Rock thermo-acoustic emission and basin modeling technologies applied to the study of maximum paleotemperatures and thermal maturity histories of Lower Paleozoic marine shales in the western middle Yangtze area

Shales of Lower Paleozoic marine strata in the western middle Yangtze area are considered to be of a high degree of thermal evolution. It is, however, very difficult to accurately determine their thermal maturities (vitrinite reflectance, R_o) due to the lack of vitrinite in organic macerals in marine shales of these Lower Paleozoic formations. The objective of the present study is to restore the maximum paleogeotemperature experienced by these shales and then to reconstruct their thermal evolutionary histories using the basin modeling technology with the data obtained from thermo-acoustic emission experiments and kerogen FTIR (Fourier transform infrared spectroscopy) analysis. The results of thermo-acoustic emission experiments illustrated that Lower Paleozoic marine shales have a good thermal Kaiser effect and the rock thermo-acoustic emission signal varies with geotemperatures remarkably. For instance, the maximum paleogeotemperature experienced by the Lower Cambrian Shuijingtuo Formation ranges from 293℃ to 324℃, while the maximum paleogeotemperature of the Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation ranges from 210℃ to 256℃. Furthermore, the sensitivity of the thermal Kaiser effect was tested by reheating experiments, which suggested that the thermo-acoustic emission could be applied to the measurement of maximum paleogeotemperatures experienced by marine shales. Considering the measured maximum paleotemperature as a constraint, in typical well simulation of the thermal maturity modeling of Lower Paleozoic marine shales, the calculation results of the thermal maturity modeling demonstrated that the simulated values of vitrinite reflectance (R_o) for the Lower Cambrian and Upper Ordovician-Lower Silurian marine shales range from 4.0% to 4.5% and 2.6% to 3.2%, respectively. Therefore, the organic matter maturities of marine shales in the Lower Cambrian Shuijingtuo Formation, Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation are all in a high-maturity to overmature stage of thermal evolution, which is consistent with the data obtained from the kerogen FTIR analysis of the Lower Paleozoic marine formations.