打开文本图片集

摘 要：泥页岩的热演化是其在不同地质时期的成熟度状态，对油气藏的勘探开发与油气资源评价都具有重要意义。泥页岩的热演化主要受时间与温度的控制，其中又以温度为主。利用等效镜质体反射率与磷灰石裂变径迹古温标数据重建川东地区热史，分析川东地区下志留统龙马溪组热演化史，讨论热演化与页岩气的关系。结果表明：川东地区晚元古代—晚古生代热状态稳定，热流较低（45～50 mW·m-2），于海西期开始热流逐渐升高，晚二叠世（250 Ma左右）达到最高值（60～80 mW·m-2），随后热流持续降低直至现今（45～65 mW·m-2）；龙马溪组成熟度演化与生烃过程呈阶段性，存在两次快速成熟，分别对应海西期东吴运动地壳拉张与晚三叠世以来的地层快速埋深；龙马溪组于晚白垩世（约80 Ma）达到最高热演化程度，随后开始遭受抬升降温，生烃作用停止；泥页岩热演化与页岩气密切相关，龙马溪组页岩气成藏可划分为生物气阶段（250～430 Ma）、热解气阶段（80～250 Ma）与抬升改造阶段（0～80 Ma），经历快速成熟演化保证了充足的气量并促进了储集空间的形成，后期快速抬升降温改善了泥页岩储集性能，有利于页岩气的保存。

关键词：热演化；地温场；镜质体反射率；磷灰石裂变径迹；页岩气；下志留统；龙马溪组；四川盆地

中图分类号：P618.130.2 文献标志码：A

Thermal Evolution of Lower Silurian Longmaxi Formation

in the Eastern Sichuan Basin

CAO Huan-yu1，2， ZHU Chuan-qing1， QIU Nan-sheng1

（1. State Key Laboratory of Petroleum Resources and Prospecting， China University of Petroleum，

Beijing 102249， China； 2. Exploration Company of SINOPEC， Chengdu 610041， Sichuan， China）

Abstract： Thermal evolution of shale， which is the maturity stage in different geological times， has great importance in hydrocarbon exploration and development as well as hydrocarbon resource assessment. Thermal evolution of shale is mostly controlled by time and temperature， and especially by temperature. The thermal history in the eastern Sichuan Basin was reconstructed by geothermometer data of equivalent vitrinite reflectance and apatite fission track； the thermal evolution history of Lower Silurian Longmaxi Formation in the eastern Sichuan Basin was analyzed； the relationship between thermal evolution of shale and shale gas accumulation was discussed. The results show that the thermal state is stable from Late Proterozoic to Late Paleozoic in the eastern Sichuan Basin， and the heat flow is low （45-50 mW·m-2）； the heat flow begins to increase during Hercynian， and reaches the peak （60-80 mW·m-2） in Late Permian （about 250 Ma）， and then persistently decreases to the present value （45-65 mW·m-2）； the maturity evolution and hydrocarbon generation process of Longmaxi Formation have two rapid maturation stages， including the crust extension of Dongwu movement in Hercynian and rapid bury of stratum since Late Triassic； the thermal evolution of Longmaxi Formation reaches the peak in Late Cretaceous （about 80 Ma）， and the following intensive uplift and cooling lead to the termination of hydrocarbon generation； the thermal evolution has close relationship with shale gas accumulation， which can be divided into biogenic gas stage （250-430 Ma）， pyrolysis gas stage （80-250 Ma） and uplifting and reforming stage （0-80 Ma） in Longmaxi Formation； rapid maturation and hydrocarbon generation provide the abundance of gas， and accelerate the formation of reservoir space， and the following rapid uplift and cooling improve the reservoir property of shale， and are advantageous for the preservation of shale gas.