Based on low-temperature thermochronological data (i.e., apatite fission-track (AFT) and (U–Th)/He (AHe)), structural evolution, burial and thermal history, this paper examines the relationship of multi-stage evolution between the upper Ordovician Wufeng and lower Silurian Longmaxi formations (i.e., the WL formation) and rapid exhumation at the Changning shale gas field in the southern Sichuan basin. AFT ages are generally young from southeast to northwest, decreasing from ca. 40 to 15 Ma while AHe single-grain ages range from ~35 to ~5 Ma. Inverse thermal histories show that a multi-stage cooling history with initial cooling began in the Late Cretaceous to early Cenozoic (middle Eocene), followed by accelerated rapid cooling in the late Cenozoic, with cooling rates of 2–4 °C/Myr across the Changning shale gas field. In particular, thermal models of samples in the western Changning area show a substantial increase in the cooling rates, i.e., from less than 1 °C/Myr to 3–5 °C/Myr in the Miocene. Integrated with inverse T-t models of low-temperature thermochronological data, the burial history indicates a four-stage thermal evolution of the WL Formation in the Changning shale-gas field: Early Mature from the middle Silurian to middle Permian, Middle Mature from the late Permian to Late Triassic, Late Mature from the Early Jurassic to Early Cretaceous, and Over mature since the middle Cretaceous, reaching a maximum burial depth of ~6000 m and maximum temperature of 190–200 °C at ca. 70–80 Ma. This evolution further suggests that a normal hydrostatic pressure index dominated the WL Formations in the Paleozoic. The gas generation and pressure index, however, have substantially increased since the Late Jurassic, particularly from the Early to middle Cretaceous, with a maximum pressure index of 2.1, which is indicative of the main shale gas accumulation and enrichment period in the WL Formation. Post-gas-generation structural deformation, uplift, and exhumation had a significant impact on shale gas enrichment, mainly through their influence on shale gas preservation. This suggests some relationships among the higher pressure coefficient of the WL Formation, the higher productivity and total gas content of the WL Formation, a weaker post-gas-generation structural deformation, and a weaker uplift, as indicated by the erosion and burial depth across the Changning shale gas field. Due to a significantly stronger cooling and uplift that occurred the in Late Cenozoic across the western Changning area, the pressure index decreased rapidly from ~2.0 to 1.0 with a normal pressure condition, indicating the destruction of the reservation condition in the WL Formation.

基于低温热年代学数据（即，磷灰石裂变径迹（AFT）和（U–Th）/ He（AHe）），结构演化，埋藏和热历史，本文研究了多级演化之间的关系。四川盆地南部长宁页岩气田的上奥陶统五峰组和下志留统龙马溪组（即WL组）和快速发掘。从东南到西北，AFT年龄一般都比较年轻，从大约 40至15 Ma，而AHe单粒年龄为〜35至〜5 Ma。逆向热史显示，从白垩纪晚期到新生代早期（中始新世）开始了多级冷却历史，包括最初的冷却，随后在新生代晚期加速了快速冷却，整个期间的冷却速率为2-4°C / Myr。长宁页岩气田。特别是，长宁西部地区的样本热模型显示，中新世的冷却速率显着提高，即从低于1°C / Myr升至3–5°C / Myr。与低温热年代学数据的逆Tt模型相结合，其埋藏历史表明长宁页岩气田WL组有四个阶段的热演化：中志留统至中二叠统早熟，二叠纪晚期为中熟期到三叠纪晚期，早侏罗纪至白垩纪晚期成熟，以及自白垩纪中期以来的超成熟，大约在1976年达到最大埋藏深度〜6000 m和最高温度190-200°C。70–80马。这种演变进一步表明，正常的静水压力指数主导了古生代的WL层。但是，气体的产生和压力指数 自侏罗纪晚期以来，特别是早白垩纪至中白垩世以来，其最大压力指数为2.1，这表明在页岩层中主要页岩气的富集和富集期显着增加。瓦斯产生后的构造变形，隆升和放化对页岩气富集有重大影响，主要是通过影响页岩气的保存。这表明WL地层的较高压力系数，WL地层的较高生产率和总含气量，较弱的生气后构造变形和较弱的隆起之间存在某些关系，如横跨整个盆地的侵蚀和埋藏深度所表明的那样长宁页岩气田。由于长宁西部地区晚新生代发生的降温和隆升作用明显增强，