The Wufeng-Longmaxi (WL) shale is widely distributed in the Sichuan Basin and adjacent areas in southwest China. The basin experienced multiple-stage complex tectonic movements, whose influences on burial, thermal maturation and gas generation histories in different areas are poorly understood. Based on a detailed study of the denudation stages, strata thickness, and thermal history of the basin, burial and thermal maturation histories of seven wells in different areas were modelled using PetroMod software. Due to the high maturity of the WL shale, a low-maturity Silurian Polish Llandovery shale was used for gold tube closed-system pyrolysis experiments to obtain kinetic parameters for evaluating methane generation history. The Polish shale was selected due to its depositional age, sedimentary environment and organic type, which are similar to the WL shale. The burial history of the WL shale can be divided into five stages: I. Early to Middle Silurian rapid burial; II. Caledonian uplift and denudation; III. Permian to Triassic sustained burial and denudation; IV. sustained burial since the Late Triassic; and V. Late Cretaceous to present sustained uplift and denudation. The thermal maturity of the WL shale in all wells increased with burial depth during stage IV. In addition, high calculated reflectance increments in wells JY1 and N201 during stage III occurred due to the relatively high basal heat flow and deep burial depth, resulting in higher current thermal maturities than in the other wells. The late Permian–Early Triassic and the Middle Jurassic–Early (or Late) Cretaceous were the key methane generation periods for wells JY1 and N201. In contrast, the other five wells had a single methane generation stage, mainly determined by burial and thermal maturation processes. The time of uplift and the amount of denudation during stage V, the current burial depth, the development of faults and fractures, high proportion of retention and the seal capacity of the overlying caprock are key factors for shale gas preservation. Hence, this study will help guide future shale gas development in the Sichuan Basin.

中文翻译：

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构造演化过程对四川盆地及邻近地区五峰-龙马溪页岩埋藏、热成熟及产气历史的影响


五峰-龙马溪 （WL） 页岩广泛分布于四川盆地及西南邻近地区。该盆地经历了多阶段的复杂构造运动，其对不同地区的埋藏、热成熟和气体生成历史的影响知之甚少。基于对盆地剥蚀阶段、地层厚度和热历史的详细研究，使用 PetroMod 软件对不同区域的 7 口井的埋藏和热成熟历史进行了建模。由于 WL 页岩的高成熟度，低成熟度的志留纪波兰 Llandovery 页岩被用于金管闭式系统热解实验，以获得用于评估甲烷生成历史的动力学参数。选择波兰页岩是因为其沉积年龄、沉积环境和有机类型，与 WL 页岩相似。WL 页岩的埋藏历史可分为五个阶段： I.志留纪早期至中期快速埋葬;II. 喀里多尼亚隆起和剥蚀;III. 二叠纪至三叠纪持续埋藏和剥蚀;IV. 自晚三叠世以来的持续埋葬;和 V. 晚白垩世呈现持续的隆起和剥蚀。在 IV 阶段，所有井中 WL 页岩的热成熟度都随着埋藏深度的增加而增加。此外，由于相对较高的基底热流和较深的埋藏深度，在 III 阶段，JY1 和 N201 井的计算反射率增量很高，导致当前热成熟度高于其他井。二叠世晚期至早三叠世和中侏罗世至早（或晚）白垩世是 JY1 和 N201 井的关键甲烷生成时期。 相比之下，其他 5 口井只有一个甲烷生成阶段，主要由埋藏和热成熟过程决定。V 期的隆起时间和剥蚀量、当前埋藏深度、断层和裂缝的发育、高比例的保留以及上覆盖层岩的密封能力是页岩气保存的关键因素。因此，本研究将有助于指导四川盆地未来的页岩气开发。