精细热年代学约束的页岩气藏差异隆升动态过程与保存关系研究

Shale gas is the key and hot point for petroleum exploration and development in China. Compared with North America, the typical shale gas reservoirs found in the Middle-Upper Yangtze regions, all have experienced the strong tectonic superposition and transformation twice, which happened during the Mesozoic-Cenozoic period, but the dynamic uplift processes of the study area during these period, the pressure evolution processes of shale gas reservoirs and the shale gas diffusion and preservation during these strong tectonic superposition and transformation events are relatively less concerned. In this project, we will take the shale gas reservoirs developed in the Ordovician Wufeng Formatiom-Silurian Longmaxi Formation found in the Middle-Upper Yangtze regions in the south of China as the study objects. Firstly, by systematic fine thermochronology analysis, we will reconstruct the dynamic process of tectonic uplift, denudation and paleo-temperature evolution of these typical shale gas reservoirs experienced during the Mesozoic-Cenozoic period. Then, combined with fluid inclusion analysis and basin modeling, reconstruct the paleo-pressure of the gas reservoirs happened in the key tectonic period. Based on the results of tectonic uplift process and paleo-pressure, comprehensive analysis of Multi factors include the characteristics of shale gas reservoir, the change of confining pressure, the paleo temperature evolution and the characteristics the roof and floor of the shale gas reservoir, we will try to reveal reconstruct the paleo-pressure evolution history and reveal the mechanism of shale gas preservation during the tectonic uplift process during the Mesozoic-Cenozoic period. Finally, we will try to establish a new comprehensive evaluation system for shale gas preservation, which is based on the dynamic process of tectonic uplift and take the pressure evolution as the main line; then use this new comprehensive evaluation system to serve shale gas exploration and development.

页岩气是目前我国油气勘探开发的重点和热点领域。与北美相比，中上扬子地区典型页岩气藏都经历过中-新生代两期强烈的构造叠加改造，而目前对已知页岩气藏中-新生代构造隆升动态过程、构造叠加改造过程中页岩气藏压力演化过程及该过程中页岩气扩散与保存的研究相对较少。本项申请，拟以我国南方中上扬子奥陶系五峰组-志留系龙马溪组页岩气藏为研究对象，首先通过系统的精细热年代学定年研究，重建典型页岩气藏中-新生代构造隆升-地层剥蚀-古地温演化动态过程。然后利用流体包裹体和盆地模拟等手段，恢复页岩气藏关键构造期古地层压力。在此基础上，综合页岩气储层特性、围压变化、古地温演化、顶底板等因素，重建中-新生代构造隆升过程中页岩气藏地层压力演化过程并揭示页岩气保存机理，建立以精细热年代学约束的构造隆升动态过程为基础、页岩气压力演化为主线的页岩气保存条件综合评价体系，进而开展页岩气保存条件综合评价，服务于页岩气勘探开发研究。

在大量的热年代学、流体包裹体和盆地模拟分析，明确了川东地区不同构造单元包括宜昌斜坡地区、湘鄂西地区、利川-石柱地区及川东地区中新生代构造-热演化差异对比，宜昌斜坡地区抬升时间不晚于介于早-中侏罗纪（~178Ma）之间，湘鄂西地区不抬升开始最晚不晚于145Ma，利川石柱在130-100Ma之间，而川东地区最晚、整体在~100-80Ma之间，重点对比了不同地区中新生代构造-热演化差异。重点对比了川东地区焦石坝地区五峰-龙马溪组超压页岩气藏、川东地区彭水地区五峰-龙马溪组常压页岩气藏及宜昌斜坡寒武系牛蹄塘组常压页岩气藏关键构造古压力、明确该三个典型页岩气藏成藏过程的差异性，建立页岩气藏古压力演化过程；在压力演化研究的基础上，建立中新生代构造抬升改造过程中典型页岩气藏抬升过程压力衰减-天然气散失的动态过程，进一步明确川东典型页岩气藏压力演化-页岩气保存的控制因素。.