川中地区须家河组温压场演化规律及其对致密气成藏的影响

The Xujiahe Formation in the Central Sichuan Basin is one of the most important areas of tight sandstone gas exploration in China. However, the distinct heterogeneity in reservoirs and complex accumulation processes result in explorations are very low efficient. Preliminary studies suggest the evolution of temperature and pressure in the the Xujiahe sandstones are very complex, which seriously restricts understanding of the hydrocarbon accumulation in the tight reservoirs. Hence, we attempt to reconstruct the paleo-temperature and paleo-pressure, and then study their impact on the tight gas reservoirs. The main research works include: 1) temperature and pressure reconstruction. We utilize Raman spectra analysis and molten capillary silicon tubes experiments to determine the inner pressure of fluid inclusions. Multiple thermometers, and fluid inclusion analysis combined with numerical simulation were used to reconstruct the paleo-temperature and paleo-pressure, respectively. 2) Diagenesis and hydrocarbon accumulation processes analyses. Petrography and geochemical analyses are carried out to reveal the mechanisms of water-rock interactions in tight sandstone reservoirs, and determine the relation between reservoir evolution and hydrocarbon accumulation. 3) By comparing the temperatures and pressures, diagenetic characteristics and hydrocarbon accumulation processes among different gas reservoirs, we attempt to conclude the impacts of temperature and pressure on the Xujiahe tight sandstone reservoirs. The project will be capable of producing original achievements because the idea and design are innovative and the applicant has excellent research experiences.

川中地区须家河组是我国最主要的致密气勘探领域之一，但其非均质性显著，成藏规律不明，勘探效率低。初步研究发现，须家河组温压场复杂的时空演化是制约致密气勘探的重要因素。因此，本课题从恢复温压场演化入手，深入剖析温度、压力对致密砂岩气成藏过程的影响。具体研究工作包括：1)古温压恢复。开展流体包裹体激光拉曼光谱分析，结合熔融毛细硅管实验，恢复包裹体内压；通过多种古温标参数、流体包裹体分析与盆地数值模拟相结合分别恢复致密气藏的温度和压力的演化过程。2)储层成岩和油气成藏过程分析。揭示储层致密化过程中水-岩反应机理，建立储层成岩与油气成藏的耦合关系。3)对比研究典型气藏的温压演化和成藏过程，确定温压场对致密砂岩气藏的作用。本课题在思路与理念上具有一定的创新性，申请人具有良好的研究积累，具备取得一些创新成果的基本条件。

川中地区须家河组是我国最主要的致密气勘探领域之一，但其非均质性显著，成藏规律不明，勘探效率低。本项目系统揭示了须家河组现今温压场特征和超压成因机制；利用流体包裹体激光拉曼分析技术和数值模拟手段恢复了地层压力演化过程；发现了致密砂岩储层中成岩相的分布规律和优质储层的发育模式。取得的如下主要成果认识：1）川中地区大地热流（60~70mW/m2)和地温梯度(24~30℃/km)都高于盆地周缘地区，须家河组发育异常高压，压力系数为1.2~1.9，向盆地西北方向逐渐增强；2）须家河组超压受欠压实作用和生烃作用共同控制，其先后经历了增压-降压过程；3）致密砂体中成岩相在垂向上对称分布，地球化学分析表明流体-岩石相互作用导致物质重新分配，在砂体中部形成优质储层段。本项目取得的研究成果对四川盆地油气勘探开发具有重要作用，对全球其它盆地致密气研究都有参考价值。