非常规油气致密储集层微观结构研究进展*

致密储集层储集性能差, 孔喉以纳米级为主, 孔喉连通复杂。中国南方高过成熟海相页岩有机质纳米孔与粒内孔大小约为20～890 nm；陆相泥页岩孔喉类型为有机质孔与基质孔, 主体介于30～200 nm之间；致密砂岩微米级孔喉为粒间溶孔、颗粒溶蚀孔与微裂缝, 主体介于10～200μm之间, 纳米级孔隙大小介于70～400 nm之间, 以原生粒间孔与自生矿物晶间孔为主；致密灰岩孔喉类型有方解石粒内溶孔、粒间溶孔与微裂缝, 大小介于50～500 nm之间。页岩微孔喉总体随热演化程度增高呈先减少后增加趋势, 致密含油砂岩中油气赋存有4种状态, 粒间微孔为油气赋存最有利位置。针对非常规油气储集层独特特征, 仍需在仪器研发、技术方法与评价参数等方面加强研究探索。

Research advances of microstructure in unconventional tight oil and gas reservoirs

Nano-pores dominate the storage space of tight reservoirs and the connectivity of pore throat system is complex. The diameter of organic matter pores and intra-particle pores in marine shale with high maturity of southern China are 20～890 nm. The pores in terrestrial shale are organic matter pores and matrix pores, with diameter between 30～200 nm. The storage space in tight sandstone includes dissolution pores and micro-fractures with diameter in 10～200 μm. Nano-pores are composed by inter-particle pores and inter-crystal pores with diameter 70～400 nm. The calcite dissolution pores, inter-particle dissolution pores and micro-fractures dominate the nano-pores in tight limestones and the diameter is 50～500 nm. Reservoir digenetic modeling data indicates that total porosity in shale increases firstly and decreased later with the increase of|temperature and pressure. Four occurrences of oil in nano-pores have been distinguished and inter-particle pores are the most favorable for the oil accumulation. Moreover, due to the special characteristics of unconventional oil and gas, further work should be focused on the instrument improvement, technology innovation and evaluation parameter optimization.