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为查明四川盆地龙马溪组页岩储层孔隙控制因素及演化规律,利用场发射扫描电子显微镜和氮气吸附实验等方法对页岩储层孔隙类型及孔隙结构进行研究。页岩储层孔隙类型包括有机孔、晶间孔、晶内溶孔和粒间孔,有机孔是主要孔隙类型之一,且有机孔中微孔所占的孔体积和比表面积大,是页岩气储集的主要空间。通过对有机质丰度(TOC)、有机质成熟度(Ro)、成岩作用和构造作用对页岩孔隙度的影响研究,结果表明:1有机质丰度对孔隙度的影响可以分为4个阶段:快速增大(TOC为0%~2%)、缓慢减小(TOC为2%~3%)、快速增大(TOC为3%~4%或6%)、快速减小(TOC>4%或6%);2四川盆地页岩成熟度对孔隙度的影响可分为3个阶段:快速减小(Ro为1.5%~2.2%)、快速增大(Ro为2.2%~2.7%)、快速减小(Ro>2.7%);3高热演化阶段有机成岩作用强于无机成岩作用;4构造作用对孔隙度影响较大,构造作用越强烈的区域孔隙度越小。四川盆地龙马溪组页岩孔隙度演化经历5个阶段:未熟快速压实阶段(Ro<0.7%)、成熟生烃溶蚀阶段(Ro为0.7%~1.3%)、高成熟孔隙封闭阶段(Ro为1.3%~2.2%)、过成熟二次裂解阶段(Ro为2.2%~2.7%)、过成熟缓慢压实阶段(Ro>2.7%),其中成熟生烃溶蚀阶段和过成熟二次裂解阶段是最有利的页岩孔隙发育阶段。
In order to find out the controlling factors and evolution rules of the pores in the Longmaxi Formation shale reservoirs in Sichuan Basin, the pore types and pore structure of the shale reservoirs were studied by field emission scanning electron microscopy and nitrogen adsorption experiments. The types of pores in shale reservoirs include organic pores, intergranular pores, intragranular dissolved pores and intergranular pores. Organic pores are one of the major pore types, and the pore volume and specific surface area occupied by pores in organic pores are large The main space for rock gas storage. The effects of organic matter abundance (TOC), organic matter maturity (Ro), diagenesis and tectonism on shale porosity were studied. The results show that: 1 The influence of organic matter abundance on porosity can be divided into four stages: rapid (TOC = 0% ~ 2%), slow decrease (TOC = 2% ~ 3%), rapid increase 6%). 2 The influence of shale maturity on porosity in the Sichuan Basin can be divided into three stages: rapid decrease (Ro 1.5% -2.2%), rapid increase (Ro 2.2% -2.7%), rapid (Ro> 2.7%). (3) The organic diagenesis is stronger than the inorganic diagenesis in the stage of high thermal evolution. (4) The tectonism has a great influence on the porosity, and the stronger the structural tectonics is, the smaller the porosity is. The porosity evolution of the Longmaxi Formation shale in Sichuan Basin experienced five stages: the immature rapid compaction stage (Ro <0.7%), mature hydrocarbon dissolution stage (Ro = 0.7% ~ 1.3%), and the stage of high mature pore closure 1.3% ~ 2.2%), over mature stage (2.2% ~ 2.7% Ro), slow compaction stage (Ro> 2.7%), mature stage of hydrocarbon generation and dissolution and over ripe stage The most favorable shale pore development stage.