摘要
Nanostructure morphology of shale reservoirs was investigated using a field-emission environmental scanning electron microscope and adsorption-desorption isotherms were measured with low-temperature nitrogen adsorption experiments.Combined with high-pressure mercury injection,further investigation into characterization of pore structures in shale reservoirs was gained.Results show that pores in shale reservoirs are generally in a nanometer grade,it can be classified into five types: organic nanopores,interparticle pores between clay minerals,mineral pores in rock skeletons,apertures in palaeontologic fossils and microfractures,of which the most common ones are organic nanopores and interparticle pores between clay minerals.The pore-size distribution of shales are complex,which includes not only predominant mesopores(2~50 nm),but also a certain amount of micropores(<2 nm) and macropores(>50 nm).Micropores and mesopores with a diameter less than 50 nm amount to most of specific surface area and pore volume of shale pores,and mainly are places for gas adsorption and storage.Shale is characterized by high threshold pressure,good-sorting pore throats,poor connectivity and low efficiency of mercury withdrawal.In addition,mesopores in shale apparently contribute a lot to gas percolation,while micropores in shale are mainly for gas storage.