页岩气储层类型和特征研究——以四川盆地及其周缘下古生界为例

通过对四川盆地及其周缘下寒武统和上奥陶统—下志留统41块黑色页岩的野外观察、显微薄片、扫描电镜及X衍射等实验分析,对页岩储层特征、裂缝特征和孔隙特征等进行了研究。认为页岩气藏的储集类型主要有裂缝和孔隙2类。根据页岩气藏特征、裂缝对页岩气成藏的控制作用及裂缝的性质,按裂缝的发育规模分为巨型裂缝、大型裂缝、中型裂缝、小型裂缝和微型裂缝等5类;按孔隙类型将孔隙分为有机质(沥青)孔和/或干酪根网络、矿物质孔(矿物比表面、晶内孔、晶间孔、溶蚀孔和杂基孔隙等)以及有机质和各种矿物之间的孔隙。不同的裂缝类型、裂缝规模、孔隙类型和孔隙大小对页岩储能、产能的贡献不同,作用也不同。孔隙是页岩气藏中气体的储存空间,很大程度上决定着其储能,而裂缝是页岩气藏中气体渗流的主要通道,决定着其产能,由于页岩基质的低孔低渗性,裂缝的发育规模决定着页岩气藏的品质。 

Types and characteristics of shale gas reservoir: A case study of Lower Paleozoic in and around Sichuan Basin

Through field observation,slice,SEM and X-ray diffraction analyses of 41 black shale samples from the Lower Cambrian and the Upper Ordovician-Lower Silurian in and around the Sichuan Basin,the characteristics of reservoir,fracture and pore of shale were studied.There are mainly 2 types of shale gas reservoir: fracture and pore.According to the features of shale gas reservoir,the control of fracture on gas accumulation as well as the nature of fracture,the generation of fracture is classified into 5 degrees: giant,large,medium,small and microfracture.Pores include organic matter(bitumen) pore and/or kerogen network,mineral pores(mineral specific surface,inner,intercrystalline,corrosional and complex-based ones) as well as the pores between organic matter and minerals.Different fracture type,fracture scale,pore type and pore size have different control on shale storage and produce capacity.Pores serve room for gas storage in shale and determine storage capacity.Fractures work as pathways for gas migration in shale reservoir and determine produce capacity.Due to the low porosity and permeability of shale matrix,the generation scales of fracture control the quality of shale gas reservoir.