| The Lower Silurian Long Ma Xi formation in South Sichuan has developed a set of organic shale,which has favorable geological conditions for shale gas accumulation and has been commercialized.Based on field geological survey and regional geological data,the relationship between shale gas development and shale gas accumulation in the shale of Long Ma Creek formation in southern Sichuan is deeply explored in combination with XRD,optical microscopy,low temperature liquid nitrogen and mercury pressure testing.Results the geochemical index showed five peaks group and the lower part of Longmaxi shale sedimentary environment for deep-water shelf facies,Shallow water and shallow water shelf facies.The mineral composition of shale samples is mainly composed of quartz and clay,and the content of brittle minerals is high.The clay minerals are mainly mixed with illite and illite.The content of organic matter in shale can reach more than 4%,The type of kerogen is mainly I type,Part II is type 1,and vitrinite reflectance is 2.37%~3.43%,which is over mature stage,and the main source is dry and dry gas.In the graptolite fossil rich shale,graptolite evolution mainly includes five aspects: Graptolite simplification,the change of growth direction,the change of cell wall and tube change and change the mode of development.The main peak is five divided graptolite zone group four graptolite zones,longmaxi group has nine graptolite zones,the statistics on the abundance of graptolite shale,Law of vertical change for graptolite abundance is not obvious,the five peak group of middle and bottom Longmaxi graptolite high abundance.Shale is mainly composed of organic matter pores,intergranular pores,intragranular pores and bedding joints.Its pore structure is complex,and there are many kinds of pores,such as water bottle hole,plate hole,open hole and ink bottle hole.The pore volume contributes to the volume of the total pore of the shale at all stages,Specific surface area is mainly contributed by micropore and mesoporous.The bedding surface is usually weak in mechanical properties.It is easy to peel off and form bedding joints and horizontal laminae.The development of horizontal bedding fractures leads to higher permeability of shale in horizontal direction.The calcareous stone is mainly stored in shale in three ways: flattened carbonaceous film,semi-solid to three-dimensional pyrite and solid or semi-solid specimen.The study area five peak and bottom Longmaxi graptolite mainly in the first way to save,save the pyritization way the upper part by semi solid to solid graptolite Longmaxi group.The correlation between shale organic carbon content and the Richstone content is not obvious,indicating that organic carbon content is affected by many factors.But the main way to graptolite carbonaceous film flattening preservation,pyrolysis and pyrolysis gas chromatography analysis showed that the main components of graptolite organic carbon,respectively 42.93% and 71.34%,the graptolite has made a significant contribution to the total organic carbon content.There are a large number of graptolite fossils in shale,developing a large number of bedding,the permeability of shale is obviously inhomogeneity,the difference of vertical and horizontal permeability is great.parallel permeability is several times to several hundred times of vertical permeability.In parallel direction observation development of nano pore distribution along more slender periderm and micro cracks in the graptolite.The pores are mainly composed of nanoscale pores,vertical bedding direction,Lead to more development of graptolite bedding fissure.The nano pores and the micro cracks and graptolite bedding fractures formed a main channel.At the same time,as a main channel,the stone is also connected with the discrete organic matter in shale,forming a connected organic pore system in shale. |
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