Pore Structure Characterization And Its Control Factors Of The Lower Cambrian Niutitang Formation Shale In Northeast Chongqing

Shale reservoir pore structure is the content of shale gas resource potential evaluation and core area evaluation,determining the shale gas occurrence state,and the size of the gas content.The Niutitang formation of Northeast Chongqing show a good exploration potential and hydrocarbon showings,but the research of shale reservoir pore structure and its control factors is less.Using field emission scanning electron microscopy and Nano-CT technology qualitatively observe pore structure characteristics,and integrating CO2 adsorption,N2 adsorption experiment and high pressure mercury injection experiment get the pore volume and specific surface area,etc.,then applying the weighted average method and pore image binarization technology to quantitatively realize Whole-Aperture pore structure characterization.Meanwhile,the basis geochemistry characteristics including TOC,R_O and mineral composition are explained,the relationship between these factors and the pore structure parameters is respectively analyzed,thus discussing the control factors of the shale pore structure.It turned out that pore structure types can be divided into inter-granular pore,intra-granular pore and organic hole in this area,among which inter-granular pore developed well;The average micro-pore volume is 0.0051cc/g,accounted for 23% of the total pore volume,meso-pore volume is 0.019 cc/g,accounted for 45%,macro-pore is about 0.023 cc/g,the rate is 43%,so meso-pores contribution to the volume is larger,followed by macro-pore,micro-pores in the end;The specific surface area of micro-pore is 15.15m~2/g,accounted for 52% of the total area,meso-pore are distributed in 14.3m~2/g,accounted for 48%,macro-pore volume is about 0.02m~2/g,closely no proportion,micro-pore provides the main specific surface area,next to the meso-pore,macro-pore has little contribution;Whole-Aperture pore structure distribution is complex,the pore size of 0.3 ~ 1 nm,1.2~ 10 nm and 100~ 1000 nm provides main pore volume,and 0.3 ~ 1nm and 1.2~ 5nm contribute the main specific surface area,these dimensions of the pore are the main place to gas adsorption and storage;Inter-granular pore diameter is mainly between 20 nm~4?m from binary images analysis,its average areal porosity is about 2.35%,intra-granular pore are distributed at 10~1000 nm,areal porosity rate is 1.364%,organic hole size is about 4~33 nm,its areal porosity rate is 0.312%.For pore development,TOC plays an absolutely dominant role,quartz is the next,and clay minerals content also has a weak role.