Microscopic Characterization Of Reservoir Pores In High Maturity Gas Shale

The degree of maturity in the West of Zhejiang province is generally higher.Allkinds of features are complexby the impact of tectonic-sedimentation.The samples collected in the field are studied in organic geochemistry characteristics,rock characteristics,physicalcharacteristics,microscopic porouscharacteristics,adsorption capacity and other aspects in the paper.The characteristics of high maturity gas shale in the region were analyzed quantitatively and qualitativelyto determine formation mechanism and influencing factors of each characteristic and the relationship between each other.The author made the main conclusions as follows:(1)Tectonic evolution is complex and volcanic and magmatic activity is intense in the region,resulting in generally higher Ro of shale.The average Ro of the shale is 3.5%,the most are in the stage of too mture-quasi metamorphic,the main type of organic carbon can be defined as Itype,the content of TOC is high,so it is a good gas shale.(2)In high maturity gas shale in the region,the content of brittle quartz-based mineral is high,generally higher than 80%,and the main component of clay minerals are illite.Quartz content is increased with the rise of the TOC and decreased with the rise of the Ro.When TOC is less than 10%,illite content is decreased with the rise of TOC.When TOC is higher than 10%,illite content is increased with the rise of TOC.(3)Physical properties of shale in the region are low porosity and permeability.Porosityandpermeability both of which are increased with the rise of TOC.Porosity is decreased with the rise of Ro.There is a weak positive correlation between permeability and Ro.(4)Adsorbed gas content of the shale in the region is generally higher.Adsorbed gas content has some positive correlation with TOC,porosity and permeability.There is a weak correlation between adsorbed gas content and Ro:When Ro is less than 3.5%,adsorbed gas content is decreased with the rise of Ro;when Ro is higher than 3.5%,illite content is increased with the rise of Ro.(5)There are three main shale reservoirs manner:microcracks,inorganic hole(hole corrosion,intergranular pore,intragranular holes),organic hole.Diverse mineral composition like the titanium-rich organic-rich mixture is also visible.Pore morphology on the development of different mineral aggregates also have their own characteristics.Based on the above results,the pore microscopic features are for further study,using BET experiments to test various structural characteristic parameters and analyzing the morphology of the pores,pore size distribution and pore development factors.Eventually we found:shale porosity is mainly mesoporous,pores of different scales have different contributions to specific surface area and pore volume.Porosity development is affected by many factors such as TOC,Ro and mineral composition.