Affect Magma Intrusion On Shale Reservoir Characteristics And Shale Gas Accumulation In Xuancheng Area

High temperature,high-pressure and hydrothermal fluid by magmatism impact rock fabric,and control the reservoir physical properties and the organic matter structure characteristics,finally they control the evolution of hydrocarbon generation and enrichment mechanism of the reservoir,which lead to shale reservoir maintain special under the influence of magmatism,the particularity increases uncertainty of shale gas exploration at the magma intrusion frequent area.In this paper,laser Raman spectra,Fourier infrared spectrum,X-ray diffraction spectrum,total organic carbon content determination,reflectivity measurement,X-ray diffraction,optical microscope,high resolution scanning electron microscopy,atomic force microscopy,high-pressure mercury injection experiment,low temperature liquid nitrogen adsorption at and CO₂adsorption experiments were used as research tools,under the influence of magmatism,Gufeng formation of Permian was utilized as the research object at the Liqiao area of Xuancheng of the Yangtze,we could study the shale of organic chemical and crystal structure and its evolution law,physical characteristics and evolution mechanism under magmatism,and analysis the impact of magmatism on the shale reservoirs and shale gas accumulation.The vitrinite reflectance and total organic carbon content decrease with the decrease of the distance between the intruder and the magma.Laser Raman spectrum parameters(Intensity,Raman peak shift and Peak height half height width,R1,R2 and R3)appear jump,the range of jump 283.84?294.7?(2.80%to 3.05%)is the temperature response threshold range of the organic structure appeared saltation,suffered from the influence of magmatism of organic matter is given priority to with the amorphous carbon structure,its structure disorder first decreases increased,which controlled by degree of condensation,stacking height and each average aromatic carbon crystallite layers,after carbonization,and gradually to the direction development of graphite.Temperature and supercritical CO₂ fluid control structure evolution of organic matter,they lead to CH₃/CH₂,aromaticity and degree of condensation decreased with increasing the degree of thermal evolution,A and C factor decrease.Their evolution law show that aromatic carbon and degree of condensation is reduced,aliphatic chain length,aliphatic carbon and the oxygen containing functional groups increases,organic matter evolution path including low and high temperature phase,and in turn removal oxygen containing functional group and aliphatic functional groups.the closed system in high temperature and high-pressure and the catalytic action of metal ions caused the horizontal stack size,stacking height and average each average aromatic carbon crystallite layers of kerogen increase when they close to the intrusion,but the layer spacing is reduced,and the kerogen crystal diffraction peak structure evolution show that the crystal structure of ordered degree and metamorphic grade increase in the near intrusion.Affected by magma abnormal heat,the closer the intrusion,the higher the content of quartz,the lower the content of clay minerals content,appear augite and anatase metamorphic minerals,reservoir compaction,the reduction of clay minerals and organic matter content,hydrothermal precipitation and thermal decomposition and dissolution of carbonate mineral cause the pore volume reduce when it closed the intrusion,and the evolution of the chemical and crystal structure of kerogen,clay minerals and organic matter content decrease results in the decrease of specific surface area,and average pore diameter increases,the closer to the intrusive body,the pore type changes from small pore to large pore,and the micropore almost disappears,and the complexity and heterogeneity of pore structure are reduced.For the micropore structure,the length of aliphatic chain,stacking height,average number of aromatic layers and layer spacing of each carbon microcrystal controlled the pore structure of mesoporous and micropores,the temperature range between 295.61?and 305.24?was the temperature response threshold range that controlled the evolution of pore structure.When magma intrudes into the formation,extrusion stress leads to the development of small oblique fractures,pore fluid pressure leads to the development of vertical fractures,magma cooling contraction leads to the development of bedding fractures.Although the preservation conditions of the Gufeng Formation in the contact metamorphic halo are poor,the preservation conditions in the basin scale are good.Magmatism controls the accumulation and enrichment mechanism of shale gas by controlling the microscopic physical properties of reservoirs.Therefore,the enrichment mechanism of shale gas reservoirs affected by magmatism is"hydrocarbon generation in situ,migration in short distance,and accumulation in different places".Within the contact metamorphism because of the organic matter hydrocarbon generation ability,total pore volume and porosity,specific surface area and micropore decreases,and thus the closer the intrusive body is,the more unfavorable the shale gas enrichment is,but on basin scale,due to the wide range of contact metamorphism and the bedrock of plugging effect,this led to a huge amount of hydrocarbon generation,the sill effectively prevents the escape of shale gas,so the"sill intrusion pattern"is good for shale gas enrichment and accumulation,and the"dike intrusion pattern"and"laccolith intrusion pattern"are inverse.The determination of chemistry and crystal structure evolution of organic matter and microscopic physical properties and evolution mechanism provides a theoretical basis for the generation and enrichment of shale gas in the magmatic thermal anomaly shale reservoir.This thesis has 48 figures,12 tables,212 References.