Coupling Effect Of Pressure,Temperature And Hydrodynamic Fields On No.3 Coal Seam And Its Influence On CBM Enrichment In AnZe Block,Southern Qinshui Basin

Based on the geological data of array acoustic logging,conventional logging,well test and hydraulic fracturing,this paper studies the buried depth and thickness of No.3 coal seam,coal petrology characteristics,coalbed methane components and gas content characteristics of Anze block by using Aquachem hydrological analysis software and Surfer,SPSS and Origin mathematical statistical analysis software.The distribution characteristics of Hydrodynamic field,in-situ stress field and temperature field in coal seam and their coupling effects on gas content in coal seam are studied and analyzed.(1)The physical properties of No.3 coal reservoir in Anze block are analyzed.The buried depth of No.3 coal seam is 555.65?1418.43m,and the average thickness is 6.77m.The macerals of coal rocks are mainly vitrinite,and the average content of inertinite is 78.86%,and the average content of inertinite is 21.11%,without exinite.The coal metamorphism is high,and the average value of R_o,max is 2.11%;The main components of coalbed methane are methane,nitrogen,and carbon dioxide,of which methane accounts for 84.05-99.45%.The gas content of coal seam is5.5?25.2 m³/t.According to the gas content value,the study area is divided into:5?10m³/t for low gas content area,11?20m³/t for medium gas content area,20?25m³/t for high gas content area.(2)The distribution characteristics of the ground hydrodynamic field in the Anze block are ascertained.Using Aquachem hydrological analysis software,it is clear that the groundwater mineralization degree of coal seam in the study block is low in the west and high in the east,and high in the northeast.The water type is mainly Na HCO₃,and the direction of water flow is consistent with the increasing direction of coal seam buried depth and salinity.According to the degree of hydrodynamic activity,the study area is divided into runoff area,transition area and retention area.(3)The distribution characteristics of in-situ stress field of No.3 coal seam in Anze block are revealed.Firstly,based on 65 sets of data from No.3 coal seam in array acoustic logging,a shear wave prediction model with fitting degree R²of 0.901 was established.Then combined with hydraulic fracturing and conventional logging data,based on Huang's model,the maximum and minimum horizontal principal stresses of the study block are 17.88?55.75MPa and7.31?24.90MPa,respectively,and the vertical in-situ stresses are 14.93?32.74MPa.In the spatial range,the in-situ stress presents a state distribution of"low in the west and high in the east",and the in-situ stress presents an increasing trend with the deepening of coal seam burial.(4)The characteristics of the present geothermal field in the study area are clarified.Based on the temperature measurement data of 30 Wells,the results show that the temperature of the coal reservoir in the study area is between 25?and 37.25?,and the temperature of the coal reservoir increases with the deepening of the burial of the coal seam.(5)The control effect of the three-field coupling on the gas content of coal seams is analyzed.Based on the distribution characteristics of three fields,the study shows that the areas with low hydrodynamic activity,large horizontal stress difference and moderate coal reservoir temperature are conducive to the preservation of coalbed methane.The areas with high hydrodynamic activity,small horizontal stress difference and high coal reservoir temperature are not conducive to the preservation of coalbed methane.