Quantitative Characterization Of Deep Geological Conditions In The Western Fukang Block

Taking the steep-dip coal strata in the Western Fukang block,southern Junggar,Xinjiang as the research object,based on the drilling water pumping test and CBM production data from coal resource exploration,the fluid characteristics of coal reservoir in the study area and its significance to the accumulation and production of CBM are analyzed;based on the temperature measurement results of continuous strata,different coal seam gas content and vitrinite reflectance test,the characteristics of geothermal field and coal rank distribution in the study area are analyzed,and its influences on gas content of coal seam are discussed;According to the test results and logging data of CBM parameter wells,the elastic mechanical parameter of coal seam and the main in-situ stress are calculated,and vertical distribution characteristics are analyzed;Based on three-dimensional seismic data,the geological model of 14-15 coal seam is established and imported into FLAC3 D software.The three-dimensional distribution characteristics of stress field are numerically simulated,and the influence of buried depth and coal seam dip angle on stress distribution is discussed.The results show that: in the deep groundwater stagnation area,the sodium chloride coefficient,calcium magnesium coefficient and desulfurization coefficient are low,the salinity is high,the reservoir sealing is strong,and the gas content is high;the average geothermal gradient is 1.48?/hm,and the reservoir temperature is controlled by syncline structure,showing a decreasing trend from southwest to northeast;the coal rank gradient is0.016%/hm,the gas content of coal reservoir is controlled by coal rank,and the change of gas content is consistent with that of Langmuir volume;with the increase of buried depth,the type of in-situ stress field changes from reverse fault stress field to transition stress field,and then to normal fault stress field.The critical depth distribution of transformation is around 600 m and 850m;the fracture pressure of coal reservoir is controlled by elastic mechanical parameters,and the permeability and reservoir pressure are affected by horizontal stress;burial depth and dip angle of coal reservoir are the key factors to control the value of principal stress,determine the direction of principal stress and the type of in-situ stress field;with the increase of burial depth,the normal stress of fracture surface with different dip angles in coal reservoir gradually increases,and the response of parallel bedding direction to burial depth is the largest,and that of vertical bedding direction is the smallest.