Chemical Characteristics And Dynamic Field Simulation And Prediction Of CBM Produced Water In Southern Shizhuang

The hydrodynamic condition,which control and influence the occurrence and output of CBM,is the key factor of CBM exploration and development.It has very important theoretical and practical significance to analyze hydrodynamic field of Taiyuan Formation aquifer in the south of Shizhuang block.For example,It can explore the generation,migration,accumulation of CBM on the 15#coal and predict the coalbed methane enrichment zone.In a word,It can provide a reference to discharge mining in high water CBM wells.By mans of water chemical analysis and environmental isotope test,Hydrogeochemical characteristics of CBM produced water in the study area have been synthesis analyzed.To dentified the quality and source of produced water,the combination and connection between coal bed and roof seam.CBM produced water is characterized by high chloride and high salinity.The water quality is mostly Cl-HCO3-Na or HCO3-Na type,besides Na-Cl type individually.The ?D values are between-85.5‰ and-80.0‰,average-83.2‰;The ?18O values are between-11.8‰and-10.2‰,average-11.2‰.All the values plot slightly nearby the meteoric water line,indicating that the aquifer in mining field has unified supply water from the meteor waters.Through multivariate correlation analysis and calculation of potential sources water and CBM produced water with gray related degree,we can concluded that produced water have the highest contact with coal seam water(from 0.72 to 0.87),followed by the roof limestone water(from 0.5 to 0.89).Based on the calculation of the mixed water proportion and recharge area elevation,The groundwater recharge area located in the eastern mountains and highlands of study area.Now the proportion of water in the coal seam are between 73.3%-95.3%,The limestone water ratio ranges from 4.7%to 26.7%,which will further increase with the mining in progress.Based on the hydrogeology investigation of the southern Qinshui Basin,The 15#coal measures aquifer has been streamline simulated with IES and PetroMod softwares.The result indicates that:The reticular unidirectional groundwater runoff in aquifer from the Northeast to the Southwest on the whole,Sometimes it converges locally.Finally it develop the ZaoYuan and the Panzhuang retention area respectively.But the hydrodynamic conditions are different in parts,causing the different productivity of CBM and water in study areas.At last,we coupling analysis of the relationship between hydrodynamics and gas content,and predict favorable targets for coalbed methane prospecting.It has been divided into the unfavorable,more and the most favorable area from the boundary to the centre,respectively.At the same time,through simulation and prediction of level fluctuation and drop funnel variation during extraction of CBM well TS-626 with Visual Modflow4.2 software.It shows that depression cone gradient is steep within 40m around drainage well,and the range of depression cone is less than 150m during 90 days.Overall,Its changing trend is the form of "slow-fast-slow".Increasing the permeability of roof limestone,along with the increase of the supplies of limestone water for coal bed,resulting in the slow expansion of coal reservoirs drop funnel when roof and floor permeability is less than coal permeability.