Discussion on the causes of abnormally high water production of coalbed methane wells under the control of structural conditions and hydraulic fracturing

The operation of coalbed methane (CBM) shows that the phenomenon of low or even no gas production is common in CBM wells with high water production，which has become an important reason for the low efficiency of CBM development.In order to analyze the main controlling factors of abnormally high water production，taking the CBM wells in the Shizhuangnan Block of Qinshui Basin as the research object，based on a large number of production data of the CBM wells in the study area，the quantitative index of abnormally high water production was determined through a single factor variance analysis and non⁃linear fitting method. Moreover， the causes of abnormally high water production under the control of different factors were analyzed，and the corresponding countermeasures were discussed. The results show that the quantitative index of abnormally high water production is that the average water production is more than 3.22 m3 / d for the high rank CBM vertical well with 8⁃year drainage time in the Shizhuangnan Block in Qinshui Basin.The sandstone aquiferin the upper part of coal reservoir is a prerequisite for high water production.The abnormally high water production phenomenon is more common under a complex structural geological background.Nat⁃ ural fractures are developed near the fault and collapse column and the high risk areas are within 600 m and 900 m from fault and collapse column.In the weak tectonic activity area，the fractures caused by hydraulic fracturing and lo⁃ cal hydrodynamic field become the main control factors.The lower the coal seam elevation in local sub⁃sag and the lar⁃ ger the fracture scale and height，the easier it is to lead to abnormally high water production.Also，the risk of CBM wells with vertical or high angle inclined shear fractures is higher.Therefore，the well location should be arranged ac⁃ cording to the principle of keeping away from complex structures such as faults and collapse columns.In addition， it needs to consider the adaptability between aquifer development characteristics and fracturing fracture scale， especially it needs to control the fracturing fracture scale of CBM wells at the relative low elevation of coal seam in lo⁃ cal sub⁃sags in order to prevent the communication with aquifer，so as to avoid the inefficient development of CBM wells.