Research progress on produced water geochemical from CBM wells in China

According to the important role that geochemical study of produced water from coalbed methane(CBM)wells to the identification of the sources of drainage water and its geological significance,this paper systematically summarizes the geochemical characteristics of conventional ion,trace elements and hydrogen and oxygen isotopes and its geochemical response in CBM wells produced water,and discusses the existing problems and future development trends in the currentstudy of produced water.The research shows that worldwide CBM wells produced water has similar ionic characteristics,but with different ion features in diverse drainage phases.With the drainage development,the contents of characteristic trace elements increased first and then decreased.The hydrogen and oxygen isotopic compositions in CBM wells produced water are mostly distributed near the regional atmospheric precipitation line and have obvious D drift characteristics,which explaines a source of atmospheric precipitation.When the contents of width=167,height=17,dpi=110 and trace elements,are relatively high,and hydrogen and oxygen isotopes are relatively heavy,it will imply a closed hydrological environment,conducive to the CBM enrichment and preservation.And a variety of geochemical comprehensive indexes,reflecting CBM enrichment and high production,and identification templates of produced water source,have been established.Finally,it is pointed out that more attentions should be paid to the accurate identification of CBM wells produced water source,the establishment of geochemical prediction model for CBM high production,the further discussion of gas and water linkage interaction during drainage process,and the quantitative description and elimination of fracturing fluid effects.