Ions dynamics of produced water and indication for CBM production from wells in Bide-Santang Basin,Western Guizhou

Based on the R cluster analysis,ions are classified and their meaning are discussed. The Z-6,Z-7,Z-10 well in Bide syncline are fracturing fluid pollution wells,with exceptionally high Cl- ,Na+ and Br- concentrations. As drainage proceeds,the concentrations of K+ ,Ca2+ ,Mg2+ ,Si4+ present an increasing trend while SO24- presents a decrea- sing trend,which reveals the closure degree of produced water becomes higher. Cl- +Na+ concentration is extracted as a typical index for discriminating the interlayer interference degree and productivity effect of commingling wells,with high production well ranging 833. 18 - 1 768. 26 mg / L and averages 1 321. 55 mg / L,low production well ranging 259． 22-519． 4 mg / L and averages 380. 72 mg / L. High production well has higher Cl- +Na+ concentration in produced water than low production well,and the threshold value ranges 600-800 mg / L. High closure degree produced water are corresponding to high CBM production. The interlayer interference discrimination template for CBM commingling wells based on Cl- and Na+ concentrations in produced water is established,preliminarily. Considering the drainage layers, the upper CBM system has poor joint mining compatibility with middle and lower CBM systems,and the middle and lower CBM systems should be regarded as a priority for development in the future.