Variational Characteristics of Water Quality of Produced Formation Water in Coalbed Methane Production Area

Abstract

The produced formation water samples and the stored water samples of the tanks in coalbed methane production area were sampled, and their pH, the ion concentration were tested, the variational characteristics of pH, the distribution and the variation with time of the ion concentration, the variational characteristics of the salinity and the conductivity from the produced formation water and the water of the tanks were discussed in order to investigate the variational characteristics of water quality of the proudced formation water in coalbed methane production area. The results show that the produced formation water are alkalescent, the pH of the produced formation water and the stored water in the tanks are near to or beyond the maximum of Chinese irrigation water quality standards. The anions of the produced formation water are mainly HCO3- and Cl-, the ion concentration haven’t dearease effectively during the discharge of the produced formation water, the concentration of Cl- in the produced formation water and the stored water of the tanks from the partial coalbed methane wells is beyond the limit of the national standards. The salinity of the produced formation water and the stored water of the tanks are between 1500 mg/L and 2000 mg/L, and they are between the maximum of the non-saline areas and the maximum of the saline area according to Chinese irrigation water quality standards. The total hardness and the conductivity of the produced formation water and the stored water of the tanks in coalbed methane production area are relatively low, and they can meet the national discharged standard of sewage.