Identification of Interwell Interference Based on Hydrogeochemical Characteristics of Produced Water from Coalbed Methane Wells: A Case Study in the Southern Qinshui Basin, China

Summary Interwell interference is the superposition effect of coalbed methane (CBM) reservoir pressure. This study aims to provide a new direction for the quantitative analysis of interwell interference from the hydrogeochemical characteristics of produced water from CBM wells. A total of 24 produced water samples collected from the Panhe (PH) group, Shizhuangnan (SZN)-1 group, and SZN-2 group in Qinshui Basin were selected for the comparative analysis. The water type of all water samples is characterized by Na-HCO3, with Na+ being the main total dissolved solids (TDS) provider. The self-similar major ionic characteristics of the PH and SZN-2 groups are prone to the occurrence of interwell interference. The δD and δ18O show that the main source of produced water is atmospheric circulating water. The similar isotope characteristics of produced water in the PH and SZN-2 groups represent that there is remarkable interwell interference. Sr, As, Cu, Ga, Li, Rb, Sn, Mo, and V are selected as indicator elements. In the cluster analysis, all CBM wells form a single cluster in the PH and SZN-2 groups in the first three iterations, indicating interwell interference. According to the established fuzzy discriminative model, interwell interference is divided into two types—strong interwell interference and weak interwell interference. Most CBM wells in the PH and SZN-2 groups show strong interwell interference. This study can provide theoretical foundations for the dynamic pressure regulation and well pattern infilling of CBM wells.