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

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 delta D and delta O-18 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.