Chemical Characteristics and Development Significance of Trace Elements in Produced Water with Coalbed Methane in Tiefa Basin.

Coalbed methane (CBM) is an unconventional natural gas resource. CBM mining releases a large amount of coproduced water, and the trace elements of CBM coproduced water can provide a basis for the exploration and development of CBM. The contents of eight major trace elements in the produced water from wellhead were tested and analyzed based on seven CBM wells in Tiefa Basin. The research indicates that Sr and Ba are the dominant trace elements with the highest concentrations in produced water. There is a positive correlation among Li, Sr, and Rb by cluster analysis and correlation analysis, which may be affected by the total dissolved solids and pH in the groundwater. The contents of Li, Sr, and Ba increase with the burial depth of coal seam and could be influenced by the fault. The gas production of CBM wells is affected by the depth of the coal seams, and there is no significant correlation between water production and the coal seam depth. However, faults have an important impact on gas and water production. The productivity of coalbed methane is affected by hydrogeological conditions and structure because the productivity of CBM wells located in different tectonic locations varies with the change of Li, Sr, and Ba contents.