This study investigates the chemical signature of produced water from the Huntly coalbed methane (CBM) using a newly proposed Cl-HCO3-B ternary diagram. This ternary diagram is used to identify the source of fluid in the different aquifers (ground water, CBM and deep basement) and the potential communication between these aquifers. A comparison study of Huntly with other CBM fields (Maramarua, Powder River Basin, San Juan Basin, Raton, Atlantic Rim, Liulin and Alberta) was also carried out to help characterize and verify the water being abstracted. Results from the ternary diagram show that produced water samples from Huntly CBM wells are plotted in the middle along chloride-bicarbonate axis. This indicates that the water samples are CBM water originated from moderate to good permeability coal seams. The water samples also indicate that they have some communication with shallow aquifer due to significant bicarbonate concentration. Meanwhile water samples from basement well (B1) are plotted near to Boron side along Boron-chloride axis, which signifies basement water. The water originated from low permeable formations and afar from recharge area. Furthermore, results from schoeller diagrams show that Huntly water samples from CBM wells, shallow monitoring well and basement well exhibit distinct water chemistry patterns. The CBM water pattern shows sodium, bicarbonte and chloride as the predominant ions. It is similar to the typical CBM water pattern and comparable with CBM water from selected methane producing CBM fields with minor differences. Water samples from the basement well on the other hand shows sulfate and magnesium as the primary ions and the concentration for all ions are lower than CBM water. Shallow water sample exhibits the lowest concentration for all ions compared to CBM water and basement water with bicarbonate as the main ion. In conclusion, this ternary diagram is a reliable tool to identify the possible links between deep and shallow aquifers, formation permeability and origin of the water in one diagram. It enhances the understanding of the natural CBM reservoir setting for future field development, wastewater management and water quality monitoring.

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