Coalbed methane produced water in China: status and environmental issues

Area of Science:

• Environmental Science
• Geochemistry
• Resource Management

Background:

• Coalbed methane (CBM) is a significant unconventional gas resource globally.
• Produced water from CBM extraction, known as coalbed methane produced water (CMPW), presents major management challenges.
• While studied in the USA, Canada, and Australia, CMPW's environmental effects in China remain largely overlooked.

Purpose of the Study:

• To highlight the environmental issues and management challenges of CMPW in China.
• To analyze the variable quantity and quality of CMPW in Chinese coal basins.
• To compare China's CMPW treatment and utilization practices with international standards.

Main Methods:

• Review of existing literature on CMPW management and environmental impacts.
• Analysis of reported CMPW quantity and quality data from Chinese coal basins.
• Comparative assessment of treatment and utilization strategies.

Main Results:

• CMPW in China exhibits wide variations in volume (10–271,280 L/well/day) and total dissolved solids (691–93,898 mg/L).
• CMPW in China is typically alkaline (pH > 7.0) with Na-HCO3 and Na-HCO3-Cl as dominant water types.
• Current CMPW management in China relies heavily on surface impoundments and evaporation, lagging behind international practices.

Conclusions:

• Significant environmental risks associated with CMPW in China require urgent attention.
• Lack of specific regulations and environmental impact assessment (EIA) guidelines for CMPW hinders effective management.
• Key environmental concerns include water quality monitoring, groundwater level decline, and groundwater pollution from hydraulic fracturing.