The environmental friendliness of fuzzy-ball drilling fluids during their entire life-cycles for fragile ecosystems in coalbed methane well plants.

To protect the vulnerable ecosystems in coalbed methane(CBM) well plants from the pollution of drilling fluids, the environmental friendliness of fuzzy-ball drilling fluids was evaluated. Further, the combination of solidification and in-situ landfill were proposed to optimize their waste disposal. Firstly, the samples for tests were collected from the well plants. Then, their environment-related properties were evaluated with the indicator vector from wastewater perspective to monitor their environmental friendliness. Lastly, comparative analysis of two wells in Linfen, China was conducted concerning engineering and economic parameters. Results showed that these indicators of the new fuzzy-ball drilling fluids and their raw materials were within the ceiling limits of related national standard, whereas those of waste fuzzy-ball drilling fluids exceeded the limits. The mechanical strengths of the waste drilling fluids solidified directly could meet the practical transport demand, and their leachates met the standardized requirements due to the strong biodegradability of fuzzy-ball fluids. Field studies demonstrated the economic effectiveness of fuzzy-ball drilling fluids, reconciling the conflict between environment-protecting and cost-reducing. In conclusion, fuzzy-ball drilling fluids are feasible for fragile ecosystem protection in CBM well plants. The environmental friendliness relies on their material, structural and functional basis.