Pollution characteristics and effect of integrated treatment technology of solid wastes from water-based drilling for natural gas exploitation: taking Sulige Gas Field as an example

shIn the process of natural gas exploitation, a large amount of drilling solid wastes are produced, which contains toxic and harmful substances such as petroleum hydrocarbon, inorganic salt and refractory organic matter. The solid wastes produced by different well types, different well sections at typical drilling sites in five blocks of Sulige Gas Field were sampled, their performance characteristics and pollution characteristics were analyzed, the technical parametshers of the integrated process of classified management and control, stabilization pretreatment and high-temperature incineration and oxidation of drilling solid wastes were studied, and the variations of drilling solid waste pollutant concentration before and after treatment with this technology were analyzed. The results showed that the concentrations of pollutants in the solid wastes and leachates of shallow surface drilling met the requirements of the maximum allowable limits of Integrated Wastewater Discharge Standard (GB 8978-1996) after treatment by fine stabilization pretreatment technology. The reduction rate of petroleum hydrocarbons in drilling solid wastes in the deep well section was more than 98.6%, and the concentrations met the screening value requirements of category Ⅱ of construction land soil pollution in Soil Environmental Quality Risk Control Standard for Soil Contamination of Development Land (GB 36600-2018). In the meanwhile, the concentrations of heavy metals and organic matter in the residue decreased significantly, which were in line with the limit requirements of GB 8978-1996. Moreover, the volume of solid wastes was reduced by 41.2%. The integrated treatment technology of ‘classified control-stabilization pretreatment-high temperature oxidation’ could solve the problem of solid wastes treatment and disposal of natural gas exploitation and drilling from the source. Compared with the existing traditional unclassified treatment technologies, the overall cost of the integrated technology was reduced by 52%, which had a good prospect for promotion.