Enhancing Drilling Sludge Dewatering By Conditioning And Ultrasound Assisted Sulfate Radical Oxidation

With rapid development of drilling technology,the requirement of stability and fluid keeping rate of drilling fluid are getting higher and higher.Drilling sludge is produced from the drilling fluid after drilling operation,which is generally stable suspension.The dewatering of drilling sludge is a bottleneck during harmless disposal process.Since the drilling sludge has stable system,its dewaterability is poor.Inorganic cations conditioning and ultrasound assisted sulfate radical oxidation are used to improve drilling sludge dewatering,respectively,and the mechanisms were studied in this paper.The effects of different inorganic cations on the filterability and settleability of drilling sludge were investigated in the inorganic cations conditioning.The experimental results showed inorganic cations could improve filtration rate and settleability to a different degree.The effects were in the following order:Fe³⁺>Ca²⁺>Mg²⁺>K⁺>Na⁺.Multivalent cations performed better than monovalent cations.At the same valence,the cations with smaller hydrated radius got superior conditioning results.By analyzing zeta potential and particle size,it was found that the main effects were neutralization potential and compression of electric double layer.However,inorganic cations conditioning could not achieve the desired requirement of dewaterability.Ultrasound assisted sulfate radical oxidation was put forward to improve the drilling sludge dewatering through analyzing of the existence of water.Water content,specific resistance,transmittance of filtrate and volatile suspended solids were tested before and after oxidation treatments.Based on the analysis of physical and chemical properties,the mechanisms were elucidated.Ultrasound assisted sulfate radical oxidation could further improve sludge dewaterability and obviously reduce the reaction time compared to individual ferrous sulfate activated persulfate oxidation.This method could promote the hydrolysis of organic substances in the drilling sludge and cracked stable system.Besides,it promoted the trapped water transform to free water.Consequently,the dewaterability of drilling sludge was improved.