Study On The Stability Of Waste Drilling Fluid And Bactericide

Waste drilling fluid is characterized by complicated components,which contains a lot of water,oil,clay particles and some other chemicals,many toxic and harmful components.Waste drilling fluid not only endangers human health,destructs the ecological environment of our society,pollutes the water resources,but also lead to soil compaction.At present,a series of methods have been applied for the disposal of waste drilling fluid,however,they cannot solve the pollution problem fundamentally.At the same time,since the waste drilling fluid contains a large amount of available active components,the recycling technology of waste drilling fluid is considered to be one of the most promising methods for disposal of waste drilling fluid in recent years,but it is necessary to ensure the stability of the waste drilling fluid before reutilization.Waste drilling fluid is prone to produce large amounts of sulfate reducing bacteria and iron bacteria during the placement process,which can make the waste drilling fluid metamorphose and instability.Therefore,a fungicide is added to kill the bacteria.Therefore,bactericide was usually added to the waste drilling fluid to eliminate bacteria.Using single conventional bactericide for a long time can bring about the drug resistance of the bacteria and increase the amount of bactericides dosage.In this paper,the basic properties the waste drilling fluid were studied and polymeric quaternary ammonium salt bactericide was synthesized.The basic properties and stability conditions of the waste drilling fluid taken from Shengli oilfield were studied,an accurate and convenient method has been developed for determining the stability of waste drilling fluid.The conditions for stable storage of waste drilling fluids have been explored by using zeta potential and Turbiscan Lab stability analyzer methods.The results indicated that when the particle size is less than 21 ?m,and the content of electrolyte is less than 1%,the waste drilling fluid is stable.The Turbiscan Lab stability analyzer could determine the stability of the waste drilling fluids without destroying the sample and reduce the experimental error.Polymeric quaternary ammonium salt bactericide was synthesized through the polymerization reaction by using epichlorohydrin and dimethylamine as the monomers,diethylenetriamine as cross-linking agent.The effects of molar ratio of two monomers,dosage of cross-linking agent,reactive temperature and time on the bactericidal ratio and the viscosity of the polymer were studied.The results indicated that the optimal synthesis conditions were: n(epichlorohydrin):n(dimethylamine)=1.5:1,the dosages of diethylenetriamine was 4%,the reaction temperature and time were 70°C and 5 h respectively.Single agent and compound experiment of newly synthesized polyquaternary ammonium salt bactericide and common bactericide dodecyl dimethyl benzyl ammonium chloride were measured by extinction dilution method.The number of bacteria in the waste drilling fluid before and after adding bactericide was measured and the bactericidal ratio was calculated.The single factor method and orthogonal experiment were used to explore the optimal sterilization conditions of the compound bactericide for sulfate reducing bacteria and iron bacteria in waste drilling fluid.The results showed that the optimum ratio of polyquaternary ammonium salt bactericide and dodecyl dimethyl benzyl ammonium chloride in the compound bactericide was 3:2,the dosage was 80 mg/L,the bactericidal temperature was 35°C,the contact time was 24 h,and the p H was 9.The bactericidal rate of sulfuric acid reducing bacteria and iron bacteria in waste drilling fluid were over 99% and 97% respectively.