Environmental Impact Assessment And Harmless Treatment Of Waste Water-based Drilling Fluids

During the process of crude oil development,a large amount of drilling fluid needs to be used to carry cuttings,cool the drill bit,and balance the formation pressure.Organic treatment agent pollutants are difficult to degrade and even poisonous.If the waste drilling fluid are directly discharged without treatment,they will cause serious environmental pollution and threaten the health of animals and plants.Therefore,the environmental impact of waste water-based drilling fluids and their treatment agents were discussed in this paper.(1)The oil content,biotoxicity and biodegradability of 4 kinds of waste water-based drilling fluids were evaluated..(2)20 kinds of water-based drilling fluid treatment agents were studied,and their toxicity,biodegradability and heavy metal content were determined: natural polymers are usually non-toxic;PAM treatment agents are slightly poisonous,it may be that PAM itself has unreacted acrylamide monomer.With the increase of hydrolysis degree,the toxicity of the polymer can be reduced.Most of the waste drilling fluid treatment agents are relatively difficult to degrade.(3)The inorganic flocculants were chosen,and PAC was selected as the inorganic flocculant according to the appearance,sedimentation velocity,turbidity,COD and dosage.The effects of p H,temperature and salinity on the flocculation effect of the PAC-CPAM system were studied.The flocculation effect of the flocculant PAC-CPAM was the best when the p H was near neutral.The increase of temperature will increase the effect of flocculation,while the salinity has little effect on the flocculation performance of PAC-CPAM flocculant,but has a greater effect on the settlement.The flocculation mechanism of PAC-CPAM was analyzed by particle size distribution and zeta potential analysis.The mechanism may be the result of the synergistic effect of net trapping precipitation,electric neutralization mechanism and adsorption bridging mechanism.4 kinds of water-based drilling fluids were treated with PAC-CPAM organic-inorganic flocculant.And oil content,biotoxicity and biodegradability were studied.1,3 and 4 drilling fluids all can meet the emission standards.