Study On The Effect Of High Temperature And High Pressure On The Biodegradability And Toxicity Of Sulfonate Drilling Fluid Additives

With the development of the oil and natural gas industry,the scope of drilling development industry is continuously expanded,and drilling fluid additive has been widely used in the drilling and mining industry.Usually,components of drilling fluid additive are complex and more refractory.When these drilling fluid additive follows the drilling fluid into environment,it often causes a series of environmental impacts.Detecting and analyzing the types of contaminants in the drilling fluid additive,and predicting the change process of the contaminants after the drilling fluid additive under the condition of high-temperature and high-pressure conditions.They can not only evaluate the environmental pollution caused by the drilling fluid additive,but also can provide reference for the development and treatment of drilling fluid additive.In this study,two sulfonates of the drilling fluid additive,sulfonated asphalt and sulphon ated lignin,were selected as the research object.The high-temperature and high-pressure reactor was used to simulate the downhole environment.The change law of biodegradability and bio-toxicity were studied under different conditions of time,temperature and pressure.Modern analytical instruments,Fourier infrared spectroscopy and gas chromatography-mass spectrometry were used to analyze the change of functional groups and material components of sulfonated asphalt and sulphonated lignin before and after downhole high temperature and high pressure conditions.Then,preliminary derivating the degradation mechanism,and systematically evaluating the pollution characteristics of sulfonated asphalt and sulfonated lignin.The results showed that:(1)After high temperature and high pressure,the biodegradability of sulfonated asphalt and sulfonated lignin was increased significantly.The COD removal rate of untreated sulfonated asphalt and sulfonated lignin wastewater were 52.61%and 43.55%,respectively.BOD5/COD values were 0.0105 and 0.08,respectively.After high temperature and high pressure treatment,the COD removal rates of sulfonated asphalt and sulfonated lignin reached up to 83.61%and 72.7%,and the BOD5/COD values reached 0.0214 and 0.296,respectively.(2)For the biological toxicity,six water samples showed no toxicity to the acute toxicity of zebrafish.The toxic equivalent of HgCl2 of sulfonated asphalt under the three treatment conditions was 0.041 mg/LHgCl2,0.023 mg/LHgCl2,and 0.021 mg/LHgCl2,respectively.The toxicity of sulfonated asphalt decreased significantly under high temperature and high pressure.The EC50 values of the semi-effective concentrations of luminescent bacteria were 338.6 mg/L,282.5 mg/L,and 231.0 mg/L,respectively.The toxicities were all poisoned and the toxicity was elevated after high temperature and high pressure.(3)The sulfonated asphalt and sulfonated lignin before and after high temperature and high pressure treatment were analyzed by Fourier transform infrared spectrometry and gas chromatography-mass spectrometry.The results showed that the composition of sulfonated asphalt and sulfonated lignin wastewater was very complicated.The main organic pollutants in sulfonated asphalt include alkanes,esters and aromatic compounds.The main organic pollutants in sulfonated lignin include alkanes,esters,amides and aromatic compounds.The high-temperature and high-pressure change the position and structure of the functional groups in sulfonated bitumen and sulfonated lignin,and convert refractory organic macromolecules into easily degradable small molecule compounds to improve their biodegradability.At the same time,the type of degradation products after high temperature and high pressure had changed,which impacted on their biological toxicity.