Study On The Influence Behavior Of Surfactants In Oilfield Water

With most of the oil fields in China entering high water cut period,and the continuous upgrading of crude oil extraction technology,the performance of surfactant is also continuously improved.Surfactant flooding technology has the characteristics of low investment and high return,so it is widely used in the oilfield exploitation industry.However,a large number of used surfactants will inevitably enter the ecological environment with oilfield produced water,which will bring a series of environmental hazards.Therefore,in order to ensure that the applied surfactants can bring great economic benefits and minimize environmental harm,it is necessary to carry out environmental effect prediction and assessment before the application of surfactants.In this paper,the effects of heavy alkylbenzene sulfonate anionic surfactant（HABS）and betaine amphoteric surfactant（TCJ）into oilfield water environment were investigated.（1）The effects of two surfactants on the oil content,suspended solids concentration,corrosion rate,TN,TP,NH₄⁺-N,p H value and turbidity of produced water were investigated.（2）The physiological and biochemical indexes of the organisms in oilfield produced water before and after the addition of two kinds of surfactants were determined,and the effects of two kinds of surfactants on the metabolic activity and community structure of the organisms were analyzed.（3）The bacteria to luminous bacteria as a model,to determine the EC₅₀ value of two kinds of surfactants,to identify biological toxicity grade of oil displacement agent,with E.coli and S.aureus to model the fungus,from bacterial growth status,the structure of the cell membrane integrity and cell surface morphology of the microbial toxicity mechanism of surfactant make inferences;（4）Investigate the corrosion characteristics of Q235 carbon steel sheet in two kinds of surfactant solution,and judge whether the surfactant will bring corrosive harm.Experiments show that:（1）TCJ surfactant with oil field produced water system,the content of TN,NH₄⁺-N,emulsified oil and TCJ basic linear relationship,the surfactant concentration and TP,p H and turbidity value affected small,suspended solids content and corrosion rate has a certain influence,have been rising TCJ concentration reaches a critical value after a smaller effect;In the system of HABS surfactant and produced water,turbidity showed a strong linear relationship,suspended solids content,emulsified oil content,corrosion rate increased with the increase of adding amount,while TN,NH₄⁺-N,TP and p H were stable.（2）With the increase of TCJ dosage,the physiological and biochemical indexes of microorganisms increased first and then decreased.When the dosage is 0.2 g/L,the biomass,protein content,dehydrogenase activity intensity and polysaccharide content showed the highest values,which were increased by 25.9%,25.99%,13.82%and 20.38%compared with blank control group,respectively.The effect of promoting at low concentration and inhibiting at high concentration appeared in the HABS action system.Adding 0.3 g/L HABS had the highest biomass,protein content,dehydrogenase activity intensity and polysaccharide content,which were increased by22.2%,39.68%,39.12%and 33.49%compared with blank control group,respectively.（3）The highest relative abundance of Enterobacter was 92.56%,followed by Pseudomonas（4.62%）,only a small amount of Acinetobacter（2.92%）and other bacteria（1.24%）.HABS surfactant can effectively improve the relative abundance of Enterobacter,and has significant inhibitory effect on Enterobacter;Under the effect of TCJ surfactant,Enterobacter was the most dominant bacteria,accounting for 90.87%,Pseudomonas was the second dominant bacteria,accounting for 6.32%,Acinetobacter and other bacteria accounted for only 2.81%.TCJ could significantly increase the relative abundance of Pseudomonas and further decrease the abundance of Enterobacter.（4）Both the amphoteric surfactant and the anionic surfactant of HABS were slightly toxic,but the EC₅₀ value of TCJ was lower than that of HABS,and the toxicity of TCJ was higher than that of HABS.（5）Both TCJ and HABS could prolong the time of E.coli and S.aureus to enter logarithmic growth phase to more than 24h,and the cell membrane structure was incomplete and the cell morphology changed.（6）In the TCJ amphoteric surfactant system,the corrosion time is inversely proportional to the corrosion rate.The corrosion is mainly controlled by H⁺and is suitable for neutral acid environment.In HABS anionic surfactant system,with the increase of concentration,the corrosion rate first increases and then decreases,which is inversely proportional to the corrosion time.The corrosion rate was greatly affected by temperature.The optimum p H range was 3～7.It mainly inhibits the dehydrogenation reaction of anode and has a certain effect of corrosion inhibition.Mixed corrosion inhibitors for anodic dehydrogenation.The surface of the steel sheet is coarse.The corrosion products mainly contain Fe,C and O elements.It is speculated that the main corrosion product is Fe₃O₄.