Study On Pyrolysis And Coking Of Oil-base Drilling Cuttings From Fuling Shale Gas Development

Oil-base drilling cuttings are the mixture of oil based drilling fluid and soil,shale,etc,which is one of the high oil pollutant HW08 in the national hazardous waste list.Direct discharging the oil based drilling cuttings without appropriate treatment will cause harm to the surrounding environment and ecological security.Using the pyrolysis technology to deal with the oil base drilling cuttings can not only achieve the purpose of reducing,removing oil and eliminating biological toxicity but also reuse the recovery oil to deploy oil base drilling fluid.However,due to the lack of understanding about the chemical and physical changes in the process of oil based drilling cuttings pyrolysis,there are still many problems to be solved in the actual production process.Therefore,it is still necessary to do some indoor experiment research on the mechanism.Among them,the coking phenomenon of recovery oil during pyrolysis is one of the key problems that affect the stability and safety of oil based drilling cuttings pyrolysis technology.According to the purpose of oil base cuttings pyrolysis treatment we carry on the pyrolysis experiment of oil based drilling cuttings from Fuling shale gas developmentin tubular pyrolysis furnace.The results show that among the factors that affect the pyrolysis effect of oil based drilling cuttings,the temperature has the greatest influence.With the increase of temperature and holding time,the pyrolysis effect of oil base drilling cuttings was improved,and the oil content of residue decreased.However,with the increase of heating rate,the pyrolysis effect of oil base drilling cuttings decreased and the oil content of residue increased.The effect of nitrogen flow rate on the pyrolysis effect is that when the gas exchange rate is low,the gas velocity increases and the pyrolysis efficiency increases,but when the gas exchange rate is higher,the pyrolysis effect of oil based drilling cuttings decreases with the increase of air exchange rate.Besides the state of oil based drilling cuttings also has some influence on the pyrolysis process,the dry material has much better effects than the wet material at low temperature,but this division narrowed when the tempreture continuously increasing.The two were almost identical when pyrolysising at 500?.In addition,we also obtained the optimum conditions of oil based drilling cuttings pyrolysis by orthogonal test.When the oil-base drilling cuttings were pyrolysised in the final temperature of 500?,holding time 60 min,the heating rate 20?/min and the nitrogen flow rate 0.10L/min,the oil content of non drying oil base cuttings was 0.039% and the oil content of dry content was 0.030%.In order to study the coking feature of recovery oil at different conditions,we take the coking amount of unit mass recovery oil as index to design a set of experimental flow include controling the variables of coking—oil washing by ultrasonic extraction—determining the coking by ultrasonic extraction,and the changes of components in the coking process were investigated by FT-IR analysis.The results show that:The effect of temperature on coking of recovery oil is relatively large,and the coke production is different under different temperatures.With the increase of temperature and time,the amount of coke increases and the total sediment decreases.Different gas injection rate will lead to the different generation amount of coke,too fast or too slow can lead to a reduction of the amount of coke.When the gas injection rate is in the range of 0.04~0.08SL/min,it is the most optimum condition to the occurrence of coking reaction.With the conducting of coking process,unsaturated hydrocarbons and aromatic rings are formed by oxidative crosslinking and cyclization of saturated alkanes and the coke is formed by the oxidation and pahs.