Study On Environmental Health Risk Assessment Of Oil Drilling Cuttings In Fuling Shale Gas

Nowadays,the development of novel energy has drawn increasing attention globally.Shale gas,as one kind of novel energy,has been widely investigated due to its clean and low-carbon properties in recent years.The exploitation of shale gas could release the stress of energy shortage and simultaneously optimize the energy structure in China,so that to dramatically increase the efficiency of energy utilization.However,the exploitation of shale gas may cause environmental pollutions like the oil base drilling cuttings.The researches on the pollutions caused by oil base drilling cuttings in China are rarely reported.The immature treatment technologies and regulations could cause the soil contamination,which contributes to the high risk of environmental pollutions.Therefore,the risk assessment of pollutions causing by the exploitation of shale gas is essential and crucial.Based on the contamination risk assessment technologies,this research estimated the health and contamination risk of the sites contaminated by the oil base drilling cuttings during shale gas exploitation,and determined the target value for soil recovery.Furthermore,the hazard quotients of oil base drilling cuttings were studied when treatment efficiency meet different standards through different treatment methods such as landfill and road subgrade padding.These researches could provide a theoretical basis for the formulation of emission standard of oil base drilling cuttings,which is necessary and crucial for the management of oil base drilling cuttings in China.The results of this research suggesting that:(1)petroleum was the main pollutant in the factory area where there are wells with accumulation of oil base drilling cuttings.The concentration of petroleum reaches as high as 30745.9433mg/kg.At the sensitively land utilization condition,the noncarcinogenic hazard quotient of >C8-C10 and >C12-C16 aliphatic hydrocarbon in pollutions are greater than 1,which exceed the acceptable standard of risk assessment.At the insensitively land utilization condition,the noncarcinogenic hazard quotient of >C12-C16 aliphatic hydrocarbon is greater than 1,which still exceed the acceptable standard of risk assessment;(2)At the sensitively land utilization condition,while the concentration of >C8-C10 and >C12-C16 aliphatic hydrocarbon are 760.10mg/kg and 620.80mg/kg respectively,and the corresponding target value of petroleum is 1408.67mg/kg,the noncarcinogenic hazard quotient exhibit within the acceptable range under all the exposure methods.At the insensitively land utilization condition,when the concentration of >C12-C16 aliphatic hydrocarbon and the corresponding target value of petroleum are 2236.48mg/kg and 5074.84mg/kg respectively,the noncarcinogenic hazard quotient exhibit within the acceptable range under all the exposure methods.(3)The petroleum target value of 3000mg/kg in Contamination Control Standards for Agricultural Sludge(GB4284-1984)and that of 20000mg/kg in Contamination Control Standards for Oil Field Sludge(DB23/T1413-2010)are much more than the petroleum limitation corresponding with the acceptable hazard quotient,representing the high risk of petroleum contamination caused by oil base drill cuttings at this site.Based on the exposed quantity of cut fractions of petroleum calculated under six exposure pathways and the acceptable hazard quotient at national standards,the contaminant concentration was calculated inversely.The result shows that only when the concentration of petroleum in oil base drill cuttings is less than 1408.67mg/kg,the noncarcinogenic hazard quotient is within the acceptable range in this area using the pollution dispersion model selected in this research.(4)When oil base drill cuttings were utilized as subgrade padding for road and paddings for wellsite and wiper trip road in oil field,as well as the concentration of >C12-C16 aliphatic hydrocarbon and the corresponding target value of petroleum are 4553.24mg/kg and 10331.84mg/kg respectively,the noncarcinogenic hazard quotient exhibit within the acceptable range under all the exposure methods.The petroleum target value of 50000mg/kg in the national standard of Highway Subgrade Design Standard(JTGD30-2004)and that of 20000mg/kg in related regulations are much more than the petroleum concentration of 10331.84mg/kg corresponding with the acceptable hazard quotient,demonstrating the necessity for the improvement of contamination control standards.