Study On Solid Waste Pollution Characteristics And Resource Environmental Risk Of Shale Gas Exploitation In Fuling Area

Shale gas is an unconventional oil and gas field,and a national strategic emerging industry.However,the node and processing technology of solid waste in the mining process are not yet clear.It is difficult to determine the pollution characteristics of solid waste and treated residue.At the same time,the use of shale gas solid waste residue to produce unburned bricks is an effective way to achieve recycling.But in the actual application process,pollutants will probably affect the environment and human health.Therefore,it is necessary to determine the pollution characteristics of the solid waste and the product after the shale gas exploitation,to explore the release characteristics of the pollutants in the burning free bricks and to carry out the environmental risk study.So as to reduce the pressure brought by solid waste in shale gas treatment and disposal of municipal solid waste.This paper selects solid waste from shale gas in Fuling area as the research object.Through data investigation and field investigation,the shale gas mining technology and shale gas drilling fluid system are understood,and the solid waste is determined mainly by the water drilling cuttings of the ducts,one open and two open wells,the water based drilling cuttings in two open wells and the oil based drilling Iiwa of the three open horizontal wells.Typical single well producing ordinary drilling cuttings(water and drilling cuttings)and oil based drilling cuttings produce about 1085.44m~3 and 150m~3~220m~3,respectively.The content of heavy metals and polycyclic aromatic hydrocarbons(heavy metals and polycyclic aromatic hydrocarbons)in the solid waste of shale gas mining and oil based drilling cuttings,as well as the concentration of oil content in oil based drilling cuttings,are analyzed.It is found that Ba in water based and oil based drilling cuttings is significantly higher than other heavy metals.Heavy metal pollution of oil drilling cuttings at No.1 disposal station is more serious.The concentration of sigma PAHs in water based drilling cuttings has not reached the specified concentration in the Identification of hazardous wastes,identification of toxic substances content.(GB5085.6-2007),which is mainly 4 ring PAHs.The concentration of sigma PAHs in oil base drilling in No.7 station is the highest,with 5-6 ring(74.49%).The oil based drilling cuttings of 188 drilling platform,No.1 and 2 station are dominated by 4 ring PAHs.The hydrocarbon content of oil based drilling cuttings is 112400.96 mg/kg~212770.14mg/kg.According to the study of the pollutants in the residue after the shale gas extraction,the concentration of Cr,Ni,Cu,Zn and Pb in the residue increased by 2.2,1.8,1.4,8and 0.9 times respectively after the treatment of water base drilling cuttings,and some heavy metals in the oil based drilling cuttings increased,some decreased,and the regularity was different.However,the concentration of polycyclic aromatic hydrocarbons(PAHs)in water based drilling cuttings has increased,and polycyclic aromatic hydrocarbons and petroleum hydrocarbons in oil based drilling cuttings have decreased.The removal rates of sigma PAHs in No.1,No.2 and 7 disposal stations are72.49%,95.31%and 92.99%,respectively.The removal rates of petroleum hydrocarbons in No.1,No.2 and No.7 disposal stations were 88.99%,93.89%and93.19%,respectively.The highest effective concentration of Ba in unfired brick mixed with water based and oil based drilling debris residue is the highest.Through the water tank leaching experiment,it was found that Cu,Zn and Pb were not detected in the leaching liquid of the two bricks,and the Ba accumulated the largest amount.During the whole leaching process,the release mechanism of Ni and As in the unburned bricks mixed with water based drilling cuttings is diffusion control,Cr is surface erosion,and Ba is dissolution.Cr,Ni,As and Ba in the unburned bricks of oil based drilling cuttings are diffusion control functions.Four kinds of elements in two bricks were released at low speed.On the 0-9 day,the release rate of the two kinds of unburned bricks is faster than that of the PAHs,and the release rate gradually slows down.The maximum release rate of PAHs and benzo(a)pyrene is greater than that of"drinking water health standard"(GB5749-2006).Therefore,making use of shale gas solid waste residue to prepare unburned brick has greater risk for sigma PAHs environment.