Keywords:oil production plant;soil pollution in-vestigation;risk assessment
Abstract:
This study is aimed at four typical oilproduction plant station of Daqing oilfield ofChina petroleum (union station,transfer station,production wells and injection wells),where thesurrounding shallow soil environmental back-ground(pollution)status.Collecting the informationnearby the typical stations within the scope of eval-uation of geological and hydrogeologicalinformation and the surrounding soil environmentinformation of the sensitive area.Building aconceptual model of the site.According to the char-acteristics of pollutants,pollution,the siteconditions and environmental sensitivity,select andoptimize the economic and applicableremediation of petroleum pollution inferring to thedifferent situations of soil.
1.Project Overview
China Petroleum Daqing oilfield(called Daqing oil-field for short)is located in Daqing,HeilongjiangProvince.The first oil production plant of Daqingoilfield(called the 1st oil plant for short)is located inthe middle of the Sazhong development area ofChangyuan Saeteroilfield.The 1st oil plant is themain production plant which is the oldest plant,thelargest scale,the highest yield,the best benefit,pro-found culture,science and technology,and hasearned many awards.And it’s also the largest oilproduction plant in China.Founded in the October1960,the management area is 161.25 square kilo-meter,the geological reserves of 12.275 tons,andthere’re 12488 oil wells totally.There are 934 allkinds of stations and 14701 staffs.It has the stable
production which is more than 10000000 tons ofcrude oil for 34 years.In September 2006,it becomethe first national cumulative production of crude oilexceed 5 tons of oil production plant.In this pa-per,we research the petroleum contaminated soilpollution investigation and the selection of remedi-ation technology in the 8 typical target station onthe oil production plant.The specific target of thestation as shown in Table1.
North 1-2 union station is built in October 1987and located in the east of Nanzhongshi Road,Biaoervillage,in the north of the spark a change machineproduction brigade.The pit road is linked with theZhongshi Road and 207 Station Dedicated Ra-od.It’s mostly grass around the site,scattered dis-tribution of oil pumping well and measuramentroom.South 1-1 union station is built in December,1990.It’s 400 meters to the southwest of theChen’s countryyard.Here is the power sewagetreatment plant 200 meters to the northeast.150meters east is the oly sewage discharge standardstation.It’s near the Century Avenue in the Iron-man village intersection north of 1500 meters.It’sthe Danan 1 village on the south side of 1000metersNew middle 108 transfer station is built inOctober,2009,is located in Saertu District Houlong-gang bridge 300 meters north.Around the site,therest is almost the grassland besides the single wellstation,transmission lines and other lines outsidethe region.This station covers an area of 10577 m2,the building area is 1600 m2.Middle 202 transferstation is built in October,1992,belonging to the oilfactory 205 production team the 2nd oilfield,locatedin the west side 1500 meters of the Saertu Districtof Daqing.It’s the Youyi Avenue in the 500 meterswest,and it’s the North highway on the 300 metersto the south.Around the site,the rest is almost thegrassland besides the single well station,transmis-sion lines and other lines outside the region.It’still retains the low-lying marshes in the 30 metesof west.North 1-1 side oblique 037 wells is set up inSeptember,1982,located at one or two north areaand drainage area.Around the site of grass,scat-tered distribution of oil pumping well and measure-ment room,it’s the highway in the 150 meterswest.North 1-Ding 3-38 well is set up in September1981,located at one or two north area and drainagearea.It’s the grassland around the site.Here is therailway 100 meters away to the south side.North 1-Ding 2-64 injection station is set up in Novem-ber,1973,is located in the north east one or tworows of Portuguese basic well pattern.It’s thegrassland around the site,scattered distribution ofinjection wells and pumping wells.The factories arein the south.North 1-4-P134injection station is setup in November,1995,is located in the north east offault.There is space around the site,scattered dis-tribution of oil pumping wells,the highway is to the30 meters south,100 meters west.Contaminatedsites present situation are shownin Figure 1.1
2.Site Investigation
(1)The overview of region and site.The 1st oil plantis in the north of the Changyuan in Daqing.The ele-vation of this region is between 139.4 metersand152.5 meters,relatively flat terrain,groundslope is small,small changes in complex terrain,the basic landform is formed by projections,biogas,small vesicles hill shaped depressions and flat hill-ock.Due to the factors of the geological structureand topography,there’s no natural rivers in theproject area,which belongs to the water closeddrainage area.The project area was covered withupper phreatic groundwater,the recharge ofgroundwater is mainly phreatic water in filtration,precipitation,surface water,diving more currentsupply of confined water and groundwater lateralrunoffre charge,confined aquifer between the leakage recharge.It is excreted by evaporating.Thegroundwater depth is between 2.6 meters to 3.0 me-ters.The project site is veryflat,the groundelevation is from 126 meters to165 meters,it be-longs to the quaternary red,alluvial plain.Accordingto the field survey results,in the drilling depth,fromtop to the bottom stratum silty clays,the thicknessis about 2 meters,there are local thickness of lessthan 0.5 meters of sand.
(2)Survey methods and steps.Four joint stationsand oil transfer station in the typical stationlayout of sampling points at stations outside the boundary of the oil wells and water wells,samplingpoint layout in the reasonable range.The drillingdepth to the water table diving,every 0.5 meters-1.0 meters to collect soil samples,according to thesoil hole drilling,the naked eye identification,odorjudge and portable photoionization detector pre cal-ibrated using(PID)to determine the soil pollutionsigns.From each borehole,we select the represen-tative soil samples sent to the Daqing lab and ALSlab for analysis.The laboratory analysis programare given in Table 21
(3)Test Result.Particle analysis:This site is mainsilty clay,clayey silt and sandy silt and a little siltysand.Powder is mainly composed of particles,thetotal particle 50%-90%;clay exists in every stationin the study,it’s 3%-23%;sand distribution in thestudy site,it’s 6%-56%of the total particles.Thephysical indexes of natural state:the water rate inthe soil in each site in this study is between 15%to35%;density values to the distribution is from 1.5g/cm3 to 2.1 g/cm3;the relative porosity density isfrom 30%to around 50%.The permeability coeffi-cient and ignition loss analysis:vertical and hori-zontal soil permeability coefficient is almost thesame,the permeability coefficient of the soil anisot-ropy,permeability coefficient in the 10-4 to the 10-6cm/s distribution,low permeability.Thermal igni-tion loss is between 1.5%to 5%,It shows thatchanges in organic matter content in soil is large.(4)Site Contamination.North1-2 Station:in thesouthern part of the site,observation pollution area is about 20m2～30m2,PID maximum reading of400 ppm,the highest concentration of the oil was401 mg/kg,it’s more than oil background value,total petroleum hydrocarbon concentration is50446.0mg/kg.North 1-1-skewed 037:North of thesite observation pollution area is about 10m2,thehighest PID reading of 32.2 ppm,the highest con-centration of the oil was 396 mg/kg,more than oilbackground value;the east of the site on-the-spotobservation pollution area is about 250m2,thehighest PID reading of 146.0ppm,the highest con-centration of oil was 70.5 mg/kg,more than oilbackground value;the southern part of the site ob-servation pollution area is about 10m2,the highestPID reading of 1.6 ppm,the highest concentrationof olwas 145 mg/kg,more than oil backgroundvalue.North1-D2-64:in east of the siteobsevation ofsporadic pollution occurs,the total area isabout10m2,the highest PID reading is 168 ppm,thehighest concentration of oil was 63.5 mg/kg,lowerthan the background value of oil.South 1-1 unionstation:in the north of the site,sporadic pollutionoccurs,the total area is about 50 m2,the highest
PID reading is14.5 ppm,the highest concentrationof oil was 84.4 mg/kg,more than oil backgroundvalue.Middle202 transfer station:the East of the siteobservation pollution area is about 130 m2,thehighest PID reading is 295.8 ppm,the highest con-centration of oil was 46.6mg/kg,less than the oilbackground value;the southern part of the site ob-servation pollution area is about 200m2,the highestPIDreading is 76.9ppm,the highest concentration ofoil is 59.2mg/kg,lower than the background valueof oil;(3)to observe the north of the site is about1300m2,the highest PID reading is 649.5ppm,thehighest concentration of oil was 764mg/kg,morethan oil background value,total petroleum hydro-carbon concentration is 24309.0mg/kg.New middle108 oil transfer station,North 1-D 3-38 and North1-4-P134:not found signs of pollution.
(5)Summary of Site Contamination.According tothe results of laboratory analysis,all oil fields nrandom survey of Daqing typical stations have oil 1 detection,we have found the volatile,semi volatileorganic compounds and the total petroleum hydro-carbon detection in part of the sites.This paper se-lects “the impact on soil environment because ofDaqing oil field development and construction”,weadd 2 times of the standard deviationas(70.4mg/kg)to the background value results as theenvironmental background values.
3.Risk Assessment
The objective of risk assessment is to evaluatewhether the soil pollutants site adverse health ef-fects on human receptor,and establish target basedon health risk.Firstly establish the site conceptualmodel of health risk assessment,and then from theexposure assessment,Toxicity evaluation,riskcharacterization,uncertainty analysis four aspectsto consider assessment,finally
established target value[4].
(1)The Site Of Conceptual Model.The site conceptu-al model is a comprehensive description of site con-tamination released form pollution sources such assoil,water,air and other environmental media,rela-tionship model into the site and surrounding envi-ronment of human contact site receptors and recep-tor and influence on receptor.Only full potentialrisks associated with migration pathway receptoronly in the source of the association,the integrity ofsomeelements in
Table 3.are listed in detail.
(2)The Exposure Assessment.This project includesRoutes of exposure:Long term exposure pathways:direct contact with contaminated soil(accidental in-gestion and skin contact),dust pollution caused bysoil release induced by inhalation of dust,causedby soil pollution gas gas inhalation
Short term exposure pathways:inhalation of thegas in the maintenance of soil pollution caused bythe process of excavation,excavation in accidentalingestion and skin contact with contaminated soil.Long term exposure corresponding risk thanshort-term exposures,so consider the principle ofthe conservation,the risk assessment only considerthe risk of long-term exposure.Exposure scenariosconsidered the worst condition in reasonable con-text,evaluated the potential health risks affectedwhich the exposure parameters is given by the re-lated guidelines document(ASTM 2002;Ministry ofenvironmental protection,China 2009).In this Ap-plication of risk ,The exposure and risk level to cal-culate the risk assessment.is by RBCA Tool Kit forChemical calculation of Releases
(3)Toxicity Evaluation.The risk assessment ofhazard identification is limited to benzene,polycy-clic aromatic hydrocarbons,total petroleum hydro-carbons,the toxicological data whichdose responseassessment used is the main based on the UnitedStates Environmental Protection Agency Risk Infor-mation System or other similar databases.
(4)Risk Characterization.Risk characterization isprocess which is assess for the possibility and gradehave any negative impact on population exposureestimation.In the risk characterization if the hazardquotient and hazard index ratio greater than 1,thenwe think the pollutant exposure can potentially un-acceptable risk.From the viewpoint of Health secu-rity,the risk assessment using 10-6 as acceptablecancer risk value.If the cancer riskis higher than10-6,we think thatthere is a high potential forcancer risk.The risk assessment of the site level ofrisk are
summarized in the Table 4.
Table 4.Each Site Risk Summary
(5)Risk-based restoration goals.Risk assessmentcarried out by the existing data and The survey re-sults,the benzene and the total petroleum hydro-carbons in the soil may be through accidental in-gestion,skin contact,inhalation bring health haz-ards of high way for workers.The Repair suggestionpollutants value was Deductioned According theCalculation formulas and parameters come formGuidelines for risk assessment of China .the repairsuggestion target values in Table 5
ties、Site investigation no-complete and Model un-certainty Lead to The uncertainty of risk assess-ment.In the health risk assessment method toreduce the uncertainty mainly includes Applicationof field data and reliable data quality standards.Conservative assumption of the risk assessment in-clude:1)don,t consider the degradation of pollut-ants in soil;2)hypothesis the action or reaction ofsomething(as a machine or substance)under “bad”human behavior;3)all pollutants and health effectsof exposure
pathway for additive effect;4)toxicity data applica-tion is far lower than the negative effect on thehealth of the threshold.In summary,the health riskassessment of uncertainty is estimated by thehigher potential health risk to deal with.
(7)The Results Of The Risk Assessment.Accordingto the survey and the results of risk assessment,comparison site petroleum background values,thedepot repair priority screening,Table 6.
(1)Remediation Extent.According to the risk assess-ment,the main concerned contaminates of the siteare benzene and total petroleum hydrocar-bons(TPH).Soil pollution investigation of contami-nated site show the two main pollution type areground raw oil and its pollution to soil and soil pol-lution caused by oil-bearing wastewater andgroundwater,and the form of pollutants are groundraw oil and adsorbed type.Ground raw oil has lessvertical impact,the depth of impacted site common-ly less than 1.5 meters.The concentration of ad-sorbed oil gradually reducefrom top to bottom.Based on investigation of the pollution scope andcontamination degree on the horizontal directionand the vertical direction,preliminary estimated thedepth,area and volume of contaminated soil on typ-ical sitesSeen from the pollution range,contami-nated areais roughly 10 to 1300 m2on the horizon-tal direction,and the volume of contaminated soil isapproximately 20 to 5000m3
(2)Alternative Remediation Scheme.According tobasic facilities of Daqing Oil Field station,regional environmental conditions,the sensitive re-ceptors information all around and hydrogeologicaland geological condition,carrying out comparativeresearch after considering a full range of factorssuch as soil type,pollution scope and depth,con-tamination degree and type,preliminary selectedbelow several scheme that can compliant for DaqingOil Field station remediation[1].In-situ phytoreme-diation:Phytoremediation eliminate pollution bymeans of plant systems and its root system that canremove,volatilize or stabilize pollutants in soil,orby reducing toxic of pollutants remediate the soil.The mechanism of phytoremediation consist ofstrengthen the rhizosphere microbial degradation,plant extraction,phytodegradation and phytostabil-isation.In-situ cultivation of soil bioremediation:Using equipment plough contaminated soil,whileadd selected bioremediation agents and fertlizer,ir-rigation at the same time,to provide a good environ-ment for microbe as much as possible,making suredegradation start up in whole soil layers,petroleumpollutants in soil are degradated to carbon dioxideand water gradually.Durning remediation periodplowing and montoring need to be carried out peri-odically.According to the actual remediation prog-ress to determine whether need additional flora andnutrients.Feasibility experiment need to be carriedout before site operation.Soil samples were collect-ed to determine whether there is petroleum-degrad-ing microorganisms on contaminated soil,and labo-ratory test was carried out to determine the effect ofmicrobial degradation and various factors impactedmicrobial degradation[2].In-situ soil mixing chemi-cal remediation:Using equipment mixed pollutedsoil,adding chemical oxidizers simultaneously,most of the petroleum pollutants were removed bychemical degradation.Residual petroleum pollut-ants were degradation gradually by microbial catal-ysis which created by chemical oxidizers additional-ly.Chemical oxidizers include Fenton reagent,
Ozone,Hydrogen peroxide,Potassium permanga-nate and Chlorine dioxide,and oxidation reactioncan occur instantly.The method is compliant for
soil and ground water contaminated by petroleumsimultaneously[3].Comprehensive evaluation of al-ternative remediation scheme:In conclusion,therelative cost,implementation and the effect of reme-diation of alternative remediation scheme showed inTable 7,below project cycle were derived based onthe remediation time of one site.It can be seen fromTable 7,scheme 2(In-situ soil mixing chemical re-mediation)and scheme 3(In-situ cultivation of soilbioremediation)can be considered as main remedi-ation scheme,which have reasonable project cycleand highest score in comprehensive evaluation.
Note:—Evaluate weights;The more number ofsymbols,the better evaluate level which schemeachieved.Due to widespread uncertainly of site re-mediation,project cycle is mainly point at the con-centration of pollutants significantly reduce forin-situ remediation and ex-situ biological remedia-tion.The final project cycle depends on remediationobjective,hydrogeological characteristics of the site,pollutant characteristics and many factors,there isa certain degree of uncertainty.
(3)Proposal For Remediation Scheme.Simple reme-diation scheme has certain degree of limitation,andcan’t resolve the problem of soil remediation com-prehensive in a large scale.Therefore,joint use oftechnology has become current and future trends insoil remediation.A series of contaminated soil re-mediation schemes were defined after summarizingand analyzing the critical parameters of Daqing OilField such as pollutants characteristics,mean-while,the impact of site conditions,pollutant type,geological and hydrogeological situation,controls ofpollution sources and remediation measures all inconsideration.
According to the severity of contamination,Con-taminated soil can be divided as below:Free stateground raw oil and soil which have oil phase;soilcontaminated at residual saturation state;soil pol-luted at adsorption state.Combining in-situ andex-situ,choosing appropriate remediation methodsaccording to the severity of contaminated soil cangive full play to the advantages of each method,andcan optimize cost-effectiveness of the remediation tothe largest extent in general.
In combination with characteristics of petroleumcontaminated sites at Daqing Oil Field and existingconditions in the oil field,a set of soil remediationschemes were selected based on investigation of al-ternative remediation scheme,shown in Table 8:
Noe 4:Unit cog of remedation is baed an he estent of conaminaed sil reatment cepacity of 8 siesinvestigaked Ne include the cost of scheme design,on-sie gidace,coratruction marugment and aceptincemomkxing from professkeul remediation company.
5.Conclusion And Recommendations
(1)Summary Of Pollution Situation.
Survey results of 8 sites show that petroleum con-centration in soil of 5 sites is higher than back-
ground value puls 2 times standard deviation(70.4mg/kg)derived from ‘study on constructionof Daqing Oil Field impact on soil environment’,and over standard rate of survey sites is 62.5%.Over standard rate of soil was found in 2 joint sta-tion,1 oil transfer station and one production wellsurveyed.
The thickness of the unsaturated zone and con-taminated soil type:In survey station,the thicknessof the unsaturated zone is between 0.6 to 2.8meters,individual station greater than 3.5 meters.The stra-tum is mainly silty clay from top to bottom withinthe maximum depth of drilling hole.Average thick-ness of silty clay is about 2 meters.
According to the laboratory analysis results,pe-troleum pollutants were discovered widespread insoil sent to the laboratory of Daqing Oil Field.Totalpetroleum hydrocarbons were detected high concen-tration in soil samples sent to shanghai ALS labora-tory.Analysed from the causes of pollution,themain types of pollution are ground raw oil and itspollution to soil and soil pollution caused by oilywastewater.
Pollution area is roughly 10 to 1300 square metersin the horizontal direction at sites found contamina-tion,and the volume of contaminated soil is rangingfrom 20 to 5000 cubic meters substantially.In thevertical direction,the depth of ground raw oil im-pacted is less than 1.5 meters.Petroleum pollutantsconcentration of soil pollution caused by oily waste-water decrease from top to bottom.
(2)Summary of Health Risk Assessment
Risk assessment results show that total petroleumhydrocarbons in soil at part of sites have high healthrisk on the station staff,including the North 1-2united station and center 202 oil transfer station.
Based on the risk assessment,the main concernedcontaminates of the site are benzene and total petro-leum hydrocarbons.Risk-based remediation targetare derived from calculation:Benzene(0.62 mg/kg);total petroleum hydrocarbons(C6~C9:160 mg/kg;C10~C14:360 mg/kg;C15~C28:11450 mg/kg;C29~C36:11450 mg/kg).
(3)Summary of Soil Remediation Scheme
For ground raw oil and soil severely contaminatedby ground raw oil directly,suggested remediationscheme is excavation and send the excavated soil toground raw oil processing station to dispose.
For shallow soil contaminated by crude oil and oilywastewater,suggested remediation scheme is in-si-tu cultivation of soil bioremediation.
For shallow to deep soil contaminated by crude oiland oily wastewater,suggestion remediationscheme is in-situ soil mixing chemical remediation.For contaminated soil located in restricted areasuch as underground facilities and pipelines,sug-gested remediation is combine system control andmonitored natural attenuation.
(4)Suggestion
Based on the results of the risk assessment,groundraw oil contaminated areas identified outside thehigh-risk research station need centralize disposedby Daqing Oil Field.Degradation ability and degradation cycle of micro-bial in Daqing Oil Field soil for totalpetroleum hydrocarbons were investigated in labo-ratory level,and the feasibility of monitored naturalattenuation was inspected.
Preliminary experiments for in-situ soil mixingchemical remediation and in-situ cultivation of soilbioremediation was carried out on the high risk siteswhich need remediation preferentially,which lay afoundation for technical storage and remediationdemonstration project in subsequen
Adding many kinds of remediation methods such asincineration,making a difference on discrepant cir-cumstances,using targeted methods,the petroleumpollutants are disposed in the principle of mostvaluable cost performance.
References
[1]Li,Jianbing;Song,Xinyuan;Hu,Guangji.Ultra-sonic desorption of petroleum hydrocarbonsfrom crude oil contaminated soils[i]Journal of envi-ronment al science and health parta-toxic/hazardous substances and environmentengineering 2013.48(9)1378-1389
[2]Agwu,Ogochukwu A.;Ilori,Matthew O.;Nwa-chukwu,Simoncyril U.Utilization of DrillingFluid Base Oil Hydrocarbons by MicroorganismsIsolated from Diesel-Polluted Soil[J]SOIL &SEDIMENT CONTAMINATION 2013.22(7).817-828
[3]Iturbe,R(Iturbe,R);Flores,RM(Flores,RM);Torres,LG (Torres,LG).Subsoil contaminatedby hydrocarbons in an out-of-service oil distributionand storage station in Zacatecas,Mexico[J].ENVIRONMENTAL GEOLOGY.2003.44(5).608-620
[4]GE jia,LIU zhenhong,Yang qing.Investigationand assessment:oil leakage contamination at agas station and the health hazards due to its con-tamination[J].The environment safety andscientific.2013.13(2)97-101
[5]wu guo zhong;coulon,f;yang yue wei.combiningsolvent extracting and bioremediation forremoving weathered petroleum form contaminatedsoil[J].PEDOSPHERE.2013.23(4).455-46336
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