Study On Analysis And Environmental Behavior Of Petroleum Pollutants In Daqing Oilfield

In oilfield development, much oily wastewater and solid wastes generated. On the other hand, since the accident, unnormal operation and maintenance, petroleum hydrocarbons would emit. These pollutants may cause the serious pollution of environment. Some of the pollutants exist in the water in the form of floating oil, emulsified oil and dissolved oil. Other pollutants exist in the deposits because of the sediment adsorption. This kind of pollutant may emit under the special conditions and causes the secondary pollution of the water, and then cause potential threat of the water resource. So the study on the petroleum pollutants and environmental behaviors has important realistic meanings for the polluted source treatment and the petroleum pollutant controlling.In this paper, the main environmental pollution technology, pollution source and characteristic pollutants were identified based on the study on the environmental geography and oil development technology. The main pollutants and their source were determined from analysis of the operation wastewater, solid wastes and pollutants in lakes and ditches in Daqing oilfield show. The experimental study and mathematical modeling were used to invstigated the environmental behaviors, migration, transformation and degradation law of the petroleum pollutants. These studies can be used to propose the controlling methods of the petroleum pollutants.This paper contains four parts as follows.1. Analysis and evaluation of pollution sorce and the characteristic pollutants of Daqing oilfieldBased on brief analysis of the environmental geography and oil development technology and detailed analysis of production, content and chearteristics of the pollutants in the oilfield development, the single factor contaminant index method, environmental standard and the background value in the soil were used to identify and evaluate the main characteristic pollution source in the development of Daqing oilfield. The production, amount and contents of three characteristic pollution sources, i.e. wastewater from the oil production testing and fracturing, and wasted tilter materials were analysis and evaluated. About them, little is known. The results show that in the development of Daqing oilfield, the main characteristic pollution sources are operation wastewater, i.e., wastewater from the oil production testing, fracturing and oil extraction, solid contaminants from well drilling. The main pollutants are petroleum organic contaminants.2. Investigation of petroleum pollutants in the main lakes and ditches of Daqing oilfieldThe content, composition and distribution of petroleum organic pollutants in the sediments of main lakes in development area of Daqing oilfield were studied using the methods of field sampling, solvent extracting, sample stacking, group composition analysis and Gas chromatography/mass spectrometry (GC/MS) analysis. The results are as follows.(1) The contents of petroleum organic pollutants in the dry mud samples of most lakes in Daqing oilfield all reach to several hundred mg per kg. For some dry mud samples, the value even gets to several ten thousands of mg per kg. It shows that the sediment in each lakes was polluted at different degree. The total compund contents of the samples from nine lakes are all higher than the background value in the soil of Daqing (50 mg/kg).(2) The ratio of light components to heavy compents of the petroleum organic compounds shows the migration speed and degradability of the petroleum components. From the investigation, is known that the ratio ranges from 1 to 3. It is lower than that of normal value of the crude oil in Daqing oilfield. This result shows that in the sediment samples from the lakes, the speeds of migration and degrade of the light component are higher that those of heavy compents.(3) In the sediments, the main petroleum pollutants are alkanes, in which the relative content of C13～C33 is about 30%～70%. Biphenyl compounds, naphthalene and anthracene are also exits in the sediment samples. This means that the organic compounds in these samples come from the petroleum pollutants. The difference of the sediment age (the time for the compund drained into the lake), preservation conditions, migration and degrade speeds of the petroleum pollutant reslult the differenc of the content and composition.(4) The spatial distribution pattern of petroleum organic compounds was studied. The results show that the organic compound distribution has a certain relationship with the depth. The content of the petroleum organic pollutants on the surface of the sediment is the highest. With the increasing of the depth, the content decrease. The pollution depth in the sediment is about 20cm. The pollutants are mainly adsorpted in the depth range of 0 to 10cm. At the water inlet of the lakes, the organic compounds are easy to adsorpted in the depth range of 10 to 20cm. At the position far from the water inlet, the organic compounds are adsorpted in the depth range of 0 to 10cm.3. Invstigation of the petroleum pollutants migration, transformation and degradation The content and composition of petroleum organic pollutants in water and in the sediments of four arterial canals, i.e., western main canal, central main canal, eastern main canal and Donger main canal, in development area of Daqing oilfield were studied using the methods of field sampling, solvent extracting, sample stacking, group composition analysis and Gas chromatography/mass spectrometry (GC/MS) analysis. The environmental pollution condition, pollutant species, pollution sources, pollutant contents and composition, and the distribution of the organic pollutants in the main canals were found out.The results are as follows.(1) The organic content in four main canals ranges from 4.0mg/L to 342.9mg/L. On the surface of sediment, the content ranges from 74.29 mg/kg to 1670 mg/kg. The content around sewage outfall is higher. The canals were all polluted in different degree. On the whole, the main organic pollutants are petroleum compounds, the sediment of the four main canals were all polluted by the petroleum pollutants in different degree. The total compund contents of the samples from these four canals are all higher than the background value in the soil of Daqing (50 mg/kg).(2) Comprehensive analysis results show that the Donger main canal and the western main canal have the low-degree pollution. The central main canal was contaminated most seriously. The organic contents in the sediments are all high. In the four main canals, the different point pollution source results the obviously different organic species and contents at the sampling point. At some point, the characteristic pollutants is obvious. In the eastern main canal and the western main canal, the petroleum compounds are the main pollutants at each sampling point. In the Donger main canal, the content of life pollutants is higher. In the central main canal, the contents of petroleum and life pollutants are all high. In the western main canal, the petroleum compounds are the main pollutants.(3) In the four main canals, the point pollution source has great influence on the contents of the organic pollutants. At different sampling point, the organic contents are different. In the sediment and on the surface of the four main canals, the contents of organic pollutants along the flow direction increase from the upstream to the downstream.(4) In the four main canals, the contents of organic pollutants on the surface of the sediment is the highest. With the depth increasing, the contents decrease. The decreasing speed in the depth range of 0 to 10cm is high. In the depth range of 10 to 20cm, the speed is low. The area in the sediment with the depth range of 0 to 10cm is the main adsorption area for the organic pollutant.4. Investigation of migration properties and law of petroleum pollutants in Daqing Oilfield The experimental study and mathematical modeling were used to invstigated the migration properties and law of petroleum pollutants in Daqing Oilfield. Based on the investigation of methods and means for the petroleum organic compounds migrate into the water and soil of the oilfield, existing form, and migration means and characteristics analysis of the compounds in the soil of oilfield. The experimental study and mathematical modeling all show that the petroleum pollutants in the soil of Daqing oilfield have the characteristics as followsIn horizontal direction, the petroleum pollution degree is inversely proportional to the migration distance. In vertical direction, the petroleum mainly aggregates in the subsurface of soil within the depth of 25～35cm. In the depth range of 0～5cm, the pollutant content is the highest. With depth further increasing, the content decreases exponentially. When the equilibrium is reached, the influence depth and the pollution depth of the petroleum pollutants are 40～50cm and 30～40cm respectively, that is to say, the migration ability is very weak.The migration properties and law of petroleum pollutants in Daqing Oilfield environmental obtained from the experimental studies are conside with those from the mathematical modeling.