Risk Assessment Oil and Gas

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OILGAS
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4.6.3.3. Oil Spray Stressor
Oil contamination of the air can occur during the drilling and production process. During drilling a “blowout” of a highly pressurized field can lead to large releases of oil into the air and terrain. The Priobskoye field is under low pressure, so the risk of blowout is small. After production begins, the pumping stations and other equipment can produce small leaks that produce aerosols. The pathway of the aerosol is largely dependent on the wind. The characteristics of the aerosols depend on the oil type, water content, aperture size, pressure, and ambient temperature. In the frigid conditions typical for half the year, freezing of the water and/or oil is a complex problem that may require empirical studies. During the summer, conditions are more amenable to modeling. The contamination is at nearly ground level but the spray may have an upward component. In addition, there may be updrafts, which give another vertical component. Thus the oil droplets become projectiles influenced by horizontal wind and air drag and gravity to produce a trajectory described in the algorithm section. The model spray trajectory described in the algorithm section (4.6.2) is a good illustration of the effects of uncertainty. With a large uncertainty in the oil spray parameters, the extent of the oil spray plume and its resultant damage could potentially include a very large area. Careful measurement of spray parameters would likely limit their range of deposition and lower the risk to forest areas. For the oil spray result shown in the Figure 17, the range of wind speeds and directions was taken from the Surgut meteorological station as reported in the Amoco EIS (1995). The droplet size distribution was modeled with a gamma distribution with a 50 micron mean for purposes of illustration. Similarly, the height distribution was a gamma distribution with a mean of 100 meters.
In conclusion, the research on the impact of light hydrocarbons on photosynthesis and viability of trees is not comprehensive. It seems that airborne impact of light hydrocarbons is considerably less than its impact through soils. Moreover, if light hydrocarbons do not cover the ground and are brought into the area by wind, then, most likely, the concentration of such hydrocarbons is relatively low and could cause harmful effect only on edge tree stands.
Based on the aforementioned factors, it can be noted that, in general, forests experience significant disturbance caused by volatile hydrocarbon particle under the conditions of chronic impact. It’s likely that high ecological risk would characterize vegetation in the area adjacent to

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Figure 17

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such sources of constant pollution as pump stations and central oil collection units. Wind direction and speed should also be considered in calculating the area of pollutant dissemination.
Another atmospheric risk to the environment is oil burn-off. The impact is caused by oxygen depletion, thermal emission, and contamination of air, vegetation, and soils with products of incomplete burn-off of hydrocarbons, carbon monoxide, nitrogen oxide, sulfur dioxide, and other chemical compounds. The radius of direct thermal destruction ranges from 10 to 25 meters for soils and 50-150 meters for vegetation. In violation of oil development regulations, liquid components of oil will periodically penetrate into the oil burn-off units and pollute adjacent territories since such components will not burn up completely.

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