Numerical Simulation Of Petroleum Pollutant Transport In Soil

Petroleum pollution in soil is another pollution problem following pesticide and heavy metal in recent years. Petroleum is a kind of compound composed of alkane, cyclane and aromatics, which have the potentiality leading to cancer, deformity and mutation. Petroleum can be found on the ground everywhere around the oil wells in the process of petroleum development and transport. With the advancing of petroleum industry, human being comes to focus on the petroleum pollution. In this thesis, on the basis of characteristic recognition in the oilfield, the transport and change law of petroleum pollutant in the soil is analyzed and summarized. The pollutant by migration, transformation and leaching in the soil enter the groundwater system in three stages: â… Leaching through the vadose zone; â…¡Diffusing into the saturated water zone from the vadose zone; â…¢ Entering the saturated water zone and polluting the groundwater. The pollutants migrate in the vadose zone in three physical states: remaining liquid pollutants (liquid oil); gas pollutants; pollutants resolved in the porous water (or NAPLs). According to the mechanism of solute migration and transformation in the soil that considered as a kind of porous media, the numerical simulation model for petroleum pollutant migration and transformation in the vadose zone is presented on the basis of comparing other models and comprehensively studying the relative effective factors. As for the numerical solution of partial differential equation (PDE), this thesis solves PDE by Alternating Direction Implicit Method, which has stable difference form and linear equation set that can be easily solved by Thomas. Meanwhile the necessary parameters can be measured through the laboratory and field experiments and by the document study. By this model the distribution, migration and transformation of oil pollutant in the soil can be predicted around the oil wells. The result shows that the oil on the ground, which mainly accumulates more than 30cm in the soil, can permeate 60cm in depth at most, which accords with the measured result. It also proves that the prediction method used in this thesis is practical and feasible. The conclusion can be drawn that this method can provide rational reference and evidence for the petroleum development and treatment of polluted soil.