Mathematical Model Of Transportation And Conversion Of Valatile Organic Compounds In Vadose Zone

With the increasing development of international industrialization,the requirement of energy resources is improving.Nowadays more and more wast- e oil and water containing oil ingredient are produced along with the petroleum exploitation and refinement.The waste water produced viapetrochemicals and mechanism manufacture industry includes many kinds of oil and the problem of surface spills or subsurface leakage exists mostly in gas stations and underground oil tanks everywhere.All the waste oil,waste water and leaked oil transfer perpendicularly and pervade breadthwise,causing contamination towards groundwater system meanwhile damaging human's health.Thus,it is necessary to analyze and simulate the kinetic process of such materials and forecast their pollution range and component concentration in the subsurface in order to provide evidences for the treatment and risk evaluation.The research of transportation and conversion of volatile organic compou- nds in vadose zone began at the 20th century.Now we think that it is a nonline- ar physical and chemical process composed of water-oil-gas three phases flow and coupling multi-physical factors.So that in this paper, we established the water-oil-gas three phases flow mathematic model, Under the isothermal con_dition and other hypothesizes, using theories of the petrophysics and reservoir numerical simulation and groundwater numerical simulation for refer- ences, applying the conservation of mass and the continuum medium mechan- ics method. It made the formation process of mathematic model more integrate and legible. We can apply generalized difference methods to separate the above water-oil-gas three phases flow equations and concentration equations and introduce damp parameters Newton descending method to resolve that equations system. This method can escape the shortcoming that the iteration was broken down when the Jacobi matrix is singularity or morbidity, and extend the local convergence to the global convergence.We designed a physical modle to validate the mathematic modle and found that : the leak oil seep vertically by the gravity and spread horizontally along the surface .A small quantity of leak oil was hold almost in the upper porous medium of capillary zone, and the horizontal extend range is narrow. the capillary zone is the main enrichment zone for the leak oil. When a great deal of oil was leaked out, except a little oil is hold by the upper porous medium of the capillary zone, the leakage oil can overcome the entry pressure of the interface between oil and water to enter the capillary zone, and seep vertically by the gravity. Lastly, it penetrates through the capillary zone, then float on the table of groundwater.