Development of a generalised compositional multiphase model for flow and transport in porous media

Abstract

Fresh water is one of the most important natural resources. However, like other natural resources, the usable water is limited while the demand for water increases as industrialization proceeds and the population grows. What makes matters worse is that water resources are being reduced by pollution. Groundwater is an important water resource. However, in many countries, it has not been fully developed yet, either because of sufficient surface water sources, technical problems, or geographical conditions. Generally groundwater is relatively clean and is better protected from pollutants than surface water. Thus groundwater is an important subject for water engineers and scientists who have focused on its development and protection. In both cases, research into the movement of pollutants plays an important role in the effective exploitation of groundwater. Recently hydrologists concerned with groundwater pollution have studied multiphase flows in the subsurface because many pollution problems are characterized by multiphase contamination. The simplest multiphase pollution problem is solute transport in the unsaturated zone. More complex multiphase pollution problems involve organic matter such as petroleum products discharged to use oil. Since many of organic products are essential to our normal life and industry, the potential for groundwater pollution by them is significant unless they are controlled properly. In multiphase problems, the organic compounds may form their own flows that are distinct from the subsurface water flow but partly dissolve with the water phase and cause low concentration long term pollution of the water phase. There have been many efforts dedicated to predicting the movement of pollutants. A lot of mathematical and numerical models have been developed with the aid of laboratory and field works. However almost all models have been developed to solve a few restricted scenarios. Model users are obliged to invest considerable time in understanding the various models; their numerical accuracy and coding.The purpose of this study is to categorize the pollution patterns in the subsurface and to develop a numerical model that can be applicable to a wide variety of subsurface contamination. The general primary variables and generalizing procedures are employed to make the numerical model applicable to various pollution patterns. Many kinds of tracers can be used to know the behaviors of fluid phases in the subsurface. Because the model is able to describe partitioning of mass of a component among fluid phases, tracer problems also can be simulated by the model.