The temperature and pressure as well as the compositions of the reservoir fluids vary with depth. While the deeper the depth, the higher the temperature and pressure, the compositions of the reservoir fluids are not necessarily changed monotonously. In general, the concentrations of the light components decrease with the depth while that of the heavy components increase. The changes of the compositions cause the changes of the fluid properties, such as, density and viscosity, etc. It is, therefore, very important to understand the composition gradient with the depth in reservoir in order to assess the reservoir and to make strategic plan in exploration and production.
There are many factors that lead to the variation of the reservoir fluid compositions, for example, biodegradation, and mass transfer caused by the convection of the reservoir fluids. In this module of cloud computing, the equations of state are applied for the calculations of fluid compositions and properties changed with the depth in reservoir that are driven by fluid gravity, heat diffusivity and chemical potential.
The results of the calculations are displayed in terms of tables and 3-D phase diagram. The attached plot shows the phase behavior changed at the depth of 2,500 meter to 2,520 meter for a given reservoir fluid.