The Role of Adsorption Isotherms on Chemical-Flooding Oil Recovery

摘要

The injection of chemical solutions plays an important role in increasing the recovery factor of mature fields. Compositional models considering adsorption phenomena describe polymer/surfactant flooding as a function of the chemical component concentration and salinity of reservoir/injection water. The concentration part of the solution for 1-D multicomponent polymer/surfactant flooding is completely defined by adsorption isotherm and is independent of relative permeabilities and phase viscosities. The one-phase displacement solution has been already developed and it is a well-known problem. The continuous injection of chemical solutions is a Riemann problem solved by introduction of a self-similar variable. In this paper the solution of the twophase problem for chemical flooding is presented. It is considered the injection of two dissolved components considering adsorption phenomena for two different isotherms: Langmuir and Henry. A flow potential associated with the conservation of the aqueous phase is introduced as a new independent variable instead of time. This change of variables allows the system splitting in one equation and a thermodynamic system. The number of auxiliary equations is less than the number of equations in the compositional model by one. The solution of the thermodynamic part was done by the method of characteristics and it is completely determined by the adsorption isotherm. Once the two-component adsorption problem is solved, the two-phase flow behavior can be predicted. The applications include the choice of the chemical components to be injected for each reservoir, and also evaluate water compatibility. Another important utilization is testing of numerical compositional simulators by checking the independence of compositional dynamics on transport properties and by comparison of the numerical and analytical solutions. The obtained analytical solutions may be used in the development of streamline chemical EOR simulators.