Front Tracking Using a Hybrid Analytical Finite Element Approach for Two-Phase Flow Applied to Supercritical CO2 Replacing Brine in a Heterogeneous Reservoir and Caprock

Christoper McDermott, A.E. Bond, W. Wang, O. Kolditz

Research output: Contribution to journalArticlepeer-review

Abstract

Predicting fluid replacement by two-phase flow in heterogeneous porous media is of importance for issues such as supercritical CO sequestration, the integrity of caprocks and the operation of oil water/brine systems. When considering coupled process modelling, the location of the interface is of importance as most of the significant interaction between processes will be happening there. Modelling two-phase flow using grid based techniques presents a problem as the fluid-fluid interface location is approximated across the scale of the discretisation. Adaptive grid methods allow the discretisation to follow the interface through the model, but are computationally expensive and make coupling to other processes (thermal, mechanical and chemical) complicated due to the constant alteration in grid size and effects thereof. Interface tracking methods have been developed that apply sophisticated reconstruction algorithms based on either the ratio of volumes of a fluid in an element (Volume of Fluid Methods) or the advective velocity of the interface throughout the modelling regime (Level set method). In this article, we present an "Analytical Front Tracking" method where a generic analytical solution for two-phase flow is used to "add information" to a finite element model. The location of the front within individual geometrical elements is predicted using the saturation values in the elements and the velocity field of the element. This removes the necessity for grid adaptation, and reduces the need for assumptions as to the shape of the interface as this is predicted by the analytical solution. The method is verified against a standard benchmark solution and then applied to the case of CO pooling and forcing its way into a heterogeneous caprock, replacing hot brine and eventually breaking through. Finally the method is applied to simulate supercritical CO injected into a brine saturated heterogeneous reservoir rock leading to significant viscous fingering and developement of preferential flow paths. The results are compared with to a finite volume simulation.
Original languageEnglish
Pages (from-to)545-573
Number of pages29
JournalTransport in Porous Media
Volume90
Issue number2
DOIs
Publication statusPublished - 1 Nov 2011

Keywords

  • Two-phase flow
  • Hybrid analytical numerical
  • CO2 sequestration
  • Caprock integrity
  • Front tracking

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