Continuation of the tie-simplex space for threephase thermal-compositional systems

Alireza Iranshahr, D. Voskov, H Tchelepi

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review


Modeling the phase behavior associated with compositional flow simulation of systems that form more than two phases (e.g., steam, or CO2 injection) is a challenging problem. In addition to the coupling of thermodynamics with the nonlinear equations of flow and transport, accurate phase-state identification for mixtures that form three (or more) phases, as function of pressure, temperature and composition, is the subject of active research. We describe a general negative-flash method for multi-component thermal systems that can form three, or more, fluid phases, including a convergence proof. This extended negativeflash approach integrates quite nicely with flow simulation based on adaptive tie-simplex compositional space parameterization. We prove that tie-simplexes change continuously with pressure, temperature, or along a continuous trajectory in compositional space. Continuation of the tie-simplex space provides theoretical justification for the tie-simplex based flow modeling, in which interpolation in pressure and temperature for a limited number of tie-simplexes is performed during a simulation run. We also show how a tie-simplex associated with a given composition can degenerate as a function of pressure and temperature. We focus on the complex behaviors of the tie-triangles and tie-lines associated with threephase, steam-injection problems. The algorithms that capture the degeneration of the tie-triangles into tielines are described in detail. Interpolation in the parameterized compositional space is used to identify the phase-state and proves to be as reliable as a 'conventional' phase-stability test for three-phase mixtures. This extended negative-flash algorithm has been integrated into our tie-simplex based flow simulation framework. We demonstrate the effectiveness of the framework using several compositional steaminjection problems with complex behaviors.

Original languageEnglish
Title of host publicationECMOR 2010 - 12th European Conference on the Mathematics of Oil Recovery
Publication statusPublished - 2010
Externally publishedYes
Event12th European Conference on the Mathematics of Oil Recovery - Houten, The Netherlands, Oxford, United Kingdom
Duration: 6 Sep 20109 Sep 2010


Conference12th European Conference on the Mathematics of Oil Recovery
Country/TerritoryUnited Kingdom


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