We consider numerical modeling of compositional two-phase flow in porous media, and we propose a nonlinear formulation that employs a variable-set based on compositional space parameterization. In the formulation, the phase-fraction and saturation change 'continuously' in the immiscible region of the compositional space. Inside the two-phase region, these variables are identical to the saturation and phasefraction of the standard approach. In the single-phase regions, however, these variables can become negative, or larger that unity. We demonstrate that when this variable set is used, the EOS computations are resolved completely within the general Newton loop. That is, no separate phase-stability or flash computations are necessary. The number of general Newton iterations grows only slightly, and overall savings lead to more efficient simulations. We discuss using this variable set, which can be thought of as an extension of the natural variable, in two ways. The first scheme honors the nonlinear dependence of the overall density on phase-fractions and saturation, and the second employs a linearized relation for the overall density. Both schemes are compared with the standard natural-variables formulation using several challenging compositional problems. We also describe how the proposed approach can be used for modeling multi-contact miscible displacement processes.
|Title of host publication||ECMOR 2010 - 12th European Conference on the Mathematics of Oil Recovery|
|Publication status||Published - 2010|
|Event||12th European Conference on the Mathematics of Oil Recovery - Houten, The Netherlands, Oxford, United Kingdom|
Duration: 6 Sep 2010 → 9 Sep 2010
|Conference||12th European Conference on the Mathematics of Oil Recovery|
|Period||6/09/10 → 9/09/10|