Liquid Dropout In Gas Condensate Reservoirs: A Pore Scale Approach

ABSTRACT

Description Gas-condensate reservoirs have a significant share of the world’s gas supply. Recovered condensate of these reservoirs has a high value in the market as well. However, when the reservoir pressure declines below its dew point pressure, liquid may drop out of gas inside the reservoirs and consequently leaves a major part of this resource irrecoverable. In the present work, we investigate condensate drop out at the pore scale using a virtual porous medium. This can help to predict and manage production behaviour at the reservoir scale. Virtual Porous Media (VPMs) are created from 2D and 3D pore scale images. Pressure depletion scenarios are applied to the VPMs as potential recovery processes. An integrated numerical package is assembled to simulate pore scale physics in gas condensate reservoirs using computational fluid dynamics and VPMs. The volume of fluid (VOF) based numerical scheme is coupled with a proper phase change model to simulate mass transfer and condensate dropout phenomena. Post processing algorithms generate condensate dropout profiles and gas relative permeability curves for various depletion scenarios. Applications Understanding of liquid drop out phenomena, the regions that liquids block pores and also parameters affecting the severity of condensation in porous media such as pressure decline rates are essential for optimization of production from gas condensate reservoirs. Moreover, generated relative permeability curves can be potentially used in full field reservoir simulation. Results and Conclusions We perform a parametric study to reveal the important factors on liquid recovery. For instance, the effect of pressure decline rates and presence of various minerals, i.e. Clay, Feldspar and Quartz, are thoroughly analyzed. It is revealed that mineral complexity in terms of solid surface properties or heterogeneous wettability can significantly affect the regions of condensation and blocked pores. The results show that that dropout first occurs in larger pore bodies. It blocks a number of pores/throats and cease flows. Hence, the relative permeability is reduced which leads to lower gas productivity. Technical Contribution In this paper we apply pore scale physics at low interfacial tension to investigate condensation related phenomena in reconstructed reservoir rocks. Condensate nucleation sites, complex mineralogy and liquid dropout movement, which affect well productivity and condensate recovery, are analyzed.

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