Title: Visual investigation of residual gas saturation in porous media

Authors: Mahnaz Hekmatzadeh; Mitra Dadvar; Mohammad Ali Emadi

Addresses: Department of Petroleum Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran; IOR Research Institute, National Iranian Oil Company, Tehran, Iran ' Department of Chemical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran ' IOR Research Institute, National Iranian Oil Company, Tehran, Iran

Abstract: Residual gas saturation (RGS) is a key property for estimating the amount of gas reserves in water drive gas reservoirs and can lead to possible decisions on enhanced gas recovery. Most of the previous studies correlate RGS with petrophysical parameters [initial water saturation (IWS), permeability and porosity] regarding experimental data in core scale that show inconsistent results. Therefore, determining effective parameters that affect RGS remains an outstanding challenge in core experiments. Since the fundamental behaviour of multi-phase flow in porous media is influenced by displacement mechanisms at pore scale, it is necessary to study pore-scale behaviour in gas-saturated micromodels to recognise the important parameters affecting RGS. Glass micromodels with different patterns are used in experiments to study the effect of heterogeneities, flow rate and imbibition displacement type (co-current or counter-current) on RGS. The experimental results indicate that RGS is increased by increasing network heterogeneity, decreasing pore and throat size, increasing aspect ratio and decreasing angularity. Counter-current imbibition causes higher RGS and lower recovery factor compared to co-current imbibition. According to the results, RGS is decreased by increasing imbibition rate in co-current imbibition. However, RGS is increased in counter-current imbibition at higher flow rates. Therefore, boundary condition and water encroachment rate should be considered properly for estimating RGS in core scale. [Received: February 10, 2013; Accepted: December 31, 2013]

Keywords: micromodelling; residual gas saturation; RGS; water encroachment; film flow; porous media; gas reserves; water drive gas reservoirs; enhanced gas recovery; initial water saturation; permeability; porosity; imbibition displacement; network heterogeneity; pore size; throat size; aspect ratio; angularity.

DOI: 10.1504/IJOGCT.2015.070836

International Journal of Oil, Gas and Coal Technology, 2015 Vol.10 No.2, pp.161 - 178

Received: 11 Feb 2013
Accepted: 31 Dec 2013

Published online: 30 Jul 2015 *

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