Experimental determination of permeability in the presence of hydrates and its effect on the dissociation characteristics of gas hydrates in porous media Anjani Kumar a,1 , Brij Maini a, ⁎, P.R. Bishnoi a , Matthew Clarke a , Olga Zatsepina a , Sanjay Srinivasan b a University of Calgary, Calgary, Alberta, Canada b University of Texas, Austin, USA abstract article info Article history: Received 7 August 2008 Accepted 26 October 2009 Keywords: Gas hydrate Porous media Hydrate dissociation Permeability Although there are many uncertainties in hydrate dissociation process in porous media, numerical simulation gives useful information in evaluating economically feasible gas recovery processes from gas hydrate reservoirs. Furthermore, there are several unknown parameters involved in the numerical model and determination of accurate values of these parameters is essential for reliable production forecasts. One of these parameters is the variation of permeability of the porous media in the presence of hydrates. In this study the permeability to gas was experimentally determined at varying hydrate saturations in a porous medium made of packed glass beads. By comparing the experimentally determined permeability with those calculated using the empirical permeability correlations it was found that for initial water saturations less than 35%, hydrate tends to form on the grain surfaces. However, for initial water saturations greater than 35%, the experimental results indicate a pore filling tendency of hydrate formation. The experimental permeability values were also correlated with the Masuda et al.'s (1997) permeability model and a value of 3.0 was obtained for the permeability reduction exponent. To evaluate the impact of permeability reduction exponent on the dissociation process, a one-dimensional numerical model was developed for dissociation of gas hydrates in porous media by depressurization. The numerical model includes the three mechanisms i.e. kinetics of hydrate decomposition, heat transfer and fluid flow; that might be associated with the dissociation of hydrates in porous medium. The effect of permeability reduction exponent on the dissociation characteristics of hydrate was analyzed using this simulator. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Natural gas hydrates represent an immense hydrocarbon resource underlying large portions of the world's arctic continental areas and sub-sea continental shelves (Collett, 1995; Boswell, 2007). While these deposits may potentially yield important sources of energy for the world, scientific and engineering research needs to be undertaken to make their production feasible. Presently there are no commer- cially proven recovery techniques for exploitation of this enormous resource, but it is obvious that realization of even a small part of their potential would provide a very significant new source of natural gas to meet future energy requirements. Interest in natural gas hydrates is increasing with the foreseen future demand for large volumes of natural gas as a relatively clean hydrocarbon fuel. Today, the U.S. Geological Survey estimates that methane hydrate may, in fact, contain more organic carbon than all the world's coal, oil, and non-hydrate natural gas combined. The magnitude of this previously unknown global storehouse of methane is truly staggering and has raised serious inquiry into the possibility of using methane hydrate as a source of energy. However various issues need to be resolved to convert gas hydrate from an energy resource to an energy reserve of real commercial value. Although the resource of gas hydrates is enormous, production of gas from hydrates is extremely challenging and yet to be realized. Many production schemes have been proposed for the recovery of natural gas bound in the solid state. The three most practical schemes under investigation and active research are: 1) Thermal stimulation 2) De- pressurization and 3) and Inhibitor injection. The potential of gas production through these different production techniques is still uncertain and is in the investigation stage. One method of investigation is with the use of mathematical/numerical models but that requires reliable estimates of various petrophysical and other parameters. Several types of predictive models for gas hydrate dissociation have been published in the literature. These models vary from simple energy balance models, to single-phase analytical porous-flow models, to robust three dimensional, three-phase numerical simulators (Hong, 2003; Moridis et al., 2002; Moridis, 2002; Masuda et al., 1999; Swinkels and Drenth, 1999 etc.) All reported models require several parameters involving physical properties of porous media in the presence of hydrates. In the absence of experimentally determined data for these parameters, researchers have made use of correlations or assumed values for use in the Journal of Petroleum Science and Engineering 70 (2010) 114–122 ⁎ Corresponding author. E-mail address: bmaini@ucalgary.ca (B. Maini). 1 Now with Computer Modeling Group. 0920-4105/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.petrol.2009.10.005 Contents lists available at ScienceDirect Journal of Petroleum Science and Engineering journal homepage: www.elsevier.com/locate/petrol