Van der Waals interactions in systems involving gas hydrates

Abstract

International audienceThe goal of this work is to quantify the Van der Waals interactions in systems involving gas hydrates. Gas hydrates are crystalline compounds that are often encountered in oil and gas industry, where they pose problems (pipeline plugging. etc.) and represent opportunities (energy resources. gas transport, etc.). We focus on methane hydrate, which is the most common one. and calculate its Hamaker constant. Two methods are used and lead to results in good agreement. The Hamaker, microscopic, approach gives a first estimate of the Hamaker constant of 4.59 x 10(-21) J for the hydrate-water-hydrate system. The Lifshitz, macroscopic, method used in combination with the Kramers-Kronig relationship gives a value of 8.25 x 10(-21) J. The Hamaker constant is also computed for three phases systems (gas hydrate clathrate and liquid water with ice, dodecane, quartz, sapphire, Teflon, metals). The interaction potential in different geometrical configurations is then calculated by a hybrid method and various cases of practical interest are studied

Synchrotron X-ray computed microtomography study on gas hydrate decomposition in a sedimentary matrix

“…The presence of such a water film is likely to be an intrinsic property of quartz‐GH interfaces and has been already inferred in early light microscopic investigations [ Tohidi et al ., ] and predicted by several computer simulations [ Bagherzadeh et al ., ; Bai et al ., ; Liang et al ., ]. In frame of the Hamaker approach this residual water can be seen as a consequence of molecular interactions between quartz and clathrate that favor a transitional disordered, liquid layer over a direct contact [ Bonnefoy et al ., ]. Following this argumentation, the chemical activity of gas molecules in this water film is likely to approach that of GHs but due to molecular interactions the crystallization is inhibited.…”

Laboratory Insights Into the Effect of Sediment‐Hosted Methane Hydrate Morphology on Elastic Wave Velocity From Time‐Lapse 4‐D Synchrotron X‐Ray Computed Tomography

“…We no longer should view hydrate as pore-bridging in the sense of solid-solid contacts, as developed initially (e.g., Ecker et al, 2000;Priest et al, 2009). We should account also for the presence of a water film between hydrate and sediment surface as seen in Figure 6 and other studies (e.g., Bonnefoy et al, 2005;Chaouachi et al, 2015;Sell et al, 2018;Tohidi et al, 2001). Gas hydrate-bearing sediment should be viewed as a three-phase system of interlocking solid hydrate and host grain frameworks separated by water.…”

Review of natural gas hydrates as an energy resource: Prospects and challenges

“…Gas molecules in the hydrate reservoir are trapped within cages formed by water molecules by van der Waals forces in molecular level [70]. Therefore, in addition to creating conduits for gas flow, techniques to recover methane from gas hydrates involve dissociating the natural gas hydrates in situ.…”