Utilizing Non-Equilibrium Thermodynamics and Reactive Transport to Model CH4 Production from the Nankai Trough Gas Hydrate Reservoir

Abstract

Abstract:The ongoing search for new sources of energy has brought natural gas hydrate (NGH) reservoirs to the forefront of attention in both academia and the industry. The amount of gas reserves trapped within these reservoirs surpasses all of the conventional fossil fuel sources explored so far, which makes it of utmost importance to predict their production potential and safety. One of the challenges facing those attempting to analyse their behaviour is that the large number of involved phases make NGHs unable to ever reach equilibrium in nature. Field-scale experiments are expensive and time consuming. However, computer simulations have now become capable of modelling different gas production scenarios, as well as production optimization analyses. In addition to temperature and pressure, independent thermodynamic parameters for hydrate stabilization include the hydrate composition and concentrations for all co-existing phases. It is therefore necessary to develop and implement realistic kinetic models accounting for all significant routes for dissociation and reformation. The reactive transport simulator makes it easy to deploy nonequilibrium thermodynamics for the study of CH 4 production from hydrate-bearing sediments by considering each hydrate-related transition as a separate pseudo reaction. In this work, we have used the expanded version of the RetrasoCodeBright (RCB) reactive transport simulator to model exploitation of the methane hydrate (MH) reservoir located in the Nankai Trough, Japan. Our results showed that higher permeabilities in the horizontal direction dominated the pressure drop propagation throughout the hydrate layers and affected their hydrate dissociation rates. Additionally, the comparison of the vertical well versus the horizontal well pattern indicated that hydrate dissociation was slightly higher in the vertical well scenario compared to the horizontal.

Comparison and Optimization of Methane Hydrate Production Process Using Different Methods in a Single Vertical Well

“…Two pressure sensors are connected to the pipe at the top and bottom of the container for the measurement of the system pressure. horizontal well, Qorbani et al [9] suggested a slightly higher hydrate decomposition rate with the former well pattern than the later. From these studies, it is easy to recognize that there are few studies focusing on the effects of the application of different exploitation methods on NGH production in a vertical well, especially aiming at the in-situ electric heating without mass injection and the comparison of production effects in different depressurization and heating modes.…”

“…Furthermore, they also thought the mass and heat transfer mainly dominated the hydrate decomposition by depressurization in the pilot-scale simulator. Besides, after the comparison of NGH exploitation in a vertical well with that in a horizontal well, Qorbani et al [9] suggested a slightly higher hydrate decomposition rate with the former well pattern than the later.…”

“…The occurrence of gas hydrate is strongly dependent on the factors including temperature, pressure and constituent components, which result in the formation of NGH in polar and oceanic regions [7][8][9]. In polar regions, NGH exists in the permafrost at both onshore and offshore of the continental shelves.…”

“…It is inevitable to study NGH exploitation as NGH is a kind of high-reserved energy resource, which can help to cope with the growing global energy demand [8,11,12]. Therefore, it will become the research focus all over countries to ensure the efficiency and safety of NGH exploitation, and then the commercial exploitation will be realized in the near future [4,7,9,13].…”