Toward Production From Gas Hydrates: Current Status, Assessment of Resources, and Model-Based Evaluation of Technology and Potential

Abstract

Gas hydrates are a vast energy resource with global distribution in the permafrost and in the oceans. Even if conservative estimates are considered and only a small fraction is recoverable, the sheer size of the resource is so large that it demands evaluation as a potential energy source. In this review paper, we discuss the distribution of natural gas hydrate accumulations, the status of the primary international R&D programs, and the remaining science and technological challenges facing commercialization of production. After a brief examination of gas hydrate accumulations that are well characterized and appear to be models for future development and gas production, we analyze the role of numerical simulation in the assessment of the hydrate production potential, identify the data needs for reliable predictions, evaluate the status of knowledge with regard to these needs, discuss knowledge gaps and their impact, and reach the conclusion that the numerical simulation capabilities are quite advanced and that the related gaps are either not significant or are being addressed. We review the current body of literature relevant to potential productivity from different types of gas hydrate deposits, and determine that there are consistent indications of a large production potential at high rates over long periods from a wide variety of hydrate deposits. Finally, we identify (a) features, conditions, geology and techniques that are desirable in potential production targets, (b) methods to maximize production, and (c) some of the conditions and characteristics that render certain gas hydrate deposits undesirable for production. Introduction Background. Gas hydrates are solid crystalline compounds in which gas molecules (referred to as guests) occupy the lattices of ice-like crystal structures called hosts. Under suitable conditions of low temperature T and high pressure P, the hydration reaction of a gas G is described by the general equation G + N H H 2 O = G•N H H 2 O,……………………………………………………………………………………………………(1) where N H is the hydration number. Hydrate deposits occur in two distinctly different geographic settings where the necessary conditions of low T and high P exist for their formation and stability: in the permafrost and in deep ocean sediments (Kvenvolden, 1988). The majority of naturally occurring hydrocarbon gas hydrates contain CH 4 in overwhelming abundance. Simple CH 4-hydrates concentrate methane volumetrically by a factor of 164 when compared to standard P and T conditions (STP). Some modeling suggests that the energy needed for dissociation could be less than 15% of the recovered energy (Sloan and Koh, 2008). Natural CH 4-hydrates crystallize mostly in the structure I form, which contains 46 H 2 O molecules per unit cell. Structure I hydrates have a N H ranging from 5.77 to 7.4, with N H = 6 being the average hydration number and N H = 5.75 corresponding to complete hydration (Sloan and Koh, 2008). Natural gas hydrates can also contain other hydrocarbons (alkanes C ν H 2ν+2 , ν = 2 to 4), but may also co...

Numerical Investigation of the Production Behavior of Methane Hydrates under Depressurization Conditions Combined with Well-Wall Heating

“…1.15 × e 49.3185−9459/T Cumulative gas production after 90min, V gas (SL) 17 (experimental result of ∆P 6 ) [17] Cumulative gas production after 90min, V gas (SL) 53 (experimental result of ∆P 6 + ∆T) [17] In our hydrate dissociation model, some assumptions have been made [8,27,28,34,39]: (1) the methane hydrate is deemed as sI type hydrate; (2) the methane gas produced from hydrate does not dissolve in water; (3) hydrate is assumed to accumulate in the pore space [34]; (4) gas-liquid two phase flow accords with Darcy's law; (5) the hydrate-bearing sediments are homogeneous and the solid phase (i.e., hydrate and porous media) is incompressible and stagnant.…”

“…Natural gas has been successfully extracted by injection of hot water and by depressurization at the permafrost reservoir of the Mallik site in Northwest Canada [21]. The first offshore production test has been carried out in the Nankai Trough, Japan, the technical feasibility of the depressurization technique is confirmed [24] and this method appears to be the most promising and economic one [3,26].…”

“…The natural gas hydrate resource has been considered as a potential strategic energy resource for the future [2,3]. Several efficient and feasible gas recovery methods for in-situ CH 4 recovery from the hydrate reservoirs have been proposed, such as hot water injection [4,5], in situ combustion [6,7], depressurization [8][9][10][11], inhibitor injection [12,13], CO 2 replacement [14,15] and the combined methods [16][17][18][19][20].…”

Numerical Studies on Two-Way Coupled Fluid Flow and Geomechanics in Hydrate Deposits

“…Reservoir engineering is replete with examples of such strongly coupled flow-geomechanics processes with a significant impact on production and economic consequences: stability of borehole and surface facilities, hydraulic fracturing for fluid production from low-permeability reservoirs, reservoir compaction (especially in highly compressible systems) and land surface subsidence, sand production during reservoir fluid production from unconsolidated or unstable formation, system responses during geologic CO 2 sequestration, gas production from hydrate accumulations, etc. -see Bagheri and Settari (2008) Hydrate reservoirs are considered as potentially substantial future energy resources (Moridis, 2003;Moridis et al, 2009aMoridis et al, , 2011 because of the vast quantities of hydrocarbon gas (mainly CH 4 ) they trap (Sloan and Koh, 2008). Hydrate deposits that are desirable gas production targets almost invariably involve coarse, unlithified, unconsolidated media (such as sands and gravels).…”

Study of constant-pressure production characteristics of class 1 methane hydrate reservoirs

“…It has been also estimated that the current world energy consumption could be sustained for about 200 years by recovering just 15% of the estimated gas hydrate resource (Makogon et al 2007). The feasibility of gas production from class 1 methane-hydrate reservoirs has been examined by several researchers (e.g., Holder and Angert 1982;Burshears et al 1986;Moridis 2003;Pooladi-Darvish 2004;Sun et al 2005;Moridis et al 2007Moridis et al , 2009Moridis et al , 2011Mahajan et al 2007). The simulation results from previous studies showed the good potential for gas production from class 1 gas-hydrate accumulations.…”