Modelling and economic analysis of gas production from hydrates by depressurization method

Abstract

he estimates of natural gas within gas hydrate deposits worldwide are so large that they represent an unconventional source of T natural gas for the new millenium. The potential of gas hydrates as an unconventional gas resource is particularly attractive when one considers hydrates as a concentrated form of natural gas. Naturally occurring gas hydrates contain approximately 160-1 80 standard cubic metre (SCM) of gas per cubic metre of hydrates and have a composition of approximately 80-85 mol% water and 15-20 mol% gas. The gas within hydrates is predominantly methane. In terms of energy content, they are more similar to heavy oil and tar sand bitumen than to other unconventional gas resources. While hydrates contain 40-50 SCM of hydrated gas (42-53 MI) per cubic metre reservoir based on 30% porosity, coalbed methane contains 8-1 2, tight sands contain 5-1 0, Devonian Shale and geo-pressured aquifers contain only 1-2 SCM of gas per cubic metre of reservoir (Mutalik, 1989).Gas hydrates exist in reservoirs as relatively immobile and impermeable solids. The first step in production is to decompose gas hydrates into gas and water by various means. The process of hydrate decomposition requires that the heat of hydrate decomposition be provided to the decomposing hydrate surface in order to shift the equilibrium associated between hydrates, gas and water. Through energy balance calculations, it can be shown that the energy required for decomposition of gas hydrates into gas and water is approximately one-tenth of the energy value of the produced gas. This heat of decomposition is dependent upon the pressure, temperature, gas composition and concentration of inhibitor used, if any. Thus, the energy efficiency ratios (EER) in the range of 10 to 13 represent the highest that can be achieved in a most thermodynamically efficient process. Higher energy efficiency ratios are only possible with the use of inhibitor, which reduce the decomposition energy.Various methods of gas production from hydrates include depressurization, thermal stimulation and injection of inhibitors. The depressurization method is probably the most practical among these methods, however, it may be applicable to only those arctic and oceanic reservoirs that contain hydrates and associated free gas (Sira, 1991). In this method, the reservoir pressure is reduced below the three phase vapour-liquidhydrate equilibrium pressure, causing the hydrate to decompose. Heat required for decomposition of hydrate comes from the adjacent formations as a result of temperature gradient created by reduction in pressure, thereby eliminating heat losses, which can be significant in 'Author to whom correspondence may be addressed. E-mail address: ffsk@uaf.eduThe Canadl an Journal of Chemical Engi neeri ng, Volume 80. February 2002 Gas production from a hydrate reservoir involves decomposition of the solid hydrate. An analytical model is developed to predict reservoir performance for gas production by the depressurization method from a hydrate reservoir containing associated ...

Numerical Simulation of Methane Production from Hydrates Induced by Different Depressurizing Approaches

“…Gas production from hydrates in the Messoyakha free gas/gas hydrate reservoir in Siberia via depressurization method is the only field case of long-term production [5], and the mentioned depressurization is a method encouraging the gas hydrate to dissociate by decreasing the wellbore pressure below the hydrate stability pressure at a specified temperature; this is regarded as the most promising mode for gas hydrate production compared with the other suggested methods [6]. However, scarcity of data about this reservoir limits to learn the gas production behaviors of natural gas hydrate reservoirs.…”

Parameter optimization for solid fluidization exploitation of natural gas hydrate in South China Sea

“…Siberia area (Makogon and Omelchenko, 2013;Khataniar et al, 2002) 1970 Messoyakha Depressurization 700-800 m Chemical agent injection Canada (Dallimore et al, 2005) 2002 Mallik Depressurization 890-1200 m Heat injection Alaska (Hunter et al, 2011;Moridis et al, 2011) 2011 Elbert Depressurization 2000-2200 m CO 2 replacement USA (Dawe and Thomas, 2007) 2012 Eileen CO 2 replacement 792.5 m Japan (Jin et al, 2016;Suzuki et al, 2015;Konno et al, 2017) 2013 Nankai Depressurization 277-337 m Japan (Yu et al, 2019;Chen et al, 2018) 2017 Nankai Depressurization 270 m China (Lin et al, 2018) 2017 Shenhu Depressurization 100-200 m China (Chen et al, 2019a, b) 2017 Shenhu Solid fluidization 100-200 m Table 1.…”

Design and Techno‐Economic Analysis of a Process for Transforming Pig Manure into a Value‐Added Product

“…The methodology employed in this design study is somewhat similar to those described by Filion et al (2001) and Khataniar et al (2002), who used a techno-economic analysis to evaluate the design of processes for the incineration of hazardous wastes with a plasma burner and the production of gas from hydrates. The design methodology described in this paper is more systematic and it employs design tools to evaluate the critical controllable and uncontrollable risks.…”