Hydrate Production Philosophy and Thermodynamic Calculations

Bjørn Kvamme, Jinzhou Zhao, Na Wei, Wantong Sun, Navid Saeidi, Jun Pei and Tatiana Kuznetsova
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Bjørn Kvamme: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Xindu Road No.8, Chengdu 610500, China
Jinzhou Zhao: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Xindu Road No.8, Chengdu 610500, China
Na Wei: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Xindu Road No.8, Chengdu 610500, China
Wantong Sun: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Xindu Road No.8, Chengdu 610500, China
Navid Saeidi: Environmental Engineering Department, University of California, Irvine, CA 92697, USA
Jun Pei: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Xindu Road No.8, Chengdu 610500, China
Tatiana Kuznetsova: Department of Physics and Technology, University of Bergen, 5007 Bergen, Norway

Energies, 2020, vol. 13, issue 3, 1-34

Abstract: The amount of energy in the form of natural gas hydrates is huge and likely substantially more than twice the amount of worldwide conventional fossil fuel. Various ways to produce these hydrates have been proposed over the latest five decades. Most of these hydrate production methods have been based on evaluation of hydrate stability limits rather than thermodynamic consideration and calculations. Typical examples are pressure reduction and thermal stimulation. In this work we discuss some of these proposed methods and use residual thermodynamics for all phases, including the hydrate phase, to evaluate free energy changes related to the changes in independent thermodynamic variables. Pressures, temperatures and composition of all relevant phases which participate in hydrate phase transitions are independent thermodynamic variables. Chemical potential and free energies are thermodynamic responses that determine whether the desired phase transitions are feasible or not. The associated heat needed is related to the first law of thermodynamics and enthalpies. It is argued that the pressure reduction method may not be feasible since the possible thermal gradients from the surroundings are basically low temperature heat that is unable to break water hydrogen bonds in the hydrate–water interface efficiently. Injecting carbon dioxide, on the other hand, leads to formation of new hydrate which generates excess heat compared to the enthalpy needed to dissociate the in situ CH 4 hydrate. But the rapid formation of new CO 2 hydrate that can block the pores, and also the low permeability of pure CO 2 in aquifers, are motivations for adding N 2 . Optimum mole fractions of N 2 based on thermodynamic considerations are discussed. On average, less than 30 mole% N 2 can be efficient and feasible. Thermal stimulation using steam or hot water is not economically feasible. Adding massive amounts of methanol or other thermodynamic inhibitors is also technically efficient but far from economically feasible.

Keywords: hydrate; non-equilibrium; production (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (5)

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