Methane Hydrate Pellet Transport Using the Self-Preservation Effect: A Techno-Economic Analysis

Abstract

Within the German integrated project SUGAR, aiming for the development of new technologies for the exploration and exploitation of submarine gas hydrates, the option of gas transport by gas hydrate pellets has been comprehensively re-investigated. A series of pVT dissociation experiments, combined with analytical tools such as x-ray diffraction and cryo-SEM, were used to gather an additional level of understanding on effects controlling ice formation. Based on these new findings and the accessible literature, knowns and unknowns of the self-preservation effect important for the technology are summarized. A conceptual process design for methane hydrate production and pelletisation has been developed. For the major steps identified, comprising (i) hydrate formation; (ii) dewatering; (iii) pelletisation; (iv) pellet cooling; and (v) pressure relief, available technologies have been evaluated, and modifications and amendments included where needed. A hydrate carrier has been designed, featuring amongst other technical solutions a OPEN ACCESSEnergies 2012, 5 2500 pivoted cargo system with the potential to mitigate sintering, an actively cooled containment and cargo distribution system, and a dual fuel engine allowing the use of the boil-off gas. The design was constrained by the properties of gas hydrate pellets, the expected operation on continental slopes in areas with rough seas, a scenario-defined loading capacity of 20,000 m 3 methane hydrate pellets, and safety as well as environmental considerations. A risk analysis for the transport at sea has been carried out in this early stage of development, and the safety level of the new concept was compared to the safety level of other ship types with similar scopes, i.e., LNG carriers and crude oil tankers. Based on the results of the technological part of this study, and with best knowledge available on the alternative technologies, i.e., pipeline, LNG and CNG transportation, an evaluation of the economic competitiveness of the methane hydrate transport technology has been performed. The analysis considers capital investment as well as operational costs and comprises a wide set of scenarios with production rates from 20 to 800 10 and transport distances from 200 to 10,000 km. In contrast to previous studies, the model calculations in this study reveal no economic benefit of methane hydrate transportation versus competing technologies.

Enhanced clathrate hydrate formation kinetics at near ambient temperatures and moderate pressures: Application to natural gas storage

“…Few of the key existing challenges include the need for severe operating conditions (low temperature and high pressure requirement for hydrate formation) and the slow kinetics of hydrate formation. In addition, the storage temperature of 253 K at atmospheric pressure is based on the anomalous 'self-preservation' effect [9][10][11][12][13]. Further, high costs incurred due to the potential gas precompression and agitation (required during hydrate formation) along with cooling costs (both during hydrate formation and storage step) hinder the large scale deployment of SNG technology.…”

Natural Gas Hydrate as a Storage Mechanism for Safe, Sustainable and Economical Production from Offshore Petroleum Reserves

“…The Subterranean Gas Reserves (SUGAR) [2] project funded by the German government, performed an economic analysis comparing various production, storage, and transportation mechanisms for stranded gas. The economic summary presented the optimal production scheme (pipeline, CNG, LNG, and Natural Gas Hydrate or NGH) as a function of the reservoir characteristics.…”

Risk Assessment for Natural Gas Hydrate Carriers: A Hazard Identification (HAZID) Study

“…Consequently, it is considered reasonable that the risks criteria established for safety of conventional ships are applicable to this system. Various international activities for the enhancement of safety of ships have been carried out since the late 1990s [17]. One of the IMO dicuments was taken into consideration as the most appropriate one in this stud, thus risk evaluation criteria for discussion and decision of the HAZID team during the workshop were defined considering "The Guidelines for Formal Safety Assessment for use in the IMO rule-making process (MSC/Circ.1023-MEPC/Cir.392)" proposed by IMO (2007) [18].…”