Review of Energy Efficiency of the Gas Production Technologies From Gas Hydrate-Bearing Sediments

Abstract

Even in the carbon-neutral age, natural gas will be valuable as environment-friendly fuel that can fulfill the gap between the energy demand and supply from the renewable energies. Marine gas hydrates are a potential natural gas source, but gas production from deposits requires additional heat input owing to the endothermic nature of their dissociation. The amount of fuel needed to produce a unit of energy is important to evaluate energy from economic and environmental perspectives. Using the depressurization method, the value of the energy return on investment or invested (EROI) can be increased to more than 100 for the dissociation process and to approximately 10 or more for the project life cycle that is comparable to liquefied natural gas (LNG) import. Gas transportation through an offshore pipeline from the offshore production facility can give higher EROI than floating LNG; however, the latter has an advantage of market accessibility. If the energy conversion from methane to hydrogen or ammonia at the offshore facility and carbon capture and storage (CCS) can be done at the production site, problems of carbon dioxide emission and market accessibility can be solved, and energy consumption for energy conversion and CCS should be counted to estimate the value of the hydrate resources.

New Insights into the Occurrence and Implications of Mobile Water in Gas Hydrate Systems

“…These processes will promote reservoir compaction and particle mobilization, resulting in potential clogging of pores by fines and general petrophysical degradation of the reservoir. All water that enters the wellbore will need to be lifted to the surface, managed in accordance with flow assurance, and disposed, adding logistical burdens to the operations and negatively impacting the life cycle energy return on investment . Mobile solids will need to be held within the reservoir or produced and managed in a manner to limit damage to wellbore equipment and excessive development of completion “skin” .…”

Economic evaluation of production capacity for natural gas hydrate industrial exploitation in the South China Sea

“…In this study, the production life for each well is 30 years, while the parameter used by the MH21-S R&D consortium is 8 years. Considering that most of the life span investigated for simulation of gas hydrate exploitation is about 20-30 years or even longer (Cleveland, 1992;Walsh et al, 2009;Yamamoto and Nagakubo, 2021;Chen et al, 2022a;Chen et al, 2022b), it is more reasonable…”

“…Although the exploitation of marine NGH is similar in many respects to that of offshore conventional gas, there are still some differences in a number of ways, some of which will have a significant effect on the overall economics (Walsh et al, 2009). Unlike conventional gas that can be produced by natural flow, NGH should be first dissociated into a fluid phase (gas and water) that can consume energy (Yamamoto and Nagakubo, 2021). In addition, because the water production from a gas hydrate reservoir could be highly variable, a gas hydrate development will require artificial lift such as electric submersible pumps (ESPs) or gas lift, which will also increase front-end costs in most cases, as well as operating costs over the life of the field (Walsh et al, 2009).…”

Review of Past Gas Production Attempts from Subsurface Gas Hydrate Deposits and Necessity of Long-Term Production Testing

“…Even if the water volume is in the controllable range, lowering of the GWR causes a reduction in the energy return on the input (EROI, ratio of methane combustion heat to energy consumption by pump) due to the increase in the volume the pump should handle. The past production test record could realize 100 or higher EROI, but a slight reduction of EROI in the later stage of the marine production tests was observed . The GWR increases observed in the Nankai wells might indicate that the containment of the reservoir of the test area was not perfect.…”

“…The past production test record could realize 100 or higher EROI, but a slight reduction of EROI in the later stage of the marine production tests was observed. 46 The GWR increases observed in the Nankai wells might indicate that the containment of the reservoir of the test area was not perfect. Such increases are common in predictions of reservoir performance due to the nonzero permeability of the unconsolidated water-saturated and hydrate-free sediments that surround gas hydrate reservoirs.…”