scholarly journals Prevention of Potential Hazards Associated with Marine Gas Hydrate Exploitation: A Review

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2384 ◽  
Author(s):  
Fangtian Wang ◽  
Bin Zhao ◽  
Gang Li
Keyword(s):  
Gas Hydrate ◽  
Production Control ◽  
Clean Energy ◽  
Gas Production ◽  
Production Test ◽  
Production Methods ◽  
Exploitation And Utilization ◽  
Marine Engineering ◽  
Lifecycle Management

Marine gas hydrates (MGHs), which have great potential for exploitation and utilization, account for around 99% of all global natural gas hydrate resources under current prospecting technique. However, there are several potential hazards associated with their production and development. These are classified into four categories by this paper: marine geohazards, greenhouse gas emissions, marine ecological hazards, and marine engineering hazards. In order to prevent these risks from occurring, the concept of “lifecycle management of hazards prevention” during the development and production from MGHs is proposed and divided into three stages: preparation, production control, and post-production protection. Of these stages, economic evaluation of the resource is the foundation; gas production methods are the key; with monitoring, assessment, and early warning as the guarantee. A production test in the Shenhu area of the South China Sea shows that MGH exploration and development can be planned using the “three-steps” methodology: commercializing and developing research ideas in the short term, maintaining economic levels of production in the medium term, and forming a global forum to discuss effective MGH development in the long term. When increasing MGH development is combined with the lifecycle management of hazards prevention system, and technological innovations are combined with global cooperation to solve the risks associated with MGH development, then safe access to a new source of clean energy may be obtained.

Comparison of Simplistic and Geologically Descriptive Production Modeling for Natural-Gas Hydrate by Depressurization

SPE Journal ◽  
2019 ◽  
Vol 24 (02) ◽  
pp. 563-578 ◽  
Author(s):  
Yilong Yuan ◽  
Tianfu Xu ◽  
Yingli Xia ◽  
Xin Xin
Keyword(s):  
Gas Hydrate ◽  
History Matching ◽  
Nankai Trough ◽  
Flow Behavior ◽  
Test Site ◽  
Gas Production ◽  
Production Test ◽  
Hydrate Reservoir ◽  
Hydrate Saturation ◽  
Production Modeling

Summary Marine-gas-hydrate-drilling exploration at the Eastern Nankai Trough of Japan revealed the variable distribution of hydrate accumulations, which are composed of alternating beds of sand, silt, and clay in sediments, with vertically varying porosity, permeability, and hydrate saturation. The main purposes of this work are to evaluate gas productivity and identify the multiphase-flow behavior from the sedimentary-complex hydrate reservoir by depressurization through a conventional vertical well. We first established a history-matching model by incorporating the available geological data at the offshore-production test site in the Eastern Nankai Trough. The reservoir model was validated by matching the fluid-flow rates at a production well and temperature changes at a monitoring well during a field test. The modeling results indicate that the hydrate-dissociation zone is strongly affected by the reservoir heterogeneity and shows a unique dissociation front. The gas-production rate is expected to increase with time and reach the considerable value of 3.6 × 104 std m3/d as a result of the significant expansion of the dissociation zone. The numerical model, using a simplified description of porosity, permeability, and hydrate saturation, leads to significant underestimation of gas productivity from the sedimentary-complex hydrate reservoir. The results also suggest that the interbedded-hydrate-occurrence systems might be a better candidate for methane (CH4) gas extraction than the massive hydrate reservoirs.

Soaking effects on CH4-CO2 replacement efficiency in gas hydrates

2020 ◽  
Author(s):  
Jongwon Jung ◽  
Jaeeun Ryou ◽  
Joo Yong Lee ◽  
Riyadh I AI-Raoush ◽  
Khalid Alshibli ◽  
...  
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
Production Efficiency ◽  
Gas Permeability ◽  
Gas Production ◽  
Production Methods ◽  
Injection Method ◽  
Development Organization ◽  
Replacement Method ◽  
Hydrate Saturation

<p>Gas hydrates are potential energy resources which can be formed at low temperature and high pressure. The number of recoverable gas hydrates are limited due to the specific temperature, pressure conditions and technical limitations of gas production. Various production methods have been studied around the world to overcome these technical limitations. Gas production methods from gas hydrates are divided into methods of dissociating gas hydrates and non-dissociating gas hydrates. The dissociation methods including depressurization method, thermal injection method, and chemical inhibitor injection method can decrease in effective stress of the ground due to phase conversion. On the other hand, CH<sub>4</sub>-CO<sub>2 </sub>replacement method is geomechanically stable because it does not dissociate gas hydrates. Also, CH<sub>4</sub>-CO<sub>2 </sub>replacement method has the advantage of sequestering carbon dioxide while producing methane. However, CH<sub>4</sub>-CO<sub>2</sub> replacement method has the disadvantage such as low production efficiency and understanding kinetics of gas production. In this study, soaking, gas permeability of gas hydrate layer and hydrate saturation are considered in order to promote the production efficiency of CH<sub>4</sub>-CO<sub>2</sub> replacement method. Results show that production efficiency increases with the number of soaking process, the higher gas permeability and hydrate saturation. According to the experimental results in this study, the production efficiency can be increased by considering the soaking time, procedure and selecting the proper gas hydrates site.</p><p>Acknowledgement</p><p>This work is supported by the Korea Agency for Infrastructure Technology Advancement(KAIA) grant funded by the Ministry of Land, Infrastructure and Transport (Grant 20CTAP-C152100-02). Also, it is supported by partial funding from NPRP grant # NPRP8-594-2-244 from the Qatar national research fund (a member of Qatar Foundation) and  the Ministry of Trade, Industry, and Energy (MOTIE) through the Project “Gas Hydrate Exploration and Production Study (20-1143)” under the management of the Gas Hydrate Research and Development Organization (GHDO) of Korea and the Korea Institute of Geoscience and Mineral Resources (KIGAM).</p>

Mechanical Response of Reservoir and Well Completion of the First Offshore Methane-Hydrate Production Test at the Eastern Nankai Trough: A Coupled Thermo-Hydromechanical Analysis

SPE Journal ◽  
2018 ◽  
Vol 24 (02) ◽  
pp. 531-546 ◽  
Author(s):  
Jun Yoneda ◽  
Akira Takiguchi ◽  
Toshimasa Ishibashi ◽  
Aya Yasui ◽  
Jiro Mori ◽  
...  
Keyword(s):  
Gas Hydrate ◽  
Mechanical Response ◽  
Nankai Trough ◽  
Water Pressure ◽  
Compressive Force ◽  
Gas Production ◽  
Production Test ◽  
Frictional Stress ◽  
Well Completion ◽  
Hydrate Saturation

Summary During gas production from offshore gas-HBS, there are concerns regarding the settlement of the seabed and the possibility that frictional stress will develop along the production casing. This frictional stress is caused by a change in the effective stress induced by water movement caused by depressurization and dissociation of hydrate as well as gas generation and thermal changes, all of which are interconnected. The authors have developed a multiphase-coupled simulator by use of a finite-element method named COTHMA. Stresses and deformation caused by gas-hydrate production near the production well and deep seabed were predicted using a multiphase simulator coupled with geomechanics for the offshore gas-hydrate-production test in the eastern Nankai Trough. Distributions of hydrate saturation, gas saturation, water pressure, gas pressure, temperature, and stresses were predicted by the simulator. As a result, the dissociation of gas hydrate was predicted within a range of approximately 10 m, but mechanical deformation occurred in a much wider area. The stress localization initially occurred in a sand layer with low hydrate saturation, and compression behavior appeared. Tensile stress was generated in and around the casing shoe as it was pulled vertically downward caused by compaction of the formation. As a result, the possibility of extensive failure of the gravel pack of the well completion was demonstrated. In addition, in a specific layer, where a pressure reduction progressed in the production interval, the compressive force related to frictional stress from the formation increased, and the gravel layer became thin. Settlement of the seafloor caused by depressurization for 6 days was within a few centimeters and an approximate 30 cm for 1 year of continued production.

Natural Gas Hydrate as Potential Energy Resources in the Future

2012 ◽  
Vol 462 ◽  
pp. 221-224 ◽  
Author(s):  
Xian Guo Yang ◽  
Ming Ju Qin
Keyword(s):  
Natural Gas ◽  
Potential Energy ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Clean Energy ◽  
Gas Production ◽  
Energy Resources ◽  
Total Carbon ◽  
Significant Implication ◽  
Oceanic Sediments

On the worldwide basis, gas hydrate is about two times the total carbon in coal, oil and conventional gas in the world. The enormous size of this resource, if producible to any degree, has significant implication for worldwide clean energy supplies and global environmental issues. This paper deals with the potential of gas hydrates as a source of energy which is widely available in permafrost and oceanic sediments. It discusses methods for gas production from natural gas hydrates. Many questions remain to be answered to determine if any of this potential energy resources technically and economically viable to produce.

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