Development of Marine Natural Gas Hydrate Mining Technology and Equipment
01 Jan 2020-Chinese Journal of Engineering Science (Engineering Sciences Press)-Vol. 22, Iss: 6, pp 32-39
TL;DR: In this paper, the authors focus on existing hydrate exploitation method and analyze key technologies and processes involved in two trial production modes (i.e., depressurization and solid-state fluidization).
Abstract: Natural gas hydrate (NGH), especially marine NGH, is a new source of clean unconventional energy, and it is expected to replace traditional fossil fuels. There are high global reserves of NGH. However, its exploitation is still in the research stage because commercial large-scale exploitation is hindered by challenges with respect to technology and equipment. In this study, we focus on existing hydrate exploitation method and analyze key technologies and processes involved in two trial production modes (i.e., depressurization and solid-state fluidization). These processes were adopted in the pilot production projects of offshore natural gas in Japan and China. In the study, we summarize the development status of relevant technology and equipment in China and across the world and also propose development suggestions for marine gas hydrate exploitation, which are suitable for reservoir and equipment technology in China. The results of the study indicate that China lags behind other countries with respect to key technologies and equipment for hydrate, oil gas, and subsea metal mining (i.e., deep-sea mining vehicles and dual-gradient drilling technology for loose shallow layers). In the field of special key technologies and equipment (i.e., sand control technology and equipment, pre-inclined directional drilling technology for shallow hydrate-mining, and combined production of hydrate, free gas, and conventional natural gas), China’s technology has advanced to an international level. Nevertheless, the advancement does not satisfy the requirements of commercial mining. The development of exploitation technologies and equipment for marine NGHs in China is expected to enter a leading stage in 2035, and the establishment of an engineering equipment system for commercial development is expected. Hence, we recommend the development of a research and development plan for marine NGH exploitation technology and equipment at the national level to promote the commercial development of hydrates. Furthermore, this is necessary to accelerate research and application of special and general technologies and equipment for offshore non-diagenetic hydrate exploitation.
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TL;DR: In this paper , the authors proposed a novel device to test time-dependent deformation and the ultrasonic response of hydrate-bearing sediment (HBS) under high pressure and low temperature.
Abstract: Clarifying the creep behaviors of hydrate-bearing sediment (HBS) under long-term loading is crucial for evaluating reservoir stability during hydrate exploitation. Figuring out a way of characterizing deformation behaviors and their geophysical responses to HBS is the basis for modeling creep behaviors. In this study, we propose a novel device to test time-dependent deformation and the ultrasonic response of HBS under high-pressure and low-temperature. The experimental device consists of a high-pressure chamber, an axial-load control system, a confining pressure system, a pore pressure system, a back-pressure system, and a data collection system. This testing assembly allows temperature regulation and independent control of four pressures, e.g., confining pressure, pore pressure, back pressure, and axial loading. Columned artificial HBS samples, with a diameter of 39 mm and a height of 120 mm, can be synthesized in this device. Afterward, in situ creep experiments can be achieved by applying stable confining pressure and axial load, together with geophysical signals acquisition. During loading, the stress-strain relationships and ultrasonic data can be obtained simultaneously. Through analyzing the stress-strain relationship and ultrasonic data, the macroscopical failure and microcosmical creep deformation law of the samples can be figured out. Preliminary experiments verified the applicability of the device. The method provides some significance for field observation of reservoir failure via geophysical techniques during hydrate exploitation.
9 citations
9 citations
TL;DR: In this article, the effects of the drilling fluid parameters on the decomposition behavior of near-wellbore hydrates are presented, and the simulation results show that the adjustments of drilling fluid density within the mud safety window have limited effects on the NGH decomposition.
Abstract: Horizontal wells can significantly improve the gas production and are expected to be an efficient exploitation method for the industrialization of natural gas hydrates (NGHs) in the future. However, the near-wellbore hydrate is highly prone to decomposition during the drilling process, owing to the disturbance aroused by the factors such as the drilling fluid temperature, pressure, and salinity. These issues can result in the engineering accidents such as bit sticking and wellbore instability, which are required for further investigations. This paper studies the characteristics of drilling fluid invasion into the marine NGH reservoir with varied drilling fluid parameters via numerical simulation. The effects of the drilling fluid parameters on the decomposition behavior of near-wellbore hydrates are presented. The simulating results show that the adjustments of drilling fluid density within the mud safety window have limited effects on the NGH decomposition, meanwhile the hydrates reservoir is most sensitive to the drilling fluid temperature variation. If the drilling fluid temperature grows considerably due to improper control, the range of the hydrates decomposition around the horizontal well tends to expand, which then aggravates wellbore instability. When the drilling fluid salinity varies in the range of 3.5–7.5%, the increase in the ion concentration speeds up the hydrate decomposition, which is adverse to maintaining wellbore stability.
9 citations
TL;DR: In this paper, a mixed-flux model for gas hydrate accumulation is established and then used to simulate the process of methane gas migration into the shallow stratum to form a hydrate reservoir.
4 citations
TL;DR: In this paper , a review comprehensively reviews the drilling techniques and engineering measures that can be used to develop gas hydrate, focusing on the research advancement of important hydrate drilling technologies and the enlightening significance of these developments in the application of hydrate well drilling.
Abstract: Securing energy means grasping the key link in the national development and security strategy. Under the goals of carbon peak and carbon neutrality, the overall tendency of energy development is to increase the proportion of natural gas while stabilizing oil consumption, and the global primary energy is entering the era of natural gas. Gas hydrate in deep seabed shallow strata and extremely cold permafrost regions has piqued the interest of researchers due to its abundant resources, widespread distribution, and high energy density. Although the drilling of hydrate wells is still fraught with unknowns and challenges due to the technological barriers between countries, complex on-site working conditions, and unique physical chemical properties, accumulation forms, and occurrence characteristics of gas hydrate, more than ten successful trial productions around the world have opened the door of hope for the development of this potentially new energy. The gas hydrate reservoir drilling technique is the frontier and hotspot of scientific and technological innovation and competitiveness around the globe today, reflecting the level of oil and gas technical advancement. At the national level, it possesses strategic and revolutionary features. Innovative drilling techniques, scientific well location layout, appropriate wellbore structure and well trajectory design, efficient drilling fluid, qualified drilling and completion equipment, and successful pressure-temperature preserved coring may all provide a strong guarantee for the successful completion of gas hydrate wells. This review comprehensively reviews the drilling techniques and engineering measures that can be used to develop gas hydrate. It focuses on the research advancement of important hydrate drilling technologies and the enlightening significance of these developments in the application of hydrate drilling. This work will deliver valuable experience as well as comprehensive scientific information for gas hydrate exploration and drilling.
4 citations
References
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TL;DR: In this article, the authors review various studies on resource potential of natural gas hydrate, the current research progress in laboratory settings, and several recent field trials, and discuss possible limitation in each production method and the challenges to be addressed for large scale production.
1,236 citations
"Development of Marine Natural Gas H..." refers background in this paper
...The total amount of CH4 gas contained in global NGH resources is approximately 3×10(15) m(3), and it mainly exists in the undersea and terrestrial permafrost regions; marine NGH accounts for more than 95% of the total hydrate reserves [3]....
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01 Mar 2018
TL;DR: Based on nearly two decades' studying on the reservoir characteristics in the South China Sea (SCS) and the knowledge of reservoir system, the China Geological Survey (CGS) conducted the first production test on an optimal target selected in Shenhu area SCS in 2017 as mentioned in this paper.
Abstract: Natural gas hydrates (NGH) is one of key future clean energy resources. Its industrialized development will help remit the huge demand of global natural gas, relieve the increasing pressure of the environment, and play a vital role in the green sustainable growth of human societies. Based on nearly two decades’ studying on the reservoir characteristics in the South China Sea (SCS) and the knowledge of reservoir system, the China Geological Survey (CGS) conducted the first production test on an optimal target selected in Shenhu area SCS in 2017. Guided by the “three-phase control” exploitation theory which focused on formation stabilization, technologies such as formation fluid extraction, well drilling and completing, reservoir stimulating, sand controlling, environmental monitoring, monitoring and preventing of secondary formation of hydrates were applied. The test lasted for 60 days from May 10th when starting to pump, drop pressure and ignite to well killing on July 9th, with gas production of 3.09×105 m3 in total, which is a world record with the longest continuous duration of gas production and maximal gas yield. This successful test brings a significant breakthrough on safety control of NGH production.
567 citations
TL;DR: In this paper, the authors report the first offshore methane hydrate production test conducted at the eastern Nankai Trough and show key findings toward future commercial production, which indicates that hydrate saturation reaches 80% and permeability in the presence of hydrate ranges from 0.01 to 10 mD.
Abstract: Marine methane hydrate in sands has huge potential as an unconventional gas resource; however, no field test of their production potential had been conducted. Here, we report the world’s first offshore methane hydrate production test conducted at the eastern Nankai Trough and show key findings toward future commercial production. Geological analysis indicates that hydrate saturation reaches 80% and permeability in the presence of hydrate ranges from 0.01 to 10 mdarcies. Permeable (1–10 mdarcies) highly hydrate-saturated layers enable depressurization-induced gas production of approximately 20,000 Sm3/D with water of 200 m3/D. Numerical analysis reveals that the dissociation zone expands laterally 25 m at the front after 6 days. Gas rate is expected to increase with time, owing to the expansion of the dissociation zone. It is found that permeable highly hydrate-saturated layers increase the gas–water ratio of the production fluid. The identification of such layers is critically important to increase the en...
419 citations
TL;DR: In this paper, the dynamics of CH 4 replacement in the CH 4 hydrate with saturated liquid CO 2 at 273.2 K was measured with a high pressure optical cell, and the results showed that CH 4 in the hydrate gradually moved to the liquid CO2 phase while CO 2 in the liquid phase penetrated into the hydrates from quantitative analysis.
284 citations
"Development of Marine Natural Gas H..." refers methods in this paper
...However, low replacement rate and efficiency [11] restrict the application of this method....
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TL;DR: In this paper, a second attempt at producing gas from a naturally occurring methane hydrate (MH) deposit in the Daini-Atsumi Knoll in the eastern Nankai Trough area off Honshu Island, Japan was made in April to June of 2017 at a nearby location using two producer wells sequentially and applying the depressurization method.
Abstract: Following the first attempt at producing gas from a naturally occurring methane hydrate (MH) deposit in the Daini–Atsumi Knoll in the eastern Nankai Trough area off Honshu Island, Japan in 2013, a second attempt was made in April to June of 2017 at a nearby location using two producer wells sequentially and applying the depressurization method. The operation in the first borehole (AT1-P3) continued for 12 days with a stable drawdown of around 7.5 MPa and 41 000 m3 of methane gas being produced despite intermittent sand-production events. The operation of the other borehole (AT1-P2) followed, with a total of 24 days of flow and 222 500 m3 of methane gas being produced without sand problems. However, the degree of drawdown was limited to 5 MPa because of a higher water production rate than expected in the second hole. The pressure and temperature sensors deployed in the two producers, along with the two monitoring holes drilled nearby, gathered reservoir response data and information about the long-term MH dissociation processes in the vicinity of the production holes in the temporal and spatial domains. Although the ratio of energy return to the input was considerably larger than that for the depressurization operation, some observations (e.g., the high contrast in the production rates between the two holes and the almost constant or slightly reduced gas production rates) were not predicted by the numerical models. This failure in prediction raises questions about the veracity of the reservoir characteristics modeled in the numerical simulations. This paper presents the operation summaries and data obtained with thought-experiment based-anticipated production behaviors and preliminary analysis of the obtained data as the comparison with expected behaviors. Detailed observations of gas and water production, as well as the pressure and temperature data recorded during the gas flow tests, indicate that the heterogeneous MH distribution within the reservoir was mainly responsible for the discrepancies observed between the anticipated and actual behaviors. Furthermore, the motion of the water that does not originate from MH dissociation introduces complexity, such as the occurrence of concentrated water-producing intervals and unexpected gas production responses to decreases in pressure, into the production behavior. The influence of heterogeneity should be clearly understood for the accurate prediction of gas production behavior based on MH reservoirs.
209 citations
"Development of Marine Natural Gas H..." refers background in this paper
...The mining operation was forcibly switched to the second mining well because of serious sand production problems at the bottom of the well [16]....
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