The exploitation of natural gas hydrate reservoirs will alter the temperature and pressure conditions that sustain their existence, leading to the decomposition of natural gas hydrates. Therefore, if the control of temperature and pressure conditions cannot be effectively achieved during the extraction of 'flammable ice', a series of environmental problems may occur, such as the intensification of the greenhouse effect, changes in marine ecology, and submarine landslides.
On November 28th, People's Daily Online reported: "'Flammable ice' is the clean energy most likely to change the current energy structure. The significance of successfully drilling for natural gas hydrates (commonly known as 'flammable ice') in the permafrost zone on the southern edge of the Qilian Mountains in Qinghai Province is no less than discovering the Daqing Oilfield," said Zhang Hongtao, Chief Engineer of the Ministry of Land and Resources and Deputy Director of the China Geological Survey Bureau.
China's successful drilling of 'flammable ice' in terrestrial permafrost zones has attracted high attention both domestically and internationally. While some people celebrate this achievement, others have started to worry: Is China about to carry out large-scale mining of these 'flammable ice' deposits? What impact will the extraction of 'flammable ice' have on the environment? To address these questions, reporters specifically interviewed relevant experts from the Ministry of Land and Resources, the China Geological Survey, and the Chinese Academy of Geological Sciences.
"Development can only proceed with assurance of environmental safety." In interviews, Zhang Hongtao, Chief Engineer of the Ministry of Land and Resources and Deputy Director of the China Geological Survey, repeatedly emphasized, "We cannot conduct large-scale commercial extraction before environmental issues are resolved."
Natural gas hydrates exist within marine sediments and terrestrial permafrost zones, crystallizing under high-pressure, low-temperature conditions through the combination of natural gas and water. Under standard conditions, one unit volume of natural gas hydrate can decompose to produce up to 164 unit volumes of methane gas.
"The exploitation of natural gas hydrate reservoirs alters the temperature and pressure conditions necessary for their existence, causing the decomposition of natural gas hydrates. Therefore, if effective control of temperature and pressure conditions cannot be achieved during the extraction of 'flammable ice', it may trigger a series of environmental problems, such as the intensification of the greenhouse effect, changes in marine ecology, and submarine landslides," Zhang Hongtao explained.
According to him, methane, as a potent greenhouse gas, ranks second only to carbon dioxide in its influence on atmospheric radiation balance. "The global amount of methane contained in natural gas hydrates is approximately 3000 times that in the atmosphere. Even if only 0.5% of the methane released from the decomposition of natural gas hydrates enters the atmosphere, it could significantly accelerate the process of global warming."
In addition to the greenhouse effect, the extraction of seabed natural gas hydrates poses more problems. He provided an example: if methane gas is discharged into seawater, its oxidation would consume large amounts of oxygen, harming the growth and development of marine microorganisms; if the amount of methane discharged into seawater is particularly large, it could cause seawater vaporization and tsunamis, resulting in catastrophic consequences.
Furthermore, during the extraction of natural gas hydrates, they decompose to produce large amounts of water, releasing pore space in rock layers, which causes consolidation properties in their storage areas to deteriorate, triggering geological disasters such as submarine landslides. "Recent studies have found that reduced stability in continental slope zones due to the decomposition of seabed natural gas hydrates is a significant cause of submarine landslide events," Zhang Hongtao introduced.
He stated that China has already actively initiated research on the environmental effects of natural gas hydrates, utilizing existing data and data collection to achieve phased results in aspects such as types and distribution of seabed geological disasters and seabed engineering geological characteristics. "Next, we will increase our research efforts on the environmental effects of 'flammable ice' development in terrestrial permafrost zones," he added, indicating that large-scale extraction similar to conventional mineral resources will not occur until ideal extraction methods addressing environmental impacts are found.
"We cannot rely on mature technologies developed by foreign countries. The formation mechanism and reservoir theory of 'flammable ice' have yet to form a complete theoretical framework, and seabed extraction technology is extremely complex. These are common challenges worldwide and represent the bottleneck for the commercial development of 'flammable ice'," Zhang Hongtao said. Precisely because of this, all countries approach the development of 'flammable ice' with caution.
Therefore, although 'flammable ice' has become a focus of attention for many countries and international organizations, research on it around the world mostly remains at the scientific exploration stage, without entering the substantive commercial development phase.
It is understood that in 2002, five countries—America, Japan, Canada, Germany, and India—collaborated to experimentally develop a natural gas hydrate well in the Mackenzie permafrost region of Canada. By injecting drilling mud at 80 degrees Celsius, methane gas was successfully extracted from a hydrate layer 1200 meters deep, and experiments using the depressurization method also succeeded. "This is the most successful trial development of natural gas hydrates so far," introduced Zhu Youhai, a researcher at the Institute of Mineral Resources of the Chinese Academy of Geological Sciences.
"There is still a distance from trial extraction to commercial application. It mainly accumulates experience and derives ideas and standards for development," Zhang Hongtao indicated. The mainstream prediction currently is that commercial development of terrestrial permafrost zone natural gas hydrates could be realized around 2020, and commercial development of seabed natural gas hydrates might be possible between 2030 and 2050.
Due to a late start, compared to other countries, China’s research progress on flammable ice lags behind by 5 to 7 years. "Therefore, we feel very urgent. Although some countries have already achieved experimental development, the technical details are highly confidential. We cannot wait for others' technology methods to mature before we use them; we must expedite the autonomous development of appropriate methods and technologies," Zhang Hongtao said.
"If we say that in the last decade, we solved the problem of 'whether there is or not,' then in the next decade, we need to answer the question of 'how much there is.' Next, we need to continue conducting surveys on natural gas hydrates while developing suitable exploration methods for different geological conditions," Zhang Hongtao said.
He believes that optimistically, if the aforementioned work can be completed within 10 to 15 years, trial extraction can be conducted, followed by another 5 years of trial extraction, which might lead to commercial extraction. He appeals that to achieve this goal smoothly, the Chinese government should include flammable ice research projects in the '12th Five-Year Plan.'
Source: Science and Technology Daily
(Original Source: People's Daily Online, Author: Yu Wenji, Cao Xiuying)