In this blog post, we’ll explore the concept and characteristics of gas hydrates—commonly known as “burning ice”—their potential as an energy source, their distribution patterns, and the current status of exploration and development in South Korea and around the world.
What Is a Gas Hydrate?
A gas hydrate is a solid crystal that resembles dry ice in appearance; it is a substance formed when natural gas and water combine under conditions of low temperature and high pressure. While natural gas consists of components such as methane, ethane, propane, and butane, most gas hydrates are primarily composed of methane, which is why they are also called methane hydrates. It earned the nickname “burning ice” because the methane inside burns when ignited.
Gas hydrates are highly sensitive to changes in temperature and pressure; if their stable conditions are disrupted, they easily decompose into water and gas. During this process, the stored methane is released; it is generally known that approximately 1 m³ of methane hydrate produces about 160–170 m³ of methane gas under standard conditions. It is often explained that it can produce approximately 164 m³ of methane gas.
Advantages as an Energy Resource
Methane hydrate is regarded as a future energy resource with a very high energy density. Since they can store large amounts of methane in the same volume, they offer excellent energy storage efficiency, and the produced methane can be utilized in various fields—such as power generation, industry, and heating—in the same way as conventional natural gas.
Furthermore, gas hydrates are not concentrated in specific regions but are widely distributed in low-temperature, high-pressure environments, such as permafrost regions like the Arctic and the deep-sea seabed around continental shelves. Although global reserves have not yet been precisely determined, they are estimated to potentially far exceed existing natural gas reserves. However, since reserve estimates vary significantly depending on the research institution and survey methods, it is more appropriate to view gas hydrates as a resource with immense potential rather than presenting specific figures definitively, as was done in the past.
Distribution and Potential Reserves in South Korea
In South Korea, it is known that gas hydrates are highly likely to be found primarily in the Ulleung Basin in the East Sea. In the past, potential reserves of approximately 600 million metric tons were suggested, and some analyses indicated that this amount could supply natural gas for about 30 years based on consumption levels at that time. However, these figures are no longer considered confirmed reserves, and detailed research is ongoing to determine the actual economically viable resource volume.
Nevertheless, the Ulleung Basin is evaluated as the most promising gas hydrate deposit area in Korea and is becoming a key research focus for the future development of next-generation marine energy resources.
Geophysical Exploration and Seismic Survey Methods
Since most energy resources are located deep underground, accurately identifying their distribution prior to development is crucial. Geophysical exploration is a method that estimates the potential presence of resources by analyzing differences in the physical properties of target strata and surrounding strata; in gas hydrate exploration, reflection seismic surveys play the most critical role.
In South Korea, full-scale exploration in the Ulleung Basin of the East Sea began in 2005 under the leadership of the Korea National Oil Corporation (KNOC). Data acquired through reflection seismic surveys undergo various processing steps—such as filtering, muting, velocity analysis, and correction—to remove unnecessary signals and enhance the necessary information. By interpreting the resulting stratigraphic sections, it is possible to more accurately assess the potential presence and distribution characteristics of gas hydrates.
What Seismic Indicators (Exploration Signals) Signify
In reflection seismic surveys, various indicators suggesting the presence of gas hydrates can be identified. Representative examples include the BSR (Bottom Simulating Reflector), amplified reflectors (strong negative amplitudes), acoustic blanking zones, and columnar structures.
A BSR is a reflector that appears nearly parallel to the seafloor and exhibits characteristics distinct from actual stratigraphic boundaries. This occurs because a solid gas hydrate layer above it has a high seismic wave velocity, while the methane gas layer below it has a relatively low velocity, resulting in a significant velocity difference between the two layers. Due to these characteristics, the BSR is used as one of the most representative exploration indicators for determining the presence of gas hydrates.
Additionally, when gas is contained within highly permeable sand layers, an amplified reflection surface with a strong negative amplitude may appear due to differences in the reflection coefficient. An acoustic gap refers to a phenomenon in which the presence of gas hydrates or free gas within sedimentary layers weakens the seismic signal, causing sedimentary structures to appear faint. A columnar structure refers to a form in which such acoustic gaps develop in a column-like shape. During exploration, these various indicators are comprehensively analyzed to more reliably assess the potential presence of gas hydrates.
Results of Gas Hydrate Exploration and Current Development Status in Korean Waters
The Ulleung Basin in the East Sea of Korea has long been recognized as an area with the potential for large-scale gas hydrate deposits. Early reflection seismic surveys identified various signals suggesting the presence of gas hydrates in the waters around approximately 36° N, 130–131° E. In particular, the observation of a bottom-simulating reflector (BSR) led to the assessment that this area had a high potential for gas hydrate deposits. Subsequent refraction seismic surveys analyzed the velocity structure of the strata and confirmed that the BSR was distributed over a relatively wide area; several other exploration indicators were also discovered.
Based on these research findings, the Gas Hydrate Development Project Team was launched in 2005, and detailed exploration centered on the Ulleung Basin began in earnest. The research team conducted repeated seismic surveys and drilling surveys, and in 2007, they succeeded in obtaining actual gas hydrate samples through deep drilling. Subsequent drilling took place in 2010, and research into the deposit forms and occurrence characteristics was further deepened. This research served as a crucial foundation for South Korea to develop its own seabed gas hydrate exploration technology.
However, the 2015 commercialization target proposed in the past was not achieved. Although gas hydrates are attracting attention as a future energy source due to their vast methane reserves, challenges remain in ensuring economic viability and developing stable production technologies. In particular, the process of decomposing gas hydrates to recover methane in deep-sea environments is technically very complex, and sufficient verification is required regarding seabed stability issues that may arise during production, methane leaks, and the impact on the marine environment.
Currently, South Korea has not yet reached the commercial production stage and is continuing to assess resource reserves and conduct research on production technologies, primarily in the Ulleung Basin. Research institutions are using drilling data and geophysical survey data to analyze resource reserves with greater precision and are focusing on securing core technologies for future pilot production and economic feasibility verification. Furthermore, as research on gas hydrate production technology and test production continues in various countries—including Japan, the United States, China, and India—competition in this field is intensifying.
Gas hydrates are regarded as a next-generation energy resource with high energy density, as suggested by their nickname, “burning ice.” Although there are still many technical and economic challenges to overcome before commercial development can begin, the diverse exploration achievements accumulated in the Ulleung Basin demonstrate that South Korea has established a solid research foundation in the field of next-generation marine energy resource development. If production technology and environmental safety assessments continue to advance and economic viability is confirmed, gas hydrates have the potential to play a significant role in long-term energy security and future energy supply.
