The oil and gas industry has been on the constant search for new frontiers to explore alternate sources of energy to cope with the ever growing world demand. One such frontier is the hidden gas hydrates source. It is a great form of energy found beneath seabed and its major component is methane. It is an ice-like structure referred to as clathrates settled in the bottom of the sea. Mapped global hydrate resources are estimated to be twice of all known reserves of oil and gas combined. Hence this could emerge as a major source of future hydrocarbon fuel in the 21st century.
Many countries are trying to use this source to compete with shale gas phenomena of Northern America to achieve economic and fuel independence. Unlike shale gas, Methane clathrates are found either beneath the seafloor or underneath the Arctic permafrost.
As an alternate fuel, gas hydrates promise to be an environmental friendly fuel which can help in achieving green energy proposition. The key composition in the gas hydrates is methane which is the cleanest fuel as it releases minimum residues to the environment. This clearly makes the difference when compared to conventional fuels such as gasoline, gas oil, etc. Natural gas extracted from hydrates produces far lesser carbon dioxide than oil or coal per unit of energy. Hydrate extraction is considered a clean fuel technology producing just two substances: 100% pure methane and water.
Gas hydrates find their application primarily in power generation, fertilizer manufacturing and for home heating purposes.
History and Origin of gas hydrates exploration
The idea of gas hydrates formation underneath sea was first proposed in the 1970s by Russian scientists. With the help of deep water exploration over a period of time, it was confirmed that these naturally formed clathrates could be an exploitable source of energy. They were estimated to have a vast energy potential base of about 270 m trillion cubic feet of natural gas that is still untapped.
Today, more than 30 countries have carried out research and exploitation on gas hydrates and made their own gas hydrate commercial production programs. These countries include the United States, Japan, Canada, New Zealand, Germany, China and India. The United States, Canada, Japan are leading countries that have carried out basic gas hydrate research drilling tests and exploration. After successfully conducting research on extraction of gas from gas hydrates between 2009 and 2015, Japan became the first country to master submarine gas hydrate exploitation technology.
Methods of extracting gas hydrates
The production of methane hydrates is essentially different from the extraction of oil and natural gas. These conventional fuels flow naturally through the pores of the reservoirs to the well. Hydrates, on the other hand, are solid, and must first be separated before the methane gas can be extracted. Various methods are used in the extraction of gas hydrates. Before getting to know more about these methods, it is important to understand a terminology known as hydrate stability zone, which refers to the depth of marine environment at which methane clathrates naturally exist. Primary factors on which the stability depends are pressure and temperature. The following methods are the most widely used to extract gas hydrates:
- Thermal stimulation
- Chemical inhibition
The depressurization method employs the technique of lowering the pressure at which the hydrates exist and thereby hydrate stability zone starts to decompose. In the process, the freed gas starts moving upward and escapes through the wellbore set up for that purpose. This is a simple and effective method.
When thermal stimulation method is used the temperature of the hydrate stability zone is increased substantially by directly injecting steam. This again is intended to decompose that area to facilitate extraction of the gas.
The third main method is chemical inhibition which is again primarily employed to disturb the state of the stability of the hydrate zone. In this method, a liquid inhibitor chemical is injected in the intended area to create disequilibrium in the hydrate state.
The gas hydrates are transported in multi modes. Gas hydrates are transported through regular conventional mode of pipelines to the intended storage point. It is also possible to convert these gas hydrates into middle distillates and then transport the same through vessels. Another way of transportation is by converting it into solid state of crates from its original gaseous state and then shipping it through vessels to the intended destination.
Barriers to commercial use
There exists many challenges and barriers in extracting methane clathrates and it remains a major challenge as the deposits are spread far and wide, making it highly expensive and complicated drilling procedure. Barriers are technical, commercial and environmental.
Gas hydrates are available in deep underwater cold environment hence the cost and technical challenges for commercial exploitation of methane gas from hydrate deposits is still prohibitively high. Specialized and highly expensive equipment are required to drill and depressurize the hydrate deposits to separate the methane from ice. The gas is then extracted and piped to the surface.
Another major concern is the fact that methane gas is a greenhouse gas due to its carbon dioxide content, and the release of this gas into the environment can cause negative repercussions on the climate change and contribute to global warming. However, when compared to the conventional sources of energy, it is still a cleaner fuel. Explorers are grappling to extract this gas without causing ecological and environmental damage to the air and seabed. Burning the natural gas, methane on extraction produces good amount of carbon dioxide. Further drilling deep into oceanic deposits could impact both marine life and the seabed, potentially causing sediment to slide down the continental slope and trigger tsunamis. Scientists are exploring the possibility of pumping the carbon dioxide into the undersea lattices after methane extraction to create a carbon neutral process. However, this was attempted by Conoco-Phillips in the North Slope of Alaska in 2012 but it did not yield the desired result.
In conclusion, gas hydrates promise to be a game changer subject to the techno-commercial and environmental issues. This could propel the industry to a win-win situation and challenge the conventional sources of energy in the decades to come.