The oil and gas industry is on a continuous search for new frontiers to exploit alternate sources of energy to cope with the ever-growing world demand. One such frontier are hidden gas hydrates sources, which have an ice-like structure known as clathrates that have settled to the bottom of the sea. Mapped global hydrate resources are estimated to be twice that of all known oil and gas reserves combined. Hence this could emerge as a major source of future hydrocarbon fuel in the 21st century.
Where Gas Hydrates are Found
Many countries are trying to use this source to compete with the shale gas phenomena of Northern America to achieve economic and fuel independence. (Learn more about shale gas in the article Is Shale Gas Losing Its Sheen?) Unlike shale gas, methane clathrates are found either beneath the seafloor or underneath the Arctic permafrost.
A Promising Green Energy Source
As an alternate fuel, gas hydrates promise to be an environmentally friendly green energy fuel. The key ingredient in the gas hydrates is methane, which is one of the cleanest fuels because it releases minimal residues to the environment. This clearly makes a difference compared to conventional fuels such as gasoline and gas oil. Natural gas extracted from hydrates produces far less 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.
History and Origin of Gas Hydrates Exploration
The idea of tapping gas hydrates formations under the 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 million trillion cubic feet of natural gas that is still untapped.
Today, more than 30 countries have carried out research and exploitation of gas hydrates and have 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 and Japan are leading countries that have carried out basic research drilling tests and exploration. After successfully conducting research to extract gas from gas hydrates between 2009 and 2015, Japan became the first country to master submarine gas hydrate exploitation technology.
Gas hydrates are primarily used for power generation, fertilizer manufacturing and home heating.
Methods of Extracting Gas Hydrates
The production of methane hydrates is very different from the extraction of oil and natural gas, which flow naturally through the pores of the reservoirs to the well. (Find out more about porosity in the article The Significance of Porosity to Original Hydrocarbon in Place.) Hydrates, on the other hand, are solid, and must first be separated before the methane gas can be extracted. Various methods are used to extract gas hydrates.
Before examining these methods, it is important to understand the hydrate stability zone, which refers to the sea depth at which methane clathrates naturally exist. Pressure and temperature are important factors upon which methane clathrates depend.
The following are the most widely used methods to extract gas hydrates:
- Thermal stimulation
- Chemical inhibition
The depressurization method lowers the pressure at which the hydrates exist and therefore the hydrate stability zone begins to decompose. In the process, the freed gas starts moving upward and escapes through a wellbore installed for that purpose. This is a simple and effective method.
For the thermal stimulation method, the temperature of the hydrate stability zone is increased substantially by directly injecting steam. Again, this is intended to decompose that area to facilitate extraction of the gas.
Chemical inhibition is primarily employed to disturb the stability of the hydrate zone. In this method, a liquid inhibitor chemical is injected into the intended area to create disequilibrium in the hydrate state.
The gas hydrates are transported by several means. They can be transported through conventional pipelines to the intended storage point. It is also possible to convert gas hydrates into middle distillates and then transport them via vessels. Another transportation method involves converting it into a solid form, crating it, and then shipping it by vessels to the intended destination.
Barriers to Commercial Use
There are technical, commercial and environmental challenges to extracting methane clathrates because the deposits are spread far and wide, making drilling very expensive and complicated.
Gas hydrates are found in cold, deep underwater environments, so the commercial exploitation of methane gas from hydrate deposits is relatively expensive. Specialized and expensive equipment is required to drill and depressurize the hydrate deposits in order to separate the methane from the ice. The gas must then be extracted and piped to the surface.
Another major concern is the fact that methane gas is a greenhouse gas, and the release of this gas into the environment can cause negative repercussions for climate change and contribute to global warming. However, it is still a cleaner fuel compared to conventional sources of energy.
Explorers are trying to find ways to extract this gas without causing ecological and environmental damage to the air and seabed. Drilling deep into ocean 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 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 did not yield the desired result.
Gas hydrates promise to be a game changer, subject to the outstanding technical and environmental issues. Once overcome, gas hydrates could challenge conventional sources of energy in the decades to come.