Heavy oils and natural gas hydrates, which exist in vast reserves, could potentially become a significant source of energy, but these resources are much more difficult and expensive to produce than conventional sources of oil and natural gas. At a March Meeting session on the future of fossil fuels and a related press conference, speakers provided assessments of these potential alternative sources of oil and natural gas.
Natural gas consumption has been rising rapidly, and is expected to increase 70% by 2025, said Timothy Collett of USGS. The United States currently consumes about 25 trillion cubic feet of natural gas per year.
An alternative could be found in gas hydrates, reported Collett. Hydrates are ice-like solids, in which water molecules trap the methane molecules in a cage-like structure. Hydrates look a lot like ordinary ice, but they burn when lit with a match.
Like conventional natural gas, most gas hydrates are methane-based, and thus produce relatively clean burning fuel. Burning methane adds less carbon dioxide to the atmosphere than burning coal or oil.
Hydrates, first discovered in 1983, can be found on the sea floor near the coasts and underneath the arctic tundra. Earth contains vastly more natural gas in hydrates than in conventional natural gas, said Collett in a press conference at the March Meeting. “Hydrates are a very large, known source of natural gas,” he said. There has been increasing international interest in recovering and using these resources, he said.
Several missions have recently explored some of these deposits and estimated how much natural gas hydrate they contain. Estimates range from 100,000 to 300,000,000 trillion cubic feet of natural gas hydrates on Earth, compared with 13,000 trillion cubic feet of conventional natural gas. The US has about 320,000 trillion cubic feet of gas hydrates, but only 1200 trillion cubic feet of conventional natural gas reserves.
More research is underway to assess more accurately how much hydrate natural gas exists and how much of it might be recoverable, Collett said.
Recovering the gas is challenging, but possible. Several research projects have shown that gas hydrates can be produced by either heating the hydrates or decreasing the pressure to release the gas. More testing of these methods is still needed, said Collett.
Environmental concerns associated with hydrate production include possible damage to the sea floor or possible accidental release of methane gas. Any project that produces gas hydrates would have to deal with these concerns, said Collett. However, accidental release of methane is unlikely, he said.
Based on the limited studies done so far, Collett believes hydrates could become economically competitive with conventional natural gas.
Another promising source of energy is heavy oil, Doug Schmitt of the University of Alberta reported. Significant heavy oil reserves exist in Canada, South America, and Colorado, while most of the world’s light oil reserves are in the Middle East.
Heavy oil looks like sand with tar added, Schmitt said. Though heavy oil is abundant, because it is so thick–its viscosity is similar to peanut butter–it is difficult to extract and use. “The real problems are accessing it and being able to produce enough,” said Schmitt.
Heavy oil can be extracted using a process called steam assisted gravity drainage. This involves drilling two horizontal bore holes and injecting steam into one of them. The steam heats the heavy oil, making it flow more easily. The process works, said Schmitt, but is costly.
In order to make the process as efficient as possible, Schmitt says it is important to improve our knowledge of the properties of the heavy oil and the surrounding rock. He and his group are using sensitive seismic imaging techniques to monitor the heavy oil production process. They have used these techniques to locate where the largest oil deposits are within the rock. They have also been able to trace the steam as it is injected during the extraction process, potentially making it possible to use the steam more efficiently. Alternative technologies to extract the heavy oil are also being investigated, Schmitt said.