Researchers receive grant to harness hazardous energy source

University of Arizona researchers are helping to develop an energy resource that could help remove America's dependence on foreign supplies of natural gas.

The deposits are called 'gas hydrates,' and consist of pressurised methane trapped in a cage of water ice. Although geologists and petroleum engineers have known about these deposits for many years, they have considered them hazards to avoid because of their danger to oil rigs.

Inadvertently drilling into a gas hydrate deposit releases tremendous pressure that can blow the pipe out of the well, creating a methane firestorm.

But what was once a hazard is now being recognised as a vast energy reserve that can be found in many places including the continental shelves near Japan, Europe, India, the Gulf of Mexico, the US western seaboard and Alaska.

UA has received a four-year, $2.5 million grant from the Department of Energy to estimate the amount of gas hydrate on the Alaskan North Slope and to pinpoint the deposits. The researchers also are developing a detailed understanding of gas hydrate reservoir characteristics and the geological conditions that cause these deposits to be formed.

'Estimates of the amount of gas hydrate on Alaska's north slope vary from about 6.7 trillion to 66.8 trillion cubic meters,' said Mary Poulton, department head in Mining and Geological Engineering (MGE). 'If we want to develop this resource, we have to more accurately determine how much is there and pinpoint the location of the deposits.'

Researchers from MGE and the UA Geosciences Department will analyse data sets covering a 1,000-square-mile area to look for deposits. The data includes detailed information from core samples taken at oil wells and seismic reflection data.

'The principle is analagous to radar,' said geosciences Professor Roy Johnson, 'We send an acoustic signal and measure the time it takes for the echoes to come back. This allows us to interpret the geologic conditions.'

The data comes from BP Exploration (Alaska) Inc. and other exploration companies. They have gathered the data since the 1970s while exploring for deep oil reserves.

Gas hydrate deposits occur within 2,000 feet of the surface -- much higher than the deep oil reserves. 'Now we're going back and looking through these wonderful data sets as a key to understanding the occurrence of these deposits and to assess the total reserves under this area,' said MGE Adjunct Instructor Robert Casavant.

Data from the well cores provides detailed information about a small area.

'We want to integrate this highly detailed data with the seismic reflection data to determine where the deposits are in areas away from the wells,' Casavant explained. 'We know what conditions are like at one well, and we know the conditions at another well, and we want to create a model that will help us determine the conditions between them so we can measure how much gas hydrate is out there and where it is.'

BP Exploration is the lead agency for the entire project, which is funded at $21 million. DOE is providing $12 million, with the rest coming from matching contributions and the estimated value of the data sets.

UA is the lead science organisation on the project. The University of Alaska at Fairbanks will design the new engineering technology needed to safely drill into the methane hydrate.