NZ Offers Geothermal Potential for Abandoned Oil and Gas Wells

New Zealand [RenewableEnergyAccess.com] After compiling an inventory of New Zealand's abandoned wells, Dr. Agnes Reyes, a geothermal scientist of GNS Science, reports that temperatures at the bottom of about half of New Zealand's 360 abandoned on-shore oil and gas wells are hot enough to produce geothermal power.

"New technology means that much of New Zealand's subsurface has become one big geothermal source. As drilling wells is expensive, it makes sense to explore the possibilities offered by existing wells."

-- Dr. Agnes Reyes, a geothermal scientist of GNS Science By tapping in to the geothermal properties of these abandoned wells, she says, New Zealand could potentially harness up to 160 megawatts (MW) of electricity.

"Abandoned oil and gas wells and sedimentary basins have been overlooked as a possible geothermal energy source in New Zealand because they are mostly outside the traditional geothermal areas," Reyes said, after realizing the heat within the wells could potentially provide enough electricity to power a city the size of Christchurch, New Zealand. The rest of the 360 abandoned wells, she found, had enough heat for direct industrial applications and geothermal heat pumps, which operate efficiently at temperatures between 10 and 30 degrees Centigrade (C).

"France, the United States, Australia, Germany, Switzerland and Japan have shown it is feasible to harness geothermal energy from unconventional sources," said Reyes. "The technology developed for this purpose is called Enhanced Geothermal Systems or EGS," which, she explained, can overcome "engineering and geological issues that are traditionally seen as barriers to geothermal development."

The scientist's work to date in this area has largely been an add-on to her government-funded research on New Zealand's low-temperature geothermal systems. These typically have surface springs with temperatures lower than 90 degrees C. Most are outside the central North Island's volcanic zone. Reyes believes there is so much untapped heat in sedimentary basins and unused wells that it warrants a systematic evaluation to see if this type of energy production is feasible in New Zealand.

The first step would be to assess the condition of the abandoned wells, but research on the engineering, scientific and economic issues requires funding and the support of the oil and gas exploration industry. There is presently only one oil and gas well being used commercially to produce geothermal energy in New Zealand, Reyes said. The Bonithon-1 well in New Plymouth, drilled in 1908, is a source of thermal water for the Taranaki Mineral Pools. In other parts of New Zealand, revival of abandoned wells could provide a boost to flagging provincial economies. On the South Island's West Coast, for instance, there may be potential for commercial spas to be developed at well locations.

Estimated temperatures at the bottom of abandoned wells in New Zealand range from 20 degrees C in the shallowest wells to nearly 180 degrees C in the deepest wells, some of which are nearly 5 kilometers deep.

Abandoned oil and gas wells are not the only potential new energy source. New wells could be drilled into onshore areas around New Zealand to harness high temperatures at depths of 2500 meters and below. This could deliver another 800 MW of geothermal power for New Zealand, Reyes says. But, she added, "New technology means that much of New Zealand's subsurface has become one big geothermal source. As drilling wells is expensive, it makes sense to explore the possibilities offered by existing wells."

The release adds that in the U.S. momentum for harnessing this unconventional energy source has been growing steadily, as scientists recently estimated the geothermal energy is potentially available from unused oil and gas wells in Alabama, Arkansas, Florida, Louisiana, Mississippi, Oklahoma, and Texas and could contain at least 5000 MW of electricity.



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-- Martin Dorantes, 19 April 2006
I am glad to read more research for possible energy extraction with those abandoned wells. Since 2001, we have been working on a modified organic rankine cycle to convert temperatures as low as 10 degree centigrade. We have to tailor the working fluid and expander-generator to the hi-low range of the low grade thermal source.