When oil and gas wells approach their final days -- as water cuts increase at the expense of oil and gas produced -- the cost of electricity to produce these marginal wells can become prohibitive. Viewed by many as a liability, the warm water that's co-produced with oil and gas may be transformed into an asset, extending the commercial lives of stripper wells.
Geothermal waters found in the Western Canadian Sedimentary Basin (WCSB) represent a new form of abundant and cheap energy that's sequestered in underground aquifers. The renewable energy stored in these subsurface aquifers is sufficient to power geothermal heat pumps and heat exchangers to generate electricity.
The Alberta Geological Survey (AGS) and the Alberta Research Council (ARC) have teamed up to study the technical and economic feasibility of harnessing Alberta's low temperature (10 to 40 degrees Celsius) to medium temperature (40 to 140 C) geothermal resources. Preliminary estimates suggest that -- given current technologies -- the potential energy locked in Alberta's geothermal waters is on the order of two to five trillion barrels of oil equivalent.
According to Rick Richardson, manager of the AGS, even one percent of the energy contained in the subsurface aquifers could dwarf the remaining oil and gas reserves in the WCSB.
"We have a huge resource endowment that's untapped, combined with a huge oil and gas infrastructure," said Richardson, who was the EMD technical program vice chair for the 2005 AAPG Annual Convention in Calgary. "The Earth is always producing heat and transferring it into aquifers."
The study, he added, will focus on non-potable and saline underground aquifers.
"We're trying to match the geology to the technology," he said. "You can't just do it anywhere -- there has to be an end user with fairly substantial heating and cooling needs."
At present, there are more than 30,000 heat pump installations in personal residences and commercial facilities across Canada.
At Springhill, Nova Scotia, heat pumps extract energy from 18-degree C waters in a flooded coal mine to heat and cool a nearby industrial complex. According to Natural Resources Canada's Office of Energy Efficiency, the Springhill geothermal project offsets the need for oil-fired electrical power generation, creating an annual energy savings of $45,000.
During the 1980s and 1990s, the Geological Survey of Canada pioneered the study of geothermal resources across Canada, describing the WCSB as the largest "accessible" warm water resource in the country. According to the Survey, many of the basin's subsurface geological formations have adequate porosity and permeability to yield both hydrocarbons and warm waters.
Temperatures in the WCSB correspond with depth, increasing on average about 3.3 degrees Celsius for every 100 meters.
Richardson points to the WCSB's large number of abandoned and orphaned wells, considered liabilities by many, saying, "We're trying to turn oil and gas infrastructure into assets."
The Viking Formation, one of many prolific oil and gas reservoirs in Alberta, is buried -- from east to west -- between 1,000 to 3,000 meters. Correspondingly, the Viking's geothermal aquifers range in temperature from 33 to 99 C.
According to Richardson, the Viking Formation has been penetrated by 189,000 wells to date -- 60,000 of these wells are producing, 100,000 wells are abandoned and 20,000 suspended.
Historically, the economics of geothermal energy projects failed due to the high costs associated with drilling and completing wells.
"We believe that this project is viable at the moment, but the question is timing," said Ian Potter, an engineer and ARC's director of Sustainable Energy Futures.
There are many unknowns, Potter added, including the condition of the province's boreholes and the replenishment rate of energy (or heat) in subsurface aquifers.
"We don't want to find that we've just killed our heat source," Potter said.
Taking the Next Step
Potter's mandate is to examine technology gaps in geothermal energy extraction and conversion.
"We're taking heat pump technology to the next level," he said. "And, there's a role for hybridization of technologies."
One new technology that Potter will evaluate is Arizona-based Deluge Inc.'s Natural Energy Engine™, a noncombustible engine that uses geothermal energy, essentially replacing conventional diesel- or gasoline-powered pump jacks at wellheads.
The engine contains high-pressure, liquefied carbon dioxide that is heated and cooled, causing expansion and contraction -- this change in volume pushes and pulls on a piston, creating mechanical energy.
In September, Deluge won the 2005 Outstanding Technology Development award from the U.S. Federal Laboratories Consortium for field-testing its engine at the Naval Petroleum Reserve near Casper, Wyo. Deluge demonstrated that its engine was capable of pumping an oil well at depths ranging from 120 to 480 meters, with power to spare.
In addition to petroleum producers, other suitable end users for direct use geothermal energy include:
- New housing subdivisions.
- Industrial research parks.
"The role of the ARC is to showcase the natural resources of the province," Potter said. "It's the start of a new business in Alberta."