Geothermal energy has been described as an engineering problem that, when solved, provides the clean, reliable, safe, and affordable energy being sought globally. It is highly likely that the engineers who play the biggest role in solving that problem, and the technologies they adapt and advance, will come from oil and gas. There is enough energy in the earth’s crust, just a few miles down, to power all of humanity for ages, according to the US Advanced Research Projects Agency-Energy. The problem is how to tap into it safely, efficiently, and cost effectively.
After many years of failure to launch because of technology or cost limitations, new companies and technologies - and smarter ways of leveraging those that already exist - are bringing geothermal out of its doldrums, to the point that it may finally be ready to scale and become a major player in the transition to cleaner energy, according to Jamie Beard, executive director of the Geothermal Entrepreneurship Organization (GEO) at The University of Texas at Austin (UT-Austin). “The cutting-edge technological developments in geothermal are devoted to drilling into ever-deeper, hotter, and harder rock,” she said, “and oil and gas holds the key to cost reduction for all of these concepts.”
Eric Van Oort, drilling and well engineering expert, educator, and scientist, agrees. The UT-Austin engineering professor and director of the rig automation and performance improvement in drilling (RAPID) industry consortium, said, “Fifty to seventy-five percent of the cost of geothermal development is tied up in drilling and well construction. To scale it, we have to reduce that cost.”
Designing for Extremes
Well design for geothermal wells is similar to that for oil and gas wells. The challenges arise from drilling deeper and deeper, into hotter and hotter rock. Heat ranging from 150°C (302°F) to 373°C (703°F) and above can be used to profitably generate electricity. Oil and gas well designs traditionally have not had to contend with these extremes.
Thermal considerations are unavoidable in deep geothermal well construction. Temperature and thermal effects, chemical composition of produced fluids, and rate of production or pressure depletion pose significant challenges to well casing and design.
Nick Cameron, reservoir characterization manager at BP and leader of the supermajor’s studies into geothermal energy, said his company is using corporate data, geological understanding, and oil and gas expertise and experience to look at where their technology can reduce risk and drive down the cost of development. “Metallurgical understanding of materials and how they handle heat is crucial to these efforts,” he said. “Fortunately, there have been significant advancements in this area in recent years.” Cameron said that much work is also being done into changing the chemical composition of the fluids that flow through the geothermal reservoirs.
The Utilization of Abandoned Petroleum Wells in Geothermal Energy Sector. Worldwide Trends and Experience
