Tech Transfer: Oil States Targets Geothermal Energy

Oil States International is digging deep into its oilfield services toolkit, tailoring proven oil and gas technologies to help solve challenges with geothermal energy generation.

Geothermal well integrity and issues involving cement around casing is among them, according to Connor Whitelaw, principal engineer for Oil States International’s OSI Renewables.

“Essentially, robust cementing is needed from reservoir to surface to manage the thermally induced axial stresses but high temperatures degrade the conventional cementing,” Whitelaw said. “So, as a result you need to have special cement for that job. It limits your options there straightaway and in today’s society we want to try and keep costs as low as possible.”

The lack of tensile strength could cause cracks and methane venting, he added. With temperatures for geothermal wells typically ranging from 200 C to 420 C, casing corrosion, cement failure and casing collapse are potential risks that geothermal developers aim to avoid as they drill deep—hundreds to thousands of feet deep—to economically harness heat and convert it into electricity.

GeoLok technology developed by Oil States aims to improve geothermal well integrity and reduce cement-related problems, while lowering operational costs and enhancing energy production. The company utilized its oil and gas tendon equipment expertise for the geothermal technology offering.

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The technology transfer is taking place as some geothermal developers ramp up efforts to extract heat from the earth to provide low-carbon, round-the-clock energy. In the U.S., geothermal energy accounts for less than 1% of electricity generation. However, efforts are underway to change that with support from the Trump administration among others.

Geothermal energy projects are also gaining traction in the U.K., where Oil States also operates.

Developers of geothermal projects have been tapping proven oil and gas techniques and technologies in recent years to help strengthen the sector, looking to improve economics and remedy technical challenges.

Most of the technology used today in geothermal, including on the wellhead side, is repurposed existing oil and gas equipment. “The tried and true method to prevent casing collapses is to cement to surface. So, what we’re doing is we’re only cementing what’s known as shoe to shoe,” Whitelaw explained. “We’re not cementing all the way to surface. In doing so, when we pull tension on the casing string, that is eliminating the failure mode that is caused by a casing collapse.”

The integrated tensioning system improves rigidity, helping to better manage thermal stresses as temperatures fluctuate.

The GeoLok high-temperature geothermal wellhead is suitable for both traditional hydrothermal systems as well enhanced geothermal and supercritical geothermal systems. The company said the technology decreases casing requirements and employs a ‘cut and pull’ approach that lowers material costs, reduces cementing voids and minimizes heat loss to ultimately lower geothermal well downtime and operating expenses.

Air barrier

Preventing heat loss during the process is essential to developing efficient geothermal energy. Air is an excellent barrier to heat, according to Zander McDougall, renewable business manager at OSI Renewables.

“The cement, unless you add expensive stuff, conducts heat out of the well. So, if you have cement, you will lose more heat to the well formation,” McDougall said. “If you have an air barrier, like you will have for significant parts of the well under GeoLok, that air barrier acts as an insulator. So, we keep more heat in the well. More heat in the well means more energy to the surface. More energy to surface means more efficient and more revenue per unit of water or steam combined.”

The technology’s open annulus also ensures continuous monitoring, the company said. Other features include rate of change alarms to communicate well health and mechanisms that detect corrosion. The technology is expected to result in cost savings in steel weights around the casing conductor and cementing because less will of the materials will be needed, according to McDougall.

Hopes are that the technology will help geothermal transition from being a new energy to an established, mature and widespread baseload power source, he said.

Levering core technologies

While Oil States is known mostly for its work in oil and gas, the company has been growing its presence in alternative energy by leveraging its core technologies.

Oil States International has repurposed its technology for use in other renewable energy applications, including offshore wind.

“A lot of our connector products are transferable to pretty much every energy sector,” said McDougall. “They are highly fatigue resistant, gas tight and work at high temperatures, high pressures. … The tension-leg platform [oil and gas] technology that has been used in geothermal, some of that technology has also been used in our FTLP [fixed tension-leg platform] development in offshore wind.”

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The company’s connector technology has been adapted for offshore wind towers to help scale taller, larger wind turbines. The company also has secured contracts for its connector technology for carbon capture in the North Sea.

“So anywhere that there’s oil and gas adjacent technologies or stuff needs connecting we’ve got something to offer,” McDougall said.

Whitelaw and McDougal see geothermal playing a larger role in meeting the world’s growing energy demand.

“I think it’ll be a keystone, not just in our energy portfolio but I think many countries’ portfolios as a potential new baseload energy,” Whitelaw said.

There is huge potential for geothermal across the world, including in Europe and the U.S., McDougall added. He expects geothermal to become a core part of the energy mix, “potentially as significant as the gas market for energy generation toward the next decade.

“But efficiencies are needed to make that happen, and we are offering technologies that help that journey.”