Getting hotter: Acceleware will trial its new RF heating system in the oil sands this year
InnovOil - Feb 28, 2019
Acceleware has developed a new radio frequency (RF) heating system, an update on previous versions that have been tested in Canada’s oil sands. Their version, RF XL, has been in development since 2010 after a supermajor asked them to troubleshoot some of their trials with RF heating.
Acceleware will trial its new RF heating system in the oil sands this year
Worldwide oil sands reserves are estimated to hold around 2 trillion barrels of oil, making them a major source of future hydrocarbons. While Canada is the main player in oil sands, there are exploitable reserves in Venezuela, the US, Russia and Kazakhstan.
However, different reservoirs have different compositions, making it difficult to adapt one technology between them. Even the fields currently being exploited use unconventional solutions that are expensive and put the environment at risk.
The technology most used in oil sands is steam assisted gravity drainage (SAGD). This uses two shafts, a higher injector well and a lower producer well, to pump steam into an oil sands formation. This lowers the viscosity of the oil, which is then drained by the producer well.
RF XL uses a transmission line in place of the injector well, which emits electromagnetic energy in the radiowave spectrum to heat the formation, like a microwave oven.
Attempts have been made before to use RF energy for heating oil reservoirs, but these have invariably put an antenna inside the formation. The engineering challenges created by managing large dipole antennae underground, along with the energy losses incurred charging them, made the technique too expensive.
Dipole antennae concentrate energy near their feed point (mid-antenna) at the cost of the toe and heel of the antenna, and also need a large, robust and expensive insulator at the feed point. Acceleware feeds RF energy to the reservoir down a coax, which connects to steel piping in the formation to create a “lossy” transmission line to radiate RF energy along its length.
Since water molecules are polar molecules, with one end negatively charged and the other positively charged, they absorb the electromagnetic energy and dissipate it as heat. Non-polar molecules, such as oil and bits of rock, are largely unaffected by the RF energy.
As the reservoir’s water turns to steam it no longer absorbs the electromagnetic energy, so the RF energy penetrates further into the formation to heat more still-liquid water molecules. This means that heating tends to permeate evenly.
Capital costs are lower. With no large steam plant, water treatment plant and steam transmission infrastructure Acceleware expects capital costs of around C$20,000-25,000 per flowing barrel. The standard investment in the Alberta oil sands is C$40,000-50,000 for a new project. Another bonus is that the surface plant can be easily re-deployed from reserve to reserve, extending plant life. Removing injected steam from the process also offers a chance to escape Alberta’s inherent shortage of water resources.
With SAGD lifting costs running at around US$16-18 per barrel at present (excluding taxes and royalties), RF XL seems to offer the potential to cut those by around half, and move oil sands production from being one the world’s more expensive reserves to one of its cheapest. RF XL also removes the need for external water, solvent supplies and tailing ponds.
The time profiles of SAGD and RF heating a quite different. RF heating starts oil production within a few days of commencement. SAGD can take up to six months to ‘pre-circulate’ steam before wells produce. On the other hand, RF heating does take up to 300 days to reach the toe of the well but liquids are flowing while that happens. Acceleware states that a key difference is that RF heating uses half of the input energy per barrel.
RF XL needs a pair of transmission lines in the ground, along with the producer well. On the surface the only infrastructure is a generator (or a grid connection) and an RF signal generator. Staffing costs are considerably lower, so both opex and capex are roughly halved.
Acceleware uses silicon carbide transistors to produce its RF energy, sourced from GE, to deliver up to 6,000 kW of power with 98-99% conversion efficiency to electromagnetic energy.
In the well another 3% is lost to conversion and cooling. This compares well with SAGD, which loses about 30% of its heat to boiler efficiency, steam line loses and other factors.
Power costs are obviously key. A typical RF XL installation will run at 4,000-6,000 kW per well. At current Albertan electricity prices of around C$0.022 per kWh, running costs would come out at C$2,000-3,000 per day.
However, there are a number of factors that reduce electricity use. Demand is highest at the start of the process. A mature steam chamber requires less power to sustain its flow, about 4,000 kW. RF XL is also more manageable in the short term, as it can be switched on and off at will and without run-up or run-down delays. “If you’re grid connected, you can take power only off peak,” Acceleware VP Commercialisation Mike Tourigny told InnovOil. “You can take electricity and heat it for 95% of the month, turn off during the peak hours when you’re paying much higher rates for power, and have significant (~50%) savings for your power costs.”
It is not essential to have a grid connection, Tourigny added. “You could deploy solar power and maybe capture power for eight hours a day. We ran a heavy oil scenario where we compared putting 2,000 kW into a heavy oil reservoir over 24 hours per day, with putting 6,000 kW in for eight hours per day and then go down to almost zero power, in order to mimic off peak solar. If you could take that low cost power and dump it into the reservoir, you’re essentially getting the same energy as with 2,000 kW over 24 hours, but it’s as good as or better than 2,000 kW over the course of the day. The extra intensity of the energy tends to push the energy further and generate better production.”
Alberta’s insolation is obviously highly seasonal, though it receives about 1,000 kWh per square metre per year. Solar would need to be backed up with a grid connection or some other power source if production is to be sustained at full rate in the darker winter months.
RF XL’s heating lines are common downhole steel pipe, making them simple and robust. Should something go wrong, the well can be re-completed as a SAGD well. “Once the system is up and running, it is designed to withstand subsurface conditions for a run life of 20 or more years,” said Tourigny.
Acceleware’s field test (done with a large oil company) showed the risks of using less robust material for connections and how critical it is to design a system that relies on industry standard components.
RF XL could open up a number of new deposits for oil sands development. Because it uses water from within the reservoir instead of adding new water RF XL creates less pressure, allowing its use in shallow reserves. Until now a shallow oil sands asset would have to be produced by mining – a technology that has almost disappeared from the new-project list.
RF XL could outperform SAGD in deeper wells as well. Deep wells cost SAGD considerable heat loss, but RF XL’s losses are not affected by depth. Finally, thin seams of oil sands are also potentially producible with RF XL. “There’s a lot of oil in thin pays in Canada and around the world,” Tourigny added. “We believe we can produce oil from thicknesses of 10 metres or less.”
However, because RF XL works by heating water molecules, a reservoir’s composition can affect its performance. “In all the reservoirs we’ve explored, there’s been no reservoir that’s been too dry for us to heat.” Tourigny noted. “A very low water saturation would limit our ability to transfer heat into the system, but it would also go to steam really quickly.
“We do have problems if there’s moving water, such as a water table or layer that’s moving through the reservoir. The heated water would just leave the formation.”
Acceleware is currently working with Prosper Petroleum to test RF XL’s viability, using a test RF generator being built specifically for Acceleware by GE, whose IP is Acceleware’s. The test should begin later this year.
The initial stage of the project will be six months long, during which Acceleware will heat the reservoir at 2,000 kW. “It won’t be high rates of production in those first six months,” Tourigny said. “Our goal is to match our simulation and validate all the components of the well. If that’s working at the end of six months, we’ll add another generator and bring it up 4,000 kW to get that production level to something that’s more commercial.”