The HydroFlame Steam and Flue-Gas Generator
HydroFlame or “Fire-in-Water” is a new concept of burning a fuel directly inside a rotating stream of water. Because of the direct contact between the flame and water, very high heat transfer coefficients are achieved which enables the HydroFlame steam generator to be compact enough to be placed downhole in deep heavy oil reservoirs. The HydroFlame DHSG does not have an exhaust gas stream – all of the flue gases from combustion are injected along with the steam into the heavy oil reservoir – making this a greener technology. The flue gas, being non-condensable, accumulates at the top of the payzone, pressurizes the reservoir and provides continuous drive for oil production. There is ample evidence for the positive effects of flue gases injected with steam yielding 100-900% oil recovery enhancements over steam alone. HydroFlame’s unique technology is ready for deployment in heavy oil and bitumen fields around the world as a highly efficient, environmentally friendly, and highly economic thermal enhanced oil recovery process. In light oil reservoirs, HydroFlame process can be used as flue-gas generator for conducting gas-injection EOR projects. Its compactness allows easy relocation to utilize flared natural gas as fuel for combustion. Its ability to handle poor quality water enables it to treat oil-field produced water while burning flared natural gas to generate flue-gas for EOR with zero CO₂ emissions.
In the beginning
The concept of flame in the vortex core of rotating water, referred to as the HydroFlame Concept, was invented and developed by Dr. Dandina N. Rao in the 1980s in Calgary, Canada. Dr. Rao built HydroFlame’s earliest prototypes – a 340,000 Btu/hr atmospheric pressure hot water heater and a 750,000 Btu/hr steam generator at 50 psi. He also successfully conducted propane firing with enriched-air on the 750,000 Btu/hr steam generator.
In the HydroFlame steam generator, the combustion process is carried out in the vortex core of two films of rotating water protecting the combustion chamber walls from the high temperature flame.
The novel HydroFlame direct-contact combustion process has been adapted for use in a Downhole Steam Generator (DHSG), which enables the cost-effective development of the world’s largely untapped Heavy Oil and Bitumen reserves.
The unique design concept enables the HydroFlame steam generator to:
Utilize, with minimal pre-treatment, the enormous amount of produced water for steam generation
Use oxygen for combustion if required instead of air
Be placed downhole (near sandface) for highly efficient steaming of deep heavy oil reservoirs at lower steam-oil ratios
Have periodic cyclic steaming of several wells in a field using a single HydroFlame unit while simultaneously capturing and burning flared natural gas
Eliminate CO₂ emissions by injecting all of the CO₂ generated into the reservoir
Why is there a need for HydroFlame?
According to the United States Geological Survey, more than 95% of the world’s Heavy Oil is located in reservoirs deeper than 2500 feet and 4% of the world’s Bitumen is located at depths greater than 2500 feet. Conventional steam generators cannot be applied economically to reservoirs deeper than 2500 feet, due to heat losses during delivery and the loss of steam quality at the sandface.
Because of its high efficiency and large heat-transfer coefficients, the HydroFlame process can be used to make large quantities of high pressure steam within a very compact device. The device can be placed downhole to deliver steam at sandface.
Current steaming techniques in the production of heavy oil and bitumen result in significant CO₂ emissions that are damaging to the environment.
The compact HydroFlame unit can be placed downhole in an oil well for injecting steam and/or hot water directly into the oil-bearing formation. The combustion gases are also injected in the reservoir formation along with the steam, eliminating atmospheric emissions of CO₂.
Although downhole steam generators offer major cost and water savings as well as improved environmental quality and is more energy efficient, steaming operations are currently carried out using more costly surface steam generators. This is because past downhole steam generator designs suffered from thermal degradation and limited combustor lifetime.
HydroFlame steam generator solves the problem of combustion chamber metal stress and thermal degradation by eliminating all metal-to-flame contact. The flame is always surrounded by rotating water.
Recovery and production of heavy oil with current technology is limited to giant heavy oil fields such as in California, where economy of scale is the only way to remain profitable; significant heavy oil and bitumen resources worldwide remain “stranded” and untapped because they’re too expensive to bring to the surface.
HydroFlame eliminates the expensive design flaws in current downhole steam generation technology to the point of making it feasible for use in recovering smaller, “stranded” resources worldwide. The highly mobile nature of the system enables it to be transported to different locations fairly easily.
By the middle of this century, the world population is projected to increase from today’s 6.2 billion inhabitants to 10 billion people. All forecasts indicate that fossil fuels will supply about 85% of the total world energy demand in 2030, roughly the same as today. But oil reserves that are accessible with current technology cannot sustain this. It is almost certain that, given projected increased demand from Asian and developing countries, the world will become dependent on the world’s heavy oil and bitumen reserves, which are “stranded” because they’re too expensive to access and produce using current technology.
HydroFlame technology solves the present technical and environmental problems of current technology, making the development of “stranded” heavy-oil and bitumen reserves worldwide both feasible and profitable.
How does HydroFlame work?
In this process, a high intensity flame is surrounded by two films of rotating water. The flame is in direct contact with the water. The two films of water protect the combustion chamber walls from the flame burning in the middle of the chamber. Mechanical tests conducted at the HydroFlame facility shows that the temperature of the combustion chamber walls do not rise above 120° F despite the presence of a 2400° F flame in the middle. The hydrodynamic stability of the rotating body of water and the aerodynamic stability of the flame complement each other, resulting in an elegant solution to the age-old problem of combustion containment – preventing thermal damage to the surrounding surfaces.
Air, fuel and water are supplied to the steam generator at the pressure of operation. Direct contact heat transfer results in high heat transfer coefficients, enabling a compact design that fits in the wellbore. Since the transfer of heat is direct in the DHSG without any heat transfer barriers between the hot combustion gases and the water, water of much lesser quality (than what is required for conventional steam generators) can be used.
High quality steam and fuel gases from the DHSG are injected into the reservoir resulting in natural sequestration of Carbon dioxide (CO₂)
The Advantages of HydroFlame
HydroFlame offers a technology solution to benefit businesses involved in Heavy Oil and Bitumen production. This solution offers environmental, technical, economical and global advantages.
Reduction in heat losses and increased efficiency
Reduction in greenhouse gas emissions
Production of heavy oil reserves from deep reservoirs and offshore
Pressure maintenance in oil reservoirs due to flue gases injection resulting in longer production times
Smaller footprint compared to surface steam generators
Skid mounted units provide high mobility
Direct heat transfer without any conduction materials between the hot combustion gases and water enables the user of lower quality water with minimal treatment
Absence of metal-to-flame contact eliminates thermal gradients and degradation that can cause combustor failure and shutdown
Reduction in heat losses and increased efficiency
Environmental
The production of Heavy Oil and Bitumen necessitates the generation of huge amounts of steam to reduce the viscosity of the oil so that it can be produced to the surface. Steam generation requires burning fossil fuels, which sends three to five times more climate-changing greenhouse gases into the atmosphere than drilling for conventional oil. Surface steam generators produce 80 to 140 lbm of CO₂ for every barrel of heavy oil produced at oil/steam ratios ranging from 0.3 to 0.5.
In contrast, in the HydroFlame steam generator, all the combustion gases are injected into the reservoir formation along with the steam, reducing the emission of greenhouse gases.
Financial
Major cost and energy savings occur due to reduced water treatment needs, reduced heat losses and increased efficiency. Since the transfer of heat is direct in the HydroFlame steam generator without any walls between the hot combustion gases and the water, water of much lesser quality than that used in current streaming technologies can be used. This eliminates the need for expensive water treatment.
Heat losses from conventional steam generators can be greater than 20%. Such heat losses arise from stack gas losses, pipelines and the wellbore. With the surface steam generators, large insulated pipelines from the location of the steam generator to the well head are required to reduce pipeline heat losses. Building insulated pipelines adds to the capital cost of the whole operation. In contrast, heat losses from the the downhole steam generator are negligible. Even if the HydroFlame steam generator were operated on the surface, it could be operated right next to the wellhead, eliminating both pipeline losses and stack gas losses.