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Oil shale retorting versus fracking
Oil shale retorting versus fracking
What is Fracking?
Natural gas and oil can be found in many places around the world with some of the largest deposits in "tight" rock such as shale. Tight rock is impermeable rock formations that lock in oil and gas within an infinite number of small individual pockets, which makes fossil fuel production difficult and expensive. Hydraulic fracking started with the availability of horizontal drilling technology, which enables high pressure injection of copious amounts of water, steam, chemicals, and sand into these rock formations. The high pressure will crack and splinter the rock which allows the once-trapped gas and oil to pool at large quantity in areas where it can be extracted for industrial and economic use. Fracking has and is being challenged on many aspects!
What is Oil Shale and Retorting?
Oil shale is a rock. The shale rock contains a substance called kerogen that is inside the rock. It is the precursor to the formation of natural gas and crude oil and it's origin are the remains of other organic matter, which have been buried and subjected to high temperatures and pressures for a long time. As you can see from the picture, oil shale burns, or better sufficiently hot volatile fractions of the kerogen gas out and react with atmospheric oxygen and we interpret that as a flame. If we wait for another few million years we might have natural gas and oil. But that's a bit too long. We can use a process known as retorting to convince the process to speed up. If we heat up the shale in the absence of oxygen to a temperature of around 450 degrees Celsius the kerogen that is trapped inside the shale will liquify and seep out. At the same time natural gas containing gases will also be produced. At some time, when sufficient gas and oil have pooled one can start extracting both. This may take a few months and the duration of extraction can be many years since new oil and gas is constantly produced from the ongoing conversion of the kerogen within the shale. This process is known as Retorting and can be more environmentally friendly than fracking.
The United States has significant oil shale resources, primarily in Colorado, Utah, and Wyoming. These oil shale reserves represent the largest currently known concentration of oil shale in the world.
In-situ oil shale retorting
In-situ oil shale retorting
Consider the case that the kerogen containing oil shale is not available for open pit mining but has an overburden of a thousand feet. It becomes clear quickly that the only way to produce that oil would be in-situ retorting. The picture on the left shows a simple schematic of such a system. A multitude of bore holes serve to slowly heat the ground over a period of months to several years. Once the the appropriate temperature is reached at certain levels of the shale, gas and oil will become available and can be extracted. Some of the gas and oil will be used for plant operation over the lifetime of the shale extraction process. In another scenario, we could imagine using high temperature fuel cells which will provide the required electricity plus the waste heat can be utilized in the shale heating process. I3E has significant experience in the design, development, fabrication, and test of such systems. We would welcome to opportunity to work on such a project again.
Geothermic Fuel Cell Design
Geothermic Fuel Cell Design
Geothermic fuel cells are high temperature Solid Oxide Fuel Cells places within oil shale. This can be several thousand feet under the surface. Waste heat from the fuel cell system is used to slowly heat the oil shale to a temperature at which the kerogen in the shale becomes liquid and ready for extraction. The fuel cells are fuelled with gases that are harnessed from the shale heating process, mostly natural gas. Since the main product of the fuel cells is electricity, there is no need for expensive infrastructure to transfer electricity required for the entire plant operation to the site which might be located in rather remote locations. The same goes for the natural gas supply needed to support the plant. Such self sufficient stand alone architecture offers significant advantages.
GFC's were developed at Delphi Automotive Systems, and adventure spearheaded by Dr. Fischer as the Principal Technology Engineer. The picture on the left shows a sketch of such a Solid Oxide Fuel Cell unit that was designed inside a tubular casing and lowered into a bore hole. The units were successfully tested in-situ at the Colorado School of Mines.
Of course, there are not only advantages with this approach, there never are. The environmental impact will never be zero, but it can be kept perhaps lower than other technologies. A greater level of energy independence from foreign sources might become more important in the current sociopolitical environment as we face increasing challenges in this century.
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