R&D Corner: Israeli Oil Shale Technology
Judith Levy · Jul. 13 at 11:13am
The technology was invented by the serendipitously named Dr. Harold Vinegar during his 32-year tenure at Royal Dutch Shell. Shell is exploring the use of the technology in Jordan, where there are also major oil shale deposits, but opted against exploration in Israel. Vinegar retired from Shell as Chief Scientist and made aliyah to Israel, where he began teaching petroleum science at Ben Gurion University. He then joined Israel Energy Initiatives (IEI), where he is now Chief Scientist. (I am meeting Dr. Vinegar soon and will give you a more detailed and personal account of this history.)
Before we get to the technology, a quick word on oil shale.
There are two general categories of oil: conventional and unconventional. Conventional oil is called crude, the stream of free-flowing hydrocarbons that are drawn out of the ground by the nodding, mantis-like pumps with which you're familiar. Unconventional oil is oil produced from less easily tapped sources and by methods other than by traditional wells.
One unconventional oil source is extra-heavy crude, which flows about as easily as cold blackstrap molasses and will sink if you pour some into a glass of water. Tar sands, or bituminous sands, contain a particularly viscous variety of heavy crude. Getting it out is labor-intensive, to say the least, and the proportion of usable fuel to be generated from a barrel of tar sands is relatively low. Still, as oil prices rise, tar sand oil production becomes more commercially viable.
Another unconventional source is oil shale, which does not, in fact, contain oil. Oil shale is sedimentary rock containing kerogen, which is premature oil. The rock is the product of organic debris that has been cooking below the surface of the earth for millions of years. When the kerogen in the rock is heated, its long chains of carbons begin to break into smaller and smaller pieces. Eventually, oil -- among other products -- is released.
The oil derived from the shale through IEI's process is a light synthetic condensate that is easier to refine than conventional crude. The challenge is on the upstream end -- getting it out of the rock.
Until very recently, there were two ways of doing this. One is to mine the rock, bring it to the surface, crush it, and heat it in a furnace called a retort. The other -- still in the piloting stage of development -- is to heat the rock while it is underground to expel the oil and gas from the kerogen, and then pump the products to the surface (in situ retorting). IEI's method is a variant of the latter technique.
Surface retorting requires copious amounts of water to clean shale waste, cool the retorts, and refine the shale oil. In situ retorting does not require such large quantities of water because no shale waste is generated, no retorts need to be cooled, and the hydrogen needed to refine the oil is generated during the process itself. There is still a water cost, however, when subsurface waters are diverted from their normal flow. And both methods, up to this point, have been more expensive to implement than conventional drilling.
A particular challenge in the US -- where 70% of the world's oil shale deposits are located -- is the proximity of the aquifers to the shale. During extraction, the waters are vulnerable to contamination by the hydrocarbons and must be protected. The only way to do so is to construct a freeze wall around the extraction area to prevent contact. And a freeze wall, in addition to adding to overall expense, raises the technology's carbon footprint.
Israel is a different story. Here, where the shale deposits are uniform, thick and rich, the aquifer is well below the oil shale; they are separated from one another by about 200 meters of impermeable rock. There is therefore no need for a freeze wall. And Dr. Vinegar's technology, rather than using water to function, actually generates water: the shale contains 20% water, which is produced during the extraction process. According to Dana Kadmiel, the IEI environmental engineer I spoke with, this water can be treated and subsequently used for agriculture.
The hydrogeological conditions here thus yield multiple advantages: lower water consumption, higher energy efficiencies, lower greenhouse gas emissions, and lower costs. Dana estimates that the resource will be extractable at a cost of about $40 a barrel.
IEI's version of in situ retorting works like this:
Uniformly spaced horizontal heater wells, six inches in diameter, are drilled into the target oil shale. The wells are heated, either by electricity or by a circulating heat transfer fluid, probably molten salts (salts that can be melted at a low temperature and then brought to a very high temperature). The heater wells are maintained at high temperatures for several years, cooking the shale to about 300 degrees Celsius.
Eventually, the heat causes the kerogen to expel several high-value products: oil, water, natural gas (methane and ethane), LPG, and hydrogen. Hydrogen sulfide, a toxic gas, is also produced. It will be immediately isolated and treated to make elemental sulfur for use in fertilizer.
Above ground, the gases will be separated from the liquids and the water and oil separated from one another. The water will be sent for treatment and the oil to one of Israel's two refineries for conversion into fuel.
IEI is currently in an appraisal phase and will shortly move into the pilot phase. If they are able to prove that the technology works, is economic, and is environmentally sustainable, they'll move into the commercial phase. The appraisal phase involves drilling out samples of oil shale using what amounts to an extremely long apple corer and then testing it in the lab. During the pilot phase, they will drill vertically and use electricity to heat the shale. Once they get to the commercial phase, they will drill horizontally rather than vertically and move from electricity to molten salts, which are much more efficient and environmentally friendly. Natural gas will be used to heat the salts.
Down the road, they're interested in using the sun to heat the salts, if a way can be found to make solar more efficient and economic. In the meantime, they'll be able to use the natural gas generated by the process itself for heating purposes.
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