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Energy & Resources
Shaking out more oil
Europe on Kyoto
Mineral resource of the month: Tellurium


Shaking out more oil

Earthquakes could increase oil production. That’s according to a research team studying seismic shaking and its relation to how fluids move through rocks. The researchers say it may thus be possible to simulate the shaking produced by earthquakes to enhance oil recovery.

Jean Elkhoury (front) and Duncan Agnew used water-level data from this well in Southern California to study how earthquakes could change how oil flows through rocks. Photograph is by Emily Brodsky.

People have long reported increased production in oil wells and changes in wells’ water levels following earthquakes, but the phenomenon has never been quantified or really understood. To figure out what was happening underground to cause the observed changes, Jean Elkhoury of the University of California in Los Angeles and colleagues looked at 20 years of measurements of changes in water levels in two wells at Piñon Flats Observatory in Southern California, near Palm Springs. They used the changes in water levels to measure the permeability of the rocks surrounding the wells.

The researchers found “transient changes” in the rocks’ permeability following each of nine earthquakes recorded by seismometers at the observatory, Elkhoury says. Immediately after each quake, the ease of flow at the wells increased by a factor of three, he says. In the months following the earthquakes, the permeability in the wells gradually returned to normal.

The earthquakes varied in intensity and distance from the wells, and the change in water flow varied according to the strength of the shaking felt at the wells, Elkhoury says. The increases related to the shaking are systematic and even predictable, suggesting that as shaking increases, permeability increases roughly linearly, the researchers wrote in the June 29 Nature.

Thus, says Emily Brodsky of the University of California in Santa Cruz, co-author on the paper, it might be possible to shoot seismic waves into the ground to enhance permeability near oil and natural gas reservoirs, and increase oil and gas recovery.

Although the researchers do not exactly understand how these permeability changes occur, one possibility is that the shaking is “unclogging pores” in the rocks, Brodsky says, loosening the water in much the same way as a shaken sponge works: Water is pretty stable within a sponge as it sits in the sink, but as a person picks up the sponge and shakes it, water pours out. Similarly, the shaking of the rocks in an earthquake could unclog pores, allowing oil to move more freely.

The idea that earthquakes could alter the permeability of rocks is significant in that about two-thirds of the oil in the United States is still belowground, Brodsky says, and it is not easy to extract, in part, because the permeability of the reservoirs is too low. “The higher the permeability, the easier it is to pull fluids from the ground,” she says, so it follows that if energy companies could increase the rocks’ permeability, they could “pull out a lot more oil.” The results from the wells at Piñon Flats show that the changes observed from seismic shaking are not “random physical processes,” she says, and thus might be able to be harnessed.

Shawn Maxwell, a seismologist at Pinnacle Technologies in Calgary, Alberta, says that there is “something to” the team’s hypothesis. Researchers have been looking at the possibility of seismic waves enhancing permeability in oilfields for several years, he says, but “no one has really figured out how to do it commercially yet.” This research “detailing the definite correlation between permeability increases and ground motion,” he says, will help advance the field.

Much research remains, however, Maxwell says. Many of the “microscopic details about the physics” of the permeability changes “aren’t really understood,” he says. Echoing his sentiments, Brodsky says that her team is working to understand the permeability changes in more detail so that they can model the levels of seismic shaking needed to enhance oil recovery.

Megan Sever

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Europe on Kyoto

Fourteen of the 25 EU nations missed the June 30 deadline to submit new national allocation plans on carbon emissions for 2008 to 2012 to the European Commission, which reviews the plans to ensure the country is on track to meeting its Kyoto Protocol goals.

As part of Kyoto, EU countries each get a certain amount of carbon dioxide emissions credits to use in a given year, all leading toward cutting their emissions to at least 8 percent below 1990 levels by 2012. The national allocation plans are the roadmaps each country must submit to the commission that show how they will divide up their carbon dioxide emissions credits among various industries over a given period of time.

In a set of guidelines published in January, the commission said the European Union should aim for an overall 6 percent emissions reduction in its new allocation plans. But as some countries have submitted those plans, controversy is stirring over some emissions reduction goals being less stringent than others, with some countries facing the possibility of rejection of their plans by the European Commission, according to EurActive.com.

Meanwhile, on July 4, the European Parliament voted to impose carbon emissions caps and fuel taxes on airlines. Although the parliament’s vote is not legally binding, it could influence EU rules that would force the carriers to comply with Kyoto quotas on carbon dioxide emissions. Under the action, airlines would have an emissions ceiling and would have to buy carbon permits on the carbon trading market, as reported July 5 in the Financial Times.

Links:
EurActive.com

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Mineral resource of the month: Tellurium

Micheal W. George, the tellurium commodity specialist for the U.S. Geological Survey, has compiled the following information on tellurium, a rare and expensive metal used in semiconductors and alloys.

Global demand for tellurium has grown significantly in recent years owing to increased use in solar cells in the United States and Europe, thermoelectronics (especially in China) and steelmaking worldwide. Estimated global production, however, has remained relatively unchanged over the same period, while accumulated inventories have been exhausted, leading to a supply shortfall.

Tellurium metal’s major use is as an alloying additive in steel to improve machining characteristics. Tellurium chemicals are used in the processing of rubber, as a component of catalysts for synthetic fiber production, and as pigments to produce various colors in glass and ceramics, among other applications.

High-purity tellurium is used in electronics applications, such as photoelectric and thermoelectric devices. Thermal imaging devices use a compound of tellurium — mercury-cadmium telluride, which assists in converting a raw image into a crisp picture on the screen. In the last 10 years, tellurium also has increasingly been used in the production of solar cells.

A semiconducting compound of tellurium is used in thermoelectric cooling devices, such as summertime beverage coolers. Thermoelectric coolers are most commonly used in military and electronics applications, such as the cooling of infrared detectors, integrated circuits, laser diodes and medical instrumentation. Their application in consumer products, such as portable coolers for food and beverage and automobile car seat cooling systems, continues to increase.

Although tellurium is widely distributed in nature, it has a low average abundance in Earth’s crust and does not occur in concentrations high enough to justify mining rocks solely for their tellurium content. Thus, tellurium is usually recovered as a byproduct of nonferrous metal mining, largely from the copper refining process.

U.S. reserves of tellurium, about 3,000 metric tons, are estimated to be about 14 percent of the world’s total reserves.

Owing to the growing supply shortfall, the price of tellurium jumped from $10 per pound at the beginning of 2004, to $110 per pound at the beginning of 2006, a 1,000 percent increase. Although tellurium is recovered as a byproduct of copper production, its rate of production may not be directly influenced by copper’s industrial demand: Even though global copper production has increased over the past five years, the production of tellurium is believed to have remained essentially unchanged. That’s because increased copper output has come from ores with low-tellurium content and from ores processed through leaching, which precludes the recovery of tellurium.

In 2005, the only U.S. domestic producer of refined tellurium had significantly reduced output owing to an extended strike by copper miners. While substitutes exist for tellurium for most of its uses, they usually incur losses in product efficiency or product characteristics. Unless alternative sources of tellurium are found, tellurium’s future use will likely be restricted to the more specialized, high-value-added applications.

Visit minerals.usgs.gov/minerals for more information on tellurium.

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