What is a Braided stream?
A braided river is one of a number of channel types and has a channel that consists of a network of small channels separated by small and often temporary islands called braid bars or, in British usage, aits or eyots. Braided streams occur in rivers with high slope and/or large sediment load.[1] Braided channels are also typical of environments that dramatically decrease channel depth, and consequently channel velocity, such as river deltas, alluvial fansand peneplains.Formation
Braided rivers, as distinct from meanderingrivers, occur when a threshold level of sedimentload or slope is reached. Geologically speaking, an increase in sediment load will over time increase in the slope of the river, so these two conditions can be considered synonymous; and, consequently, a variation of slope can model a variation in sediment load. A threshold slope was experimentally determined to be 0.016 (ft/ft) for a 0.15 cu ft/s (0.0042 m3/s) stream with poorly sorted coarse sand.[1] Any slope over this threshold created a braided stream, while any slope under the threshold created a meandering stream or— for very low slopes—a straight channel. So the main controlling factor on river development is the amount of sediment that the river carries; once a given system crosses a threshold value for sediment load, it will convert from a meandering system to a braided system. Also important to channel development is the proportion of suspended load sediment to bed load. An increase in suspended sediment allowed for the deposition of fine erosion-resistant material on the inside of a curve, which accentuated the curve and in some instances caused a river to shift from a braided to a meandering profile.[1] The channels and braid bars are usually highly mobile, with the river layout often changing significantly during flood events.[2] Channels move sideways via differential velocity: On the outside of a curve, deeper, swift water picks up sediment (usually gravel or larger stones), which is re-deposited in slow-moving water on the inside of a bend.The braided channels may flow within an area defined by relatively stable banks or may occupy an entire valley floor. The Rakaia River in Canterbury, New Zealand has cut a channel 100 metres wide into the surrounding plains; this river transports sediment to a lagoon located on the river-coast interface.Conditions associated with braided channel formation include:- an abundant supply of sediment[3]
- high stream gradient[4]
- rapid and frequent variations in water discharge[4]
- erodible banks
- a steep channel gradient
However, the critical factor that determines whether a stream will meander or braid is bank erodibility. A stream with cohesive banks that are resistant to erosion will form narrow, deep, meandering channels, whereas a stream with highly erodible banks will form wide, shallow channels, inhibiting helical flow and resulting in the formation of braided channels.[5]Examples
Extensive braided river systems are found in Alaska, Canada, New Zealand's South Island, and the Himalayas, which all contain young, rapidly eroding mountains.- The enormous Brahmaputra-Jamuna River in Asia is a classic example of a braided river.[6]
- Braided river system are present in Africa, for example in the Touat Valley.
- A notable example of a large braided stream in the contiguous United States is the Platte River in central and western Nebraska. The sediment of the arid Great Plains is augmented by the presence of the nearby Sandhills region north of the river.
- A portion of the lower Yellow River takes a braided form.[7]
- The Sewanee Conglomerate, a Pennsylvanian coarse sandstone and conglomerate unit[8] present on the Cumberland Plateau near the University of the South, may have been deposited by an ancient braided and meandering river that once existed in the eastern United States.[9]Others have interpreted the depositional environment for this unit as a tidal delta.[10]
Notable braided rivers in Europe:- Italy
- Tagliamento (Northeastern Italy)
- Piave (river)
- Brenta (river)
- Cellina
- Meduna
- Fella
- Magra
- Narew (Poland and Belarus)
Friday, August 14, 2015
Braided streams
Monday, August 10, 2015
What is Anthracite?
Coal 101: What is Anthracite?
Anthracite is a type of coal that is made almost entirely of carbon, and as a result is much harder than other forms of coal.
Its low pollutant content allows it to burn cleaner than other types of coal, according to United Coal Holdings (TSXV:UCL), an ability that makes it preferred in many applications. As a result, companies that mine it tend to advertise those capacities.
How is anthracite used?
Anthracite is mainly used for heating — while it’s difficult to burn, anthracite produces more heat than other varieties of coal. It is also a common charcoal ingredient. By itself, anthracite is used in steam-based power generators and in liquid form can be used to power internal combustion engines. Anthracite also plays a role in steel production, and is often used to make coal-fired food.
Despite these myriad uses, anthracite does have some disadvantages. For instance, it is quite expensive due to its high quality, and as such isn’t often used in power plants or as a replacement fuel for gasoline. It’s also difficult to ignite, though for industrial applications that barrier is easy to overcome.
Where is anthracite mined?
Anthracite is most commonly found in mountainous regions, as well as near volcanoes and in areas where earthquakes are the norm. Unsurprisingly, there is a large supply of anthracite in the Appalachian Mountains in the United States, with 6 billion tons in that region alone, as per United Coal. There are also reserves in the Rocky Mountains and the Andes.
In the US, Pennsylvania, which is located in the Appalachian region, is the state with the highest anthracite production, Coal Diver states. Though production declined precipitously in the late 1990s and early 2000s, the region still produces plenty of the fuel — in 2010, the figure was 1,842,857 tons of anthracite. That is a decrease from 1998′s record of 5,234,201 tons, but it is still a significant amount of anthracite.
Which companies mine anthracite?
- Reading Anthracite is a private Pennsylvania-based mining company that was established in 1871. It concentrates on the mining and distribution of anthracite for many purposes, and delivers standard or custom anthracite to industrial clients that need high-grade carbon. The company also provides products for space heating and water and sewage filtering.
Reading’s projects are surface-mining sites in Pennsylvania, and one of the company’s aims is to make sustainable reclamation plans for each of them. To date, its reclamation projects have resulted in wildlife sanctuaries, parks and housing developments.
- Blaschak Coal, also a private company based in Pennsylvania, was founded in 1937, acquiring its first mine in 1945. It is one of the top anthracite producers in the US, and produced close to 1 million tons of raw coal in 2012. It holds three mines and two processing facilities.
The company obtains land that was previously mined and reopens it for use in production. Like Reading Anthracite and other coal producers in the area, Blaschak ensures its projects are slated for reclamation after they close, turning them into forest land in most cases.
- Lehigh Anthracite, another Pennsylvania-based company, is a joint venture between Robindale Energy Services and BET Entities, both of which are privately owned. The company mines from the Mammoth, Forty-Foot, Primrose and Orchard seams at the Lehigh anthracite mine, which is the largest surface-mining permit in Pennsylvania. It processes its products on site and has the capacity to produce up to 500,000 tons of anthracite yearly.
Saturday, June 6, 2015
What is Oil Sands?
What is Oil Sands?
Alberta’s oil reserves play an important role in the Canadian and global economy, supplying stable, reliable energy to the world. Alberta's oil sands have been described by Time Magazine as "Canada's greatest buried energy treasure." But what is oil sand exactly?
Oil sand is a naturally occurring mixture of sand, clay or other minerals, water and bitumen, which is a heavy and extremely viscous oil that must be treated before it can be used by refineries to produce usable fuels such as gasoline and diesel. Bitumen is so viscous that at room temperature it acts much like cold molasses. New technologies are increasing the treatment methods available to oil sands producers as more research is completed.
Oil sand can be found in several locations around the globe, including Venezuela, the United States and Russia, but the Athabasca deposit in Alberta is the largest, most developed and utilizes the most technologically advanced production processes.
Historically, oil sand was incorrectly referred to as tar sand due to the now outdated and largely ineffective practice of using it for roofing and paving tar (oil sand will not harden suitably for these purposes). Though they appear to be visibly similar, tar and oil sands are different;
- Oil sand is a naturally occurring petrochemical that can be upgraded into crude oil and other petroleum products.
- Tar is synthetically produced from coal, wood, petroleum or peat through destructive distillation, it is generally used to seal against moisture.
History
The earliest documented oil sands mining operation was set up in 1745 in northeastern France, with refining capabilities added in 1857.
In 1929, the Dominion of Canada issued a patent to Dr. Karl A. Clark for the hot-water extraction process for separating bitumen from oil sands. This process laid the groundwork for the large-scale methods used by today’s producers of Canadian oil sands. Read more.
Sunday, May 31, 2015
Thursday, May 28, 2015
What is Diagenesis? | Geology
Wednesday, May 27, 2015
What are shale oil, shale gas and oil shale?
What are shale oil, shale gas and oil shale?
S.Batkhuyag. President Monationenergy (NGO), Doctor Of Science, ProfessorG.Yondongombo. Executive Director Monationenergy (NGO), PhD
Oil shale is one of the most prolific hydrocarbon resources on earth. Massive deposits are found in a number of countries around the globe, including Australia, Brazil, China, Estonia, Israel, Jordan, and the United States. Preliminary geologic surveys and evidence from oil shale outcrops indicate that Mongolia may also have oil shale resources of a size and quality that are commercially viable. Today, only China and Estonia produce oil shale commercially. With the high price of oil, decline in world conventional oil reserves, and increasing competition for oil resources worldwide, many countries and oil companies are turning their attention to this significant source of oil as the next generation of petroleum supply. Mongolia may be favourably positioned to benefit from the development of oil shale.
The United States is recognized as having the largest oil shale deposits in the world, the richest of which are located in a reasonably small area of Colorado, Utah, and Wyoming, collectively referred to as the Green River Basin. Estimates of the total resource that could be conceivably recovered, exceeds 2 trillion barrels (277 billion tons) -- eight times the size of Saudi Arabia’s reserves. In recent years, interest in development of the U.S. oil shale resource has increased significantly. Major oil companies, such as Shell, Exxon, and Total, along with numerous independent energy companies are developing new technologies. Through the Energy Policy Act of 2005 the U.S. government opened lands for oil shale research and development leases, for both subsurface (insitu) and surface production technologies. In 2008 the U.S. Department of the Interior finalized Rules and Regulations for the potential leasing of approximately 2 million acres in Colorado, Utah, and Wyoming. Though they have been challenged on legal grounds, the regulations have set the stage for eventual commercial development.
Mongolia, like the United States, may have an opportunity to develop its potential oil shale resources. This is a resource of significant national importance, the development of which could provide Mongolia with energy security in addition to export market opportunities and secure high paying employment, including engineering and technical jobs, for many people. As with the United States, Mongolia requires all types of energy resources, both conventional and unconventional petroleum, to meet their respective needs. Often the distinction between certain resources are obscured or misunderstood.
In the United States and elsewhere in the world a great deal of attention has been given to shale oil and shale gas production. These resources should not be confused with oil shale, as will be explained later. A host of European countries are looking at the development of shale gas as a means to secure a measure of independence from natural gas imports. The United States has found more than 100 years’ supply of shale gas in the Marcellus and Barnett formations. Using similar technological advances, shale oil reserves such as the Bakken and Niobrara reservoirs are producing substantial quantities of oil.
None of these resources has the size nor production potential of oil shale. The potential for oil shale production is tremendous worldwide and for detractors and skeptics, it should be noted that it was not long ago that shale gas and shale oil were thought to be both technically and economically unproductive.
Aside from the fact that we are discussing oil and gas, as mentioned, this is where the comparison between shale oil/shale gas and oil shale ends. In recent trade journals and newspaper articles there has been confusion regarding the difference between oil shale and shale oil. In certain articles the terms are used incorrectly and often interchangeably, further confusing their distinction. There is a world of difference between the two resources; comparing them is not unlike confusing oil with coal, both of which are hydrocarbons, but strikingly different in composition and methods of production and synthesis.
By definition, oil shale is a petroleum precursor, which is organic matter in the rock called kerogen. By applying heat, it can be transformed into oil and gas. Shale oil, or “tight oil” is a conventional crude oil created naturally and trapped in shale deposits -- requiring modern drilling and recovery technologies to produce. Shale gas is similarly produced from shale deposits. Advances in drilling and secondary recovery technology in the past decade have allowed companies to produce conventional oil and gas from heretofore uneconomic shale formations.
Oil shale (kerogen) deposits are entirely different from shale oil deposits. They have not sustained the time and temperature required to turn the kerogen to crude oil. Only applied heat will convert oil shale to crude oil. What mother earth failed to accomplish with time, can be obtained by the application of man-made heat.
The oil shale production process involves only the application of heat. Unlike shale oil production, there is no requirement for elaborate long-reach horizontal drilling or fracturing of the rocks to allow flow paths through which the oil and gas will be produced. There is no water or chemical reagents used to facilitate the fracturing of the reservoir in the production of oil shale. In fact, subsurface water is produced and can be cleaned and used for other purposes.
The crude oil produced from oil shale is high in light ends and is a source of quality products such as diesel, jet fuel, motor gasoline and natural gas liquids. Like China and other neighbouring countries, Mongolia is blessed with this resource and if produced in a responsible way, it can be a major part of the energy portfolio of the country.
Further information on oil shale can be found through the National Oil Shale Association at
www.oilshaleassociation.com
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