Shale how is it formed

What is Limestone? What is Marble? What is Sandstone? What is Shale? What is Slate? What is Soapstone? What is Travertine? New Store. Click image to enlarge Sample of drill cuttings of shale while drilling an oil well in Louisiana. Limey shale overlaid by limestone, Cumberland Plateau, Tennessee. Weathering shale at a road cut in southeastern Kentucky. Sample of drill cuttings of shale while drilling an oil well in Louisiana.

Although drilling to extract oil and natural gas is possible, a large amount is still trapped inside the pore spaces of the shale. This oil and gas is difficult to remove, and it takes unconventional methods to access this oil and gas. Pore spaces in shale are extremely tiny, and because of this gas cannot easily move out of the shale. However, some gas can be released through hydraulic fracturing , a method where water and chemicals are pumped down a well under pressure to fracture the shale.

In addition, horizontal drilling was found to help with the release of natural gas trapped in shale. Oil shale is rock that contains large amounts of kerogen.

This type of shale forms when kerogen is buried at a depth of kilometers and can yield both liquid and gaseous hydrocarbons if the rock is heated or treated with solvents.

However, gray shales can also be rocks that contain calcareous materials or simply clay minerals that result in a gray color. Utica and Marcellus Shale: Two black organic shales in the Appalachian Basin are thought to contain enough natural gas to supply the United States for several years. These are the Marcellus Shale and Utica Shale. Shales that are deposited in oxygen-rich environments often contain tiny particles of iron oxide or iron hydroxide minerals such as hematite , goethite, or limonite.

Just a few percent of these minerals distributed through the rock can produce the red, brown, or yellow colors exhibited by many types of shale. The presence of hematite can produce a red shale. The presence of limonite or goethite can produce a yellow or brown shale. Green shales are occasionally found. This should not be surprising because some of the clay minerals and micas that make up much of the volume of these rocks are typically a greenish color.

Natural gas shale well: In less than ten years, shale has skyrocketed to prominence in the energy sector. New drilling and well development methods such as hydraulic fracturing and horizontal drilling can tap the oil and natural gas trapped within the tight matrix of organic shales.

Hydraulic properties are characteristics of a rock such as permeability and porosity that reflect its ability to hold and transmit fluids such as water, oil, or natural gas.

Shale has a very small particle size, so the interstitial spaces are very small. In fact they are so small that oil, natural gas, and water have difficulty moving through the rock. Shale can therefore serve as a cap rock for oil and natural gas traps, and it also is an aquiclude that blocks or limits the flow of groundwater. Although the interstitial spaces in a shale are very small, they can take up a significant volume of the rock.

This allows the shale to hold significant amounts of water, gas, or oil but not be able to effectively transmit them because of the low permeability.

The oil and gas industry overcomes these limitations of shale by using horizontal drilling and hydraulic fracturing to create artificial porosity and permeability within the rock. Some of the clay minerals that occur in shale have the ability to absorb or adsorb large amounts of water, natural gas, ions, or other substances. This property of shale can enable it to selectively and tenaciously hold or freely release fluids or ions.

Expansive soils map: The United States Geological Survey has prepared a generalized expansive soils map for the lower 48 states. Shales and the soils derived from them are some of the most troublesome materials to build upon. They are subject to changes in volume and competence that generally make them unreliable construction substrates.

The clay minerals in some shale-derived soils have the ability to absorb and release large amounts of water. This change in moisture content is usually accompanied by a change in volume which can be as much as several percent. These materials are called " expansive soils. Buildings, roads, utility lines, or other structures placed upon or within these materials can be weakened or damaged by the forces and motion of volume change.

Expansive soils are one of the most common causes of foundation damage to buildings in the United States. Shale delta: A delta is a sediment deposit that forms when a stream enters a standing body of water. The water velocity of the stream suddenly decreases and the sediments being carried settle to the bottom. Deltas are where the largest volume of Earth's mud is deposited.

The image above is a satellite view of the Mississippi delta, showing its distributary channels and interdistributary deposits. The bright blue water surrounding the delta is laden with sediment.

Shale is the rock most often associated with landslides. Weathering transforms the shale into a clay-rich soil which normally has a very low shear strength - especially when wet. When these low-strength materials are wet and on a steep hillside, they can slowly or rapidly move down slope. Overloading or excavation by humans will often trigger failure.

Cannel shale has terrestrial origins, and is often classified as coal. It is made up from the remains of resin, spores, and corky materials from woody plants.

It can contain the minerals inertinite and vitrinite. Cannel shale is rich in hydrogen, and burns easily. People have been using oil shale for thousands of years. Ancient Mesopotamia ns used shale oil to pave roads and caulk ships.

Ancient Mongolians dipped the tips of their arrows in shale oil during battles, sending flaming arrows at their enemies. In the Middle East, sticky shale oil was even a component of decorative mosaic s. The modern shale industry began in the 19th century.

This industry used industrial processes to heat shale in order to extract oil. Shale oil was used for a variety of products, including paraffin wax. European countries, and later the United States, began extracting oil shale and shale oil and burning them as sources of fuel. The first U. Extracting and processing shale oil is an expensive and difficult process.

Coal, petroleum, and natural gas are less expensive to extract. Australia, Brazil, Switzerland, Sweden, Spain, and South Africa began mining oil shale in the 19th and 20th centuries, but they all stopped production by the s.

The U. Many nations, including Estonia, China, and Brazil, continue to rely on oil shale for fuel. It is burned to generate electricity , is a component in chemical industries, and byproduct s are used in cement production.

Obtaining shale oil from oil shale involves heating kerogen in a process called pyrolysis. Pyrolysis is a form of heating without the use of oxygen. Pyrolysis can either be done ex situ above ground or in situ below ground.

During the ex situ process, oil shale is first extracted from the earth by surface or underground mining. The rock is crushed, and then retort ed heated to release the shale oil. The shale oil is then refined of impurities, such as sulfur. During the in situ process, oil shale is not mined or crushed. Instead, the rock is heated to its oil window while it is still underground.

One technology used for in situ oil extraction is known as volumetric heating. In this process, the rock is heated directly with an electric current. The heating element is injected either directly in a horizontal well or into a fractured area of the rock, until the oil shale begins producing shale oil.

The oil could then be pumped directly from underground. The internal combustion process uses a combination of gas, steam and spent shale produced by ex situ processing. These compounds are burned for pyrolysis. The hot gas is continually cycled through the oil shale, pyrolyzing the rock and releasing oil.

Unfortunately, substances in the oil shale, such as sulfides, react with water to form toxic compounds that are harmful to the environment and to us. Sulfides can cause effects from eye irritation to suffocation. Water containing toxic substances is unusable, and expensive to decontaminate.

The process also produces heaps of ash. This ash can pollute ground, air, and water sources. Another method that can be used either in situ or ex situ involves chemically reactive fluids. The fluids are injected directly into the retort zone where the rock is being heated. High-pressure hydrogen is one of the most common chemically reactive fluids.

It simultaneously heats the rock, removes sulfur, and upgrades the quality of the extracted oil. When shale oil is combusted heated , it releases carbon dioxide into the atmosphere. Carbon on the earth is contained in plants, soil, fossil fuels, and all living things—including us! The carbon in fossil fuels including coal, petroleum, natural gas, and oil shale has been sequester ed, or stored, underground for millions of years.

Burning fossil fuels releases carbon into the atmosphere at a much quicker rate than the trees, water, and ground can reabsorb it. Sometimes, climates can rise faster than organisms can adapt.