Fracking

Fracking, also known as hydraulic fracturing, is a well stimulation technique. It involves breaking apart rock formations in bedrock using a pressurized liquid. This process is used to help natural gas, petroleum, and brine flow more freely. In many cases, the rocks containing these resources have very low permeability. Permeability is a measure of how easily fluids move through a material.

Scientists define low permeability as being below 0.1 millidarcies. When rocks are this tight, they are considered unconventional resources. This means they require special methods to extract the energy stored inside them.

The mechanism of hydraulic fracking relies on intense physical pressure. Workers inject a special substance called fracking fluid into a deep wellbore. This fluid is primarily composed of water. It also contains thickening agents and small grains known as proppants. These proppants are usually made of sand or aluminium oxide.

As the fluid is pumped in at high pressure, it overcomes the effective stress of the rock. This causes the bedrock to crack and form fractures. Once the hydraulic pressure is removed, the proppants remain inside the new cracks. These grains hold the fractures open so the gas or oil can escape.

There are two main types of unconventional well stimulation. The first is hydraulic fracking, which uses liquid pressure to create cracks. The second is acid fracking, also known as acidising. In acid fracking, acid is used to etch the rock. This method has a much longer history than hydraulic fracturing. While hydraulic fracking is the most common method used today, acidising is still a significant technique.

Some experts distinguish between these and conventional methods. For example, matrix acidising is often considered a conventional technique. However, hydraulic fracking is always classed as unconventional because it permanently changes the rock's permeability.

The history of well stimulation shows a long evolution of technology. In the 1860s, workers used explosives to stimulate shallow oil wells. In 1865, Colonel Edward A. L. Roberts patented an "exploding torpedo" using nitroglycerin. Companies like the Lightning Torpedo Company used these methods in Oklahoma and Texas.

Later, in the 1930s, the industry began using acid to improve well productivity. The first true hydraulic fracturing experiment occurred in 1947 at the Hugoton gas field in Kansas. This test used sand from the Arkansas River and gelled gasoline. Although that specific experiment was not very successful, it led to a patent in 1949. This paved the way for the first commercial successes in Oklahoma and Texas.

Fracking has had a massive impact on global energy production. By the year 2012, approximately 2.5 million frac jobs had been performed worldwide. Over one million of these operations took place within the United States.

This technology helped make the United States a major exporter of crude oil by 2019. The increase in production has also led to lower energy prices for many consumers. However, the process is not without its complexities. It can lead to the leakage of methane, which is a potent greenhouse gas. This leakage might even cancel out some of the environmental benefits of using natural gas.

Despite its economic benefits, fracking is a highly controversial subject. Proponents argue that it provides energy independence and economic growth. They also note that natural gas burns more cleanly than coal, emitting less carbon dioxide.

Opponents raise serious concerns about environmental and health impacts. They point to risks like the contamination of groundwater and surface water. There are also concerns regarding noise, air pollution, and the triggering of earthquakes. Some studies have even linked living near these sites to health issues like asthma and migraines. These concerns have led to many countries restricting or banning the practice.

Geologically, fracking interacts with the natural stresses of the Earth. Rocks at great depths are often held together by the weight of the layers above them. This is known as the pressure of the overlying rock strata. Fracturing occurs when the fluid pressure inside the rock exceeds its strength. This process can even help scientists understand the orientation of stresses deep underground. In nature, similar processes create mineral veins or volcanic dikes.

By studying how these fractures form, researchers can learn more about the movement of fluids and pressure within the Earth's crust.