Hydraulic fracturing is also known as fracking, fracing, hydrofracking, fracking, and hydrofracturing. It is a technique of well- stimulation. In this process, rock is fractured by a pressurized liquid. This process involves the injection of ‘fracking fluid’ into a wellbore at very high pressure.
It is done to create cracks in the deep-rock formations and these rocks are used to get natural gas, petroleum, and brine freely. The fracking fluid can be primarily water, containing sand or other proppants suspended with the help of some thickening agents.
Meaning And Brief History
Hydraulic fracturing started as an experiment in 1947 but the first commercially successful application was taken benefit of in 1950, after three years. The United States was a major exporter of Drilling and hydraulic fracing as of 2019as well as helping reduce greenhouse gas emissions. A decade-long fracking boom has made inevitable improvements in the national economy and better prices for consumers.
Hydraulic fracturing is highly under controversy these days. Some people are in its favor because of its economic benefits as it uses extensively accessible hydrocarbons, as well as replace coal with natural gas, which burns cleaner and emits half as much carbon dioxide. Some people, however, say that these are outweighed by the potential environmental impacts, including risks of groundwater and surface water contamination, noise and air pollution, and the triggering of earthquakes which results in hazards to public health and the environment. Methane leakage is also directly associated with hydraulic fracturing.
Hydraulic Fracturing Process
Hydraulic fracturing is a process to stimulate a natural gas, oil, or geothermal well to maximize the process of extraction.
Method Of Hydraulic Fracturing
The formation of a hydraulic pressure takes place by pumping fracturing fluid into a wellbore at a rate sufficient to increase pressure at the target depth to exceed that of the fracture gradient of the rock. The fracture gradient is the increase in pressure per unit of depth relative to density. Operators usually try to maintain the width of the pressure, or slow down its decline following treatment, by introducing a proppant into the injected fluid which can be any material such as grains of sand, ceramic, or other particulates which prevents the fractures from closing when the injection is stopped and pressure is removed.
During the process, the leak off of the fracturing fluid occurs. If this is not controlled now, it can cross even one-fourths of the injected volume which will for sure lead to the damage of formation matrix, interaction of adverse formation fluid, and altered fracture geometry which reduces the efficiency at the end.
Hydraulic fracturing is performed in wellbores which are usually cased, and the zones which are to be fractured are accessed by penetrating the casing at those locations.
Types Of Wells
A distinction can be made between conventional, low-volume hydraulic fracturing and unconventional, high-volume hydraulic fracturing, based on different types of wells. High-volume hydraulic fracturing requires higher pressures as compared to low-volume fracturing in which the high pressures push out larger volumes of fluid and proppant that extend farther from the borehole.
Horizontal drilling involves wellbores that have a terminal drill hole that extends parallelly with the rock layer containing the substance which is to be extracted. In contrast, a vertical well just accesses the thickness of the rock layer, typically 15–91 m. Horizontal drilling decreases surface disruptions as a lesser number of wells are required for the same volume of rock.
The main purposes of fracturing fluid are
- to extend the fractures
- add some lubrication
- change the strength of the gel
- to carry proppant to the desired place
The most common chemical used for hydraulic fracturing in the United States during the last decade was methanol, while some other chemicals which were widely used were isopropyl alcohol, 2-butoxyethanol, and ethylene glycol.
Typical fluid types are:
- Conventional linear gels which are cellulose derivatives mixed with other chemicals
- Borate-crosslinked fluids which are guar-based fluids cross-linked with boron ions.
- Organometallic-crosslinked fluids which are basically zirconium, chromium, antimony, titanium salts and are known to crosslink guar-based gels
- Aluminum phosphate-ester oil gels.
Uses Of Hydraulic Fracturing
Hydraulic fracturing increases the rate at which fluids, such as petroleum, water, or natural gas are recovered from subterranean natural reservoirs. Reservoirs are not only the porous sandstones, limestones or dolomite rocks but also include some unconventional reservoirs such as shale rock or coal beds. Hydraulic fracturing helps to extract natural gas and oil from rock formations deep below the earth’s surface which is a lot below groundwater reservoir levels. At such depth, there is usually insufficient reservoir pressure to allow natural gas and oil to flow from the rock into the wellbore at high economic return. Thus, creating some fractures in the rock which can conduct is done in extraction from naturally impermeable shale reservoirs.
Hydraulic fracturing is also used in order to :
- To stimulate groundwater wells
- To fulfill the preconditions of mining or induce rock cave-ins mining
- As a means of increasing the cure of waste, usually hydrocarbon waste or spills
- To dispose of waste products by injection deep into the rocks
- To measure the amount of stress in the Earth
- For electricity generation in areas which have a lot of geothermal energy
- To increase the rates of injection for geologic sequestration of Carbon dioxide
- Even to increase the yield of drinking water from wells. This method has been used in a number of countries, including the United States, Australia, and South Africa
Due to a reduction in the expenses of fracking and advancements in the production process, oil, and natural gas that were, in the previous years, unrecoverable are now accessible. This helps to increase the supply of both oil and gas in the world market and has meant no dependence of countries, such as the United States on energy because these can now access an abundance of these resources.