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All about Fracking
Fractures are formed in rocks which contain pressurized fluids. These fractures could be natural formations, if veins and dikes, are taken into consideration. When fractures are induced in the rock formations through various means, for the extraction of fossil fuels like petroleum, coal, or natural gas, it is referred to as fracking, or it also known as hydrofracking.
Hydrofracking is achieved by drilling a wellbore into the rock formations, and then introducing highly pressurized fracking fluids through the wellbores, and the energy of the pressurized fracking fluids leads to the formation of newer channels in the rock formations, and causes further fracturing in the rocks, and these induced fracturing will create newer outlets for the release of the containing fossil fuels.
There is a need to undertake such induced fracturing to increase the extraction rates of the fossil fuels, and also to further the cracks within the rock formations so that all the cracks would unify, and the containing fossil fuel gets collected at one point.
After the fracking fluids are injected, the fracture widths are maintained by introducing proppants. Proppant is a material which is capable of preventing the closure of the fractures when the injection of fracking fluids is stopped.
Fracking is known to cause damages to the environment, and also has some health and safety concerns, it has come under scrutiny, and the process has been either suspended or banned in certain countries.
Hydraulic fracturing is performed on both vertical wells, and also horizontal wells. Horizontal drilling is done parallel to the rock layer from which the fossil fuels need to be extracted. Horizontal drilling has had laterals extending to almost 1500 to 5000 feet, and in certain case up to 10000 feet. Vertical wells on the other hand could only reach depths of 300 feet. Drilling reduces permeability by blocking of pore spaces near the wellbore walls, which can cause a reduction of flow of the fossil fuels being extracted into the borehole from adjacent rocks, etc. Permeability is restored by hydraulic fracturing.
The fluid that is injected into rocks to cause fracturing is a kind of slurry of chemical additives, proppants, and water. The various types of proppants used could contain silica sand, man-made ceramics, and resin-coated sand. Acids are initially used for scouring and cleaning up of the wellbore area. Proppants are then used and their size and density is gradually increased. Once the well is ready, it is flushed with water under pressure.