In the first two parts of this three-part series on hydraulic fracking we discussed what hydraulic fracking is, its history, and the process of how it works. This final part of the series will cover how different well types utilize hydraulic fracking as well as the reasons and uses of hydraulic fracking.

Hydraulic Fracking for Different Types of Wells

The pressure, flow rate, and composition of fracking fluids used for hydraulic fracking will vary from well to well. Wells might be classified according to one of the following criteria:

Vertical Versus Horizontal Wells

Vertical Wells - Verticals wells are the traditional type of oil or gas well that go straight down, typically to a depth of about 50-300 feet. These wells penetrate perpendicular to the rock layer containing the oil or gas reserve. Hydraulic fracking on vertical wells is commonly used for “well stimulation” to increase the efficiency and output of the well. Compared to horizontal well fracking, this type of fracking requires lower pressure and volume. Horizontal Wells - Horizontal wells terminate with the wellbore parallel to the rock layer containing the oil or gas reserve. Horizontal wells also reach a much deeper depth than vertical wells. For example horizontal wells drilled in the Barnett Shale Basin in Texas goes down between about 1,500 to 5,000 feet, while the horizontal wells drilled in the Bakken Shale Formation in North Dakota go down to up to 10,000 feet. Due to the higher pressure associated with these depths hydraulic fracking must be done at a much higher pressure and volume.

High-Rate Versus High-Viscosity Fracking

Fracking may also be done using either a high rate of pumping to deliver the proppant or a high-viscosity slurry. Each fracking method will yield slightly different results. High-Rate Fracking - High-rate fracking uses a high rate of pumping to deliver the proppant. This is the type of fracking associated with slickwater fracking fluids because the reduced friction allows the fluids to be pumped more quickly, at a higher rate. This type of fracking generally causes a network of small, spread out micro-fractures. High-Viscosity Fracking - High-viscosity fracking uses higher fluid viscosity as its means of effectively the proppant. High-viscosity fracturing tends to be characterized by larger, more dominant fractures.

Controlling Leakoff During Hydraulic Fracking

Another consideration with hydraulic fracking is leakoff. Leakoff refers to the loss of fracturing fluid whereby instead of going into the fracture channel it seeps into surrounding permeable rocks. If leakoff is not properly controlled a very high rate (over 70%) of fracking fluid volume can be lost. Leakoff may adversely affect production efficiency by damaging the formation matrix, harming formation fluid interactions, or altering the fracture geometry.

The Reasons for Hydraulic Fracking

Hydraulic fracking offers several advantages for oil and gas recovery including: Increased Accessibility - Hydraulic fracking offers a huge benefit by radically increasing the amount of oil and gas that can be extracted from deep-level rock formations. In most cases it would not be economic or even feasible to recover the oil and gas found in these very deep formations with extremely low natural permeability. Greater Efficiency - As discussed above, hydraulic fracking can be used to stimulate and improve well production. This allows the oil or gas to be recovered more efficiently and at higher rates. Lower Costs - Due to the advantages of greater accessibility and efficiency, hydraulic fracking also creates an overall better economy for the oil and gas industry, allowing companies to reap greater amounts of product at lower costs, continue operating a well for longer, or even re-open a well that may have previously been considered dried up.

Other Uses for Hydraulic Fracking

Though the main focus of this article has been on the role hydraulic fracking plays in the oil and gas industry, it offers other additional benefits and applications such as: Water Wells - Just as hydraulic fracking is used to increase the rate and efficiency of recovery for oil and gas, it can also be used to stimulate groundwater wells. This technique has successfully been done not only in the US, but also in Australia and South Africa. Mining Applications - Hydraulic fracking also has mining applications where it can be used to induce controlled rock caving. It has also been proposed for uranium mining in which it will be used to inject substances that will dissolve the uranium so that it can then be pumped to the surface. Energy - Hydraulic fracking is used in geothermal systems to enhance heat extraction and produce electricity. Waste - Hydraulic fracking is used in waste remediation processes, to dispose of waste by injecting it into deep rock formations, and for geologic sequestration of carbon dioxide. Measurement - Hydraulic fracking can be used by geologists to measures stress levels within the Earth. Hydraulic fracking is used extensively across multiple areas of focus and industries in the US as well as globally. As the technology continues to advance it is likely to become applicable in currently unforeseen ways. In addition to fracking, the Oil & Gas industry as a whole will continue to innovate and create new processes and methodology to produce fuel sources for the world's consumption.