Hydraulic fracturing, or fracking, refers to the process of creating fractures in rocks and rock formations by injecting a mixture of water, sand and chemicals into cracks to force them open further. This results in higher extraction levels leading to economic viability of many oil and gas wells.
Background of Hydraulic Fracturing
The concept of fracking came about to meet the challenges of extracting shale gas trapped inside the rock formations in the depths of over 5000 feet. Due to their low permeability, shale rocks require different penetrative techniques compared to conventional drilling methods adopted for extracting traditional oil and gas reserves. (To learn more about shale gas, read Is Shale Gas Losing Its Sheen?)
Fracking dates back to the 1940s when several extraction and production companies tried to use this technique to extract oil reserves trapped in hard rock formations. After extensive research, an exploratory hydraulic fracturing exercise by Floyd Farris of Stanolind Oil and Gas led to the belief that fracking could produce more exploration of hidden unconventional petroleum reserves. Though this initial study was not very encouraging, a sequel exercise undertaken by Haliburton in 1949 yielded the desired results. This paved the way for commercialization of hydraulic fracturing in a big way. Until 2003, fracking was not taken up exhaustively by the extraction and production companies. Thanks to the shale play thrust by the United States government, massive fracking initiatives were undertaken.
Fracking Changed the Energy Landscape
Fracking has changed the energy scenario particularly in the United States despite its so-called adverse impact on the environment. The US energy production is focused on shale gas plays and there has been significant increase in shale production in recent years. According to the US Energy Information Administration (EIA), more than 50% of the oil production has occurred due to hydraulic fracking. In recent times there has been a glut in the energy market due to oversupply that is directly attributed to the substantial increase of shale production numbers. The numbers reported by EIA authenticate this. There were 23,000 wells during 2000 in the US that employed fracking to extract shale gas; in 2015 this figure rose to a mind-boggling 300,000. During the same period, the fracking output rose from 102,000 barrels per day to 4.3 million barrels per day. This shows the impact of fracking on the energy landscape.
Hydraulic Fracking Differs with the Type of Well
The flow rate, pressure and type of fracking fluids being used varies depending on the nature of the well. (For more on this topic, see Understanding Reservoir Drive Mechanisms.) Wells can be categorized based on the following criteria:
Vertical vs Horizontal Wells
Vertical wells are a traditional type of well in which oil and gas are found at depths of 50-300 feet (15 - 91 meters). These types of wells are perpendicular to the rock layers. Here hydraulic fracturing is adopted for “well stimulation” and hence it requires lower pressure and volume with the objective of increasing the volume flow and output. In horizontal wells, the wellbore is parallel to rocks where oil and gas is found. Here higher pressure and volume is required as reserves are found in depths even beyond 10000 feet (3050 meters). Hydraulic fracturing must be done with high pressure to obtain sufficient volumes.
High Rate vs. High Viscosity Fracking
Hydraulic fracking may also be done using a high rate of pumping to deliver the proppant or high-viscosity slurry. In the former case, a network of small micro fracturing occurs during the process. This method of fracking is also known as slick water fracking that is aimed at reducing friction to facilitate fluids being pumped out at higher rates. In high viscosity fracking, the higher fluid viscosity is used to deliver the proppant. Here the fractures tend to be large and dominant.
Positives of Hydraulic Fracturing
Clearly fracking has vastly improved production numbers significantly. With more advancement in technology, fracking has been made easy for extraction and production companies to leverage the latest techniques to extract shale. Secondly, it augurs well for the consumers, as the days of $100 per barrel of oil appear to be a thing of the past, at least for the near future. From both supply and commercial perspectives, fracking has definitely unlocked the potential of unconventional energy.
Why is Fracking a Taboo to Environmentalists?
Fracking has its darker side as well. The main concern is the pollution it creates, particularly to the underground water resources.
Apart from the basic additives such as sand, salt, water, etc., heavy chemical additives such as chemical and ceramic particles are added as proppants and injected into the well to create ruptures in the hard rock formations underneath. This action helps to extract more shale gas but also contaminates the groundwater in a significant way.
Also, environmentalists have a genuine concern that the disposal strategy that should be adopted to handle the wastewater must take into account the local geology where the wells are located. For example, in some of the fracking wells in the United States, millions of gallons of wastewater (also known as flowback) that are generated along with the shale gas are found to have traces of radioactive materials. It is estimated that the cost of handling this dangerous wastewater could go as high as 19% of the total drilling costs. This is not only an environmental disaster but also puts the economics of shale gas in a precarious situation.
Another important factor to keep in mind is leak-off, which occurs in the fracking process. Leak-off is the loss of fracturing fluid that occurs when the fluid, instead of going to the intended fracture channels, seeps into surrounding permeable rocks. This damages the formation matrix, reduces production efficiency and alters the fracture geometry. It is therefore important to control this due to the volume of fracking fluid that may be lost in the process.
Fracking is here to Stay
Despite the controversy generated over the fracking process, it has become an integral part of the energy ecosystem and is here to stay. This is evident from the production volumes of unconventional energy in recent times. However, it is important to strike the right balance between increased production and uncontrolled fracking by following safe methods to handle the shortcomings of fracking.