The intent of this report is to review deep well injection and what kind of geoenvironmental and environmental considerations this process has.
Deep well injection became popular in the United States around the 1930’s as a way for companies to easily dispose of their hazardous wastes. When well injection was first put into use, it was primarily used by oil companies to dispose of the brine wastes from oil fields. Since then, well injection has expanded into a broad spectrum of hazardous wastes, mostly consisting of different forms of liquid wastes. According to the EPA there are over 680,000 known deep wells in the United States.
This report is intended to analyze deep well injections and the geoenvironmental factors that they affect over their lifetime. These well injections have evolved overtime through regulation and by addressing different environmental considerations. This report will discuss the history of deep well injection and some of the environmental and geotechnical aspects of them that are a concern to society today.
Deep well injection is a disposal method for hazardous waste that was introduced in the 1930’s. Well injection’s primary purpose was initially for petroleum companies to dispose of their brine wastes that are produced from drilling operations. Around the 1950’s it was realized that well injections can be used for a much broader spectrum of hazardous wastes than just petroleum by-products. Deep well injection began to appeal to a larger audience as a method that made it easy to get rid of your waste and never see it again. This translated to an out of sight, out of mind approach to hazardous waste disposal. The first industrial disposal well was installed in Texas in the 1950’s. After its first introduction, deep well injection quickly became an extremely popular method for waste disposal onto the 1960’s and 70’s. In this period of time, injection wells began to be used for a much broader range of hazardous wastes, including chemicals, steel mill by-products, and pharmaceutical wastes. Deep well disposal quickly took flight in the United States as companies realized that it was the most economical way to dispose of their waste (Harding, 2003). To this day, deep well injection remains one of the least expensive methods for disposing of large volumes hazardous wastes. With the drastic increase in popularity, deep well injection has seen numerous disaster scenarios, which has led to constant changing on how they’re regulated and monitored.
Deep well injection is a disposal method that can be used for many different types of wastes, so the EPA has developed a classification system to differentiate between types of wells. The division of injection wells also helps to regulate the different types of wells to standards that best fit the given situation. The different classes of wells and their purpose is listed in the table below.
Wells used to dispose of industrial and municipal waste
Wells used to dispose of oil and gas related wastes
Wells used for extraction of minerals
Shallow wells for disposal of hazardous wastes, or radioactive injection wells
Wells used to dispose of non-hazardous fluids either into or above the underground drinking water source
Wells used for geologic sequestration
Figure 1: Classification of Injection Wells (McCurdy)
The following figure shows the rough distribution of injection wells in the United States, with Class VI being a very small fraction.
Figure 2: Distribution of Active Injection Wells (EPA, 1989)
Class I injection wells are used to dispose of hazardous and non-hazardous wastes. Class I wells are drilled into deep, confined rock formations within the ground. Class I wells are generally the deepest wells, in the order of thousands of feet. Class I wells inject waste far below the lowermost drinking water sources as to not risk contamination of them. As seen above, Class I wells account for a very small number of wells in the United States. Industry is able to inject waste using Class I wells via the Resource Conservation and Recovery Act (RCRA). Class I wells are also strictly monitored by the Safe Drinking Water Act (SDWA). The guidelines for Class I wells may be more strict in the case of hazardous waste injection, which account for around 17 percent of Class I wells.
Class II wells cover the initial purpose of injection wells, which is for the disposal of oil and natural gas production. The large majority of this is brine injection. Class II wells are one of the biggest sources of well injection, and are estimated to inject over 2 billion gallons of fluid every day in the US (EPA, 2016). About 80% of Class II wells are enhanced recovery wells. These enhanced recovery wells inject brine into oil-bearing geologic formations and in return can recover residual oil and natural gas. The brine and other wastes that are injected are able to displace the oil and the gas in the ground, making them easy to extract. The SDWA ensures that this toxic brine does not pollute the drinking water sources that could be around the well.
Class III wells are designed to inject fluid waste and can be used to extract minerals. Most Class III wells are used in order to extract salt and uranium from the ground. This is done by injecting a solution, such as lixiviant, into the ground to dissolve the uranium in the rock. Once the uranium is dissolved, the fluid is pumped back up and the uranium can be separated (EPA, 2016). This process of extracting uranium and other minerals leaves a relatively small environmental footprint compared to other mining processes. Normally, more fluid is extracted than is injected in order to prevent the fluids from moving out of the mining area and possibly contaminating the ground water.
Class IV wells are generally used to dispose of very hazardous or radioactive wastes. In 1984, the EPA banned the use of Class IV injection wells (EPA, 2016). The only Class IV wells that operate are a part of an EPA groundwater clean-up action. To obtain permission to operate a Class IV well, you need approval from either the RCRA program or the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA).
A Class V well is a well used to inject non-hazardous fluids deep underground. This is the most abundant and widely-used type of injection well there is. These wells are much less complex and are used for municipal, business, and industrial waste. Class V wells can present a risk to drinking water sources and have to be heavily regulated by the Underground Injection Control (UIC) program. This program operates under the authority of the SDWA.
Class VI wells are the newest Class of injection wells defined by the EPA. They are used to inject carbon dioxide into deep rock formations, called geologic sequestration. This is being looked at as a possible strategy to combat climate change by limiting the amount of CO2 released to the atmosphere. In 2010 the EPA published the Federal Requirements under the UIC program for carbon dioxide geologic sequestration wells final rule in order to monitor the carbon dioxide that is injected into the ground.
Figure 3: Different Classes of Injection Wells In-situ (Ground Water Protection Council)
In order to understand the different consequences of deep well injection, it’s important to understand exactly how they function. The purpose of an injection well is to provide the means to place hazardous and nonhazardous wastes (generally fluids) into porous geologic formations. The type of injection well drives what type of wastes and the location of the injection well. The construction of the injection well is driven by the primary type of waste it will be disposing of, which will also determine how deep the well will need to be drilled. These factors also factor in the decision as to where the well will be drilled. Certain geologic or hydrogeologic locations may favor a particular type of injection well over another. For this reason large flat states with open land, such as Texas or Kansas, are very popular for deep well implementation. These wells are intended to be much deeper than normal shallow wells, so they involve multiple layers of protective casing, commonly in the form of cement. Before the implementation of the well, extensive laboratory testing needs to be conducted to ensure that the injection well maintains its performance throughout its lifetime (Schlumberger, 2016). This is critical because if there were to be any sort of failure in the wells operations, it could result in the pollution of drinking water sources.
All injection wells share a similar construction sequence, with some alterations based on their Class. One of the most important considerations when building an injection well is the site location. Different sites are going to have different geologic and hydrogeologic factors that are going to influence the injection well, one of the major ones being the location of possible drinking water sources. One major consideration when considering site location is seismic activity. Tectonic stress can have detrimental effects on the well, and there is growing concern that deep injection wells can be a catalyst for seismic activity, which we will discuss more later. Once a location is chosen and it has been determined what Class of well it will be, the drilling depth must be decided. Careful considerations must be taken while drilling, such as the material to be drilled through, how large the well will be, and how deep the well will be drilled. Different Classes of wells will be drilled to different depths to ensure injection into a pocket of a certain material (such as oil), or avoiding drinking water sources and any other possible obstacles. The well itself is constructed using layers of concentric pipes. These pipes can be coupled with casings made from corrosion-resistant materials such as steel alloys or fiberglass (Simpson, 2009). The outmost layer of the well is a chemically resistant cement or epoxy resin that is used to bind the casings together and creating a barrier for waste escape.
Figure 4: General Design for an Injection Well (Simpson, 2009)
There are now numerous ways to dispose of wastes, yet the use of deep well injection continues to be extremely high in the United States. Deep well injection offers many distinct advantages over some of the other methods that are commonly used for waste disposal. One argument for well injections is that, when done correctly, it presents no threat to surface or groundwater. Other methods such as landfilling, incineration, or traditional wastewater treatment regimes can have very detrimental effects when introduced to the hydrologic cycle (Harding, Rick P.). If a well is monitored and constructed properly, it can have little to no effect on the surface or ground water. Deep well injection can permanently remove liquid and other hazardous wastes from our biosphere, theoretically making the planet a healthier place to live. When properly drilled, there should be little to no risk of waste migration to any drinking water aquifers. One of the biggest advantages of deep well injection is the cost. This is why it became so popular in the US back in the 60’s and 70’s. When compared to other methods like incineration, landfilling, and wastewater treatment, deep well injection has lower lifetime costs while being able to dispose of more waste safely (Harding, 2003).
While deep well injection is very popular, there are growing concerns associated with it. The “out of sight, out of mind” mentality that deep well injection was based on has started to come into question in a couple of different areas. There are also some concerns as to long-lasting geologic effects of deep well injection, such as seismic activity, that have been discovered in recent years. There have also been numerous cases of deep wells failing and causing significant damage to the environment. In this section of the report we will discuss some of the criticisms of deep well injections that have been presented over the years.
There is a risk of a failure in a deep well. Any type of failure involving deep well injection can result in very large amounts of toxic contaminants being released into the environment, presenting a risk to the habitat. Waste can contaminate the groundwater and make the surrounding area not safe to live in anymore. Well failures can be a result of lack of proper preparation before building the well, such as ignoring key topographical features of the site. Different waste characteristics can lead to altering pressures, chemical reactions, corrosion, or any number of things that can result in the whole well failing. There have been numerous cases of wells failing and affecting the surrounding area, some of which we will discuss here. One case of multiple failures is in Miami-Dade Florida. There are numerous deep wells in southern Florida and it has been discovered that the local geology does not provide a sufficient containment zone for the waste since the ground is somewhat permeable (Simpson, Heather). The study showed that 10 of the 17 wells were also not constructed properly, resulting in their failure. Hazardous material was found in the drinking water in the area and further EPA regulation was needed. Another case of a deep well failure is in Romulus, Michigan. After much controversy, deep injection wells were implemented in Romulus. After only being in operation for ten months, the wells already showed signs of failure. The well’s mechanical integrity was compromised and tests revealed the occurence of leakage of pipes, which could have made its way to the communities drinking water (Simpson, 2009). These are just a few examples of how possible failures can have lasting effects on a community.
One of the growing concerns with deep well injection is that it may induce seismic activity. There have been numerous documented earthquakes in Colorado, Texas, New York, and many other states that are being attributed to deep wells in the area. Further studies have been conducted to determine if these deep wells are responsible and what mechanisms can be driving this increase in seismic activity. Upon further inspection, it was discovered that mainly Class II wells could be the cause of the increase in seismic activity. These wells can be used for reclaiming things such as petroleum from the ground after injecting the waste. These recovery wells operate at very high pressures in small, contained, reservoirs that have low permeability (Nicholson, 1990). These high pressures wells, can change the state of stress on the Earth’s crust, and if located near any faults, this can induce an earthquake. These high pressure wells are a direct contrast to more common wells that operate at low pressures in large aquifers. There are only a few wells in the United States that fit these criteria that are needed in order to effect seismic activity. However, this is a growing concern for the people in that area and for the planning for future deep wells. Following is a list of recorded cases of seismic activity that is associated with deep well injection.
Figure 5: Recorded evidence of seismic activity from deep well injection (Nicholson, 1990)
As a society, we are moving into an age of increasing environmental concern. Deep well injection has not been ignored when it comes to this. This ideology of taking of most hazardous wastes and simply hiding them far into the Earth isn’t viewed well in the public eye. There is growing concern that these wells are beginning to reach their lifetime expectancy and are going to begin failing. For example, in a Los Angeles dog park near a deep well, there was contaminants found bubbling up (Lustgarten, 2012). There are over 680,000 deep wells in the United States and there is no real way to confirm how many of these are leaking. A significant part of the population doesn't know these wells even exist, but there is a growing movement to put a stop to deep well injection before it can cause any more people any harm. People are growing more and more concerned that all the precautions the EPA has taken are not enough and that there are countless leaking wells that we don’t even know about yet. The EPA has been diligent about regulating these deep injection wells, but there is increasing concern with the community. We can see communities in cities like Romulus, MI have been forming organizations with the sole purpose of preventing these injection wells from ever being built.
The intent of this report was to provide an overview of deep injection wells are and how they could be affecting the environment and geologic processes. Deep well injection has been an inexpensive, effective method for waste disposal for a very long time now in the United States. The EPA has taken care to monitor these different types of injection wells and takes every necessary precaution when building them. However, more and more criticisms have come to light in the last decade that could result in deep well injection use drop in the possible future. Growing community concern and proven failures resulted in deep well injection being considered not as safe as initially thought.