What Happens During the Underground Drilling Process?
Drilling is not a new concept. Archeologists have found evidence of crude drills made of wood and flint that date back 13,000 years, and perhaps much earlier.
Needless to say, technologies have advanced since that time. One of these is the advent of directional drilling. This process minimizes surface impact while maximizing access to resources.
Underground drilling is essential for extracting many natural resources. These include water, natural gas, and petroleum. It is also necessary for installing pipelines and utilities.
You may have wondered what drilling entails. It involves myriad planning, permitting, and operational processes.
A wealth of expertise in an array of fields goes into any given project. Geologists, surveyors, scientists, and engineers all have a hand in making sure a drilling project is successful.
Knowledge of these complex processes requires years of training and experience. But, if you want a basic understanding of underground drilling, the information below offers an introduction.
Modern Underground Drilling
Directional drilling refers to any type of drilling that does not involve boring a straight line down into the earth. For this reason, it is also known as “trenchless” drilling.
Directional drilling was first developed in the 1920s. Since then, science and industry have made many technological advances. One example is the ability to drill precise bores into the ground at great distances.
Such techniques have produced many advantages. These include enhanced recovery methods that increase efficiency and yields.
Directional drilling also is ideal for water, sewer, or gas lines. It can be used for electrical, fiber optic, or other types of cable as well.
“Directional drilling” and “horizontal drilling” are often used interchangeably. But “horizontal drilling” is a type of “directional drilling” where the borehole is greater than 80 degrees.
Advantages of Directional Drilling
A big advantage of directional drilling is that contractors can drill many wells at various angles from a central facility. It is easy to see how a single rig extracting resources that would otherwise mandate dozens of vertical rigs is cost-effective.
Another plus is that they can reach resources that are miles away and thousands of feet deep. Directional drilling also can make use of “sidetracking” techniques. These entail drilling a new hole at some point above the bottom of the original hole, to reach different areas.
The process creates a finger off of the existing borehole. This eliminates the need to drill a completely new hole from the surface. The method also can even be used in existing vertical drill holes.
Besides precision, there also is a natural advantage to directional drilling. Since reservoirs form horizontally, directional drilling can explore more of the extraction area than straight vertical down drilling.
One of the biggest advantages of directional drilling is minimal disruption to the landscape. It is a great alternative to digging under sidewalks, roads, or other types of infrastructure. This helps limit disturbance to surface areas as well as environmental impacts.
The Drilling Process
Horizontal drilling involves a machine pushing a bit at a low angle through the soil. Once the drill reaches the desired depth, it levels off until it reaches its intended horizontal location. Then contractors remove the drill and install piping or utility lines.
Before any underground drilling takes place, weeks or even months of preparation are necessary. Contractors must take into account many different factors before selecting a drilling site.
First, contractors must survey the topography and assess any environmental concerns. This includes planning around waterways, roads, buildings, and utilities.
Surveying usually entails some basic vertical drilling to gather samples of soil and rock. It can also include methods like seismic radar testing. They will use electronics like a Subsite locator, a handheld device that can identify buried utilities.
Contractors then send samples to laboratories for testing. This gives them precise subsurface conditions.
Horizontal drilling is especially effective in clay, soft soil, or sandy soil. Increased gravel in the soil can cause steering difficulties. It also has a greater potential for borehole formation loss.
It is possible to do horizontal drilling in solid rock, but it requires special tools and equipment and can take much longer. For soil with dense gravel or large cobbled rock, directional drilling is not a good option.
Next, engineers move to a design and planning stage, with layouts of the work area and drilling plans. Contractors must make calculations based on physical requirements, like the size of the pipe needed for the project.
They also must assess how the drilling site might impact surrounding areas. For example, will noise from construction affect nearby schools or businesses?
Planning teams shore up many of these issues in the permitting phase. This involves contacting relevant agencies. These are usually oil and gas commissions or state departments of environmental control.
Then, contractors submit an application. Once they pay all applicable fees for leases or permits, they can begin the drilling process.
The first step in the drilling process involves making a small (½ to 1 foot in diameter) pilot hole. It goes all the way to the intended extraction point. The mechanism emits drilling fluid into the surrounding soil that will help with the next phase.
The pilot hole also gives contractors valuable information about many things. These include soil conditions, which are important to selecting the proper drilling equipment. It also allows them to gauge rates of penetration, so they can estimate the timeline of a project.
Once they complete the pilot hole, contractors remove the drill bit. Then the opening or “reaming” process of the hole begins. Contractors continue to add drill fluid to the borehole for lubrication purposes.
The types of tools used depend on how dense the soil and the presence of rock formations. There are different types of control systems for drill bits. Some drill heads send signals to a rig computer.
Swabbing is the process of removing cuttings and excess drill fluid from the borehole. Finally, contractors begin the process of placing pipelines into the borehole, or “pullback.” Once this process is complete, contractors remove all drilling equipment from the site.
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