Drilling is an important part of oil and gas extraction from the ground, but it’s not as straightforward as you’d think. Normally, wells of any kind, be it fossil fuel or water, are vertical. However, there’s also another type of drilling called horizontal drilling.
In this post, we’ll talk about directional drilling, in general, and horizontal drilling, in particular. It has become a valuable method of drilling over the last few decades, allowing explorers to dig in places that are rather complicated.
Learning about these techniques isn’t just important for those in the oil and gas industry but for anyone linked with it directly or indirectly, such as parties who receive mineral royalties.
What is Directional Drilling?
Drilling in an angle or direction other than vertical is called directional drilling. While most wells are vertical, as they are drilled perpendicular to the surface of the Earth, some are drilled at angles other than standard 90 degrees.
In certain scenarios, drilling vertically cannot stimulate reservoirs. In such cases, a different direction may allow diggers to accurately steer the well and stimulate the reservoir to produce minerals.
The difficulty in drilling vertically isn’t the only factor that calls for directional drilling. There can be other reasons as well, such as a new reservoir right next to an existing one that could be easily reached with horizontal directional drilling.
What is Horizontal Drilling?
Horizontal drilling is directional drilling in which the digging angle is at least 80 degrees from the perpendicular wellbore. This type of drilling is becoming very popular but isn’t really new, as its inception goes all the way back to the 1920s.
Prior to the 1980s, this kind of drilling technique wasn’t really common as most companies dug wells vertically right above the main reservoir. That’s obviously a much easier and simpler approach, but it doesn’t work everywhere.
In 2010, the horizontal drilling in Austin Chalk Play in Louisiana led to the popularity of this directional drilling. Thanks to new technologies, companies can now dig at angles, resulting in better yield from existing wells as well as recruiting new sites that were previously unreachable.
Horizontal drilling is often used in conjunction with hydraulic fracturing to explore gas reservoirs that were previously not tapped on. You can consider it as an alternative drilling technique for vertical drilling.
Advantages of Horizontal Drilling
Now that you understand horizontal directional drilling or HDD meaning, it’s also important to understand its many benefits:
Reach Areas Vertical Drilling Cannot
The most common reason for drilling horizontally is it because it’s impossible or difficult to drill vertically to the reservoir of fluid mineral.
For instance, if the well is located underneath a town with people, it would be unlawful and unethical to drill vertically as that would mean destroying infrastructure overground. In such a scenario, horizontal drilling can give access to the reservoir without disturbing the properties and life directly over it.
Similarly, if there’s an obstacle underground over the reservoir, directional drilling can make it possible to access it regardless.
Drain More Area From a Single Point
Horizontal drilling can allow oil and gas companies to drill multiple wells for a single drill pad. In other words, it allows oil and gas companies to group wells, making less disturbance on the surface with fewer oil rigs.
The best example of this would be the 22 wells dug on University of Texas Arlington grounds. The gas field covers 1100 acres of the campus with just one drill pad.
More Pay Zone
Horizontal drilling increases the pay zone in a rock unit. Sometimes, the possible length of the vertical well is short. However, with horizontal drilling, it can potentially increase the pay zone of that well.
In simpler words, horizontal drilling can increase the productivity of the well by increasing the pay zone accessible by the wellbore.
Good for Fractured Reservoir
Horizontal drilling can also be very useful when dealing with a fractured reservoir. With directional drilling, multiple fractures of the reservoir can be targeted with a single wellbore. The dominant fracture is typically reached vertically. From there, the well is dug directionally to reach most of the fractures possible.
Disadvantages of Horizontal Drilling
This kind of drilling isn’t without its obstacles or disadvantages:
One of the reasons why horizontal drilling wasn’t that popular in the beginning is that it was more time-consuming, and, therefore, costly as well. However, this is changing, thanks to new and better technology.
Earlier, when drilling horizontally, the companies had to stop frequently and do surveys once again to determine the right direction for downhole motors.
At times, horizontal drilling can lead to reservoirs whose mineral rights may belong to some other party. That can lead to legal issues for the company and owners. There have been such scandals in the past where companies or even whole countries were accused of stealing resources through directional drilling.
Horizontal Drilling and Shale Oil and Gas
Horizontal directional drilling has also been extremely useful for the extraction of shale gas and oil in North America. The discovery and extraction of these fields has allowed the US to be self-sufficient for its oil needs.
As shales comprise rocks with very low permeability, horizontal drilling helps in stimulating organic shales better than vertical drilling. That’s because it can target the main source of shale.
Of course, hydraulic fracturing also plays a big role in this process. It uses frac sand to increase the permeability of the rocks.
Horizontal drilling (directional drilling) has proven to be both efficient and cost-effective by allowing digging companies to cover more areas and achieve a better yield.
All this, of course, wasn’t possible without improvements in oil well-digging technologies. Nevertheless, those digging these wells have to be wary of the extent they can drill into. It can raise the risk of digging beyond their rights.
With careful planning, such disputes and conflicts can be avoided. Horizontal drilling can also reduce the surface area consumed by oil extraction infrastructure.