Directional Drilling

Ally Fumo
3 min readApr 26, 2022
Directional Drilling

What’s Directional Drilling?

Directional drilling, also known as slant drilling, is a technique used to access underground reservoirs for oil, natural gas or water. It involves drilling at a non-vertical angle.

Most wells for subsurface reservoirs are vertical , drilled straight down. This is not always possible or practical. It could be because of environmental restrictions, for example, reaching reservoirs in pipelines and other utility corridors, under bodies of water, nature reserves and other environmentally sensitive areas.

Directional drilling follows a predetermined path to reach a specific target.


Pilot hole

Drilling a pilot hole is the first stage of the process. The pilot hole is a small-diameter bore from the entry point to the exit pit. It’s drilled along a predetermined path. Its main purpose is to help guide hole opening operations and deliver the drill bit to the surface at the exit point.

The size of a pilot hole varies depending on the soil type and conditions.


Pre-reaming is the second stage of the process. Once the pilot hole has been completed, a reamer is used to enlarge it to the size needed. The new opening needs to be at least 50% larger than the outside diameter of the product pipeline. For example: to install a 12-inch pipe, the hole needs to be at least 18 inches.

Pre-reaming usually involves multiple passes of consecutive larger reamers. The process enlarges the pilot hole to minimize the pullback force during installation.

Pull back the pipe

Pullback; the most important stage of the process. It installs the product pipe to complete the project.

Once the hole is enlarged to desired size, drillers put the prefabricated and tested product pipeline on rollers and position it to enter the bore.


Directional drilling has many benefits. It’s a very efficient process. It allows operators to cut costs and lessen the environmental impact in the communities where they operate.


Directional drilling is increasingly becoming a go-to technique in the exploration and exploitation of oil and gas resources. It has the ability to expand pay zones. In shale formations, producers use it, along with hydraulic fracturing, to dramatically increase their yields.

Directional drilling can hit multiple pockets. The best example of this is a 2010 study by the University of Texas Arlington where a single pad was used to access 22 wells that drained natural gas from 1100 acres beneath the campus.


Directional drilling helps operators cut operation costs. Using fewer drilling pads, operators reduce costs associated with setups and maintenance. Fewer pads also help cut costs associated with surface restoration.

Vertical drilling sometimes runs into dry wells. By drilling into a blanket formation, directional drilling exposes a large production area. It almost guarantees a flow.

The Environment

The biggest benefit of directional drilling is its ability to safely access reservoirs in environmentally sensitive areas. These could be highly populated areas, water bodies, wetlands or nature reserves.

Accessing multiple wells on a single pad has financial as well as environmental benefits. It considerably reduces soil disturbance and the overall footprint of the operation. It cuts down the number of wells, drilling pads and access roads required for the operation.


With the advancement in technology that improves the efficiency, safety, and reliability of the technique, this highly specialized niche has a promising future. The technique is also used in other operations beyond explorations and exploitation of oil and gas. Directional drilling is becoming a major player in the disposition of waste.



Ally Fumo

Former GIS Analyst in Oil and Gas industry turned Copywriter.