Casing Basics and Levels in Oil Drilling Rigs, Part 1

When a given oil well is being drilled, one of the single most important components involved in this process is casing. Casing is the structural foundation of a well, set inside the drilled area to protect the space, stabilize the sides of the well and stop any potential of cave-in risks.

At Oilfield Equipment & Manufacturing, we offer a wide variety of downhole oil and gas products, including several areas and tools that relate directly to casing. For those just becoming familiar with the industry and the important components involved in it, this two-part blog series will offer a valuable primer on everything you need to know about oil drilling casing and tubing products, the role they play in a drilling rig and much more.

casing levels oil drilling rigs

Conductor Casing

Oil well construction comes with several “strings” of casing that allow the well to reach the required depth. We’ll begin with the string closest to the surface, which is known as the conductor casing.

Conductor casing is the first string that will be run into a given well, generally with a depth range from 40 feet to 300 feet. The conductor pipe will be hammered by a pipe hammer in soft formation or offshore areas, while a larger hole will be required for harder rock areas because hammering is not realistic in these areas.

Conductor casing is a vital product for protecting the formation of the drill washout at the shallowest depth ranges. It also limits loss circulation in these areas, plus provides a fluid conduit from the drill bit to the well’s surface. Finally, conductor casing is valuable because it decreases the risk of hole-caving issues.

Surface Casing

Next in many drilling areas will be the surface casing, also known as the structural casing. This is an extra casing that runs from 500 feet to 1,000 feet, one that requires drilling a hole before running it.

When used, surface casing limits circulation loss at shallow depths, plus provides a similar conduit as the conductor casing. It also prevents hole-caving and covers weak formations, plus supports the blow-out preventor and covers shallow fresh-water zones so they are not contaminated.

Intermediate Casing

It’s important to note that our next format, intermediate casing, may appear multiple times in a single well. Intermediate casing generally requires higher mud weight, which is part of the goal of this casing to begin with – it protects weak zones while drilling at such higher weights.

In addition, intermediate casing isolates certain formations that cause drilling issues, supporting their weight individually. Like our other casing formats, it also provides a fluid conduit to the drill bit itself.

For more on the important casing components to be aware of in a drilling rig, or to learn about any of our oil drilling tools, speak to the staff at Oilfield Equipment & Manufacturing.