posted by Rod McCoremick, Blog author, Fordia Powered by Epiroc
November 5, 2020
The casing advancer system is a tool that may not be used at every drill site, but when ground conditions contain a lot of shale, sand or have a crumbly texture and a lot of overburden, it can save you a lot of time. Parts of the USA, western Canada and Africa are areas where the casing advancer is popular.
In these conditions where there is a lot of overburden, a casing advancer may be the tool that can really help you advance more quickly. Geotechnical drillers are probably more familiar with the casing advancer system, but diamond drillers can also benefit from its use. The casing advancer system allows you to install casing through overburden until you reach bedrock. It is a good tool to use to protect your casing shoe from breaking or becoming damaged.
The system has three parts. The first part is the outer tube which is connected to the bottom of the casing column. This outer tube has grooves on the inside to hold the inner assembly latches and keep it in place when drilling. You install your casing shoe at the bottom of the outer tube and use it to advance through the overburden.
The tricone is in the second part, the inner assembly, which is locked into the outer tube by a set of latches. The tricone protrudes in front of the casing shoe and acts like a pilot to remove the ground ahead of it. When you are dealing with ground conditions that include a lot of stones and gravel, the pebbles are too big to be flushed and remain at the bottom of the hole. The tricone can smash these pebbles so they can be flushed up and out the bore hole.
You should note that the inner assembly has no bearing, allowing it to spin with the casing. The inner assembly can be removed from the casing column and lowered back in place if needed. For example, you may remove the inner assembly because you believe you hit bedrock, then hit a void because you are really in unstable or fractured ground. You may also find yourself with a leak because your casing is not set properly. In both these cases, the inner assembly can be easily lowered back in so you can continue using the tricone.
The third part of the casing advancer system is the loading tube which is used to insert the inner assembly into the outer tube. This prevents the inner assembly latch from getting stuck in the box thread of the outer tube. If you are more of the visual type, you can view the video below and see all the parts of the casing advancer system and how they fit together.