In these days of water well and geothermal drilling boom we noticed a raising demand after systems facilitating drilling in unconsolidated geological formations. The reason is simple: Mud-rotary drilling that allows drilling in geologically awkward conditions was almost pushed away by DTH drilling which is much more efficient. In these days, geothermal drilling is done exclusively by DTH hammers. That is why drilling in unconsolidated formations is a problem and every company in the field has to face it. Companies owning none of the overburden systems (=systems for casing holes) are, in fact, out of the game.
To solve the above mentioned technical problem, many various systems (based on various principles) have been developed.
It has always been a matter of one simple thing: about ensuring the stability of the hole wall from the start to the end - until the moment of geo-loop installation. This stability is reached by installing a temporary steel casing that is pulled out after the geo-loop installation.

On the current market there are drill rigs designed to drill in such problematic geo-formations. In this context it is possible to mention two types of machine systems: Drill rigs equipped with Duplex - a system of two counter-rotating rotation heads where one of the heads revolves the DTH hammer and the second head revolves the casing string. The second type drill rigs are equipped with a so-called Grip Head (or Chuck Head) which revolves the casing string in the same direction as the DTH hammer (to the right). Overburden systems (OVBD systems) either supplement both of the machine systems or can be used individually - in that case there is no need for the drill rig to be equipped with a machine system.
There are numerous OVBD systems on the market to choose from. Every OVBD system has PROS and CONS, own character and also some gimmicks. Drilling with casing requires experienced drill masters with a clear picture about "what is going on down in the hole". Every downplay of an important rule can result in extra workingtime and also very expensive tools can be lost (OVBD sys., casing, DTH hammer, drill pipes).

Overburden (OVBD) system is a supplement to the conventional DTH hammer. It is mounted instead of the conventional drill bit (on the DTH hammer). The principle lies in reaming the drill diameter under the casing by extention elements. These elements are either symetric (Superwing, TRB) or eccentric (Stratex). As we realize that using of OVBD systems is quite difficult for the driller at the begining, it is our pleasure to provide free training with a purchase of this tool.

TRB OVBD system from Topdrill
SUPERWING OVBD system from Topdrill
GeoRocFor symetric OVBD systems
STRATEX eccentric OVBD system
Pažící systém Durawing (SIS) od Everdigm