Rotary Drilling

Key Techniques in Rotary Drilling

Rotary drilling can be used as a term to describe any drilling method that primarily employs rotational forces to effect penetration of the ground. It can broadly be broken down into two basic types: wet (flushed) and dry.

Dry Rotary Methods are those which do not require the additional use of a flushing medium to clear the spoil and arisings from drilling. Generally they rely on a mechanical method of spoil removal, usually in the form of continuous flights on the outside of the drill string. The primary advantage of dry drilling systems is that they can be used to investigate contaminated sites with no risk of contaminant mobilisation, since there is no flushwater.

Wet Rotary Methods are those rotary techniques which require high-speed cutting at the face and are therefore prone to generating large amounts of heat and fine spoil. The bit must be cooled, lubricated and the hole kept clear, so it becomes necessary to use a flush medium. This will usually be water, air or a mixture colloquially known as “air-mist”.

Wet drilling is generally unavoidable in hard or consolidated ground, due to the high frictional and mechanical forces required to break the rock. Many techniques are available in order to allow sampling from depth and casing.

Ecologia Dry Drilling – The Wireline Hollow Stem Auger (HSA)

As an environmental consultancy, Ecologia recognises the risk that water flush techniques can present in contaminated land. For this reason, we are one of the few companies in the UK to operate a Hollow Stem Auger with Wireline retrieval, allowing us to take continuous undisturbed samples through most types of surficial geology

The Wireline HSA System consists of a hollow tube drill string of 125mm internal diameter. The outside of the tube is fitted with flights as per a standard continuous flight auger. The lead Auger is fitted with a latch which accommodates the drive system of the internal cuttng tool. At the start of the drill run the cutting tool is fitted into the lead auger and driven into the ground, as per normal augering. When sampling, the string is driven in 1m runs. Upon conclusion of the run, a fishing tool is lowered through the drill string where it mates with the release catch of the drive mechanism, detaching it from the drive auger. The tool and sampler are then retrieved from the drill string and the sample extracted from the sampler barrel. Ecologia uses a plastic liner system to ensure that an undisturbed core is retrieved for analysis. This system does away entirely with the traditional rod-driven systems of augers, halving the preparation time between runs, reducing overall tool mass and freeing resources.

Ecologia also operates conventional solid stem augers in 3” and 8” diameters for open holing in shallow competent ground, or for toolsetting the upper parts of deeper rotary holes.

Ecologia Wet Drilling

While dry techniques are preferred for working in contaminated land, there are many applications both within and outside the environmental sector where deep bores are required, necessitating the use of low-torque, high speed methods. Ecologia strives to provide the best possible balance of methods in order to maximise the value of our product. To these ends, we have assembled a toolset that we believe offers the best possible range of solutions:

• B-101 Rotary Coring: For simple work in unconsolidated ground and very hard rock, a 101mm OD single tube core barrel
• T6-101 Dual Tube Rotary Coring: A 101mm Outer Diameter Dual tube core barrel for sampling 1.5m runs in competent ground and rock. The outer tube cuts while the inner tube is held steady by a thrust bearing. This provides an excellent quality sample.
• SWF Dual Tube Coring with Triplex Liner: A 150mm OD dual tube core barrel, modified to run a plastic liner in the inner tube. Essentially this provides the same capability as the T6, but with the added advantage of being able to take confined samples from unconsolidated overburden as well as hard rock. Ecologia runs a 3m core barrel to increase speed of sampling.
• Open Hole Systems: For simple drilling jobs in competent ground, Ecologia employs a variety of bit sizes in both tricone (“rock roller”) and drag bit formats.

Casing systems: Ecologia carries a range of casing sizes in stock to allow support of borehole walls in difficult conditions.

Capability

Ecologia stocks all of their rotary equipment at our head office in a container designed to ship with our rig. As a result we can mobilise any of the following to site:

• Up to 120m total drilled depth of rotary drilling equipment
• 30m of SWF (168mm OD), and 60m of 127mm OD Casing
• 101mm and 150mm OD corebarrels
• 3”, 3 ¾”, 4” and 6” Rock Rollers
• 4” and 6” Drag Bits.

Drilling Rigs

Ecologia operates two rotary drilling rigs; the Joy 4 Hybrid and the Joy 1 Rotary. The Joy 4 is capable of running all of our rotary equipment. The Joy 1 is a lightweight Rotary SI platform and will run the B101, T6 and 3” solid stem augers.