"WIRE-LINE" DRILLING SYSTEM

Initially used for rock continuous core drilling it was later modified to carry out boring in ground of whatever type. It is essentially made up of:

* Drilling rods (or "casing") inside which the core-barrel or any drilling tool is placed at the bottom.

* The drilling tool moves inside the drilling rods and has a hooking system which keeps it linked to the rods, both in terms of rotation and of thrust. The circulation fluid flows in the interspace between the external walls of the core-barrel and the internal walls of the rods - this lubricates the bore-hole and removes drilling cuttings. Depending on the type of ground, there can be different types of core-barrel (with fixed head, with greater or lesser length of the cutting blade from the rods, with double walls, etc.) or else instead of the core-barrel a no-coring tool can be placed inside the rod battery or else a sampler, or another tool can be used (as in the case of the piezocone). The tool is placed inside the rods and recovered using a wire system (thus the name "wire-line") which has an "angler" (called "overshot") at the end configured in such a way as to carry out hooking-unhooking operations. In other words, when the overshot is placed inside the rods it reaches the core-barrel and unhooks it inside the rods, and viceversa.

Wire-line operations are the following (referring to sample-taking):

* The drill rig applies rotation and thrust (variable depending on the type of ground) to the rods, inside which the core-barrel is placed (its conformation depending on the type of ground). Generally water (mud) circulates inside the rods and is discharged from the bottom, generally without interfering with the inside of the core-barrel as this comes out from inside the rods while the water flows outside.

* Once sampling has been carried out for the desired layer, the drill rig rotation head moves and the overshot is placed inside the rods where it links up to the core-barrel and recovers it.

* The sample/core is removed from the core-barrel, which is then cleaned and prepared for the next operation, if necessary substituting the lower part (called "shoe" or "bit") for better sampling quality. The core-barrel is placed inside the rods by the "angler", and once it arrives there it automatically hooks up to the rods and is ready for a new sampling operation. A new rod is added and drilling continues.