What is deep-sea drilling?
Deep-sea drilling is used to collect ocean rock with drilling gear used to explore the deep seabed. The core samples are then analysed by scientists for research. Offshore drilling is carried out either from a ship, an oil platform, or directly on the seabed with robotic drilling equipment.
How does it work?
The rock is penetrated by the drilling column consisting of rods screwed together and a drilling tool attached to the end. The rod thread and tool are driven by a powerful motor allowing their rotation. There are different types of tools suitable for drilling different rocks: tricone, crown, diamond, triple-blade bits, etc.
A drilling fluid is used to remove crushed rock that accumulates on the bottom. The drill may use compressed air or water with additives to vary the density and viscosity of this fluid. As the drill sinks, the rock is trapped in the rod thread. A corer system threaded into the drilling column enables the rock sample to re-surface.
What can we study through drilling?
Drilling provides scientists with knowledge of the geology of the deep seabed after laboratory analysis and study of the cores. By multiplying drilling in one area, we obtain a fairly precise idea of the structure of a geological object in three dimensions.
For example, drilling is used to delineate the extent and depth (and therefore volume) of a polymetallic sulphide deposit. By also using X-ray techniques on rock cores that provide the chemical composition and metal content, geologists can estimate the economic value of a polymetallic sulphide deposit.