Oil drilling is the process of drilling a circular cross-sectional hole from the surface of the Earth to reservoirs, where the hydrocarbons are deposited. The process helps to extract the deposited hydrocarbons from the subsurface formations to the surface.
Offshore drilling involves drilling of an oil or gas well into the water body, i.e., into the oceans. Offshore rigs like floating, drillship, semi-submersible, or Jack-up rigs are used in this type of drilling.
Once the final intermediate casing string is run and cemented, the drilling process is again resumed to reach the wellbore's final depth.