Drilling for oil and gas is performed from a drilling rig that may have various configuration to suit tha actual needs.

Drilling for oil and gas is performed either done offshore or onshore

Onshore (on land) 

• Land rigs

Offshore (on sea)

• Platform rigs (on fixed platforms),
• On mobile units (jack up rigs, Semisubmersaible rigs, drillbarges and tension leg platforms)

The purpose of the drilling:

• Find and confirm that an area contains oil and gas
• To establish the limits of the reservoir, the productivity of wells in it and the properties of the oil or gas
• To make it possible to drain rge reservoir and to bring the hydrocarbons (oil and gas) to the surfaced of the earth.

Main stages of drilling:

• Planning
• Drilling
• Completion

Planning
Well planning is a demanding aspect of drilling engineering. It requires the integration of engineering principles, established strategies and philosophies together with experience. There are many approaches to well planning but the goal is that the drilling is carried out safely, that the cost of drilling is as low as possible and that the well allows optimum oil and gas production.

Some common challenges related to well planning:

• Safety – personnel, facilities and environment
• The geology of the area.
• Avaialability and limitations of the drilling equipment
• Temperature
• Casing limitations
• Sizing of the hole
• Sizing of the hole

Safety hall always have first priority during well planning and drilling.

Well planning activities:

• Data collection
• Pore-pressure analysis
• Fractyre estimation
• Design of tubing and casing and and setting depth.
• Hole geometry selection
• Design of completion, casing strings, and cementing plans.
• Design of directional drilling plans.
• Design of drilling fluids programs.
• Design of drill string and drill bit programs.
• Specifying equipment, material and ratings and grades to be used in the drilling process.
• Performing drill time projections
• Performing cost estimates and analysis.
• Developing contracts with vendors