In simple words, drilling is nothing but creating a Hole using machines & tools such as drill bits, rock cutters, etc. In technical terms, drilling can be defined as the process of boring or drilling a hole through soil and rock so that geologic reservoirs that contain oil and gas can be accessed.
An oil or gas well can either be drilled in:
- Vertical direction
- Horizontal direction
Drilling of an oil or gas well requires certain drilling steps namely:
- Boring – In this process, drill bits and pipes are used to cut the sand and rock vertically in the ground. In case, the presence of hydrocarbons is under residential areas, a directional drilling can be performed at an angle. In directional drilling, the boring is done in vertical position initially and then angling it towards the reservoir.
- Circulation – In this process, the drilling fluid, primarily mud mixed with water, brine solution, chemicals and gel is being pumped when the drill bits are cutting the rocks. This ensures heat control and frictionless operations.
- Casing – Once a hole is drilled at certain depth, the wellbore has to be strengthen by putting a steel casing and cementing the annulus so that casing remains at its place and prevent well from collapsing. Casing also helps in keeping the outside materials such as mud, stones, grit, etc, away from the hydrocarbon production stream once the oil well is commercialized.
- Completion – After casing, well has to be prepared for completion, perforations are made in the lower most area of the casing that goes inside the reservoir. Through these perforations, oil and gas is sucked inside the wellbore.
- Production – This is commercial phase of oil well that was drilled few months / years back and finally producing.
- Abandonment – This phase comes at the end of the field life i.e. the well bore is covered with sand and rocks. It is simply closing the oil well and making the site conditions normal as if no oil well ever existed.