There are a variety of different kinds of well drilling rigs which are used to create holes in the ground. These rigs can be huge structures that hold equipment to drill oil wells, natural gas extraction wells, water wells. Some also can be small enough they can be moved manually by just one person and these are called augers.
Well drilling rigs can be mobile equipment that are often mounted on trucks or trailers or they can also be permanent fixtures based on land or they can be marine based as well such as oil platforms which are commonly known as offshore oil rigs.
The small well drilling rigs can be used for mineral exploration drilling, for making water wells and for environmental investigations. These rigs are usually portable as well. The rigs that generally drill for water are a lot heavier because they are often used for long term drilling jobs and are often permanent or at least semi-permanent.
The oil industry will use large well drilling rigs for both oil and natural gas and can identify geologic reservoirs and create holes that will allow for the extraction of oil or natural gas from these geologic reservoirs. For the onshore oil and gas fields, the well drilling rigs will be moved off the well and then a service rig will take its place. This is a smaller rig that is purpose built to complete the job that needs to be done with the well on line. This then frees up the well drilling rig to be used to drill another hole or well and helps to streamline the operation and also allows for specialized services.
For drilling water wells there are new portable drilling technology that can use much smaller and portable trailer mounted well drilling rigs and these rigs for water wells can often be operated by just one or two people and requires a minimal amount of skill and knowledge. The heavier water well drilling rigs are far more complicated and they require a lot more skill to run and they are far more difficult to handle safely because their drill pipe can be 20 to 30 feet in length. They also require a higher overhead clearance in order to operate properly.
There are a variety of different kinds of well drilling rig classifications categorized by the power used, pipe used, their height, method of rotation and position of derrick:
Power used: Mechanical, electric, hydraulic, pneumatic, and steam.
Pipe used: Cable, conventional or coil tubing.
Height: This is measure by how many connected pipes it has. Single, double, triple or quadri.
Rotation method: No rotation, rotary table, top drive, sonic or hammer.
Derrick position: Versicle or slanted at a 45 degree angle.