There are various types of drilling rigs used in the search for oil and natural gas under the ocean. Usually, a submersible rig is used for the job. These floating vessels are basically supported on large pontoon-like structures that are submerged below sea levels. Semisubmersibles are ideally attached to the ocean floor with the use of string wire cables or chains. Paul Favret mentions that further offshore, particularly designed rigs mounted on ships are used to drill a well. Paul‘s years of experience in the oil and gas industry have made him pretty well acquainted with its workings.
There are several types off offshore platforms or rigs used for oil and gas exploration and drilling. A few of them are fixed to the ocean floor, while others are floating vessels or platforms. Each of them, however, is designed for varying purposes and water depths. Certain floating production systems may even include refinery or storage facilities.
Here are some of the key types of offshore oil rigs:
- Barge rigs: These rigs are meant for shallower waters, typically if it is lesser than 20 feet deep. Subsequent to being floated to the drilling location, the hull is brought to a rest on the ocean floor, thereby creating a stable platform for drilling.
- Submersible rigs: Such rigs are used in waters too deep for a barge, but still less than 50-70 feet deep. Posts or columns are submerged into the water and then filled to particular levels that determine their depth. Drilling equipment on a platform drives a floating drill unit below.
- Jack-up rigs: As one moves deeper into the waters, a mobile platform known as “jack-up” rig becomes useful. This rig is directly moved over the location to pump oil or drill. The rig can be self elevated from the bottom of the ocean floor in order to secure it in place. Jack-up rigs are generally used for shallow waters of 400 feet or less.
- Platform Rigs: A number of offshore rigs are anchored platforms, and use a steel framework anchored to the ocean floor as a foundation for an equipment or surface drilling rig. Platforms might drill several directors from their base, and are divided into particular categories suited for various depths
- Floating rigs or floaters: It is not practical to attach an offshore rig to the bottom of the ocean in very deep waters. Floating oil rigs are ideally kept in place by dynamic positioning systems or anchors that keep them above the target. There are multiple types of floaters used at distinguished deep water drilling locations across the world.
According to Paul Favret, the use of drill ships or semisubmersibles is preferred for deeper waters up to 12,000 feet. Their work-decks float on top of the water, and the vast majority of their mass is contained below the water in order to stabilize the platforms and keep them in place.