This article describes about basic information of jack up legs – Cylindrical Legs vs Trussed Legs, Three-Legged Jack Up vs Four-Legged Jack Up and Three-Chorded Legs vs Four-Chorded Legs.
Cylindrical Legs vs Trussed Legs
Since the hull needs to stay above the storm wave crest, withstand certain pressures, and transmit different loads between the footing and hull, every Jack Up unit will have legs of some sort. Similar to the footings, there are two different types in trussed legs and cylindrical legs.
Cylindrical legs can vary slightly but the basic premise involves hollow steel tubes. However, some units will have internal stiffening and others may have rack teeth or small holes to allow the hull to move up and down the legs. Generally, these cylindrical legs are used on units that stay shallower than 300 feet of water depth. With the newer units that are designed to work in environment deeper than 300 feet, they tend to use trussed legs and this is because trussed legs require less steel for the same resistance and same elevated response.
Figure 1 – Cylindrical Leg Jack up (dsboffshore.com, 2018)
A Jack Up is a type of offshore drilling rigs. It is made up of a hull, legs, and a lifting system and a jack up rig can be towed to the offshore site, and then lower its legs into the seabed to lift up the hull, providing a stable work deck which is strong enough to cope with the required environmental loads.
Another advantage of Jack Up rigs is that they can operate in high wind speeds and with significant wave heights, as well as in water depths reaching 500 feet. Since the Jack Up will be ultimately supported by the seabed, they are usually preloaded upon arrival at the intended site to simulate the kind of leg loads that they will be exposed to. This ensures that once the rig is fully jacked up and in operation, the seabed will be able to provide a strong foundation for the rig.
The offshore industry has made significant use of Jack Up rigs for over 60 years now. They are especially useful for exploration drilling since they are relatively easy to set up, and also provide ample production, accommodation, and maintenance areas. Over the years, Jack Ups have been pushed to their limits in terms of what they can do. This includes their deck load carrying limits both when afloat and when elevated, their environmental and drilling limits, and the soil, or foundation, limits. By pushing these limits, drilling companies have been able to explore deeper waters, drill deep reservoirs in harsh conditions, and even drill in areas with unstable soils and foundations. Continue reading →
Offshore structures (rig and production platform) are complex facilities to drill wells (options) and produce gas from wells from offshore locations. This is one of the most fascinating structures in the world and this article will show 5 largest offshore structures on the planet.
1. Berkut Platform
Berkut Platform (Courtesy of Rosneft)
Berkut is the world’s biggest oil platform which has begun commercial production at the Sakhalin-1 offshore project in Russia’s Far East. The Berkut oil rig is expected to extract 4.5 million tons of oil annually. The Sakhalin-1 Consortium was formed in 1996 is the first major shelf project in Russia created under terms of a Product Sharing Agreement (PSA). The international consortium is made up of the US major ExxonMobil (30 percent), Japan’s Sodeco (30 percent), Russia’s Rosneft (20 percent) and India’s ONGC Videsh (20 percent). The Berkut platform is expected to produce 12,000 tons of oil daily or about 4.5 million tons annually, raising the total output of the Sakhalin-1 Consortium to 27,000 tons a day. Continue reading →
Perro Negro 6 Incident – Jack up rig capsized and sank was happen few year ago but we would like to share this case as a case study. You can watch what happen in the video below.
It is clearly seen that the rig capsized and sank in just few minutes. Jack up rig move is one of the most hazardous operation. Before a rig is moved, total number of people on board will be kept at minimum for operating the operation and non essential personnel will not be allowed on the rig. There are several considerations that rig contractors and operators must be agreed before commencing any rig move operation. For this case, we would like to emphasize that even though all safety is in place, the bad thing can be happened.
This article will explain the overview of slips and elevator which are very important tool on the rig.
Slips are wedge-shaped gripping devices which are used to suspend the drill string in the hole. They fit around the body of drill pipe and wedge in the taper of the rotary table’s opening. Slips have serrated inserts or dies that will grip the outside diameter of the tubular when it is set on the rotary table. To set the slips, rig crews place them around the pipe and the driller then slowly lowers the pipe until the slips can take up the load. The dies in the slips will firmly hold the pipe. In order to remove the slips, rig crew grasp the slip handles and as the driller picks up the pipe, they lift them out of the rotary table opening and set them aside.
You can watch this video to see how the rig crew set and remove the slips