Amazing! The offshore pipeline is laid this way
The offshore pipes are the pipeline that carrying oil, gas and water continuously. The material of offshore pipeline determines the production cost, anti-erosion ability, gravity requirement and welding property of the pipe projects. Currently, carbon steel API 5L X56 and above are generally adopted to laid on the seafloor.
To complete the installation of a submarine pipeline, the first factor to consider is the design details and the installation project face more risks. Unlike on land, We can’t transform the seafloor easily, so there are too many factors to consider from design or construction process. The seafloor consists of a variety of topographical features, such as the high sea mountains, the undulating sea hills, the long sea ridge, the deep trenches and so on. The low temperature, high pressure, high salinity, undercurrent surge, hydrate blocking, easy-corrosion, impact loss and other problems will bring too uncertain challenges,on the other hand the operating space is severely limited in the water. These problems make the installation of submarine oil and gas pipeline not only a engineering problem, but also scientific problem. For the construction work, the depth is the biggest influence factor, the different depth, the different methods of laying ways. So how is the submarine pipeline laid?
1.In the shallow areas,the pipeline can be drawn to the sea directly.
2.S - lay method. is suitable for use both in shallow and deepwater areas (up to 2500 meters water depth depending on pipe diameter) and involves welding the pipe sections horizontally area by laying ship S - lay down while welding, forming s-shaped curve in The bottom of The sea.In the process of laying pipe. There are three main tools on board: tensioner, escrow and welding line.The tensioner is used to fix the sea pipe, like a large clip holding the sea pipe.The escrow is used to control the laying of the sea pipe.In addition,limited by the operational space, the installation projects requires a professional fleet to cooperate with each other, and the cost is one to two times higher than the land in the same situation.
3.J-lay method. J-lay method is considered to be suitable for 400 m. to 3500 m. water depth depending on pipeline diameter. the pipes are assembled and welded in a vertical mode in a tower erected on the centre or side of the barge and as the platform moves forward, the jointed pipeline is lowered near vertically in a J-shape from the launching point down to the bottom of the sea. The increase of the length of the offshore pipeline leads to the increase in weight and the need to Lay the vessel under greater tension.
4.Reel-Lay method. With the development of new technology, the method of Marine pipelining is progressing. For small diameter and low strength submarine pipe,it can be built on land and roll on the drum, then shipped to sea and laid in the sea, that’s called reel-lay method. At present, the roll-drum laying barge can be divided into two types: horizontal and vertical.Horizontal laying ship, whose rotating shaft is perpendicular to the deck of the laying ship, using S-type laying (often used in shallow water). It is often used to lay the umbilical cord;And the vertical laying ship, whose rotating shaft and laying ship deck keep horizontal, using J type laid. It used in deep water. Using which methods, it should not only consider the water depth, but also combine the operating cycle and operation cost.
Some developed countries have advanced deep-water pipeline technology already. In deep area the gulf of Mexico, north Africa and Brazil, local oil companies have studied deep-water technology decades yeas ago. However, China's offshore oil and gas industry has been concentrated in shallow water area and mainly S-lay method pipeline technology in the practical operation. With the improvement of the torque capacity of the tensioning device in recent years, the capacity of s-lay pipelining is improving, but the Reel-Lay and J-lay methods are the key direction for deep water area.