A well structure situated at the sea, some distance from the shore is known as an offshore well. This well is normally drilled at the seabed using specially designed drilling equipments and different drilling techniques are used. What are deviated wells, doglegs? A deviated well is a horizontal well drilled at an angle usually greater than 80 degrees to the vertical. It involves drilling horizontal and slant-hole wells which enhance better intersection of vertical structures in tight formations.
Deviated well is essential since it prevents the fracture of vertical lines, which enhance the permeability of natural gas much higher than the unfractured rock. They increase production rate and minimize cost of ecological damage. Deviated wells can be grouped as unintentionally deviated and intentionally deviated. Unintentionally deviated implies that the well lies on a vertical or near a vertical plane. A dogleg is a sharp deviation or bend in a well’s direction or inclination.
They are characterized by being abrupt, decreasing or increasing, excessive long and permissible. It can also referred to as an elbow . . Include a section on offshore well structure /design explaining how it is designed Offshore well structures are designed to bear up all foreseeable conditions which may be weather related as well as environmental loading factors such as earthquake induced loads. Accidental loads such as collisions, fires and explosions are also considered when designing a well structure .
In designing this, a floating offshore structure which is polygon shaped and used for drilling or production purpose is used. It contains apertures on its sides meant for reducing the movement of the structure as a result of undersea currents. The structure further consists of a production platform extending above the water surface, and a series of buoyancy tanks which provide the structure with the ability to float. Apertures, surrounded by coamings, is located on each side of the structure to allow ocean currents to flow laterally through the center of the structure.
It also makes it possible and easy for oil and gas can dissipate from the center of the structure if a rupture occurs. A fluid retention tank and ballast in the structure lowers the center of gravity of the structure and make it more stable, and a centerwell running through the longitudinal center of the structure allows one or more risers to run from the ocean floor to the operating platform. The structure can then be moored to the sea floor through the use of a catenary mooring system. .
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