Submersible and Semi Submersible Rigs

ASSIGNMENT

  Submersible and semi submersible rigs

               Submitted by- Group number -5

                                                         Amrit Raj Mannu (65)

                                                        Rajat Singh Teotia (69)

                                                        Shikha Dubey (  )

                                                        Anshul Chhetri (10)

                                                        Kumar Shubham (  )

Submersible and semi submersible rigs

A drilling rig is a machine which makes holes in the earth’s subsurface. Rigs are very big structures equipment that is used for drilling different types of well like oil well, water wells or natural gas extracting wells.

            Drilling rigs are broadly of two types which are onshore (land) rig and offshore (marine) rigs.

            The offshore rigs then are classified into two parts bottom support rigs and floating rigs.  The floating rigs are then further classified into two type’s semi/submersible rigs and drill ship.

            A Submersible Drilling Rig is a vessel which is mobile in nature and can be floated to a mobile place or an area to perform offshore drilling activities. It also known as a mobile offshore drilling unit, it is mainly used as a mobile drilling structure. This drilling rig type is made with the help of structures same as a flatboat that that is moved down below the sea surface. The semi-submersible vessel was created for the need for vessels that could stay afloat and carry out their required functions in the high seas during the time of the constant flow of the waves.

History

At the starting semi-submersible rigs were made only to be used in shallow waters. Such rigs could be used in water levels up to 30 metres. But later as the time passed there was a need for rigs which could be operated in more depths, the invention of the marine equipment progressed. The first semi-submersible vessel was the launched by the Blue Water Drilling Company in 1961. The name of the rig was the Blue Water Rig No. 1. The concept of a semi submersible vessel came out towards the early 21st century. Shell Company’s Bruce Collipp is regarded as the trailblazer and the creator of these big rigs who utilised the theory of landing planes in sea platforms supported by ballast tanks in a columnar form.

Working

The semi-submersible vessel is supported by way of flatboat which is located in the water sub-surface. Over the submersed part, there are steel columns which provide rigidity and support to the semi-submersible vessel. The pontoons are ballasted which means that it becomes easier for the big ships to achieve submersion and buoyancy easily. Also in case the vessel has to move from the deeper depths of the offshore areas to the shallow areas, by removing out the water from the tanks, height can be adjusted of the vessel. The anchoring of the semi-submersible vessel is provided by the anchors which are attached to cables and wires in a set of 6 to 12. As the operating areas of the semi-submersible rigs are very high from the submersible flatboats, there is minimum to nil danger of the big ships to fall down into the water.