Platform decommissioning include surface topside removal and underwater structure removal. A lot of cutting operation is needed during the decommissioning.
Platform decommissioning include surface topside removal and underwater structure removal, all the topside and underwater structure above 15 feet below the mud line, a lot of cutting operation is needed during the decommissioning. The home position cutting include a series of cutting operation to surface and underwater, from topside to jacket base. Every parts will be lifted and placed on the cargo barge with HLV after cutting. The cutting operation to the jacket will operated from internal and outside with Diamond Wire saw cutting equipment and Internal Abrasive Water Jet cutting equipment.
The removal operation for the pipe and cable between topside and modules on the deck floor will be process and make the modules separated to individual part. The removal operation also included the cutting off the connection between deck and jacket. The removal of the topside usually have an inverse process of the installation, the only different part is the platform will be separated to two smaller parts firstly, and the deck will be done to smaller parts(8 legs will be separated into 4 parts).
All the casings need to be cut separately, all the structure above the 15’ below mudline need to be removed. Pile leg and skirt pile will be removed above the 15’ below mudline with explosion or water jet abrasive cutting method. During the installation of pile leg, the bottom mud will be squeezed into the pile and make a plug, this plug need to be removed with the Abrasive water jet cutting unit, the mud will be break and returned out of the leg. When the mud inside of the leg can’t be removed, due to some barriers, or cement or the leg have been damaged physically, then the diamond wire saw cutting will be needed. The mud beside of the legs will be removed to the cutting depth and deploy the DWS cutting tool.
Jereh offshore and our partners own a series of platform decommissioning tools, include DWS cutting tool, UHP water jet abrasive cutting unit, high pressure cleaning unit, internal sludge unit and so on.
DWS (Diamond Wire Saw) is an external cutting equipment, DWS have a multi purposes, used to cut the jacket leg, pile leg and skirt leg above water and underwater, DWS have a good potential operation in the deep water working, especially the jacket and pipe cutting. Our DWS unit can applied to most the target sizes, and relative easy deployment (diver and ROV).
Abrasive Water Jet cutting unit apply to abrasive high pressure water cutting technology in platform decommissioning field, to remove the casings, pile leg and jackets. Injecting the water and abrasive with speed of 700 m/s and pressure of 40000psi. This unit will make an air curtain underwater equal to the normal atmosphere. It also can monitor the cutting operation speed through the sound of water.
Jereh Offshore provide project planning and implement service of platform decommissioning and module cutting, platform detection and cleaning overall scheme design and technical service, and Topside blocks, jacket, pile leg, casing project design and technical services.
Jereh Offshore together with our strategy partner Yantai Salvage Bureau have finished the topside and jackets cutting operation, accumulated abundant decommissioning experience.
Wellhead P&A includes isolating the oil gas layer from the aquifer, sealing the well to prevent oil and gas from leaking into the sea, and removing wellhead components.
All the deck will be removed for the fixed platform. Floating platform will be dragged to or nearby the seacoast.