Procedur för delning av casing offshore med hjälp av vattenskärning

Sammanfattning: Within the oil and gas industry on offshore installations in the North Sea, several oil wells are closing in on the brink where they no longer are being profitable to keep producing from. When that day comes the oil wells are closed off and the boreholes are plugged with cement. Before the holes can be cemented shut the companies need to remove all their equipment that has been used for underwater exploitations of the well and if applicable remove the above water installation as well. This includes removing the casing that the holes are lined with which main purpose is to prevent the hole from collapsing on the production line and to prevent oil and gas leaks into the surroundings. This thesis focuses on removal of the borehole casing.  When performing this task problems have been raised regarding corrosion on the casing couplings, making them very hard to separate. When this problem occurs, the need for an alternative method to split them is necessary. As of today this operation is performed by cold cut sawing or with a beveling machine. This is a highly time consuming task and an alternative method to perform a faster cut is wanted. This degree work investigates the possibilities of doing this using the benefits of abrasive water jet (AWJ) cutting. The major concerns on using this technic is whether it is fast enough and if it is possible to perform in accordance with the fire and explosive hazards on a hydrocarbon producing installation. As a reference the maximum cut time is set to one minute. Calculations on theoretical cutting speeds as well as physical testing on the AWJ method has been performed and evaluated. The investigations show that the method does have the possibilities of making the cut within the target time.  The work also contains a simple concept model on how the equipment could be constructed.