Self-elevating unit, which is different from a conventional jack up drilling rig, is defined as a self-elevating, self-propelled vessel equipped with at least one crane and with open deck space that can be used for multiple purposes, including well intervention like wireline, coiled tubing and nitrogen, crane operations, pipe-laying, diver support platforms, workover and offshore construction and maintenance, temporary housing for construction and service crews, wind turbine installation and servicing and so on under the water depth of 3~150m.