Using existing wells in mature reservoirs can be an extremely cost-effective method of accessing areas that might otherwise be uneconomical to develop. As many wells incorporate completion tubing of between 2-3/8" and 5-1/2", the size of the pipe and associated drilling tools required must also be relatively small. The selection process between using coiled tubing or slim drill pipe is generally not so much a technical as an economic consideration. For example, if fully functioning rig equipment exists on the platform concerned, slim hole jointed pipe operations may be considerably cheaper than using a comparable coiled tubing system. The use of 'spaghetti pipe' is more like conventional drilling. A number of joints of pipe get screwed together until the whole string is long enough to reach the bottom of the hole. The pipe is then rotated at surface, or a down hole motor, similar to that used for coiled tubing operations, is used to drive the drill bit.