ABSTRACT This paper introduces the oil industry to a new type of downhole tools - the Well Tractors with modular power source designed for running in open hole and inside the completions of horizontal and highly deviated wells. The Well Tractors are used for cleaning, setting and pulling of plugs, operating sliding sleeves, open hole logging, running of production logs, drilling, perforation guns, cement bond logs etc. Horizontally the Well Tractors pull coiled tubing and/or wireline beyond 10,000 ft. The Well Tractors are capable of pulling more then 25,000 ft of coiled tubing and/or wireline into a highly deviated well. Furthermore the tools are designed for pushing other tools into the hole, e.g. logging tools, video cameras etc. The Well Tractors with modular power source are designed in two versions: A fluid driven version for coiled tubing operations. Powered by brine, water, mud etc. which is pumped down through standard coiled tubing. The tool is controlled from the surface via a wireline running inside the tubing. Through the wireline measurements can be transmitted to the surface. Alternatively the tool can also operate without the wireline which enables it to run with a smaller size of coiled tubing or have a higher flow rate for e.g. cleaning jobs. An electric driven version of the Well Tractor for wireline operations. Powered and controlled through the wireline. The Well Tractors are designed in 3 different sizes. A Tractor with an outside diameter of 3 1/8". A Tractor with an outside diameter of 4 3/4" and a Tractor with an outside diameter of 2 1/8".