Engineering basis of CADdy system is creating unified oil&gas field surface facilities construction model. It includes information on all aspects: master plan, external infrastructure and access roads, architecture&construction, technologies, etc., thus providing for information visualization in the form of drawings and specifications for every exact part of the project. In addition to that, within the frame of CADdy system a constant exchange of necessary data between designers is realized on all stages of the project development. Any changes, made to any part of the project, are automatically accounted for in all drawings, connected with other parts of the project. It enables to significantly reduce engineering period of the project and provide for high quality of final documentation. And, finally, all standards and regulations, currently active in oil&gas industry, are fully provided for. It is achieved due to application of data bases, containing typical graphical elements, fragments of drawings and even whole charts of different project parts with full description of their parameters. Utilization of such data bases significantly simplifies development of project graphics, which amounts up to 70-75% of the whole project volume, and, also, automates process of obtaining indexes, lists and specifications. In other words, development of the final draft of the oil&gas field surface facilitites construction project is multistaged, multipoint process, which calls for the need to agree upon and to interrelate adjacent project parts requirements.