The principles of the development of PLM-system for threaded connections of oil and gas equipment are described. In order to ensure efficiency, the PLM-system must be isomorphic to other complex systems and have their laws, in particular, the emergence and “requisite variety”. The proposed system belongs to the class of hybrid multi-agent intelligent systems that combine various methods of knowledge representation and decision making. The system contains a knowledge base with inference rules, an inference engine, a code editor, simulation models of threaded connections, the results of their simulations, and other components. The knowledge base contains facts, in which the factors that affect the reliability and durability of threaded connections, are connected by cause-effect relations “is the cause” and “is the effect”. Facts can have such properties as an information source, dependence of quantities, a simulation model, etc. The rules of inference allow you to get new facts from the knowledge base and simulation models. All system components or their software interfaces are developed in a high-level general-purpose programming language Python, which simplifies the implementation of the system and the integration of components with different types. In particular, any Python package can be easily connected to the system. Classes and individuals of ontology are declaratively described by Python classes and objects, attributes and relationships are Python-attributes. For easy editing, the system code is divided into parts, which are combined before execution.

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Drilling oil and gas wells is always accompanied by the process of screwing and unscrewing the drill-pipe connector. Its effectiveness largely depends on the accuracy and quality of the thread profile, including the profile height's accuracy. Studies show a decrease in the contact pressures and stresses between the threaded surfaces of the box and the pin of the drill string tool-joint as the working height of the profile increases. It is a positive factor influencing the durability and reliability of the drill pipe connector. On the other hand, the same increase of the working height leads to the improvement of the screwing process itself, which is an integral part of lowering and lifting operations during the operation of drill strings. The increased contact area allows the joint to handle high make-up torques without damaging the thread profile. It is also advisable to consider the design of the roots not of around but of an elliptical profile. To ensure leak-tightness and fatigue strength, the operation of joints with a reduced value of h should be avoided.