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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The tapered screw joints are widely used in the formation of the drill string. They consist of two parts - a box and a pin. During the process of screwing box and a pin the contact pressure between their thread surfaces arises, the magnitude of which affects the intensity of wear on these surfaces. For the first time, the authors offer in this work to change the contact area of the thread face by the change in the shape of the cutting edge of the threading turning tool. Previously, in the works of these authors themselves, it was offered to change the shape of the cutting edge exclusively to increase the tightness of the joint. In other works, the justification for changing the geometric parameters of such cutters was offered in order to obtain the possibility of the thread manufacturing from materials with a strength limit of more than 1300 MPa. In this paper an analysis of the influence of the geometric parameters size of the cutter on the value of the contact pressure between the thread surfaces of the box and the pin is carried out. Among above geometric parameters the work height is the most important. As a result of theoretical studies, a certain functional dependence of the contact pressure in the tapered thread joint from the shape of the cutter edge and the magnitude of its work height is obtained.

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.

Tapered thread joints used in drill pipes largely determine the productivity of drilling processes and their environmental reliability. The quality of these joints depends on the values of the rake angle of the cutting insert of turning cutters used for making tapered threads. Modern manufacturers, because of the absents of algorithms for calculating the precision of the execution of the tapered thread spiral, depending on the size of the rake angle use the cutters only with a zero value of this angle. This greatly limits the possibility of producing drill pipes from high-strength materials, which is absolutely necessary in the modern drilling methods: obliquely directional and horizontal. The kinematic analysis presented in the article proves the difference between the theoretically specified spiral and their realized in the course of machine processing with cut tools with non-zero values of the rake angle. The deviation of the thread incline angle that is realized during turning is not regulated by standard requirement, as it is variable. The precision of the pitch of the tool-joint tapered thread is regulated by standard and must be ensured by the kinematics of the lathe. However, when screwing, the spiral screw lines of the pin and the box thread may not match, provided that they are made with using of tools with different values of the rake angle. Thus, it is lead to exceed the tolerances by one pitch. The algorithm allows to calculate the axial deviations of the screw line, depending on the value of the rake angle of the cutter for any of the points of the thread profile. It brings the fit of the cutters with a rake angle up to 5 ° to ensure the accuracy of the executed helices in the tapered thread machining.

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