MODELING THE STABILITY OF DRILL STRINGS AT THE DESIGN STAGE IS ONE OF THE METHODS FOR PREDICTING THE RELIABILITY OF THEIR OPERATION
Authors:   doctor of technical Sciences, Professor, academician of the National engineering Academy of Kazakhstan, academician of the Russian Academy of natural Sciences, AKHMETOV S. , AKHMETOV N. ,   doctor of technical Sciences, associate Professor, ABUGALYEV S. ,   candidate of technical Sciences, corresponding member of the National engineering Academy of Kazakhstan
Published: March 2021

In the address of the Head of state Kassym-Jomart Tokayev to the people of Kazakhstan, announced on September 1, 2020, a number of tasks related to improving the productivity of industrial production, including the oil industry, with the broad introduction of modern IT technologies. This is evidenced by the instruction of the President sent in his Message to the Western regions of the country on issues of investment attraction for construction in the future, petrochemical complexes and creating new production runs of high value added [1]. This requires in the near future expand the set of activities for finding and developing new oil and gas fields, and in line with this, a substantial increase in drilling operations, the introduction of effective methods of deep drilling. In this regard, it is very important to ensure the reliability of drilling systems (DS) at the design stage. This, in turn, allows you to solve several tasks simultaneously: based on the use of modeling methods and digital technologies, predict the performance and working properties of DS elements in advance, before they are created, and thereby significantly reduce the risks of large capital expenditures, human and time resources, which would have acquired an irreversible process already at the stage of operation; create digital technology platforms that can become the driving force of the digital ecosystem of the industry [1], in our case, drilling and exploitation of oil and gas fields, thus complementing the electronic database with information about problem situations and effective methods of their solution (elimination). In this paper, which is a continuation of the results of the authors ' research published in [2], we consider special cases of modeling the stability and vibration of drill strings (DStr) taking into account the geometric nonlinearity of deformation. Such cases are buckling often occur with increasing depth of drilling, i.e., length, DStr, where the system becomes quite like a long stretchedcompressed tubular rods under longitudinal and transverse loads. In order to study (predict) the reliability of DS in such situations, the dynamic stability of a geometrically nonlinear DStr under variable loads is investigated, and a method for applying the finite element method to study the dynamic stability of DStr under geometric nonlinearity of their deformation is proposed. To study these phenomena under DStr loading conditions, the authors of this article consider the dynamic stability of a weighed column, taking into account its physical nonlinearity under compressive loads of time variables. Based on the analysis of the obtained theoretical dependencies, the DStr deflections are compared for both physically linear and nonlinear problems. It is established that taking into account physical nonlinearity leads to an oscillatory process with a limited amplitude, and that the presence of nonlinearity for the selected parameters leads to an oscillatory process of the column. In General, the graphical dependencies that characterize the DStr stability parameters obtained on the basis of mathematical modeling methods demonstrate the ability to predict and control the Parameters of this process at the design stage, which allows us to estimate the most optimal zones (limits, ranges) that ensure the efficiency and reliability of the DS operation by varying their values in advance.