NUMERICAL PREDICTION OF FLOW OF VISCOUS DRIP LIQUID MIXTURE WITH SOLID PARTICLES IN INLET FIELD OF ECCENTRIC ANNULAR TUBES AND CLEANING THEM FROM SLUDGE

The relevance of the research is determined by the need to understand the features of the hydrodynamics of viscous flows in the annular space between drillpipes and wellbore including changes in the shape of the cross section and wall surfaces; to detail intra- and interfacial processes of momentum and mass transfer during the flow of dispersed media with complex rheology in the fields of action of specific internal and external forces in annular eccentric pipes; to establish the capabilities of models, approaches, methods for predicting the evolution of the structure of the flow of mixtures; to develop practical recommendations for personnel on effective wellbore cleaning. The aim of the research is to study, within the framework of CFD methods, the features of the three-dimensional laminar and turbulent flow of a mixture of drilling fluid with solid particles in the coaxial and eccentric inlet area of the well, as well as to establish the patterns of complex viscous flow accompanying the transport of cuttings along the wellbore and cleaning its horizontal sections. Methodology is dominated by the approaches of complex physical-mathematical and computer modeling of processes in the mechanics of homogeneous and heterogeneous continuums, widely tested on internal complex viscous flows, as well as successfully validating and verifying the results under appropriate conditions and close to the flow regimes, heat and mass transfer, performed by other authors on the analysis of technological processes of drilling and cleaning wells. Results. The paper introduces the critical analysis of the current state of the problems of computer modeling of cuttings transport processes in drilling technologies. The features and effects formed by the presence of rotation of the drill pipe, which affect the structure of the flow, are noted. The authors have formulated in detail the problem of hydrodynamics and mass transfer of a turbulent spatially developing dispersed flow of a liquid with solid particles of cuttings in coaxial eccentric pipes of arbitrary rheology, as well as methods for studying it. The paper introduces the remarks on the formalism of the closures of the constitutive equations of the model in the framework of CFD. Calculations revealed the patterns of changes in local and integral parameters of flows and mass transfer associated with an increase in the annular, mass-average velocities resulting from a decrease in the free flow cross section due to the accumulation of cuttings. The trends towards regularization of the effects that create the cleaning are determined. The features of changes in the structure of a complex flow of a mixture in the framework of the Euler-Eulerian and Euler-Lagrangian approaches are disclosed. In conclusion, proposals for engineering prediction of flows in the horizontal section of the well are presented. The applied value of the results is determined by the possibility of making a number of generalizations that eliminate uncertainties caused by taking into account the details of the geometric and hydrodynamic configurations of the problem, as well as using the parameters of real drilling and cleaning modes.