Aspects of Computer Simulation of Transport and Cleaning Processes from Cuttings in Horizontal Well Sections

The relevance of this study is related to the need to form clear ideas about the factors involved in successful drilling operations and make a number of generalizations to existing methods for predicting the transport and cleaning of wells with a horizontal section, taking into account the features and patterns of the flow of drilling fluids in real drilling modes. The aim of this paper is to study the features of the spatial flow of a mixture of drilling fluid with solid particles in the coaxial and eccentric areas of the well; establish the patterns of the developing steady flow of the mixture through the well; and issue recommendations for applied calculations to improve the process of cleaning wells by using hydraulic methods. A well with a 12-meter horizontal eccentric section is chosen as the object of study, in which the flow is carried out in conditions that are as close as possible to actual drilling parameters. The methods of the mechanics of inhomogeneous continuums for viscous homogeneous and heterogeneous mixtures and computational fluid dynamics (CFD) combined with the ideas of a complex physical, mathematical, and numerical study of the internal flows of rheologically complex viscous media are the universal key to understanding the features and identifying the patterns of the processes considered in this study. It is established that particles can significantly affect the structure of the averaged and pulsating flow of a liquid droplet and their settling leads to the formation of an inhomogeneous anisotropic flow structure, the calculation of which requires modern two parameter turbulence models for Reynolds stresses. It is shown that in the bottom region of the annular space there is a zone with equivalent phase velocities, where the effects of a decrease in the intensity of molar transfer are manifested with an increase in the size of the sediment layer. The real drilling conditions are characterized by processes that accompany laminarization and stabilization of the mixture flow along the entire length of the well, and near the boundary of the fixed layer of settled particles, a narrow layer of their suspended state is formed. Moreover, the flow of particles of cuttings from the reservoir surface and their transition to a suspended state are mainly determined by convection-diffusion mechanisms, the intensity of the pulsating small-scale movement of vortices with an anisotropic structure, and the presence of local areas with moderately high flow velocities in contact with a curvilinear surface unstable to small disturbances of the section. The conditions for the formation of a stagnant zone in which sedimentation and growth in the size of deposits are intense are noted. In practice, a technology and algorithm for modeling the process of the interaction of two-phase flows with the walls of an eccentric pipe, based on demonstrations of CFD capabilities, is recommended. In addition, conclusions are made on improving the criterion relationships for determining the minimum flow rates of the drilling fluid, taking into account the correction of parameters characterizing the rheological features of the mixture, the intensity of turbulence, and the geometry of the annular space and connecting nodes.