CHARACTERISTIC FEATURES OF THE MOVEMENT OF ELASTIC-VISCOPLASTIC FLUID IN PIPELINES AND FORMATIONS

Numerous tasks of field practice are largely dependent on the physical properties of hydrocarbons, which include oil. The presence of paraffin, asphaltene and resins in oil has a significant impact on the movement mode, and, consequently, on the design of technological processes for drilling, well operation, field development and pipeline transport of oil. In many fields around the world, the process of pressure recovery when determining reservoir pressure lasts a very long time, in some cases several weeks or months, which is explained by the manifestation of nonequilibrium effects, i.e. elastic properties of liquid. Laboratory experiments have proven that if paraffins, asphaltenes and resins exist in the oil, then they give such oils viscoelastic properties, i.e., along with viscous properties, they also have elastic properties. These oils are considered from the perspective of nonequilibrium liquids, i.e., the rate of change in their internal structure is significantly lower than the rate of change in external conditions. To describe the behavior of visco-plastic-elastic properties, we propose a model taking into account the relaxing properties of the system. As our studies have shown, these properties cause a decrease in time of the filtration process, i.e., a decrease in the productivity of wells for hydrocarbons in a porous medium. This paper provides a model representation of the movement of such media in a pipeline and porous media. During the filtration process, the liquid appears as a suspension of small particles with a long relaxation time (elastic properties) and viscoelastic properties. It is assumed that the sizes of particles moving along with the liquid through a pipeline in a porous medium are subject to deformation, as if they harden and are fixed in the pipeline in a porous medium. The visco-elastic properties of oils can be effectively used during drilling. In a particular case, it can be suggested that when drilling intervals with anomalous oils, the hydrodynamic pressure in the well is significantly lower than the formation pressure. Keywords: visco-plasticity, elasticity, flow rate, volumetric flow rate, pressure, filtration process.