Modern drilling fluids are non-linear viscous media with an initial shear stress. In classical scientific works on hydromechanical modeling of drilling fluids motion in pipes and annular channels the Shvedov – Bingham approximation and Ostwald – de Waale power-law model were used, which did not fully account for behavior of technological fluids in a wide range of shear rates. This article presents a numerical solution for a mathematical model of drilling fluid motion of the three-parameter Herschel – Bulkley rheological model in the annular space of the well. The Herschel – Bulkley model in the rheological equation takes into account the presence of initial shear stress and a tendency for viscosity to change with shear rate, which distinguishes it from the Ostwald – de Waale and Shvedov – Bingham models. The target function in solving the equation of motion is the velocity distribution in the radial direction of the upward flow of the flushing fluid. The analysis of obtained solution is based on the theory of velocity profile influence on quality of cuttings removal during wellbore cleaning. Due to peculiarities of mathematical statement of the task, which supposes necessity of differential equation of motion solution, Wolfram Mathematica computational software has been used as a calculation tool. The analysis of numerical solution allowed to draw conclusions about the possibility of its application in evaluation of velocity profile when drilling fluid moves in annular space of the well. The possibility for application of modified excess coefficient as a relative quantitative parameter for evaluation of velocity profile uniformity was substantiated.

Problem solution analysis on finding the velocity distribution for laminar flow of a non-linear viscous flushing fluid in the annular space of a well

The article presents the results of an experiment to determine the residual saturation of drilling fluid filtrate in the pore space of a core sample. The presence of residual filtrate saturation of the pore space of the rock reduces its effective porosity and, consequently, oil permeability. The results of such studies can be useful in studying the mechanism of reducing the formation permeability for oil due to the penetration of the water phase. Optimization of the parameters of the drilling fluid and its filtrate can help reduce the negative impact on the formation during drilling.

Mozgovoi Georgii Sergeevich

Papers

Analysis of the results of the experiment to determine the saturation of the filtrate of drilling fluid of the core sample