DETERMINING THE OPTIMAL LOCATION OF THE AXIAL VIBRATION GENERATOR IN THE DRILL STRING

Abstract

The paper describes the developed methodology for determining the optimal location of the axial vibration generator in the drill string layout intended for drilling a given interval of a directional well. The proposed metho-dology is based on the analysis of the results of dynamic modeling of the system “drill string in a directional well” carried out in the time domain. To carry out numerical experiments, a number of basic simulation models have been developed in the Modelica simulation language, which allow, by changing the input parameters, to create simulation models for a significant number of typical drillstring designs in a well of arbitrary profile. In the developed simulation model, the drillstring is described using a soft-string model, and the dissipative forces acting on the drillstring include the forces of viscous friction of the drillstring on the flushing fluid and the forces of friction of the drillstring on the well wall, which are described by the nonlinear Striebeck friction model. By analyzing the re-sults of simulation modeling, a procedure for selecting the duration of the time domain of dynamic modeling was deve-loped, and indicators for evaluating the effectiveness of using an axial oscillation generator were determined. The average value of the total value of friction forces over the selected time interval acting in the drill string at the steady-state mode of its operation was chosen as the efficiency indicator. To automate a series of numerical experiments, process the results obtained, and derive recommendations on the optimal location of the axial vibration generator in the drill string, a Python program was created that provides acceptable computing time by performing simulation in several threads in parallel. The result of the program is a graph of dependencies of the average value of the total friction forces for a drill string that differs in the location of the axial vibration generator at different stages of drilling a given interval of a directional well.