An analysis of drilling fluid pumping pressure for the Maxi-HDD crossing project

Abstract

For horizontal directional drilling crossing project, pumping pressure is a key factor that influences the drilling efficiency and the stability of borehole wall. There are nevertheless many theoretical difficulties in calculating and analyzing the dynamic law of pumping pressure. This paper aims to resolve these problems based on construction features and rheological theory. The power-law fluid model is adopted to describe rheological properties of drilling fluid. In order to prevent blowout from occurring in the drilling process, the maximum allowable mud pressure at different reaming stages is calculated by numerical method under condition of complicated geological structure. The borehole pressure must be greater than minimum required mud pressure which is achieved by hydrodynamic calculation method, only meet this condition can it transport the cuttings to the ground surface. Moreover, the pressure loss in the drill string, including loss in drill rod and loss through bit nozzles, is also calculated by newly derived equations. Finally, combining with practical engineering field data, the appropriate range of pumping pressure at different reaming stages is obtained through the calculation results of three types of pressure, which can help engineers minimize the occurrence of accidents and enhance the drilling efficiency.