Avaliação experimental de variações de pressão provocadas pela movimentação da coluna de perfuração

Abstract

During drilling of oil wells, the drill string is constantly moved along the well, which can generate pressure variations in the annular region. If such changes are significant, operational problems may occur and substantially increase the final cost of the well. Precursor studies have shown that the pressure variation generated by the axial movement of the column is influenced mainly by the velocity of the drill string, geometry of the well, rheological properties of the fluids, flow regime and the presence or absence of coating. Considering this, the objective of the present work is to evaluate experimentally the variables that influence the pressure behavior inside the well. For that reason, an experimental unit that allows to reproduce experimentally the effect of the movement of the drilling string was constructed. The unit allows the control of the speed and rotation of the column, as well as the monitoring of temperature and pressure of the working fluid. The experimental apparatus consists in two pipes representing the drilling string and the well, along the well absolute pressure transducers were installed. During the experiments, the working fluid may suffer variations in pressure as the drilling string is moved. The result of the test with viscoplastic fluids corroborate the existence of a portion of pressure that is not transmitted after the movement of the column. In addition, it was observed that this small amount of pressure that was not transmitted decreased with the rotation of the drilling string. Thus, it is concluded that the rotation of the column influences the transmission of pressure, therefore, this parameter must be considered in simulators that analyze the pressures inside the well during and after the movement of the drilling string.