Projeto de aparato experimental para avaliação de pressões e vazões no reinício de escoamento de fluidos de perfuração

Abstract

The gelation of drilling fluids is a desirable phenomenon in the drilling process, because the gellified fluid prevents the deposition of cuttings from the well structure. However, when the drilling fluid flow is restarted, the pump pressure must be higher than the usual operation pressures so that the gel breaking can occur. Therefore, the flow restart generates a fluid pressure peak, but there is a possibility that these high pressures are higher than the formation fracture pressure, resulting in structural damage on the borehole walls. Moreover, the safe operating pressure window at the bottom of the wall is very narrow, intensifying the problem in great oceanic depths. In this work, an experimental apparatus for the evaluation of pressures and flow rates at drilling flow start-up is designed and built. The device will be used to evaluate the pressure peaks at the drilling fluid flow restart. The revision of previous research focuses on the main published works about thixotropic fluids. The basis for the present work is the experimental test bench built by Leôncio (2011). After the revision, a design methodology for the experimental apparatus was proposed, along with the main project goals and restrictions. In the next stage, the equipment selection and the construction details of the apparatus are presented. Finally, calibration procedures, experimental procedure for future tests and conclusions are detailed, and recommendations for future research are proposed.