Avaliação da eficiência de limpeza em bancada experimental utilizando circulação direta e reversa

Abstract

In the oil and gas industry, two main techniques are used in drilling operations to pump the drilling mud. The direct circulation, or convetional circulation, consists of the injection of the fluid through the drilling pipe, and returning through the annulus. For the reverse circulation, however, the injection of the drilling mud is performed through the annulus and its outcome exits the drilling pipe. Each technique has its own specific traits, regarding the flow hydrodinamics, affecting the cuttings carrying capacity. Thus, an experimental study was conducted in order to compare the convetional and the reverse circulation. The analyzed parameters were the cuttings carrying capacity and the force exerted by the fluid at the bottom of the well. The geometry of the bit was simplified as a contraction (β=2,7) and the fluid used waswater. As the flow rate was increased, the reverse circulation showed greater variations in the mean force, when compared to the direct circulation. This occurs because energy losses due to the presence of the contraction, in reverse circulation, only happens after the fluid’s impact. The variation of the distance from the contraction to the bottom of the well resulted in similar effects for both techniques. Regarding the cuttings carrying capacity, the convetional circulation showed to be more effective for greater contraction heights. On the other hand, it was detected that the reverse circulation can match the direct as the distance from the contraction to the bottom of the well is reduced. From the flow visualization, in the conventional circulation, it was noticed that particles are kept in recirculations close to the contraction. In field context this means that cuttings are reprocessed by the drilling bit, which may lead to reduction of the bit life. When the experimental aparattus is operating in reverse circulation, however, the particles are not recirculated close to the contraction.