Predicting the plan annular pressure using the power law flow model in horizontal directional drilling

Abstract

During horizontal directional drilling (HDD), the drilling fluid pressure must not surpass the maximum allowable pressure to minimize the risk of hydraulic fracturing; hence, a plan pressure can be used to manage the drilling fluid pressure. This paper addresses the prediction of plan annular pressure using the power law flow model. The annular pressures were predicted using the power law model with rheological parameters determined from a six-speed viscometer with varying shear rate ranges from 3 to 600 RPM for two HDD projects, and the predicted pressures were compared with the measurements. The results indicated that the annular pressure could be properly predicted, and the best prediction was achieved by the shear rate range of 6–100 RPM due to embracing the real shear rate of drilling fluid inside the annulus; this shear rate range is close to the recommendation (3–100 RPM) by American Petroleum Institute Recommended Practice.