Hole Cleaning Performance of Light-Weight Drilling Fluids During Horizontal Underbalanced Drilling

Abstract

Abstract Hole cleaning is a major consideration at both the design and application stages of a drilling operation. If the fluid velocity is lower than a critical value at horizontal or high inclinations, a stationary bed develops which may cause various problems, such as high drag, higher probability of stuck pipe and higher hydraulic requirements, etc., if not removed properly. Therefore, this becomes important and essential to identifying critical velocity. This study aims to estimate the critical fluid-flow velocity for preventing the development of a stationary bed using empirical correlations that can be used easily at the field. Also, a rough estimation of bed thickness is introduced if the flow velocity is lower than the critical velocity. For this purpose, extensive cuttings transport experiments with water, called the Cuttings Transport Flow Loop, were conducted by the Petroleum and Natural Gas Engineering Department at Middle East Technical University (METU) in order to determine various inclinations, flow rates and rate of penetrations. The inner pipe is subject to a sagging, therefore more realistic annulus representation is achieved. Observations showed that a stationary bed can be developed even when the inclination of the wellbore is down to 50°. Results showed that the critical velocity could be estimated using the proposed correlations with reasonable accuracy when compared with the experimental results. Also, for flow velocities less than the critical values, the thickness of the stationary bed can be detected mostly within an error range of ±15%.