Rheological Effects of Power Law Drilling Fluids on Cuttings Transportation in Non-Vertical Wellbores



Cuttings transportation in non-vertical boreholes is necessary for oil and gas wells. Efficient cuttings removal from a wellbore during drilling is critical for cost-effective drilling as high annular cuttings buildup often leads to high risk of stuck pipe, reduced rate of penetration and other impediments to standard drilling and completion procedures. This study investigates rheological parameters influence on the removal of cuttings in non-vertical boreholes in the course of drilling. In this study, twelve mud samples with density ranging from 8.45 – 8.50 were selected to study the rheological parameters at three different annular velocities (1.91, 2.86 and 3.82 ft/sec) and three hole angles (30o, 45o and 70o) from vertical. A programme was developed using excel spreadsheet which could determine the rheological parameters and their effect on cuttings removal from non-vertical boreholes. Results showed that better sweep of drilled cuttings is favoured by increasing annular velocity and increasing hole angle. Both the apparent and effective viscosities should increase, power law flow index should be decreased while power law consistency index should be increased. The yield point and plastic viscosity values should all be high but done in such a way that they will result in low YP/PV ratios.


Rheology; Cuttings Buildup; Rate of Penetration; Carrying Capacity; Slip Velocity

Full Text:



Anon. (2006), “Drilling Fluid Reference Manual”, Baker Hughes, 775 pp.

Anon. (2009), “Hole Cleaning in Deviated Wells – Rheological Require,” Q‟Max Solutions Inc., www.qmaxsolutions.com, Accessed: October 16, 2009.

Azar, J. J. and Sanchez, R. A. (1997), “Important Issues in Cuttings Transport for Drilling Directional Wells,” Latin American and Caribbean Petroleum Engineering Conference and Exhibition, Rio de Janeiro, Brazil, pp. 1-4.

Becker, T. E., Azar, J. J. and Okrajni, S. S. (1991), “Correlations of Mud Rheological Properties with Cuttings Transport Performance in Directional Drilling,” SPE Drilling Engineering, pp. 16 – 24.

Dominique, G. (1990), “Rheology of Well Cement Slurries: Well Cementing” Developments in Petroleum Science, Vol. 28, pp. 4-1 – 4-37.

Kelessidis, V. C. and Bandelis G. E. (2004), “Flow Patterns and Minimum Suspension Velocity for Efficient Cuttings Transport in Horizontal and Deviated Wells in Coiled-Tubing Drilling”, SPE Drilling and Completion, pp. 213-227.

Okrajni, S. S. and Azar, J. J. (1986), ''The Effect of Mud Rheology on Annular Hole Cleaning in Directional Wells,” SPE Drilling Engineering, pp. 297-308.

Pilehvari, A. A. and Azar, J. J. (1999), “State-of-the-Art Cuttings Transport in Horizontal Wellbores,” SPE Drilling and Completion, Vol. 14, No. 3, pp. 196-200.


  • There are currently no refbacks.