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

HARRISON OSEI

Abstract


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.


Keywords


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

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References


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