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Modeling of ECD in Casing Drilling Operations and Comparison with Experimental and Field Data |
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Modeling of ECD in Casing Drilling Operations and Comparison with Experimental and Field Data Authors: H. Diaz, M. Yu , S. Miska, N. Takach
Three modeling approaches to the determination of equivalent circulating density (ECD) in Casing
Drilling1 operations are considered in this study; viz., hook-load measurements, pump-pressure measurements
and conventional hydraulic models. The bottom-hole pressure is obtained by adding the calculated
annular pressure losses to the hydrostatic pressure. Since the annular clearance is very small in casing
drilling, a narrow-slot fl ow approximation model is adopted that takes into account the effect of pipe
rotation. A Yield-Power-Law (YPL) drilling fl uid is considered in this study.
Results from each of the three approaches are compared with experimental and fi eld data. The differences
between the calculated and measured bottom-hole pressures (hence ECD) are within a range of
about ±8%. In terms of the frictional pressure losses in the annulus, this range increases to about ±60%
in some instances.
It is shown that pipe rotation plays an important role in determining ECD. The experimental data
indicate an increase in the annular pressure losses with increasing pipe rotary speed. The hook-load
measurements correlate well with fl owing bottom-hole pressures. |
2009