Effect of casing eccentricity on displacement in horizontal well
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Abstract
The drilling fluid retention caused by casing eccentricity in horizontal well restricts the
improvement of cementing quality and the advantage of horizontal well. To accurately describe the retention law and
range of drilling fluid in horizontal well annulus, It was considered in the paper of the effect of driving force
caused by density difference between slurry and drilling fluid in condition of casing eccentricity in horizontal
well on extension of displacing interface. Based on the equilibrium condition of displacing interface stability, the
boundary location calculation model on displacing interface of drilling fluid at casing and well in eccentric
annulus was set up, and the effect of casing eccentricity on displacement in horizontal well was analyzed. The
results showed that the displacement efficiency decreased and the thickness discontinuity of annular cement sheath
increased as the increase of eccentricity when casing upper eccentricity, while the displacement efficiency
increased and the thickness of annular cement sheath tended to be uniform at first and to be uneven as increase of
eccentricity when casing lower eccentric. The casing lower eccentricity of 0.1 to 0.2 in horizontal well can bring
about the best cementing quality, so the casing upper eccentric should be strictly controlled to prevent whole
drilling fluid retention and uneven distribution of cement sheath thickness.
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