Page 289 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 265

2.7.3
Cementing Program [ ]

Region of highest flow

Dead area - no flow

Fig. 2-9 Fluid Flow in an Eccentric Annulus

2. Pipe movement. Rotating or reciprocating the pipe during displace-
ment has a definite beneficial effect. This is probably because pipe
movement causes side to side movement which effectively moves
the area of preferential flow around, thus getting better movement
of mud that might otherwise stay gelled up in a dead area.
It is possible to use liner hangers, which allow pipe rotation after
setting. With casings, reciprocation is easier than rotation, though
casing rotation is possible by using a rotating plug container. Hole
conditions need to be good to allow movement during displace-
ment or the casing could get stuck off bottom.
3. Gauge hole. If there are significant hole enlargements, then the mud
in the outer reaches will gel up and be very difficult to move. High
flow rates giving turbulent flow, combined with casing movement
and effective spacers and washes over a recommended 10 minute
contact time, will provide a chance to move these mud gels. Also
conditioning the mud well during the last bit run in the hole so
that gels are minimized will help. However, with very large
washouts, it may be impossible to displace mud from the outer
reaches of the washout.

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