Page 303 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 279

2.7.6
Cementing Program [ ]

2. Run in with a smaller bit (e.g., 8 1 in in a 12 1 in hole) without
/2
/4
nozzles on heavy wall drill pipe (HWDP) and drillpipe to about 30
ft above the loss zone. (Note: Do not position the bit below the loss
zone. Any cement remaining in the wellbore below the loss zone is
a waste; if slurry is left above the loss zone it can at least drop down
and enter the zone.)
3. Mix and pump 100-200 bbls of extended, low fluid loss lead
cement slurry.
4. Pump 100 bbls of extended, low fluid loss tail cement slurry with
0.5 ppb polypropylene fibers added, preferably batch mixed in
advance of mixing and pumping the lead for the best quality slurry.
5. Displace with mud. If the annulus fluid level can be estimated,
pump a quantity of mud that leaves a small quantity of cement in
the string after U-tubing. It is vital to avoid mud entering the loss
zone after displacing the cement.
6. Monitor for returns at surface while pumping and displacing
cement. If returns are seen, close the BOP and displace with mud.
Now that the annulus level is at surface, displace with the string
capacity -5 bbls instead of the originally calculated displacement.
Slow the pump if necessary so that excessive pressures are not
imposed on the well.
7. Pull out of hole (POH). Pull back two stands without filling, then
fill the annulus from the trip tank with just enough mud to replace
the open-ended pipe displacement. Pull back to the shoe and wait
on cement samples in the oven. It is better to add slightly too little
mud rather than too much.
8. Run in hole (RIH). Carefully drill out the cement. If losses are seen
right away, repeat the cement job.
9. If losses are later experienced in the same zone, repeat the process.

There are two key elements. First, place sufficient cement in the
zone around the wellbore to flood the loss channels. Cement left in the
wellbore after setting is of no benefit and may cause an inadvertent
sidetrack. Second, ensure that the unset cement is not displaced further
away from the wellbore by adding more mud than necessary to the well
as pipe is tripped out.
The first slurry should enter the loss channels easily. It is a good
sign if the fiber cement starts to plug the loss zone near the wellbore

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