Page 466 - Practical Well Planning and Drilling Manual

Appendix NEW! revised 11/00/bc 1/30/01 3:29 PM Page 442

[ ] Well Design
Appendix 2

section to confirm that the well is still able to contain the MAASP as
indicated at the casing shoe, if a weaker formation has been penetrated.
The recommended technique allows close control of the operation
to prevent formation breakdown. The amount pumped in between
each reading will depend on the depth of the casing shoe, since a
greater volume will need to be pumped for deeper casings for the same
pressure increase.

Test Procedure
Drill out the shoe and approximately 5 m of formation, circulate,
and condition mud until mud weight is consistent in the well. Pull the
bit back into the shoe. Confirm that the hole is full, then close the TPR
around the drillpipe and close in the annulus at the choke manifold.
Line up the cement pump on the drillstring.
Fill the cement pump displacement tank and note the volume.
Pump slowly until the pressure just starts to rise, stop the pump and
note the volume pumped and pressure. Allow pressure to stabilize for
a minute or so (longer if necessary). Pump increments of /4 or /2 bbl,
1
1
stopping to allow pressure stabilization each time and noting volume
vs. pressure. Either use a graph or a table to show when the increase in
pressure between readings starts to decrease.
Stop the test when either the increase in pressure per unit volume
pumped decreases or the stated limit is reached. Check the reading on
the choke manifold (i.e., the gauge that will be used during a well kill)
and use this as the end pressure. Bleed off back to the cement tank and
note the volume returned, except if there is a float in the string in
which case the pressure will have to be bled off and returns volume
measured at the choke manifold. MAASP at the mud weight in the hole
will be the pressure held at the end of the test, either at leakoff or limit.
Calculate the equivalent mud density for this pressure.
Open up the well, line up back to the mud pumps. Check that
there is enough barite on site to weigh up the entire active system to
this density and, if so, resume drilling.
Table A-1 provides an example of a tabular record for a leakoff test.

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