Page 465 - Practical Well Planning and Drilling Manual

Appendix NEW! revised 11/00/bc 1/30/01 3:29 PM Page 441

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Appendix:2

Formation Integrity Test
Recommended Procedure

An FIT is performed to determine MAASP and to check the integri-
ty of the seal of cement around the shoe. There are two types: a limit
test (where the test is stopped at a predetermined maximum if no
leakoff occurs) and a leakoff test (where the test is continued until
leakoff is seen). The techniques for both are the same. A limit test is
performed to a pressure which confirms the ability of the well to con-
tain a gas kick of a specified influx volume at the next casing depth
where formation pressures are known. A leakoff test is used where pore
pressures are not well-known or on exploration wells.
A leakoff test yields more information—knowing the pressure to
just initiate leakoff gives information relating to the minimum field
stresses. A limit test would be appropriate when a very brittle forma-
tion is exposed that should not be fractured (i.e., limestone).
An FIT should be carried out after drilling out any casing where a
BOP is in use. The drilling program will determine whether it is to be
done as a limit or leakoff. An FIT can also be repeated within a hole

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