Lot procedure presentation rev0

How to perform a LOT or FIT


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1.
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CONTENTS
1. Objective
2. How to perform a leak off test (LOT) or
formation integrity test (FIT)
I.
II.
III.
IV.
V.

Why do a LOT or FIT
LOT or FIT application
A common procedure to perform a LOT or FIT
LOT or FIT Calculation

Some high lights when performing a LOT or FIT

3. Questions and Answers


1) Objective
To provide you/students more information and
knowledge on how to perform a leak of test (LOT) or
formation integrity test (FIT) during drilling operation


2) How to perform a LOT or FIT
I.

Why do a LOT or FIT

After each casing string is cemented in place and cement is hard, an
LOT or FIT should be conducted to verify that : 1.

Casing integrity (casing leak)

2.

Cement bond quality behind the casing shoe

3.

Formation strength below casing shoe

can withstand the predicted wellbore pressures required to get to the

next designed section total depth.


2) How to perform a LOT or FIT
II. LOT or FIT application
LOT applied for : 1.

Exploration wells, including wild cat and appraisal wells

2.

Development well on a new platform or new fault block

3.

Development well in an old field, that has not been drilled in
lately

FIT applied for : 4.

Development well with valid offset data

5.

Can not perform a LOT


2) How to perform a LOT or FIT
III. A common procedure to perform LOT or FIT
1.

After the BHA tagged TOC. Ensure surface cement sample hard

2.

Drill out cement , float collar, float shoe, rate hole and 5-50 ft new
formation

3.

Circulate bottoms up and condition mud (MW in =MW out)

4.

Pull bit inside casing shoe and position tool joint

5.

Open chock and flush line through choke manifold until return
Close choke.

6.

Line up and pressure test surface line to a low and high pressure for
5 minutes

7.

Shut in blow out preventer (top pipe rams)

8.

Pump mud down the drill pipe and annular the same time with ẳ or
ẵ bpm by cement pump.


2) How to perform a LOT or FIT
III. A common procedure to perform LOT or FIT
9.

Record and plot the drill pipe pressure and casing pressure at a constant
volume increment (0.1 bbls pumped) in the graph paper.

10. Stop pumping after having gathered 4 data points from the time a break
occur (leak off test pressure = casing pressure at break occur)
Note: If for subsea well, record the subsea stack gauges(s) pressure(s)
11. Bleed off pressure and record the volume led back
12. Open BOP (top pipe ram)
13. LOT completed
For FIT
It will be the same with LOT procedures except for step #10, stop pumping
after casing pressure reach to desired pressure.


2) How to perform a LOT or FIT
IV. LOT or FIT Calculation
Formation break
down pressure( psi)

Maximum equivalent

mud weight(ppg)

Leak off test
pressure (psi)

+

Formation break down
pressure (psi)
=
Csg shoe true
vertical depth (ft)

Hydrostatic pressure of
mud to casing shoe (psi)
Leak off test
pressure( psi)

Hydrostatic pressure of
mud to casing shoe (psi)

=

=

=

Mud weight
(ppg)

*

*

Pressure recorded on
the casing gauge (psi)

0.052

0.052

*

Csg shoe true
vertical depth (ft)


2) How to perform a LOT or FIT
V.

Some high lights when performing a LOT or FIT

a.

Can perform FIT with mud pump, not LOT

b.

Can pump down drilling fluid to annulus only

c.

Can pump down drilling fluid through drill pipe from TDS for rig up a
circulating head to perform

d.

Check the line up, make sure it done properly

e.

Make sure flush out all the air in the choke manifold with drilling fluid

f.

Use top pipe rams, do not use annular preventer

g.

When pull bit inside the casing shoe, do not rotate the PDC bit

h.

When circulate bottoms up, do not bring the bit inside the casing shoe

i.

Some time, it is requested to perform the extended LOT.

4) Questions and answers
Thank you for your attention