PTRT 1321
Oil-Field Hydraulics
Chapter 8
Shut-in Procedures
Oil and Gas
Technology Program
Introduction
• Serve several purposes
– Stop the influx of formation fluid into the well bore
– Protect the crew and rig
– Provide an opportunity to organize and plan the kill
procedure
– Allow shut-in work string and casing pressures to be
determined
• A few abbreviations
– Shut-in drill pipe pressure – SIDPP
– Shut-in tubing pressure – SITP
– Shut-in work string pressure – SIWSP
• In this book the term SITP is used for all three
Oil and Gas
Technology Program
Introduction (cont)
• IF well casing is set and adequately
cemented in competent formation, usually
the well can be shut in safely when a kick
occurs
• Shut-in procedures differ whether or not
the work string is near bottom
• Off shore procedures are listed but we will
not discuss them here
Oil and Gas
Technology Program
Shut-in Procedure - I
• Surface BOP stack - Typical on land rigs
• Fluid is being circulated
• Work string is at bottom
– Several different procedures are possible
– Important that everyone involved knows
ahead of time which procedures will be used
– Example procedure uses a soft shut-in
• Flow line through choke open
• Then shut in well
Oil and Gas
Technology Program
Shut-in Procedure - I
• Stop rotating – sound alarm
• Pick up work string far enough to ensure a tool joint or coupling
is not in a ram BOP (if lower kelly cock is present make sure it
clears the rotary table)
• Stop the pumps
• Check for flow
• If well flows open the choke-manifold valve to allow flow to pit
• Close the BOP (usually the annular preventer)
• Close the choke slowly while watching casing pressure. (What
to do if MASP is exceeded should already have been discussed
and decided.)
• When the choke is closed allow a few minutes then record the
SITP.
• Record SICP
• Record the pit-level increase
Oil and Gas
Technology Program
Shut-in Procedure - II
• Surface BOP stack - Typical on land rigs
• Fluid is NOT being circulated
• Work string is OFF bottom
– Several different procedures are possible
– Important that everyone involved knows
ahead of time which procedures will be used
– Example procedure uses a soft shut-in
• Flow line through choke open
• Then shut in well
Oil and Gas
Technology Program
Shut-in Procedure - II
•
•
•
•
•
•
•
•
•
•
•
•
•
Set the work string on slips – sound alarm
Install and make up a full-opening safety valve in the work string (valve
should be in the open position)
Close the work string safety valve
Open the choke-manifold valve to allow flow to pit
Close the BOP (usually the annular preventer)
Close the choke slowly while watching casing pressure. (What to do if
MASP is exceeded should already have been discussed and decided.)
Install an inside BOP and release the valve on the work string safety
valve
Pick up and make up the kelly
Open the work string safety valve
Start the pump and open the inside BOP by increasing pressure slowly
in ¼ bbl increments (pressure should be linear with volume)
With the inside BOP open, record the SITP.
Record SICP
Record the pit-level increase
Oil and Gas
Technology Program
Hard and Soft Shut-in Procedures
• Often depends on the preference of the
operator
• Hard shut in means closing the BOP without
first opening the alternate flow path through
the choke line
– Hard shut in keeps the kick influx to a minimum
and simplifies the procedures
– Increases the likelihood of formation break down
• Soft shut in is the reverse
Oil and Gas
Technology Program
Hard Shut-in
• Choke and the remote choke-manifold (HCR), or failsafe,
valves are set closed during normal operations
• When a kick occurs
–
–
–
–
Close the preventer (adjust closing pressure as needed)
Open the HCR (or fail-safe valves)
Allow pressure to stabilize and then record SITP and SICP
Read and record the pit-level increase
• Casing pressure cannot always be recorded because the
choke-line valves are closed. May result in MASP being
exceeded without operator knowledge
• Hard shut in does NOT cause hydraulic hammer and
damage to the well bore even if gas is in the kick fluids
Oil and Gas
Technology Program
Soft Shut-in
• Choke is set full open during normal operations
• When a kick occurs
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Open the HCR (or fail-safe valves)
Close the annular preventer
Close the drilling choke
Adjust closing pressure on BOP
Allow pressure to stabilize and then record SITP and SICP
Read and record the pit-level increase
• More steps and more time
• Preferred to hard shut in by some due to inability to
read SICP
Oil and Gas
Technology Program
Kick Fluid Density and SICP
• Generally best to assume that the kick consists of gas
– Gas = 1.5 ppg to 3.0 ppg
– Oil = 5.0 ppg to 7.0 ppg
– Saltwater = 8.6 ppg to 10.0 ppg
• If the well is shut in on a gas kick SICP is generally greater
that a saltwater kick of equal volume
Where:
SICP =
FP =
HP =
Pf =
shut-in casing pressure
formation pressure
hydrostatic pressure from top of kick to surface
pressure of the kick fluid
Oil and Gas
Technology Program
Example:
TVD = 13,750 ft
Circulating fluid weight of 12.0 ppg
Annular volume = 0.0459 bbl/ft
Formation pressure = 9,180 psi
A 30 bbl kick occurs with gas having weight of 2.15 ppg
Pressure gradient of circulating fluid
Fluid rise from kick
Hydrostatic pressure of
remaining fluid
Pressure gradient of kick fluid
Hydrostatic pressure of kick fluid
Oil and Gas
Technology Program
Difference between gas and saltwater kicks
• As gas rises to surface it must expand as
pressure decreases
– SICP increases
– Pit level increases
• Saltwater does not expand as it comes to
the surface
– No appreciable pit level or SICP increase
Oil and Gas
Technology Program
Density estimate for kick fluids
Where:
Di
FW
SICP
SITP
L
Oil and Gas
Technology Program
=
=
=
=
=
density of influx, ppg
original fluid weight, ppg
shut-in casing pressure, psi
shut-in tubing pressure, psi
height of influx in the annulus, ft
Example:
Circulating fluid weight = 9.6 ppg
SITP = 400 psi, SICP = 700 psi
Pit gain is 15 bbl (volume of the kick)
Annular volume = 0.0231 bbl/ft
Fluid rise from kick
Fluid weight after influx
Density of kick fluid
Oil and Gas
Technology Program
SITP = 400 psi
SICP = 700 psi
9.6 ppg
8.89 ppg
649 ft
Oil and Gas
Technology Program
0.71 ppg