Trapped Annular Pressure

Trapped Annular Pressure:
A Spacer Fluid that Shrinks (Update)
Ron Bland, Ron Foley, Floyd Harvey, Baker Hughes Drilling
Fluids, Ben Bloys, Many Gonzales, Chevron, Robert Hermes,
Los Alamos National Laboratory, John M. Daniel, Floyd
Billings, Ian Robinson, Lucite International, Marlon Allison,
Flow Process Technologies, John Davis, Terry Cassel, Baker
Oil Tools

What is Trapped Annular Pressure?
(or Annular Pressure Buildup)
•When cement is not
circulated back to surface,
drilling fluids or spacers
become trapped in the
annulus between the top of
cement and the wellhead
•Heat from produced oil/gas
/water causes thermal
expansion of these trapped
annular fluids and can create
more than enough pressure
to collapse casing and tubing
strings

From SPE 89775 - Pattillo, et al

What is Trapped Annular Pressure?
• Mostly an issue in subsea
completed wells
• Previous mitigation techniques
include VIT, heavy walled casing,
nitrogen-based spacers, burst
disks, crushable foam, leaving
cement short of shoe, etc.

A New Approach
• Cooperative research between Chevron and Los Alamos
National Lab led to the development of a shrinking
spacer based on methyl methacrylate (MMA)
• MMA is a liquid monomer that polymerizes to form many
familiar items like plastic windows and acrylic
paperweights, and is the active ingredient in many latex
paints
• MMA shrinks 20% as it changes from emulsified liquid
MMA droplets to tiny solid poly-MMA particles

Trapped Annular Pressure
Shrinking Spacer (TAPSS) Formulation
• MMA is emulsified into a standard water-based spacer at
10–50%
•Water
•Biopolymer (for viscosity)
•Barite (1 st test – 12 ppg)
•Emulsifiers
•MMA (1 st test - 28%)
•Defoamer
•Inhibitor
•Initiator (added as spacer is pumped)
•Bicarb & caustic
•Dispersant

TAPSS Preparation Overview
MMA Monomer
Initiator
Solution
Metering
Mixer
MMA/WBM Emulsion
Transported
to Wellsite
Metering
Mixer
Pump
Downhole
Water-Based Mud

Mid-Scale Field Trial
• Test site in Bossier City,
LA had a 500-ft, cased well
• Built an annulus from 7” 7
and 9-5/89
5/8” casing, with 3-3
1/2” pipe within for hot
water injection
• Pressure tested

4500
Test Results
Trapped Annular Pressure Mitigation
TAPSS vs. Standard Spacer
4000
3500
Annulus Pressure - psi
3000
2500
2000
1500
1000
Polymerization begins
Standard Spacer
500
TAPSS
0
0 20 40 60 80 100 120 140 160 180
Minutes of Annulus Heating

TAPSS After Reaction
Thicker, but still liquid with 28% Poly-MMA

Compatibility with Drilling Operations
• Elastomers
OK
OK
OK
Buna ® (butadiene nitrile)
Viton ® (fluoroelastomer)
Urethanes
• Contamination with Cement – OK
• Contamination with KCl, NaCl or CaCl2 – OK
• Contamination with SBM – OK
• Contamination with standard cement spacer - OK

Off–Shore Procedure
• Shipped to rig in closed-top, vented tanks
• Tank(s) spotted on rig (watch wt. limits)
• Mixed with initiator solution just before going
down hole (initiator is a 5-7% feed)
• Pumped down hole using cement unit, or
similar
• Should not mix with mud system, but 15%
contamination in SBM only moderately reduces
LC50

Safety Issues
• Detailed risk analysis/mitigation process
• Pure MMA has a low flash point - 55 º F, similar to
methanol - only handled in mud plant
• The emulsified spacer has an open cup flash point of
175 º F
• Fumes can accumulate in tank head space and
become a risk (grounding)
• Plan to use the pumping unit to flush water back
through lines and pump skid to original tank

Safety Issues, cont.
• Tank bottoms, wash water, etc. will be treated
with a ‘hot’ initiator to eliminate any unreacted
MMA
• Proper PPE will be specified
• Drips pans under all connections
• Absorbents for small spills
• Surfactants make the LC 50 low, as expected – so
no offshore disposal

Detailed Operations & Safety Plans

Land Test – Carthage, TX
• A quick land trial was held in a
tubing annulus to provide a full
scale test of:
– Safety protocols
– All mixing/metering equipment
and manifolds
– Pumping, and clean-up
procedures
– Initiator behavior

Spacer Mixing Skid
• Meter in
MMA
• Emulsify in a
single pass
• Pump to
transport
tank
MMA in
High Shear
Mixer
Spacer to Tank
Mud in

Manifold

Initiator Addition Skid (rig)
• Meter in
initiator
solution
• Mix well
with spacer
• Charge
main
pumping
unit
Mud in
Initiator in
Mixer
Out to pump
unit & well

Initiator Tank and Addition Skid

Wellhead Pressure vs. Time
1200
1000
Pressure (psig) at manifold
800
600
400
200
0
0 10 20 30 40 50 60
Time (minutes)

Polymerization vs. Depth
% conversion of
monomer to polymer
120
100
80
60
40
20
0
0 1000 2000 3000 4000 5000 6000 7000 8000
Vertical Depth (feet)

Clean-Up Flushing Effective

Results
• All fluids accurately mixed and well emulsified
• Smooth displacement into well
• Pressured to 1000 psi
• Shrinkage occurred as expected (sampled
during well cleanout):
– Bottom of well (240° F) – hotter than St. Malo
production temperature – reacted quickly
– Top of well – similar temperature to St. Malo
annulus – virtually no reaction
• All equipment cleaned by flushing with rinse
water back to original tank
• No HSE incidents

Preparing for a Deepwater Trial
CVX producing properties - GOMBU
Projects – CVX Op
Projects – Non Op
Discoveries – CVX Op
Petronius
Discoveries – Non Op
Exploration Wells
Gemini
Tahiti #7
10¾” tieback annulus
Q2’09
Tubular Bells
Genesis
Blind
Faith
Cat. Deep
Tahiti
Knotty Head
Great White
Tiger
Tonga
Puma
Big Foot
Discoverer
Deep Seas
Silvertip/Tobago
Trident
Jack
St Malo
Appraisal Projects

Planning a TAPSS Application:
Determine the extent of the problem
1. Model temperatures and pressures in trapped
annulus
– During seal formation
– Maximum during flow testing/production
– Geothermal and hydrostatic
2. Compare the above with casing and seal
assembly ratings to determine the minimum
pressure reduction needed during flow
testing/production to stay within casing/seal
assembly ratings

Planning a TAPSS Application:
Is TAPSS a feasible solution?
3. Calculate fluid volume shrinkage needed at
maximum flow test temperatures/pressures to
achieve pressure reduction in ‘2. 2.’ above
4. Using new fluid volume and pressures from ‘3. 3.’
above, calculate shut-in pressures under
geothermal conditions
5. Are shut-in pressures using new fluid volume
within casing/seal assembly ratings?
6. If no, TAPSS may not be a feasible solution for
well design/flow test schedule

Tieback Example with 16” Liner
Example Deepwater Casing Diagram
Drilling Schematic
Well: Subsea Completion #1 Rig: BA Drillship #1
Mudline Location:
WBS No.
API Well Number:
BHL Location:
Latitude/Longitude.:
RT to MSL (ft): ±90'
OBJECTIVES: Water Depth (ft): ±7000
DIRECTIONAL: Straight Hole
RT to ML (ft): ±7000'
18-3/4" HPWH @ -16' 16' AML
38" Housing @ -12' 12' AML
EVAL GEOLOGIC MARKERS HOLE CASING MUD LOT
PROG OBJECTIVES MD TVD SIZE & CEMENT MW OBG/FG
±7400'
16" LS @ ±7,400
MWD/LWD t/ TD ±300' MD
36" Jetted to ±300' BML
±300' BML
26" Hole
TOS @ 8,509'
8,509' BML
±8800' MD
' BML
TVD
±8800'
10 3/4" X 9-7/8" CROSSOVER @ +/- 9,500'
22" to ±8800'
500' Tail, TOC @ Mud-line, 200% OHE
±17000 MD
TVD
17,000'
13-5/8" TOL @ < 17K'
16"to ±17000'

Planning a TAPSS Application:
Determine extent of pressure relief possible
7. If yes, TAPSS may be a feasible solution and
additional pressure relief may be possible
– Try increasing pressure reduction in ‘A’ above
– Recalculate fluid volume shrinkage required
– Recalculate shut-in pressures under geothermal
conditions using new volume
– Compare with casing/seal assembly design
ratings
– Continue iterations until casing/seal assembly
design ratings are reached

Planning a TAPSS Application:
Determine Fluid Details
8. Calculate trapped annulus volume capacity
9. Adjust for other fluids planned for annulus
10. Difference is maximum TAPSS volume possible
11. What is the desired TAPSS density as pumped
downhole?
12. Calculate TAPSS density as shipped allowing
for initiator dilution
13. Determine maximum tank loading based on
empty tank weight, TAPSS density & rig deck
load limit
14. Calculate number of tanks needed

Planning a TAPSS Application:
What are rig constraints?
15. Choose TAPSS staging area based on:
– Space
– Utility access
– Deck load limit
– Evacuation
– Cement pump if pump is on top deck
16. If cement pump on a lower deck a small HP
pump will probably be needed such as a gravel
pack pump

Thanks to:
• Management of Chevron, Los Alamos
National Laboratory, Baker Hughes Drilling
Fluids, Baker Oil Tools, Flow Process
Technology and Lucite International for
permission to present this work.
• IADC and the Programme Committee for
accepting our abstract

Happiness is No Annular Pressure
Questions?