K10-B Case History

Offshore well abandonment
with HWO unit
K10-B Platform – North Sea
K10-Bravo Platform History
• Platform located in Dutch sector of North sea
• Well depths from 1738 to 4300 mAH
• Depleted Gas Wells
• Two wells drilled in 1981
• Six wells drilled in 1983
• Two infill wells drilled in 1987 and 1989
• Eleventh well drilled in 1996
• Production shut down due to depletion of the
gas reservoir in 2001
• Gas processing facilities removed from platform
in 2003
Project objectives
• Plug and Abandon 11 wells – as per Dutch Mining Regulations
• Remove Production Tubing
• Isolate reservoirs with Cement plugs (> 50m length)
• Isolate well incl. Annulus at each Casing shoe depth with
cement plug. Perforate or mill window in the casing to ensure
comprehensive plug.
• Remove wellhead. Cut and retrieve all Casings (6m or more below
seabed).
Project Objective
Before P&A
After P&A
4-phase P&A approach
• Phase I: Evaluation of well integrity incl. Cement Bond Logs. Setting
of temporary plugs in preparation for abandonments work. Evaluation
of surface facilities.
• Phase II: Retrieve completion. Set plugs compliant to regulatory
requirements.
• Phase III: Preparations for removal of Casing and Conductors. Install
Lifting lugs to upper Casing sections to accommodate lifting of Casings
and Conductors.
• Phase IV: Wellhead removal, casing/conductor cutting 6 m below
seabed. Cut elements are lifted 1 m for confirmation and set back for
removal by heavy lifting vessel in combination with platform removal.
4-phase P&A approach
• Phase I: Evaluation of well integrity incl. Cement Bond Logs. Setting
of temporary plugs in preparation for abandonments work. Evaluation
of surface facilities.
• Phase II: Retrieve completion. Set plugs compliant to
regulatory requirements.
• Phase III: Preparations for cutting and lifting cemented casing and
conductors. Lifting pad eyes are welded to accommodate lifting of
conductors.
• Phase IV: Wellhead removal, casing/conductor cutting 6 m
below seabed. Cut elements are lifted 1 m for confirmation and
set back for removal by heavy lifting vessel in combination with
platform removal.
Equipment choice
Jack-Up Rig
Hydraulic Workover Unit (HWU)
• Independent of Platform
facilities
• Dependent of Platform
facilities
• High dayrate
• Low dayrate
Size comparison
Jack-up Rig
HWO unit
Small
Hydraulic Workover (HWU) Approach
Preparation for HWU - Considerations
• Deck space
• Platform Crane capabilities
• Accommodation – Bedspace
• Quick skidding between wells
• Pipe handling
Space Saver II (HWU)
Top view platform – Crane capabilities
10 mT SWL (Former 16T crane)
Production platform
Wellhead platform
Target wells
10 mT crane
10 mT crane
Accommodation limits
• K10-B Platform living quarter limited to 24 beds
SOLUTION:
• Upgrading Accomodation.
• Multi-disciplinary HWU crew of five personell per
12 hour shift. Able to perform both HWU duties as
all required pumping and cementing.
• Technical Advisors present to advice on cementing,
fishing, etc
• Sufficient bed space for core rig
crew, additional service companies
and company representatives
Skidding system
Skid frame
• Allows Rigging Up the unit within the
load-range of the Crane
• Allows moving the HWU between wells
rapidly without Rigging Up/Down
• Includes guy wires to secure the HWU
HWU rigged up on skidding system
Tubular handling characteristics
• 2 x 2,5T CB Winches / 1x 5T Main
winch
• Handling Single Joints only
• Dual Counter-Balance winches to
increase tripping speed
• Flexible – system adapts easily to
geometrical changes to the set-up
• No complicated machinery
• Reliable – Almost zero NPT
Execution phase II – Well isolation/setting plugs
NOTICE: The steps below are only for indication and do not reflect the
complete abandonment program. Steps can be different between wells
Objective
Work. Depth
Method
Isolate Reservoir by setting
Cement plug [#1] on the
Packer tail-pipe assembly
Pull up 5” completion and
set cement plug on top of
2600–2900 [m] permanent plug in packertailpipe assembly and
pressure test
Isolate Reservoir by setting
Cement plug [#2] at 9-5/8”
Casing Show depth
2000–2200 [m]
Isolate Reservoir and 7” X
9-5/8” Annulus by setting
Cement plug [#3] at 133/8” Casing Show depth
Punch holes in 7” Casing
1200–1300 [m] using Wireline. Spot viscous
pill. Set and test cement plug
Spot viscous pill and Set and
test cement plug.
Execution phase II – Internal Casing Removal
Objective
Work. Depth
Method
Cut and retrieve 7-5/8”
Casing
180–200 [m]
Wireline Jet Cutter / Pick up
Csg with 7-5/8 ITCO Spear
Cut and retrieve 9-5/8”
Casing
130–150 [m]
Wireline Jet Cutter / Pick up
Csg with 9-5/8 ITCO Spear
Cut and retrieve uncemented
13-3/8” Casings
120–130 [m]
Wireline Jet Cutter / Pick up
Csg with 13-3/8 ITCO Spear
180–100 [m]
Spot viscous pill. Set and test
cement plug.
Set final cement plug (#4)
Results phase II
All 9 wells were successfully plugged. All cement plugs were tested OK
during the first test.
Phase II (9 wells) was completed in 74 days (Incl; waiting on weather, parts,
maintenance, etc / Excl; Rig Up/Down time).
Average time to complete a well was 8 days
Total Rig Up/Down time was 9 days (incl. installation of substructures, etc)
ZERO INCIDENTS & ACCIDENTS!
Execution phase IV – Casing Conductor Removal
Objective
Cut and retrieve
cemented 20” and 30”
Casing in one cutting
operation Casing
Depth
6 [m]
below
seabed
Method
•
Mechanical Csg Cutter on 5” drillpipe
•
Pick up Csg with special made lifting
flange
•
Special hydraulic operated pretensioning
system during mechanical cutting
operation
•
100 mT Pre-tension during cutting
•
Lifting casing section 1 m to confirm
proper cutting before rigging down
•
For two wells also the 36” Conductor was cut togehter with the 20” and 30”
•
In case the 13-3/8”casing was cemented in the 20” at planned cutting
depth also the 13-3/8”casing was cut together with the 20 and 30”csg
Tensioning system
HWU
Cutting a window on the 30” conductor
and 20” casing mechanically, poses a risk
to the instruments used; the weight of the
components might crush the blades of the
downhole cutter tool.
Applying pre-tensioning force on the
casing relieves the blade cutters from
casing/conductor weight.
Platform
Deck
Clear indication a successful cut by lifting
Casing up for 1 m
Pretension
Assembly
Well Head
Pretensioning cylinder assembly
Tensioning system
Pretensioning cylinder assembly
Cutted 9-5/8 & 13-3/8 casing section
Results phase IV
All casings and conductors were successfully cut.
In few occasions cutting the 30” required more time than
planned. Inflow of pebbles/stones was found to be the
main cause.
Successful cut casings and conductors were left behind
waiting for the heavy lift vessel to pick them up and ship
them onshore.
9-5/8” and 13-3/8” were removed from the well direct
after cutting using the platform crane.
ZERO INCIDENTS & ACCIDENTS!
Comparison Jack-up/HWU – Workscope
Wells
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B11
Phase 1
Phase 2
Phase 3
Phase 4
Performed by HWU
Performed by Jack-up Rig
Comparison Jack-up/HWU -- Cost analyze
Chart below shows the cost impact on the budget by both the Jack-up
and HWU
Chart is based on the table given above which shows how all work was
divided between the HWU and Jack-up Rig
14,7% of the original Budget was safed
14.7
HWU 9/11 wells
29.7
55.6
Jack up 2 wells
Remaining budget
Comparison Jack-up/HWU – cost per well
The “cost per well” has been calculated based on:
•
the assumption that the workscope and workload of all wells is the same
•
the planned time to complete a well-phase is the same for Phase II and
Phase IV
•
Rig Up/Down and mobilisation costs for both the HWU and the Jack-up rig
are taken into acount and included in the cost
•
Upgrade accomodation on the platform has not been included in the costs.
Calculation:
Total Operations = 22 (phase II and phase IV counted as seperate operations)
Jack-up performed 2 operations  Cost 29.7%  29.7/2*2=29.7% per well
HWU performed 20 operations  Cost 55.6%  55.6/20*2= 5.6% per well
Comparison Jack-up/HWU -- Cost analyze
Cost per well (Phase II & IV)
Given in % of the total Budget
35
30
25
20
JackUp Rig
%
15
29.7
HWU
10
5
5.6
0
JackUp Rig
HWU
Conclusion – HWU operation
HWU was successfully used to Plug & Abandon 9 offshore wells
Rigless P&A prooved to be a economical solution
All operations were carried out with ZERO INCIDENTS & ACCIDENTS
Good project preparation and experience are key factors for success
HWU proofed to be capable of working on small platforms with limited
bedspace, deck space and crane capacity
General Conclusion
Both the Jack-up Rig and the Hydraulic Workover Unit (HWU) have
proofed to be both suitable for Plug & Abandonment Operations.
HWU has proofed to be a very economic attractive and safe solution for
P&A operations.
stefan.vonderheide@bpc.nl
chris.dontje@bpc.nl
Questions?