Offshore Gas Field Development Project Plan

Preliminary study of surface facilities concept selection to develop offshore gas field including cost estimate evaluation

1. Gas Field Development

2. 2
Basic
Engineering
Design Data
Preliminary Data:
•Wellhead flowing pressure: 500 psig
•Downstream pressure: 400 psig
•Temperature (max): 176 degC
•Condensate Rate: 600 BCPD
•Produced Water Rate: 1500 BWPD
•Gas production: 28 MMSCFD
•H2S content: 300-400 ppmv

3. 3
Basic
Engineering
Design Data
Key parameters that are necessary for the facilities to be designed, that shall be given to
the Contractor to enable them to perform FEED effectively:
•Wellhead
•Wellhead Shut-in Pressure (psig)
•Wellhead Shut-in Temperature oC
•Wellhead Flowing Pressure-Maximum (psig)
•Wellhead Flowing Pressure–Minimum (psig)
•Wellhead Flowing Temperature oC
•Gas Composition
•Component Properties: Normal Boiling Point, Molecular Weight, SG, Tc, Pc, Accentric
Factor, Volume Shift
•Wax data: Paraffin Wax Content, CloudPoint
•Other reservoir fluid contaminants:
•H2S (ppmv),
•CO2 (mole %)
•NaCl(g/L; ppmCl-)
•Mercury (ng/m3),
•Mercaptant(ppmv),
•Total Sulphur (max) (ppmv),
•Oxygen (ppmv).

4. 4
Basic
Engineering
Design Data
Key parameters that are necessary for the facilities to be designed, that shall be given
to the Contractor to enable them to perform FEED effectively
•Formation water analysis:
•Produced water properties:
•Appearance before filtration
•Appearance after filtration
•Total dissolved solids, mg/L (calc)
•Specific gravity @ 60degF
•Resistivity, ohm-metres(meas)
•Resistivity, ohm-metres(calc)
•Hydrogen SulphidePresent
•pH
•Nitrate (NO3), mg/L
•Produced water contaminants.
•Produced water flow rate.
•Sand production
•Gas production profile
•Gas pressure profile

5. 5
Main Facilities
Main Facilities to be Developed:
•Production Facilities
•Process Facilities
•Utilities
•Pipeline
•Cable
•Control and Monitoring
•Telcommunication

6. 6
Production
Facilities
Topsides
• 4 slots Well Head Platform (WHP): 2 wells installed initially
• Normally Unmanned Installation (NUI)
o No Living Quarters, day room (dog house) only
o No Firewater
• Access by boat, no helideck
• Platform Crane: Electric drive
• No processing
o Well Head Control Panel
o Chokes and manifolds
o Flowmeter
• Launchers and Receivers
o Export pipeline launcher, 8” to Process Facilities
• Drains and vent
o Closed drain drum
o Vent boom to enable blow down of platform piping
• Power via subsea Composite Cable
o Transformers (optional, if no offshore process facilities)
• Control/Communication via fibreoptic / satellite
o Subsea Composite Cable combined with power

7. 7
Production
Facilities
Fixed Wellhead
Platform
Jacket
•Braced Monopod
•30 m water depth
•Topside weight up to 800 tonnes
•4 well conductors
•8” risers or on connection bridge
•Composite Cable J-tubes
•Boat Landing

8. 8
Production
Facilities

9. 9
Process
FacilitiesNo. Equipment Capacity
1Separator (400-500 psig) 30 mmscfd
2Gas Dryer (Glycol/Solid Desiccant) 30 mmscfd
3H2S Removal (Amine/Solid Desiccant) 30 mmscfd
4Gas Compressor 30 mmscfd
5Custody Meter System 30 mmscfd
6Flare System and KO Drum 40 mmscfd
7Shutdown and Blowdown System 40 mmscfd
8Liquid Tank and Pump 1000 bbl
9Condensate Tank and Pump 500 bbl
10Flare System and KO Drum
11Power Generation c/w Switchgear and MCC
12Diesel Fire pump c/w jockey pump and fire water storage
13Produced Water Treatment and Disposal
14Potable water System
15Control and Monitoring System
16Telecommunication System
17Office Facilities

10. 10
Process
Facilities: Main
Equipment
Specification
PARAMETER VALUE
Equipment name Production Separator
Design Capacity 30 MMSCFD
Type Two-phase horizontal vessel
Design Pressure/Temperature600psig/ 300
o
F
Material CS Cladded
Production Separator
PARAMETER VALUE
Design Capacity 30 MMSCFD
Compressor Type Centrifugal/Reciprocated
Compressor Driver Type Gas Engine
Configuration 3 x 50%
Suction Pressure/temperature300-400 psig
Discharge Pressure/Temperature600-700 psig
Condition New or Refurbished
Gas Compressor

11. 11
Process
Facilities: Main
Equipment
Specification
Gas Dryer / Dehydration Unit
H2S Removal
PARAMETER VALUE
Design Capacity 30 MMSCFD
Dehydration UnitType Glycol/ Desiccant
Outlet Water Content 10 lb/mmscf
Design Pressure/Temperatur 600psig/300 F
Material Carbon Steel
PARAMETER VALUE
Design Capacity 25MMSCFD
H2SRemoval Type Amine / Desiccant
Outlet Water Content 10 ppm
Design Pressure/Temperatur 600psig/300 F
Material CS Cladded

12. 12
Process
Facilities: Main
Equipment
Specification
Flare Stack
PARAMETER VALUE
Design Capacity 40 MMSCFD
Operating Pressure/Temperaturatmosfer
Design Pressure/Temperatur 150 psig / 200 F
Material Carbon Steel
KO Drum
PARAMETER VALUE
Design Capacity 40MMSCFD
Operating Pressure/Temperaturatmosfer
Design Pressure/Temperatur 150 psig/200 F
Material Carbon Steel

13. 13
Process
Facilities: Main
Equipment
Specification
Liquid Tank
Condensate Tank
PARAMETER VALUE
Design Capacity 500bbl
Operating Pressure/Temperaturatmosfer
Design Pressure/Temperatur150 psig/200 F
Configuration 1 x 100%
Material Carbon Steel
PARAMETER VALUE
Design Capacity 1000bbl
Operating Pressure/Temperaturatmosfer
Design Pressure/Temperatur150 psig/200 F
Configuration 1 x 100%
Material Carbon Steel

14. 14
Process
Facilities: Main
Equipment
Specification
Utility Gas Scrubber
Instrument Air Compressor
PARAMETER VALUE
Design Capacity 5 MMSCFD
Operating Pressure/Temperatur300 psig/120
o
F
Design Pressure/Temperatur600 psig
Confguration 1 x 100%
Material Carbon Steel
PARAMETER VALUE
Design Capacity 125 scfm
Pressure 150 psi
Accessories
Air Filter, Air Dryer, Air
Receiver
Configuration 2 x 100%

15. 15
Process
Facilities: Main
Equipment
Specification
CastodyMeter
PARAMETER VALUE
Design Capacity 30MMSCFD
Design pressure/Temperatur600 psig / 200
o
F
Size 6”-300#
Configuration 2 x 100%

16. 16
Process
Facilities: Main
Equipment
Specification
Gas Engine Generator
PARAMETER VALUE
Rated output 650 kVa
Rated voltage 380 V –3 phase
Rated frequency 50 Hz
Power factor 0.8 at rated load
Rotating speed 1500 rpm
Enclosure protection IP 55 andIK 08
Cooling system
CACA (Closed Air Circuit
Air Cooled)
Neutral connection
Unearthed (insulated)
neutral

17. 17
Process
Facilities: Main
Equipment
Specification
Switchgear and MCC
PARAMETER VALUE
Admissible short circuit current (kA
rms/1 sec)
65
Rated peak withstand current (kA
peak)
143
Assigned horizontal bus bar 1600
Assigned operating voltage (V)380
Rated insulation voltage (V
1000 for main circuit
500 for auxiliary circuit
Neutral point arrangement IT
Material and finish of horizontal bus
bar
Cu-Tinned busbar

18. 18
Gas Treatment
Facilities
Onshore Process Facilities

19. 19
Gas Treatment
Facilities
Fixed Process Platform
Jacket
•30 m water depth
•Connection bridge to WHP
•8” risers
•Composite Cable J-tubes
•Platform Crane
•Boat Landing

20. 20
Gas Treatment
Facilities
Dual Braced Monopod Process Platform
•Dual braced monopod jacket
•1200 tonnestopside weight
•25 meter water depth

21. 21
Gas Treatment
Facilities
Floating Gas Process Barge / Floating Production Unit

22. 24
Onshore
Receiving
Facilities
1.Manual pipeline isolation valve
2.Gas pipeline ESD valve
3.Pig receiver
4.Dual parallel pressure letdown valves
5.Particle filters with a bypass
6.Gas metering skid with dual gas chromatographs,
moisture analyser, and hydrocarbon dewpoint
analyser
7.Local gas vents
8.Diesel emergency generator and diesel storage
9.Fresh water Storage
10.Control/flow computer building

23. 25
Subsea
Pipeline:
Scope of Work
•5.2 km subsea pipeline 8” from offshore facilities to onshore (ORF),
including tie-in spools and risers
•2.6 km onshore underground pipeline 8” to ARAR plant.
•Based upon a pipeline design pressure of 600 psig and a H2S content of
300ppm, the process conditions in the pipeline can be defined as sour and
it is mandatory to undertake the precautions detailed in NACE MR 0175/
ISO 15156 for the avoidance of SSC.
•Subsea pipeline: in accordance with recent Indonesian Statutory
Regulation, Ministry Regulation from HUBLA, Article 45, PM No-68/2011,
pipelines and cables shall be buried based on the water depths. This
regulation only applies if the pipelines/cables cross or routed parallel to the
boundary of a shipping channel.

24. 26
Subsea
Pipeline:
Scope of Work
•Shore Approach: crossing method is by HDD. The HDD offshore exit is
proposed to be at LAT (Lowest Astronomical Tide)-12 m. In accordance
with Indonesian Statutory Regulations, Decree of Minister of Mines and
Energy No. 300 K/38/M.PE/1997, pipelines shall be buried with a minimum
cover of 2 meters T.O.P between water depth -13 m LAT and shoreline.
•Onshore pipeline includes:
•The pipeline section, between the offshore/onshore tie-in point and
the ORF tie-in weld immediately upstream of the Onshore ESDV;
•The pipeline section, between the ORF tie-in weld immediately
upstream of the Onshore ESDV and the onshore pig receiver.
•The piping section, between the barred tee and the face of flange
upstream of the first MOV in the production line to the ORF.

25. 27
Subsea
Pipeline: Key
Elements
Parameter Details
Steel Pipe Flex pipe
From Offshore Facilities Offshore Facilities
To Onshore Onshore
Nomina dia 8 inch 6 inch
Subsea pipeline IDThe entire pipeline, offshore and onshore, including
risers and tie-in spools shall have a constant internal
diameter.
The entire pipeline, offshore and onshore, including risers
and tie-in spools shall have a constant internal diameter.
Pigging facilitiesPermanent launchers/receivers will be installed for
pipeline.
N/A
Crossing Proposed pipeline will cross existing pipelines (if any)
in the HDD section.
Proposed pipeline will cross existing pipelines (if any) in the
HDD section.
Burial status Trenched and buried pipeline is considered as base
case. The extent of burial and rock berm requirements
(if any) is to be determined. T.O.P between water
depth -13m LAT and HDD exit.
Trenched and buried pipeline is considered as base case.
The extent of burial and rock berm requirements (if any) is
to be determined.
HDD method The shore approach shall use HDD method. The shore approach shall use HDD method.
Tie-in method A Graylocor similar hub connection between the ESDV
and the riser. Conventional flanged tieinspool pieces
between the pipeline to the riser at the platform.
A Grayloc or similar hub connection between the ESDV and
the riser. Conventional flanged tiein spool pieces between
the pipeline to the riser at the platform.
Internal corrosion
protection
API Sour Pipe / Internal cladding / Chemical (corrosion
inhibitor, O2 scavanger, H2S scavanger)
N/A
External coating Riser: Splash zone (up to the hanger flange) with
monel, below the splash zone 3LPP, above hanger
flange as per offshore painting specification. The
subsea pipeline with 3LPP plus concrete. HDD section
without CWC except for HDD tail section. The above
ground pipeline will be as per offshore painting
specification.
N/A

26. 28
Subsea
Pipeline: Key
Elements
(Cont’d)
Parameter Details
Steel Pipe Flex pipe
Supplementary
protection
Any requirement for supplementary protection to the
pipelines against accidental loading caused by abnormal
and unplanned conditions including dropped objects,
trawling, dragging, anchors and any other credible
threats identified
Any requirement for supplementary protection to the
pipelines against accidental loading caused by abnormal
and unplanned conditions including dropped objects,
trawling, dragging, anchors and any other credible
threats identified
CP isolation No CP isolation is planned between the risers and
platforms. A CP isolation joint will be installed between
the HDD section (buried section) and the above ground
onshore pipeline
N/A
Cathodic protectionAluminium alloy (Al-Zn-In) bracelet anode will be
employed in the offshore section. HDD section will be
cathodically protected by an impressed current CP
system
N/A
Offshore installation
method
Pipeline installation will be by the S-lay method using a
conventional lay barge.
Flex pipe laying barge
Onshore installation
method
Onshore pipeline construction will utilize conventional
onshore/above ground piping construction techniques
Onshore pipeline construction will utilize conventional
onshore/above ground piping construction techniques
Passive fire protection Riser sections above +2.4m elevation level (LAT) will be
coated with PFP.
N/A

27. 29
Subsea
Pipeline:
Design Code
•Pipeline System Design Code:

28. 30
Subsea
Pipeline:
Scope of Work

29. 31
Subsea
Pipeline:
Linepipe
Material
•According International regulation: When partial pressure of H2S reaches
300 Pa (0.0435 psig), the line pipes used shall have the anti-acid corrosion
performance. Sour service pipe includes NACE pipe.

30. 32
Subsea
Pipeline:
Linepipe
Material
Notes: North Selegas
H2S partial pressure =
140 kPa(high sour
service)

31. 33
Subsea
Pipeline:
Linepipe
Material
Steel Pipe

32. 34
Subsea
Pipeline:
Linepipe
Material
Steel Pipe

33. 35
Subsea
Pipeline:
Linepipe
Material
•API pipe that refer to NACE MR0175 standard: API Sour Pipe (API X65 QS
(seamless), API X65 MS (welded), etc).
•13% Cr Martensitic Stainless Steel: high risk of hydrogen embrittlement, pitting
resistance if seawater ingress occurs and corrosion resistance if the external
coating and CP are not fully 100% effective. Inter-Granular Cracking (IGC) is also
a potential problem.
•22% Cr Duplex Stainless Steel still has some risks of:
•SulphideStress Cracking (SSC)
•Hydrogen embrittlement
•Chloride Induced Stress Corrosion Cracking (CSCC)
•25% Cr Super Duplex Stainless Steel offers improved corrosion resistance.
•Nickel Alloy 625 (UNS N06625) / Inconel 625: has excellent resistance to pitting
and SCC in the presence of elemental sulphurand chloride in a sour
environment
•Alloy 825 (UNS N08825): cannot be considered a seawater resistant alloy. In the
presence of elemental sulphurit is subjected to extensive pitting and maybe
subjected to environmental cracking at higher temperatures.
Steel Pipe

34. 36
Subsea
Pipeline:
Linepipe
Material
•Corrosion Resistance Alloy DP8 (UNS S31803)
•Corrosion Resistance Alloy DP3W (UNS S39274)
Notes: North Sele
gas H2S partial
pressure = 0.14
Mpa(out of range)

35. 37
Subsea
Pipeline:
Linepipe
Material
•Not all manufacturer recommends fleixiblepipe for new subsea pipeline installation.
•Composite pipeline systems use metal-free fittings, couplings and connectors. To be
resistant to corrosive condition.
•Pipes are stabalizedon the seabed using locally manufactured steel or concrete
blocks. These blocks are easy to handle and manufacture, and make sure that the
pipe is securely ancheredon the seabed. For example, they can also be stabalizedon
the seabed using an old steel cable.
•Needs precaution and protection where there is significant risk of damage to the
linepipefrom ship anchor or fishing activity.
•If water depth exceeds 164 ft(50 m),
•Keep the pipeline filled / internally pressurized to avoid collapse due to high
hydrostatic pressure.
•Use high grade product that can be used unfilled at a maximum depth of 80
metres/260 feet.
•Use external thermoplastic jacket that can be provided as a special order to
ensure collapse resistance from hydrostatic pressure when the pipe is not
internally pressurized.
Flexible Linepipe

36. 38
Subsea
Pipeline
Flexible Linepipe
Source:
Soluforce
NOV Fibrespar

37. 39
Subsea Cable:
Key Elements
Parameter Details
From Offshore Facilities
To Onshore
OD 73mm, to be confirmed by Contractor
J-Tube NPS 14” pipe (356mm), API 5L Gr. B with 25mm thickness from top
to mid and 13mm thickness from mid to bottom end of J-tube.
Configuration Subsea cable consists of 48 x 2 single mode fibre optic cables,
3cores x 95mm
2
electric cable and 3cores x 6mm
2
control cables.
Submerged Weight 67.7 N/m, to be confirmed by Contractor
Crossing The subsea cable routes have been engineered to avoid crossing the
proposed pipeline routes adjacent to each platform. At the HDD
section, the new subsea cables will cross below the existing
pipelines and cables with a minimum vertical separation of 20m.
Burial Status The subsea cable will be trenched and buried along the entire cable
route for stability and protection purpose. The target offshore trench
depth will be determined during FEED.
HDD The shore approach shall use HDD method and the route shall follow
pipeline shore approach crossing method. Cable will be pulled
through a pre-installed HDD conduit, NPS 10” pipe, API 5L Gr.B with
12.7mm thickness.
Offshore Installation Method Subsea cable will reel-lay from the installation vessel.
Tie-in Method / Termination Subsea cable offshore termination will be at the splitter box located
Point in the platform cellar deck with cable length approximately 15m from
top of J-tube.
At the onshore end, the subsea cables will be terminated at the
respective onshore splitter boxes located close to the HDD entry
points. From the onshore splitter box, separate cables (power,
communication & control cables) will be routed on cable trays up to
the termination unit inside ORF.
Supplementary Protection Any requirement for supplementary protection to the cables
against accidental loading caused by abnormal and unplanned
conditions including dropped objects, trawling, dragging anchors and
any other credible threats identified during FLRA will be assessed in
FEED.

38. 40
Cost Estimate
The scope of work for this estimation is:
•To provide a preliminary cost estimate:
•Production Facilities
•Process Facilities and Utilities
•Pipeline and Cable
•Mob / Demob
•Decommissioning
•FEED
•The estimate includes all engineering, procurement, fabrication,
installation, onshore and offshore precommissioningand contractors
project management for this scope.
•The base cost is made up of procurement, labour, and installation
equipment plus allowances for engineering, project management;
insurance, weather downtime etcadded as a percentage of the base
cost.
•Contractor’s contingency has been added to the bottom line. The
contractor’s contingency includes design growth allowances and
allowances for unknowns

39. 41
Cost Estimate

40. 42
Production
Facilities:
Platform
Wellhead Platform
•Braced Monopod JacketWeightUnitRemarks
Installed
Cost
USD/ton
Installed
Cost (USD)
1JACKET:
1.1Jacket (Braced Monopod) 315tonnes
1.2Pile 700tonnes
Subtotal Jacket Weight: 1015tonnes 15.000 15.225.000
2TOPSIDE:
2.1Deck 295tonnes 65%
2.2Equipment 78tonnes 17%
2.3Bulk, Piping, E/I 70tonnes 15%
2.4Building 12tonnes 3%
Subtotal Topside Weight: 455tonnes 44.000 20.020.000
Raw Weight: 1470tonnes Net Cost: 35.245.000
Weight Growth Factor 20% 20%
Est Installation Weight 1764tonnes Gross Cost: 42.294.000
Decommissioning 3.000 4.410.000
Note: excluding mob/demob

41. 43
Process
Facilities:
Platform
Process Platform
•Tripod / 4 LegWeightUnitRemarks
Installed
Cost
USD/ton
Installed
Cost (USD)
1JACKET:
1.1Jacket (Tripod or 4 leg)1200tonnes
1.2Pile 1000tonnes
1.3Bridge 100tonnes
Subtotal Jacket Weight: 2300tonnes 15.000 34.500.000
2TOPSIDE:
2.1Deck 600tonnes 46%
2.2Equipment 400tonnes 31%
2.3Bulk, Piping, E/I 200tonnes 15%
2.4Building 100tonnes 8%
Subtotal Topside Weight:1300tonnes 44.000 57.200.000
Raw Weight: 3600tonnes Net Cost: 91.700.000
Weight Growth Factor 20% 20%
Est Installation Weight 4320tonnes Gross Cost: 110.040.000
Decommissioning 3.000 10.800.000
Note: excluding mob/demob

42. 44
Fleet
Mobilization /
Demobilizatio
nMobilization USD/day USD
Lay Barge 16days300.000 4.800.000
Support Vessel 16days 40.000 640.000
Hookup Barge 16days150.000 2.400.000
Rock Dump Vessel 16days150.000 2.400.000
Trenching Spread 16days 15.000 240.000
Cable Lay Vessel 16days250.000 4.000.000
Net Total Cost 14.480.000
Insurance and Certification3,50% 506.800
Project Management 5% 724.000
Growth Allowance 20% 2.896.000
Gross Total Cost 18.606.800
Note: Singapore - Papua:2100nautical miles
Speed: 5knots 5,75miles/hour
Demobilization: 18.606.800

43. 45
PipelineCS X65 Pipeline
Dia. (inch)Length (m)Cost (USD)
Material Service
Pipeline 8
Subsea Pipeline 20 118 49005.393.920
HDD Crossing 20 171 300457.440
Rock Dumping 49003.920.000
Onshore Pipeline 20 80 28602.288.000
Net Total: 12.059.360
Length Growth Factor: 20%
Gross Total: 14.471.232
Installed Cost
(USD/inch/m)
100

44. 46
PipelineCS X65 Pipeline (Condensate)
Dia. (inch)Length (m)Cost (USD)
Material Service
Pipeline 6
Subsea Pipeline 20 118 49004.045.440
HDD Crossing 20 118 300247.680
Rock Dumping 49002.940.000
Onshore Pipeline 20 80 28601.716.000
Net Total: 8.949.120
Length Growth Factor: 20%
Gross Total: 10.738.944
100
Installed Cost
(USD/inch/m)

45. 47
PipelineX65 / 625 Inconel Clad Pipeline
Dia. (inch)Length (m)Cost (USD)
Material Service
Pipeline 8
Subsea Pipeline 246 168 490016.228.800
HDD Crossing 246 221 3001.120.800
Rock Dumping 49003.920.000
Onshore Pipeline 246 80 28607.458.880
Net Total: 28.728.480
Length Growth Factor: 20%
Gross Total: 34.474.176
100
(USD/inch/m)
Installed Cost

46. 48
PipelineFlex Pipeline
Installed Cost Dia. (inch)Length (m)Cost (USD)
Pipeline (USD/inch/m) 6
Subsea Pipeline 4900 -
HDD Crossing 300 -
Rock Dumping 0 -
Onshore Pipeline 2600
Net Total: -
Length Growth Factor: 20%
Gross Total: -

47. 49
CableComposite Cable (Power & FO)
Installed Cost Length (m)Cost (USD)
Cable (USD/m)
Composite Cable
(Power & FO) 638 52003.317.600
Onshore Cable 200 2600520.000
Net Total: 3.837.600
Length Growth Factor: 20%
Gross Total: 4.605.120

48. 50
Scenarios
ComparisonWHP Platform WHP Platform WHP Platform WHP Platform
Construction 42.294.000 Construction 42.294.000 Construction 42.294.000 Construction 42.294.000
Decommissioning4.410.000 Decommissioning4.410.000 Decommissioning4.410.000 Decommissioning 4.410.000
Process Platform Onshore Gas Plant Onshore Gas Plant Small FPU
Construction 110.040.000 Construction Construction Construction
Decommissioning10.800.000 Decommissioning Decommissioning Decommissioning
CS Pipeline Gas 14.221.632 CRA Pipeline 33.660.480 Flex Pipeline CS Pipeline Gas 14.221.632
CS Pipeline
Condensate 10.551.744
CS Pipeline
Condensate 10.551.744
Cable 4.605.120 Cable 4.605.120 Cable 4.605.120 Cable 4.605.120
Mob/Demob 37.213.600 Mob/Demob 37.213.600 Mob/Demob 37.213.600 Mob/Demob 37.213.600
FEED 11.706.805 FEED 6.109.160 FEED 4.426.136 FEED 5.664.805
TOTAL: 245.842.901 128.292.360 92.948.856 118.960.901
Option 1 Option 2 Option 3 Option 4
Note: Offshore gas process facilities (Option 1 and 4) shall provide longer gas well
production period by enabling gas compression adjacent to the wells when well
pressure is already declined.