The Use of Stability Maps The Use of Stability Maps in the Design - PowerPoint PPT Presentation

The Use of Stability Maps The Use of Stability Maps in the Design and Operation of in the Design and Operation of Gas- -Lift Wells Lift Wells Gas 1 and I. Guerrero Y. V. Fairuzov 1 and I. Guerrero- -Sarabia Sarabia 2 2 , , Y. V. Fairuzov National Autonomous University of Mexico National Autonomous University of Mexico 1 fairuzov@servidor.unam.mx; 2 iguerreros@iingen.unam.mx 2006 ASME/API/ISO Gas-Lift Workshop, February 15-16, 2006, Houston, Texas

Outline Outline � Introduction � Stability Maps for Continuous Flow Gas-Lift Wells � Comparison of Different Gas-Lift Stability Criteria � Stability Map Applications � Effect of Orifice Size � Effect of Tubing Diameter � Effect of Injection Depth � Effect of Inflow Performance � Selection of Stabilization Method Conclusions �

Heading in a Gas- -Lift Well Lift Well Heading in a Gas

Problems caused by flow Problems caused by flow oscillations in gas lifted wells oscillations in gas lifted wells � Operational problems – difficulties with operation of low pressure separator – compressor shutdown � Low efficiency � Problems with production control � Monitoring (more difficult to measure production rates)

Gas- -Lift Performance Curves Lift Performance Curves Gas 10 9 8 7 Production (Mb/d) 6 5 4 Wellhead Pressure 3 (kg/cm 2 ) 10 2 15 1 20 0 0 1 2 3 4 5 6 7 Gas Injection (MMscf/d)

Factors Affecting Gas- -Lift Stability Lift Stability Factors Affecting Gas Fluid properties (crude oil and injected gas) 1. Inflow performance 2. Reservoir pressure 3. Tubing diameter 4. Casing diameter 5. Orifice valve size 6. Injection depth 7. Injection gas rate 8. Wellhead pressure 9.

Existing Techniques and Existing Techniques and Recommendations Recommendations Sizing of the injection port (pressure 1. differential of 100-200 psi) ⇒ increased gas compression costs/pipe wall thickness Increasing the injection gas rate ⇒ 2. inefficient operation Choking at the surface (increasing the 3. wellhead pressure) ⇒ uneconomical production

Existing Methods to Analyze Existing Methods to Analyze Flow Stability in Gas- -Lift Wells Lift Wells Flow Stability in Gas � Sensitivity analysis based on gas-lift stability criteria (linear stability analysis) � Transient models (non-linear stability analysis) � Both methods - time-consuming and tedious procedures

Gas- -Lift Application in Lift Application in Gas Offshore Oil Production Offshore Oil Production � Large–scale oil production � High percentage of H 2 S � Gas processing- onshore � Long pipelines to transport lift gas � Pressure variations in the gas allocation network

Boiling Water Reactor (BWR) Boiling Water Reactor (BWR) Schematic Schematic Assembly Assembly

Typical BWR Stability Map Typical BWR Stability Map

Continuous Flow Gas- -Lift Well Lift Well Continuous Flow Gas 8 8 8 8 8 8 8 Oil Oil Oil Oil Oil 9 9 9 9 9 9 9 7 7 7 7 7 7 7 10 10 10 10 10 10 10 Lift gas Lift gas Lift gas Lift gas Lift gas 6 6 6 6 6 6 6 1 Reservoir 1 Reservoir 1 Reservoir 1 Reservoir 1 Reservoir 2 Packer 2 Packer 2 Packer 2 Packer 2 Packer 3 Tubing 3 Tubing 3 Tubing 3 Tubing 3 Tubing 5 5 5 5 5 5 5 4 Operating valve 4 Operating valve 4 Operating valve 4 Operating valve 4 Operating valve 5 Casing 5 Casing 5 Casing 5 Casing 5 Casing 6 Gas allocation network 6 Gas allocation network 6 Gas allocation network 6 Gas allocation network 6 Gas allocation network 4 4 4 4 4 4 4 7 Surface injection choke 7 Surface injection choke 7 Surface injection choke 7 Surface injection choke 7 Surface injection choke 8 Wellhead 8 Wellhead 8 Wellhead 8 Wellhead 8 Wellhead 3 3 3 3 3 3 3 9 Choke 9 Choke 9 Choke 9 Choke 9 Choke 2 2 2 2 2 2 2 10 Flowline 10 Flowline 10 Flowline 10 Flowline 10 Flowline 1 1 1 1 1 1

GME Computer Program GME Computer Program (Stability Map Generator) (Stability Map Generator) Specify Predict Select Specify Predict Select system system steady- steady -state state gas- gas -lift lift Gas- Gas -lift well lift well operating flow stability stability map operating flow stability stability map conditions parameters criteria conditions parameters criteria

Gas- -Lift Stability Map Lift Stability Map Gas 35 Non - Operational 30 2 ) Stability Boundary Wellhead Pressure (kg/cm 25 Fairuzov and Guerrero, 2004 Stable 20 Operability Boundaries 15 Lower limit Unstable 10 Upper limit 5 0 0 1 2 3 4 5 6 7 Gas Injection (MMscf/d) GME Ver. 3.0

Data Well Data Well Reservoir pressure 1543.31 (psig) Reservoir temperature 216.9 ( ° F) Water cut 0.0 (percent) Liquid rate 7632.0 (STB/day) Flowing bottomhole pressure 1363.5 (psig) Oil gravity 21.4 (API) Gas gravity 0.922 (sp. gravity) Gas lift gravity 0.675 (sp. gravity) Solution GOR 291.46 (scf/STB) Water oil ratio 0.0 (SBT/STB) Bubble pressure 1550.23 (psig)

Stability Map for Gas- -Lift Well with Square Lift Well with Square- - Stability Map for Gas Edged Orifice Valve Edged Orifice Valve 45 40 Non - Operational 35 Wellhead Pressure (kg/cm 2 ) Stability Boundary 30 Optimal Rate 25 Operability Boundaries Stable 20 Lower limit 15 Upper limit 10 Unstable 5 0 0 1 2 3 4 5 6 7 8 9 10 Gas Injection Rate (MMscf/d) GME Ver. 3.0

Field Data Field Data 1480 400 4.0 MMscfd Bottomhole pressure 1460 Wellhead pressure 5.0 MMscfd 4.5 MMscfd 1440 350 5.5 MMscfd BOTTOMHOLE PRESSURE [psia] 1420 WELLHEAD PRESSURE [psia] 1400 300 5.5 MMscfd (Choke size: 2.5") 1380 1360 250 3.0 MMscfd 1340 1320 200 1300 1280 150 19-15:50 19-20:38 20-01:26 20-06:14 20-11:02 20-15:50 Day - Hour [dd-hh:mm]

Comparison of Gas- -Lift Lift Comparison of Gas Stability Criteria Stability Criteria 35 Stability Boundaries Non - Operational 30 Asheim, 1988 2 ) Wellhead Pressure (kg/cm 25 Alhanati et al., 1993 Stable Fairuzov and Guerrero, 2004 20 Operability Boundary 15 Lower limit 10 Field Data Unstable Stable 5 Unstable 0 0 1 2 3 4 5 6 7 Gas Injection (MMscf/d) GME Ver. 3.0

Effect of Orifice Size Effect of Orifice Size 35 Stability Boundaries Non - Operational 30 Orifice size 2 ) 1.00 in. Wellhead Pressure (kg/cm 25 Stable 0.75 in. 20 0.50 in. Operability Boundaries 15 Lower limit 10 All cases Unstable Upper limit 5 0.50 in. 0 0 1 2 3 4 5 6 7 Gas Injection (MMscf/d) GME Ver. 3.0

Effect of Tubing Diameter Effect of Tubing Diameter (d c =11 7/8 in.) (d c =11 7/8 in.) 35 Non - Operational 30 Stability Boundaries 2 ) Tubing diameter Wellhead Pressure (kg/cm 25 5 1/2 in. Stable 20 7 5/8 in. 9 5/8 in. 15 Unstable Operability Boundary 10 Lower limit 5 7 5/8 in. and 9 5/8 in. 0 0 1 2 3 4 5 6 7 Gas Injection (MMscf/d) GME Ver. 3.0

Effect of Injection Depth Effect of Injection Depth 35 Non - Operational 30 Stability Boundaries 2 ) Injection depth Wellhead Pressure (kg/cm 25 6830 ft. Stable 20 6174 ft. 5518 ft. 15 Operability Boundary 10 Lower limit Unstable All cases 5 0 0 1 2 3 4 5 6 7 Gas Injection (MMscf/d) GME Ver. 3.0

Effect of Inflow Performance Effect of Inflow Performance (q q o =7632 bpd) ( o =7632 bpd) 35 Non - Operational 30 Stability Boundaries 2 ) Drawdown Wellhead Pressure (kg/cm 25 12.7 kg/cm 2 Stable 8.4 kg/cm 2 20 4.2 kg/cm 2 15 Operability Boundary 10 Lower limit Unstable All cases 5 0 0 1 2 3 4 5 6 7 Gas Injection (MMscf/d) GME Ver. 3.0

Selection of Stabilization Method Selection of Stabilization Method 35 Non - - Operational Operational Non Stability Boundaries 30 Design conditions 2 ) Decreased injection depth Wellhead Pressure (kg/cm 25 Well stimulation Stable Stable Reduced choke size 20 15 Lower limit All cases 10 Upper limit Only for reduced choke size 5 Unstable Unstable Design operating condition Unstable 0 0 1 2 3 4 5 6 7 Gas Injection (MMscf/d) GME Ver. 3.0

Oil Production Rate Oil Production Rate 10000 10000 10000 Pwh [kg/cm2] Pwh [kg/cm2] 10 10 9000 9000 9000 11 11 12 12 13 13 8000 8000 8000 14 14 15 15 7000 7000 7000 16 16 17 17 18 18 6000 6000 6000 19 19 Qo [bpd] Qo [bpd] 20 20 5000 5000 5000 21 21 22 22 4000 4000 4000 23 23 24 24 25 25 3000 3000 3000 26 26 27 27 2000 2000 2000 28 28 29 29 30 30 1000 1000 1000 Stable Stable Unstable Unstable 0 0 0 0 0 0 1 1 1 2 2 2 3 3 4 4 5 5 6 6 7 7 Qgi [MMpcd] Qgi [MMpcd] GME Ver. 3.0

Selection of Stabilization Method Selection of Stabilization Method 35 Non - - Operational Operational Non Stability Boundaries 30 Design conditions 2 ) Decreased injection depth Wellhead Pressure (kg/cm 25 Well stimulation Stable Stable Reduced choke size 20 15 Lower limit All cases 10 Upper limit Only for reduced choke size 5 Unstable Unstable Design operating condition Unstable 0 0 1 2 3 4 5 6 7 Gas Injection (MMscf/d) GME Ver. 3.0