Design, Operation, and Troubleshooting of Dual Gas-lift Wells

API RECOMMENDED PRACTICE 19G9 SECOND EDITION, APRIL 2015

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iii

Contents

Page

1. Scope 1

2. Terms, Definitions, Acronyms, and Abbreviations 1

   1. Terms and Definitions 1

   2. Acronyms and Abbreviations 4

3. Benefits of Dual Wells 4

   1. General 4

   2. More Efficient Drilling 4

   3. Dual Gas-lift Alternatives 4

4. Dual Gas-lift Practices. 5

   1. General 5

   2. Practices That Are Recommended 5

   3. Defining Unacceptable Wells 6

   4. Considering Alternatives to Dual Gas-lift 6

   5. Dual Gas-lift Well Design Issues 6

   6. Dual Gas-lift Operations 7

   7. Poor Candidates for Dual Gas-lift 8

   8. Considering Artificial Lift Alternatives to Dual Gas-lift 8

5. Dual Gas-lift Well Designs 9

   1. General 9

   2. Mandrel Spacing 9

   3. Gas-lift Mandrel Spacing Production Pressure Design Line Options 11

   4. Gas-lift Mandrel Spacing Design Procedure 12

   5. Installation Issues 14

   6. When One Zone Is Much Deeper than the Other 14

   7. PPO and IPO Gas-lift Valves Compared 16

   8. Unloading Gas-lift Valves 19

   9. Operating Unloading Gas-lift Valves 19

   10. Designing for Dual Gas-lift if Mandrels Spaced Too Far Apart 20

   11. Dual Gas-lift System Design Options 21

6. Dual Gas-lift Well Operations 22

   1. General 22

   2. Installing Dual Gas-lift Equipment 22

   3. Dual Gas-lift Well Wireline Operations 24

   4. Additional Recommended Wireline Procedures 25

   5. Unloading Dual Gas-lift Wells 28

   6. Kicking Off Dual Gas-lift Wells 30

   7. Operating Dual Gas-lift Wells 31

   8. Dual Gas-lift Well Optimizing 32

7. Dual Gas-lift Well Surveillance 34

   1. General 34

   2. Wireline Operations 34

   3. Pressure/Temperature Surveys 35

   4. Evaluating with Pressure/Temperature Surveys 36

   5. Fluid Levels 38

   6. Well Tests 38

   7. CO2 Tracer 39

      v

      Contents

      Page

   8. Continuous Monitoring and Control 39

8. Dual Gas-lift Diagnosis and Troubleshooting 41

   1. General 41

   2. Diagnostic Techniques 42

   3. Locating Communication Problems 47

   4. Dual Gas-lift Typical Problems 48

9. Dual Gas-lift Well Automation 50

   1. General 50

   2. Automation Logic 50

   3. Key Measurement Parameters 51

   4. Dual Gas-lift Controls 53

   5. Responding to Gas-lift System Problems 53

10. Dual gas-lift Special Issues 54

    1. General 54

    2. Gas-lift and a Flowing Well in One Wellbore 54

    3. Gas-lift and a Pumping Well in One Wellbore 55

    4. Intermitting One or Both Zones 55

    5. Important Consideration for Completing With or Without Mandrels 56

    6. Transitioning from Flowing to Dual Gas-lift Operation 57

Annex A (informative) Overview of Dual Well Gas-lift Systems 59

Annex B (informative) Dual Gas-lift Mandrel Spacing Design 79

Annex C (informative) Dual Gas-lift Unloading Valve Design for PPO Valves 84

Annex D (informative) Dual Gas-lift Practices Not Recommended 88

Bibliography 89

Figures

1. Mandrel with Injection String Beneath the Upper Packer 1

2. Gas-lift Response Curve 33

3. Flowing Pressure Survey 44

4. Inflow Performance Relationship 44

5. Gas-lift Response Curve 45

6. Gas-lift Response Curve Comparison 46

7. Production Rate vs Mandrel Depth 46

B.1 Gas-lift Mandrel Spacing 83

C.1 Graphical Method for Design 86

Tables

1 Gas-lift Valve Installation Problems 28

1. Example Well Parameters 80

2. Example Gas-lift Characteristics 80

3. Calculated Long String Mandrel Depths 82

4. Calculated Short String Mandrel Depths 82

C.1 PPO Valve Calculations 87

vi

Design, Operation, and Troubleshooting of Dual Gas-lift Wells

1. Scope

   
   

   This document provides recommended practices (RPs) for the selection, design, operation, surveillance, optimization, automation, and troubleshooting of dual gas-lift wells.

   
   

   The purpose of this document is to present RPs, guidelines, and tools to help obtain optimum production from dual gas-lift wells. This document also contains practices that should be avoided to minimize problems and inefficiencies that can be associated with ineffective dual gas-lift operations. Compared to single completions, dual completions typically have more operating problems, are more difficult to work over, and can produce less efficiently.

   
   

   It is not the purpose of this document to recommend the practice of dual gas-lift. In some cases, dual gas-lift is problematic and often ineffective. Often it is difficult or even impossible to effectively produce both completions in a dual well using gas-lift over the long term. Where there are other feasible alternatives to produce dual wells, they should be considered. However, many dually completed oil wells should be artificially lifted initially or after reservoir pressures have declined and/or water cuts have increased. In many cases, the only practical method of artificial lift for these wells is gas-lift. Therefore, every effort should be made to design and operate dual gas-lift systems as effectively as possible.

   
   

   Annexes to this RP include:

   
   

   1. an overview of dual gas-lift systems,

      
      

   2. dual gas-lift mandrel spacing designs,

      
      

   3. dual gas-lift unloading valve design for production pressure operated (PPO) valves, and

      
      

   4. dual gas-lift practices not recommended.

   
   

2. Terms, Definitions, Acronyms, and Abbreviations

2.1 Terms and Definitions

For the purposes of this document, the following terms and definitions apply.

2.1.1

automation

A system for monitoring, control, diagnosis, and optimization of gas-lift operations that includes measuring important gas-lift parameters, controlling gas-lift injection rate, detecting and diagnosing problems, and optimizing gas-lift operations.

2.1.2

bottomhole pressure BHP

Normally measured at the midpoint of the perforated interval.

2.1.3

commingling (commingle)

A process where fluids from different productive formations are combined and produced through a single conduit.

2.1.4

cross-flow

The flow of reservoir fluids from one productive formation into another.

1