Design and Operation of Solution- mined Salt Caverns Used for Natural Gas Storage

API RECOMMENDED PRACTICE 1170 FIRST EDITION, JULY 2015

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Contents

Page

1. Scope 1

   1. Overview 1

   2. Applicable Rules and Regulations 1

2. Normative References 1

3. Terms, Definitions, Acronyms, and Abbreviations 2

   1. Terms and Definitions 2

   2. Acronyms and Abbreviations 7

4. Overview of Underground Natural Gas Storage 9

   1. General 9

   2. Types of Underground Natural Gas Storage 9

   3. Natural Gas Storage in Salt Formations 9

   4. Functional Integrity 10

   5. \ Overview of Major Steps in the Development of Gas Storage Caverns 10

5. Geological and Geomechanical Evaluation 12

   1. General Considerations 12

   2. Site Selection Criteria 12

   3. Geologic Site Characterization 13

   4. Geomechanical Site Characterization 22

   5. Assessment of Cavern Stability and Geomechanical Performance 26

6. Well Design 28

   1. General 28

   2. Hole Section Design 30

   3. Casing Design 31

   4. Wellhead Design 33

7. Drilling 37

   1. Rig and Equipment 37

   2. Drilling Fluids 40

   3. Drilling Guidelines 41

   4. Logging 42

   5. Casing Handling and Running 43

   6. Cementing 43

   7. Completion 47

8. Cavern Solution Mining 47

   1. General 47

   2. Cavern Solution Mining Design 48

   3. Cavern Development Phases 51

   4. Equipment 53

   5. Instrumentation, Control, and Shut Down 55

   6. Monitoring of the Cavern 56

   7. Workovers during Solution Mining 59

   8. Workover to Configure for Gas Storage Service 60

   9. Debrining the Cavern 61

   10. Existing Cavern Conversions 63

   11. Cavern Rewatering 64

   12. Cavern Enlargement 64

       Contents

       Page

9. Gas Storage Operations 65

   1. Minimum and Maximum Operating Limits 65

   2. Equipment 65

   3. Instrumentation, Control, and Shutdown 66

   4. Inspection and Testing 68

   5. Workovers 68

   6. Site Security and Safety 69

   7. Operating Administration 71

10. Cavern Integrity Monitoring 72

    1. General 72

    2. Holistic and Comprehensive Approach 75

    3. Integrity Monitoring Program 75

    4. Review of Integrity Monitoring Methods 75

11. Cavern Abandonment 75

    1. Abandonment Objectives 75

    2. Abandonment Design 75

    3. Removal of Stored Gas 76

    4. Wellbore Integrity Test 76

    5. Removal of Downhole Equipment 76

    6. Production Casing Inspection 76

    7. Sonar Survey 76

    8. Long-Term Monitoring 76

Annex A (informative) Open-hole Well Logs 77

Annex B (normative) Integrity Monitoring Methods 80

Bibliography 86

Figures

1. Typical Cemented Casing Program for Domal Salt 29

2. Typical Solution Mining Wellhead 34

3. Typical Gas Storage Wellhead with Hanging String 35

4. Typical Gas Storage Wellhead without Hanging String 36

5. Cavern Development Phases 52

Table

1 Integrity Monitoring Methods 73

Design and Operation of Solution-mined Salt Caverns Used for Natural Gas Storage

1. Scope

   1. Overview

      
      

      This recommended practice (RP) provides the functional recommendations for salt cavern facilities used for natural gas storage service and covers facility geomechanical assessments, cavern well design and drilling, solution mining techniques and operations, including monitoring and maintenance practices. This RP is based on the accumulated knowledge and experience of geologists, engineers, and other personnel in the petroleum and gas storage industries and promotes public safety by providing a comprehensive set of design guidelines. This RP recognizes the nature of subsurface geological diversity and stresses the need for in-depth, site specific geomechanical assessments with a goal of long-term facility integrity and safety.

      
      

      This RP includes the cavern well system (wellhead, wellbore, and cavern) from the emergency shutdown (ESD) valve down to the cavern and facilities having significant impact to safety and integrity of the cavern system.

      
      

      This RP may be applied to existing facilities at the discretion of the user.

      
      

      This RP does not apply to caverns used for the storage of liquid or liquefied petroleum products, brine production, or waste disposal; nor to caverns which are mechanically mined, or depleted hydrocarbon or aquifer underground gas storage systems.

      
      

   2. Applicable Rules and Regulations

      
      

      This document was written to provide a technical reference for the development and operations of solution-mined salt caverns and is not intended to represent or reflect any Federal, State, or local regulatory requirement. Depending on location and nature of the project, the recommended practices herein may address items that are in conflict with some regulatory requirements. If this occurs, the regulatory requirement supersedes the recommended practice unless an appropriate waiver or variance is granted from the issuing agency. A thorough review of the applicable Federal, State, and local rules and regulations is to be performed prior to the design of solution-mined natural gas storage caverns to ensure ongoing compliance.

      
      

2. Normative References

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

API Technical Report 5C3, Technical Report on Equations and Calculations for Casing, Tubing, and Line Pipe Used as Casing or Tubing; and Performance Properties Tables for Casing and Tubing

API Specification 10A, Specification for Cements and Materials for Well Cementing

API Recommended Practice 10F, Recommended Practice for Performance Testing of Cementing Float Equipment

ASTM D3967 1, Standard Test Method for Splitting Tensile Strength of Intact Rock Core Specimens

1 ASTM International, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania 19428, www.astm.org.

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