Casing Hanger Function and Operating Manual

I. Overview  

A casing hanger is a critical device in oil and gas drilling and completion operations. It is primarily used to suspend the casing string, seal the annulus between the casing and wellhead equipment, and transfer loads to the wellhead. Its performance directly impacts wellbore integrity, operational safety, and efficiency.  

II. Key Functions of Casing Hangers  

1. Support Casing Weight  

   - Transfers axial loads from the casing string to the wellhead equipment (e.g., casing head or drilling spool) to prevent casing deformation due to self-weight or external pressure.  

2. Annular Sealing  

   - Isolates the annulus between the casing and wellhead equipment using metal or elastomeric seals to prevent fluid leakage (e.g., hydrocarbons, drilling mud).  

3. Pressure Control  

   - Withstands wellbore pressure in high-pressure or specialty wells to ensure pressure integrity at the wellhead.  

4. Adjust Wellhead Height  

   - Some hangers allow adjustment of the casing suspension height to facilitate subsequent completion operations.  

5. Compatibility with Downhole Tools  

   - Integrates with tools like subsurface safety valves and packers to meet multi-functional well control requirements.  

III. Classification of Casing Hangers  

1. Mechanical Hangers  

   - Utilize slip inserts or threads to lock the casing; suitable for standard well conditions.  

2. Hydraulic Hangers  

   - Employ hydraulic pressure to activate sealing and locking mechanisms; ideal for deep or high-pressure wells.  

3. Rotary Hangers  

   - Allow casing rotation after installation to support cementing operations.  

IV. Operational Guidelines  

1. Pre-Installation Preparation  

- Equipment Inspection  

  - Verify the hanger body, seals, slips, etc., for damage, corrosion, or deformation.  

  - Confirm seal materials are compatible with well fluids (e.g., H₂S, CO₂).  

- Cleaning and Lubrication  

  - Remove debris from casing threads and hanger internals; apply thread compound or sealant.  

- Specification Verification  

  - Ensure the hanger matches casing OD and wellhead ID to avoid installation failures.  

2. Installation Process  

- Centralization  

  - Maintain casing alignment during running to prevent seal failure or slip damage.  

- Control Running Speed  

  - Avoid excessive speed to prevent seal surface damage.  

- Locking and Pressure Testing  

  - Tighten slips or hydraulic systems to specified torque post-installation.  

  - Conduct low-pressure (≤500 psi) and high-pressure leak tests to confirm integrity.  

3. Special Conditions  

- High-Temperature/High-Pressure (HTHP) Wells  

  - Use high-temperature alloy materials and reinforced seals.  

  - Monitor seal performance under thermal cycling.  

- Corrosive Fluid Environments  

  - Apply anti-corrosion coatings or dual-seal designs.  

- Deep/Ultra-Deep Wells  

  - Validate hanger load capacity against total casing weight and operational loads.  

4. Maintenance  

- Regular Inspections  

  - Perform annual wellhead checks post-completion, focusing on seal wear.  

- Seal Replacement  

  - Replace aged or failed seals promptly to mitigate well control risks.  

- Documentation  

  - Archive installation parameters (torque, test results), maintenance logs, and failure reports.  

5. Safety Precautions  

- Avoid Overloading  

  - Ensure rated load exceeds casing weight + operational forces (e.g., cementing pressure).  

- H₂S Mitigation  

  - Use sulfur-resistant materials in sour wells; equip personnel with gas detectors and PPE.  

- Emergency Protocols  

  - Prepare contingency plans for hanger failure (e.g., backup seals or well-kill measures).  

V. Common Failures and Solutions