What is the Wellhead Injection Line?
A Wellhead Injection Line is also known as an injection flow line, is a pipeline used to transport fluid from surface facilities to an injection wellhead for various purpose, such as fluid disposal, enhanced oil recovery (EOR), or etc. Unlike production flow lines that transport fluids from WH to processing facilities.
Hence, the component of fluids from Wellhead Flowline and Wellhead Injection Line are difference. For example, the water injection may involve injecting produced water or treated seawater for reservoir pressure maintenance of EOR purpose. Gas injection may involve injecting natural gas or carbon dioxide for EOR or reservoir stimulation.
What are general hazards of Wellhead Injection Line?
Injection flow lines shall be designed to handle the injection rate and pressure required for the specific injection application. However, failure of some devices such as control valve, pressure regulator, and etc. can post of significant hazards.
| Undesirable Event | Cause | Detectable Process Condition |
| Overpressure | Blocked or restricted outlet Hydrate plug Upstream control valve failure Plugged formation | High pressure |
| Leak | Deterioration Erosion Corrosion Impact damage Vibration | Low pressure |
What are the Process Safety Device on Wellhead Injection Line?
| Device | Location | Function |
| High Pressure Sensor (PSH) to shut off inflow | On the WH Injection source | – To alarm when abnormal pressure is found. – To prevent overpressure |
| Low Pressure Sensor (PSL) to shut off inflow | On the WH Injection source | – To prevent of leakage |
| Pressure Safety Valve (PSV) | On the WH Injection source (MAWP< shut off pressure from injection source) | – To prevent overpressure |
| Flow Safety Valve (FSV) or check valve | On the Injection line and near the WH | – To prevent the backflow from WH |
| Additional Shutdown Valve (SDV) and independent pressure sensor (*) | On the Injection line and near the WH | – To prevent backflow from WH |
- (*) Additional Shutdown Valve and independent pressure sensor is not required on the gas lift line if the system is protected at an upstream component and if they are not subject to backflow from producing formation.
- (*) Additional Shutdown Valve and independent pressure sensor is not required if the injection line is for the purpose of injecting water and the subsurface formation is incapable of backflow hydrocarbon.
- (*) If closing of SDV can cause of rapid pressure buildup to injection line, considering the shutdown of the injection source and using double FSV in lieu of an SDV.
PROcess Safety TASK 