|
Alarm area
|
Action
|
| Core laboratory | Notify H2S safety technician |
| Core receiving platform* | Notify H2S safety technician |
| Core entry | Notify H2S safety technician |
| Core catcher bench* | Notify H2S safety technician |
| Lower 'tween deck landing | Notify laboratory officer and investigate |
| Hold 'tween deck landing | Notify laboratory officer and investigate |
| Fresh air intake plenum* | Shut down intake fans and investigate |
| Rig floor* | Notify core technician |
| Multiple alarms on "*" detectors above | Sound alarm using coded bell signals and announce H2S EMERGENCY via public address system |
| Possible blowout! |
|
Rig Floor
The two core technicians are responsible for monitoring H2S levels on the rig floor during their shift to provide 24-hr coverage. The core technician works under the authority of the offshore installation manager and the night tool pusher. Note that in the following instructions, references to the offshore installation manager include the night tool pusher or other offshore installation manager designee.
Core Receiving Platform, Core Laboratory, and Core Storage Areas
The H2S safety technicians are two marine specialists assigned the responsibility for monitoring H2S levels on the core-receiving platform and in the core laboratory. There is an H2S safety technician assigned to each shift for 24-hr coverage. The H2S safety technicians work under the authority of the laboratory officer and assistant laboratory officer.
Downhole and Logging Tools
The technicians operating these tools are responsible for monitoring any H2S that maybe trapped inside the tool.
- Use fans to ventilate work areas. Fans can keep the H2S concentration low enough so that BAs are not required;
- If stationkeeping permits, head the ship so that the wind hits the ship just off the port bow, blowing across the core-receiving platform and through the rig floor;
- Always use the buddy system when working in potentially hazardous areas;
- Always check PPE at the beginning of the work shift. Never assume that someone has left it in working order; and
- Do not let materials pile up around fixed H2S sensors.
The following guidelines apply when retrieving a core barrel or other tools deployed through the drill string.
H2S Monitoring
The core technician is responsible for monitoring H2S levels on the drill floor with a portable detector. The drill pipe opening (while opening), upper drill string connection, top of inner core barrel, and bottom of core catcher sub are areas that should be monitored.
Precautions and Special Procedures
Table T3 gives guidance on who must wear a BA before opening the drill string and measuring the H2S levels.
|
H2S hazard
condition |
Core
technician |
Rig floor
crew |
Driller
(driller's shack) |
| Watch | No | No | No |
| Alert | No | No | No |
| Danger | Yes | Yes | No |
| Emergency | Yes | Yes | Yes |
H2S Response
When H2S is detected at the drill pipe, the following procedures must be implemented, depending on the concentration detected and how it was measured.
1–19 ppm, Measured with a Portable Detector at the Drill Pipe
After a positive reading, the core technician notifies the offshore installation manager, who may change the H2S hazard condition to ALERT.
20–49 ppm, Measured with a Portable Detector at the Drill Pipe
- The rig floor crew working around the drill pipe put on BAs.
- The drill pipe is reconnected and circulation begins.
- The core technician notifies the offshore installation manager and operations manager.
- After the drill string has been completely flushed, the pipe is reopened and H2S levels are checked. If they are still >20 ppm, steps 2 through 4 are repeated unless otherwise instructed by the offshore installation manager.
- The offshore installation manager may change the H2S hazard condition to DANGER.
>50 ppm, Measured with a Portable Detector at the Drill Pipe or 
10 ppm at Rig Floor's Fixed Station
- The rig floor crew, including the driller, put on BAs.
- Personnel on the core-receiving platform put on BAs or evacuate the area.
- The drill pipe is reconnected and circulation begins.
- The core technician notifies the offshore installation manager and operations manager of the situation.
- Personnel wait for instructions from the offshore installation manager.
- The offshore installation manager may change the H2S hazard condition to EMERGENCY and notify the ship's master to sound alarms and evacuate ship personnel to safe areas.
Special Concerns
H2S Blowout
Although unlikely, a set of circumstances could occur that would cause an H2S blowout to discharge gas up the drill string. The first sign that this situation is occurring would be backflow when the drill string is opened. There are many situations other than a blowout that can cause backflow, but while drilling in an environment where H2S is present the following steps should be taken if backflow is detected unless otherwise instructed by the offshore installation manager:
- The drill string is reconnected as quickly as possible.
- The core technician checks atmosphere for H2S.
- The core technician notifies the offshore installation manager and operations manager of situation.
- Technicians await instructions from the offshore installation manager.
H2S Monitoring
The core technician is responsible for monitoring H2S levels on the drill floor with a portable detector. The bottom of the core catcher sub and bottom of the core barrel (after removing the core catcher) should be monitored.
Precautions and Special Procedures
Table T4 provides guidance to determine who must wear a BA before the removing the core catcher and measuring the H2S levels.
|
H2S hazard condition
|
Core
technician |
Rig floor
crew |
Core
handlers |
| Watch (potential) | No | No | No |
| Alert (1–19 ppm) | No | No | No |
| Danger (20–49 ppm) | Yes | Yes | Yes |
| Emergency (>50 ppm) | Yes | Yes | Yes |
H2S Response
If H2S is detected from the core barrel, the following procedures are implemented.
1–19 ppm, Measured with a Portable Detector at the Core Barrel
- The core technician notifies the H2S safety technician.
- The core technician notifies the offshore installation manager and operations manager. The offshore installation manager may change the H2S hazard condition to ALERT.
>20 ppm, Measured with a Portable Detector at the Core Barrel
- The rig floor crew opening the core barrel and the core handlers put on BAs.
- The core technician notifies the H2S safety technician.
- The core technician notifies the offshore installation manager and operations manager. The offshore installation manager may change the H2S hazard condition to DANGER.
10 ppm, Measured at the Rig Floor's Fixed Station
- The rig floor crew, including the driller, put on BAs.
- Personnel on the core-receiving platform put on BAs or evacuate the area.
- The core technician locates the source of the H2S and notifies the offshore installation manager and operations manager of the situation.
- Technicians wait for instructions from the offshore installation manager.
- The offshore installation manager may change the H2S hazard condition to EMERGENCY and then notifies the ship's master to sound alarms and evacuate ship's personnel to safe areas.
H2S Monitoring
The H2S safety technician is responsible for monitoring H2S levels on the core-receiving platform with a portable detector. The core (vent holes and cut ends), 12 in above the core, the core catcher, and core storage racks (outside the laboratory) should be monitored.
Precautions and Special Procedures
Moving Core from Rig Floor to Core Rack
- Before the core handlers receive the core from the rig floor, the H2S level is measured, as described in the section above. If H2S levels are >20 ppm at the core barrel, core handlers wear BAs while transferring the core from the rig floor to the core rack.
- Core handlers should hold the core at waist level when moving it to the core rack. The core should not be placed on the shoulder or held anywhere near the face. If the core liner ruptures, the face will have more protection from sharp core liner fragments and direct exposure to H2S.
- When working with very gassy cores, face shields and Kevlar aprons, sleeve protectors, and gloves should be worn. The H2S safety technician determines when this special protection is needed.
Curating Core on the Core Rack
-
After the core is placed in the core rack,
-in diameter holes are drilled through the liner to depressurize the core. The holes should not be drilled in a straight line, as this can cause a core liner to rupture. Rather, the holes should be staggered around the circumference and spaced apart as necessary. - As gas vents, H2S levels are monitored. Vent holes are checked to see if H2S is present.
- H2S levels at the surface of the core liner determine if core handlers and other personnel working on the core-receiving platform need to wear BAs (See "H2S Emergency Condition").
- The core is not cut into sections until after depressurization, to keep material from being extruded out of the liner.
- If any part of a core contains H2S, the core liner of each section and all whole-round samples are marked with "H2S." H2S warning stickers may be used, as well.
Moving Core Sections into the Core Entry Area of the Core Laboratory
- Sections of whole cores may be brought into core entry area provided that the core has depressurized and is no longer actively venting gas (i.e., causing core expansion gaps) and any remaining H2S diffusing from the core is <20 ppm when measured 12-in above the core.
- Sections of core that do not meet the above criteria remain outside until they do.
- Vent holes and end caps are sealed with tape if the H2S level is >10 ppm measured 12-in above the core.
H2S Response
When H2S is detected above the core liner during venting, the following procedures are followed.
1–9 ppm, Measured with a Portable Detector at the Surface of the Core Liner
- BAs are not required.
- The H2S safety technician continues monitoring until the core has depressurized (as defined above).
- The H2S safety technician notifies the offshore installation manager and operations manager.
- The offshore installation manager may change the H2S hazard condition to ALERT.
>10 ppm, Measured with a Portable Detector 12 in above the Core
- BAs are required for core handlers. All other individuals on the core-receiving platform MUST leave the area.
- The H2S safety technician continues monitoring until core has depressurized (as defined above).
- The H2S safety technician notifies the offshore installation manager and operations manager. The offshore installation manager may change the H2S hazard condition to HAZARD or higher.
10 ppm, Measured at the Core-Receiving Platform's Fixed Station
- BAs are required for core handlers. All other individuals on the core-receiving platform MUST leave the area.
- The H2S safety technician identifies the source of H2S and notifies the offshore installation manager and operations manager of the situation.
- Wait for instructions from the offshore installation manager.
- The offshore installation manager may change the H2S hazard condition to EMERGENCY and notify the ship's master to sound alarms and evacuate ship's personnel to safe areas.
Special Concerns
H2S Clathrates
Clathrates (gas hydrates) are crystalline substances composed principally of three-dimensional cages of water in which various gases (e.g., CH4 and H2S) can enter and stabilize the structure. At room temperature and pressure, a clathrate will disassociate, releasing a volume of H2S gas that can be greater than the original volume of the clathrate.
If a clathrate is recovered from a site where H2S is expected, the following steps should be taken:
- Core Handlers wear BAs.
- Personnel not handling core leave the core-receiving platform.
- The section of the core containing the clathrate is cut out.
- H2S is quickly measured while the clathrate is being removed.
- The clathrate is processed according to the scientist's instructions. Usually this involves placing the clathrate in a pressure container or into liquid N2.
- If H2S is detected, place an H2S warning label on the container.
- The H2S safety technician notifies the offshore installation manager the first time a clathrate is recovered at a particular site.
An H2S clathrate may only be brought into the laboratory in a sealed pressure container. Liquid N2 dewars holding H2S clathrates are stored outdoors, away from supply ventilations and sources of ignition, and are marked with warning signs.
H2S Monitoring
The marine specialists and the H2S safety technicians are responsible for monitoring H2S levels in the core laboratory with a portable detector. Core storage racks (inside the laboratory), air in the core splitting room, the cut surface of split cores after splitting, and the cut surface of split cores while laying out in the core laboratory are monitored.
Precautions and Special Procedures
While cores are waiting to be split or measured on the multisensor track (MST), they continue to warm up and may possibly resume degassing. Should this happen, the marine specialists remeasure the H2S levels. If the H2S level is <10 ppm, the core may remain in the laboratory. If it is >10 ppm, the core is removed from the laboratory until it can be sealed as mentioned in the previous section. Warning: cores that are no longer actively emitting H2S may release additional H2S during the core splitting process (especially if the super saw is used). The H2S levels from split cores are often greater than the levels measured in the whole round.
Prior to splitting cores two BAs must be available and ready for use. There must be at least two marine specialists in the splitting room when a core is split. During the splitting process the H2S levels are continuously monitored with a handheld detector. If the H2S level in the splitting room is >20 ppm, core splitting stops and the two the marine specialists cutting the core put on their BAs; all others leave the room.
Cores may be taken back outside the laboratory to finish degassing or left on the splitting table, covered, and vented using the flexible exhaust duct provided in the splitting room (Fig. F1). Core halves do not leave the splitting room until all signs of active degassing have stopped and the remaining H2S concentration from the core is <10 ppm. Note: some individuals may be very sensitive to low levels of H2S. The 10-ppm level may have to be set lower for these individuals or a BA provided for them to use.
All D-tubes and core boxes holding cores that have emitted H2S are tagged with H2S warning labels. H2S warning signs are placed on core refrigerators where these cores are stored.
To keep the air fresh in the core laboratory,
- Fully open the fresh air supply to the core laboratory and top deck air handlers;
- Open doors and windows, if weather permits; and
- Use fans to force additional fresh air into the laboratory.
H2S Response
When H2S is detected in the core Laboratory, the following procedure must be followed.
10 ppm at any Fixed Station in the Core Laboratory
- The immediate area is evacuated.
- The H2S safety technician identifies the source of H2S and notifies the laboratory officer of the situation.
- Technicians wait for instructions from the laboratory officer.
H2S Monitoring
Because each tool is unique, it is the responsibility of the technician operating the tool to carefully check for H2S in sampling chambers or for H2S trapped inside the tool's housing.
Precautions and Special Procedures
If the H2S hazard condition is ALERT (1–19 ppm) or higher, then the tool's sampling chambers are vented outside or in a controlled manner such that there is no chance of H2S escaping into the work area. The laboratory officer will approve such controls prior to tool's operation.
Should the technician suspect the tool's housing has been compromised and may possibly contain fluids or materials with H2S, the technician opens the housing in an open-air location.
If samples collected are transferred to another container, that container must have an H2S warning tag (see "Pressure Core Samplers, Autoclaves, Transfer/Storage/Logging Containers, and Sampling Manifolds").
H2S Response
If H2S is released, the immediate area is evacuated until the air is tested.
Pressure Core Samplers, Autoclaves, Transfer/Storage/ Logging Containers, and Sampling Manifolds
Downhole tools that return core/gas/liquid under pressure must comply with the following.
All pressure corers and pressurized transfer/storage/logging containers must have a written operator's manual that has been submitted to and approved by ODP and the ship operator's management prior to deploying the tool on the JOIDES Resolution. The manual must not only instruct the user on safe operation of the tool but also clearly state the types of hazards the tool presents to the operator. In regard to the potential release of H2S, the operator must be informed of all potential locations on the tool where pressure containment could fail (seals, valves, rupture disks, etc.).
When a pressure sampler is retrieved on the rig floor, all potential locations for containment failure must be surveyed with a handheld detector.
If the contents of the pressure sampler are transferred to secondary sample chamber or into a manifold/collection system, a handheld detector must be used to monitor the transfer operation.
When operating in a WATCH (H2S potential) or higher H2S hazard condition, then it must be assumed that the pressure sampler or transfer/storage/logging container contains H2S until the trapped gases can be sampled and determined otherwise. The following applies to both pressure samplers and transfer containers:
- Pressure samplers and transfer/storage/logging containers are tagged with an H2S hazard label.
- Pressure samplers and transfer/storage/logging containers are surveyed with a handheld detector each time they are relocated to a new storage area.
- Personnel handling pressure samplers and transfer/storage/logging containers indoors wear a personal detector.
- H2S warning signs are posted in areas where the pressure samplers and transfer/storage/logging containers are stored.
- Pressure samplers and transfer/storage/logging containers are vented outdoors in a location where personnel downwind are not affected.
