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Document Number: WEMS-01-A06Date: August 2003

Classification: Restricted to BG Group PersonnelTitle: H2S Environment ManualRev: A01 of 30

H2S Environment Manual





RECORD OF AMENDMENTS

Rev. No. Description By





Table of Contents

1 INTRODUCTION ................................................................................................................................... 5

2 H2S SAFETY PRECAUTIONS ............................................................................................................. 6 2.1 H2S DETECTION .............................................................................................................................. 6 2.2 F IXED G AS DETECTORS ................................................................................................................... 6 2.3 P ORTABLE DETECTORS (E LECTRIC ) ................................................................................................ 6 2.4 P ORTABLE DETECTORS (M ANUAL)................................................................................................... 6 2.5 P ERSONAL G AS DETECTORS (MONITORS )....................................................................................... 7

3 BREATHING APPARATUS ................................................................................................................. 8 3.1 GENERAL ......................................................................................................................................... 8 3.2 TYPES OF BREATHING APPARATUS ................................................................................................... 8

4 ADDITIONAL RECOMMENDED H 2S EQUIPMENT ........................................................................ 10

4.1 OFFSHORE .................................................................................................................................... 10 4.2 ONSHORE ...................................................................................................................................... 10 5 TRAINING ............................................................................................................................................ 11

5.1 INDUCTION ..................................................................................................................................... 11 5.2 DRILL CREW .................................................................................................................................. 11 5.3 EMERGENCY TEAMS ...................................................................................................................... 11

6 EMERGENCY PLANNING ................................................................................................................. 12 6.1 OFFSHORE .................................................................................................................................... 12 6.2 ONSHORE ...................................................................................................................................... 12

7 H2S EMERGENCY PROCEDURES WHILST DRILLING ................................................................ 13

7.1 CONDITION I (H2S < 10 PPM A IRBORNE ) ...................................................................................... 13 7.2 CONDITION 2 (H2S > 10 PPM < 20 PPM A IRBORNE ) .................................................................... 13 7.3 CONDITION 3 (H2S > 20 PPM < 50 PPM A IRBORNE ) .................................................................... 13 7.4 CONDITION 4 (H2S > 50 PPM A IRBORNE ) ..................................................................................... 14

8 H2S EMERGENCY PROCEDURES OTHER OPERATIONS .......................................................... 15 8.1 TRIPPING ....................................................................................................................................... 15 8.2 C IRCULATING OUT A KICK ............................................................................................................. 15 8.3 H2S DETECTION DURING CORING .................................................................................................. 15 8.4 H2S DETECTION DURING LOGGING ................................................................................................ 15 8.5 H2S P ROCEDURES DURING W IRELINE WORK ................................................................................ 16

9 WELL TESTING WITH H 2S ................................................................................................................ 17

9.1 INTRODUCTION .............................................................................................................................. 17 9.2 P RECAUTIONS ................................................................................................................................ 17 9.3 S TANDARD S ERVICE C ALCULATION ............................................................................................... 17 9.4 H2S CONCENTRATIONS "IN-S TREAM " DURING WELL TESTING OPERATIONS ................................. 18

10 TEST STRING RUNNING AND PULLING PROCEDURES ....................................................... 20

11 MARINE OPERATIONS ................................................................................................................. 21 11.1 GENERAL ....................................................................................................................................... 21 11.2 P ROCEDURES ................................................................................................................................ 21

12 DIVING PRECAUTIONS ................................................................................................................ 22





13 FIRST AID TREATMENT ............................................................................................................... 23 13.1 P ROCEDURE .................................................................................................................................. 23 13.2 NOTES FOR MEDICAL P ERSONNEL ................................................................................................. 23

14 H2S CHECKLIST ............................................................................................................................. 24

15 PROPERTIES OF HYDROGEN SULPHIDE ................................................................................ 26

16 PHYSIOLOGICAL RESPONSES TO HYDROGEN SULPHIDE ................................................. 27

17 PROPERTIES OF SULPHUR DIOXIDE ....................................................................................... 28

18 MEDICAL EFFECTS ...................................................................................................................... 29 18.1 NOTES FOR MEDICAL P ERSONNEL ................................................................................................ 29

19 GLOSSARY OF TERMS ................................................................................................................ 30





1 INTRODUCTION

This document is one of a series of documents within the Well Engineering ManagementSystem intended to provide Assets with a reference to best practice technical information

relating to various areas of well engineering. The information will allow Assets to makeinformed decisions during both the design and operational stages of projects. In addition, Assets will have a better understanding of important issues and therefore know what to askthe “experts” when the need arises (i.e. to be “informed buyers” of these services).





2 H 2S SAFETY PRECAUTIONS

Hydrogen Sulphide (H 2S) is a poisonous gas found worldwide. It is extremely toxic,colourless, explosive (4.3 to 46% by volume, when mixed with air) and heavier than air (1.2

relative density to air). It is recognisable in small concentrations (10 ppm in air) as anoffensive rotten egg odour. In greater concentrations (70-150 ppm in air) it becomesodourless due to paralysing the body's olfactory nerves. Exposure to higher concentrations(400-700 ppm in air) of H 2S can be fatal.

2.1 H 2S Detection

All fixed and portable H 2S detectors must be capable of sensing a minimum of 1 ppm H 2S inair, with a response time of less than 60 seconds.

All fixed and portable detectors (except Draeger tubes) must be calibrated and tested beforeentering a known H 2S-bearing zone and thereafter recalibrated and tested on a weekly basisby a competent person.

On an exploration well, all fixed and portable detectors must be calibrated and tested beforethe intermediate casing string is set and thereafter on a weekly basis by a competent person.

All test and calibration results must be recorded.

2.2 Fixed Gas Detectors

If drilling in a known H 2S formation, each rig must be equipped with an H 2S fixed monitoringsystem, which will activate audible and visual alarms at a continuously manned location. It isessential that the system will detect H 2S in air at a level at, or below, the long-term exposurelimit of 10 ppm. The system should be able to monitor those areas of the rig that could besusceptible to H 2S contamination, including:

q Shale shakersq Mud pits

q Mud logging unit

q Bell nipple

q Rig floor/driller’s console

q Spider deck

q Caisson (semi-sub MODU)

q Air intakes for living quarters

q Air intake for BA Compressor inlet

2.3 Portable Detectors (Electric)

These devices provide a qualitative indication of the presence of H 2S. The detectors maygive a read out in ppm or alarm at a set point (10 ppm). These detectors must be calibratedbefore use and at intervals of 7 days. All calibrations must be logged and a recordmaintained.

A minimum of 6 detectors must be available for use at any time.

2.4 Portable Detectors (Manual)

H2S detector tubes give a quantitative indication of H 2S by volume in air in ppm. The tube istypically broken at both ends and inserted into a bellows pump. The bellows is depressed fora set number of strokes and as the air/gas mixture passes over chemical in the tube. If any





H2S is present the chemical will discolour. By reading off the graduated scale, the percentageof H 2S will be shown.

This type of detector is not recommended for general gas detection purposes but may beused for taking samples of gas produced in well tests, gas being directed to the flare, etc.

2.5 Personal Gas Detectors (Monitors)

When operating in a known or suspected H 2S area, a supply of personal H 2S gas detectors(monitors) should be available for use by crews.

They can be of either the electronic-type, pre-set to alarm at 10 ppm or the lead acetate-typethat give a visual indication of presence of H 2S gas.





3 BREATHING APPARATUS

3.1 General

The provision of emergency breathing apparatus (BA) at specified locations on a rig is basedon the following premises:

q Any release of H 2S will activate the detectors at an early stage and allow timefor breathing apparatus to be worn

q Upon a substantial release of H 2S (> 10 PPM airborne) the drilling operationcan be suspended and the well made safe to give personnel time to vacatethe area

q BA should be designed to allow for at least one hours working duration inorder to close the well in or attempt to make the well safe by other means

The provision of BA for use in normal operations (e.g. well testing) will be based on a

separate risk assessment by a competent person (see relevant sections in this document).Platforms or production well sites where H 2S is normally present will be subject other BAprocedures

The number of sets required is based on the anticipated number of persons required to makethe well safe. It is anticipated that these numbers would be:

1 Driller

1 Assistant Driller

1 Derrickman

3 Floormen

1 OIM/Toolpusher1 Drilling Supervisor

1 Crane Operator

2 Roustabouts

2 Subsea Engineers (Semi-Sub)

This figure is rounded up to 15 sets, which should be the minimum requirement.

Spare cylinders, numbering at least 1.25 times the number of Self Contained BA setsavailable, should be provided and available for use at all times.

Sufficient “Escape Sets” equal to 1.25 times the maximum POB must be available and readyfor immediate use. Additional sets should be made available at strategic points around theinstallation for the immediate use by personnel in the event of a release of H 2S gas.

A competent person must be nominated to be responsible for the maintenance of theequipment.

Where a specialist contractor provides the breathing equipment, that contractor shall providethe competent person to be responsible for maintenance, operation and training.

3.2 Types of breathing apparatus

3.2.1 Self Contained Breathing Apparatus (SCBA)

These are personal sets with a working duration of between 30-60 minutes. SCBA shall be ofpositive pressure design with a protection factor rating of 2000 as defined in BS 4275 (ii) (or





an equivalent standard outside the UK).

3.2.2 Escape Sets

These sets are for use only to effect an escape from an area in an emergency. They are nota working set and can be of anything from 10-30 minutes duration.Smoke hoods or canister-type escape sets are not suitable for H 2S.

3.2.3 Cascade or Containerised Systems

These consist of breathing apparatus cylinders, grouped or banked together with adistribution system, to give a continuous supply of breathable air via manifolds and lines toindividual facemasks. These systems must also be provided with compressors to rechargethe cylinders.

SCBA and Escape Sets must be used with the Cascade System as a back up.

It is BG Group policy to contract a specialist service company to provide cascade systems.The contractor will provide a competent person to install, commission, maintain and trainpersonnel in the use of the equipment.

3.2.4 Cylinder Working Duration Calculation

The full working duration of BA cylinders can be calculated as follows:

)(40

)(Pr

LMin

psiessure xCylindersof CapacityWater xCylindersof Number

The nominal working duration is the full working duration reduced by a 10 minute safetyfactor, as follows:

Full Duration – 10 Minutes (Safety Margin) = Nominal Working Duration

The nominal working duration is only an estimated time. Air consumption varies betweenpersons and work being carried out can increase air consumption and reduce the durationconsiderably.





4 ADDITIONAL RECOMMENDED H 2S EQUIPMENT

4.1 Offshore

q 2 windsocks positioned so that at least one is clearly visible from any point onthe structure

q Safety harness with retrieval ropes for rescue purposes

q Chalk boards/note pads, located on the rig floor and at emergency controlpoints

q Resuscitation equipment (to be kept in sick bay)

q Explosion-proof air movers for dispersing H 2S (minimum of 3 units, explosion-proof)

q Highly visible warning signs reading: “Danger Hydrogen Sulphide H 2S.” fordisplay on each side of the rig

q Two flag poles for windsocks and operational flags (coloured red)

q Lights to illuminate all windsocks, flags and signs. These lights must beconnected to an emergency supply.

4.2 Onshore

In addition to the relevant equipment from above offshore list, the following shall be availableat onshore sites:

q Tall flare stack

q Audible and visual warning system

q Warning signs at location boundary

q Status boards at site entrance.





6 EMERGENCY PLANNING

6.1 Offshore

It is the responsibility of the rig owner, through the OIM, to have written instructions for use inthe event of any emergency, including H 2S emergencies and written procedures must be inplace describing the actions to be taken by all personnel on board. The standards in Sections8 and 9 should be used to assess the rig owner’s procedures. Any discrepancies should beaddressed with the rig owner and included in the Management Interfacing Document(Bridging document).

6.2 Onshore

It is the responsibility of the site owner (normally BG Group) to have written instructions foruse in the event of an emergency. The standards in Sections 8 and 9 should be used todevelop the H 2S site procedures. The site manager is responsible for ensuring theprocedures are adhered to.





7 H 2S EMERGENCY PROCEDURES WHILST DRILLING

7.1 Condition I (H 2S < 10 PPM Airborne)

Well Condition : Normal circulation taking place, H 2S detected.Alarm None.

Operational status Drilling operation under control.

Actions

q All personnel to be notified via PA system of status and updated in anychange in condition

q Stop all work that may give rise to a source of ignition

q H2S technician (or nominated person) to make ready all emergencyequipment

q Check location of buddy and the wind direction

q Drill crew, logging and mud engineering personnel to don breathing apparatusand be ready to go "under air"

7.2 Condition 2 (H 2S > 10 PPM < 20 PPM Airborne)

Well Condition : Normal circulation taking place.

Alarm H2S alarm sounds, sensors picked up reading of > 10 ppm.

Operational status Drilling under control, H 2S now above threshold limit value.

Actions

All procedures for condition 1 apply, plus:

q Warning to be displayed on all sides of the rig

q Drill crew, mud loggers and mud crew to go "under air"

q Shut down accommodation HVAC system (see note below)

q All non-essential personnel to remain in accommodation and issued withescape sets

Condition 2 will remain in force until H 2S concentrations fall below 10 PPM or rise above 20PPM.

Note: This needs very careful consideration as once this is done there is limited time beforeevacuation must start. Wind direction must be taken into account.

7.3 Condition 3 (H 2S > 20 PPM < 50 PPM Airborne)

Well Condition : Normal circulation taking place.

Alarm High levels H 2S detected by sensors.

Operational status Well Control Status

Actions

All procedures for Condition 1 and 2 apply, plus following drilling actions:

q Shut in well and circulate through choke





q Vent gas through flare line

q Commence circulation treatment of mud as per Condition 2

q Monitor airborne and in stream levels continuously

Condition 3 will remain in effect until H 2S concentrations fall below 20 ppm or rise above 50ppm.

7.4 Condition 4 (H 2S > 50 PPM Airborne)

Well Condition : Shut in with circulation taking place through the choke.

Alarm High levels H 2S detected by sensors.

Operational status Well Control Status.

Actions

All above procedures, plus the following:

q Fly red flags from two flagpolesq All non-essential personnel to be evacuated from the installation if safe to do

so

q Shut well in, monitor drill pipe and annulus pressures

q Carefully assess the following prior to deciding course of action:

- Location of sensor giving high readings

- Wind direction and weather conditions

- H 2S neutraliser availability

- Helicopter availability and safe landing area.

(If neutraliser is available and wind is dispersing the H 2S, carry on circulating to reduce thelevels of H 2S).





8 H 2S EMERGENCY PROCEDURES OTHER OPERATIONS

8.1 Tripping

If H2S is detected whilst tripping, proceed as for H 2S Detection While Drilling Conditions 1-4.Stop trip and circulate at trip depth, prior to running back to bottom and circulating entire mudsystem. Stripping in may have to be considered if the Threshold Limit Value is exceeded withthe bit at shallow depth.

When circulating out trip gas (normally through the choke) all essential personnel must donBA sets "under air" and keep sets on until H 2S level is below 10 ppm. A series of publicaddress announcements should be made to keep essential personnel advised of changes incondition.

8.2 Circulating Out A Kick

If H2S is detected whilst circulating out a kick, follow normal well kill procedures and

guidelines outlined in Conditions 1-4 for H 2S Detection While Drilling.If the H 2S concentration at any time exceeds or is expected to exceed 50 ppm (airborne),then the kick must not be allowed to surface until all essential personnel are wearing BA.

In the event that H 2S is encountered when it was not predicted and no BA is available, it maybe necessary to close the well in completely and bullhead 1.5 times the drill pipe volume withkill density mud down the drill pipe and 1.5 times the annulus volume with kill density muddown the kill line.

8.3 H 2S Detection During Coring

H2S procedures must be in place well before the core barrel is at surface. If H 2S is detectedwhilst cutting a core there is the possibility of some gas being trapped inside the core barrel.Therefore, when the core is being recovered, the maximum number of personnel on the rigfloor and surrounds will be:

q Drilling Supervisor/Toolpusher

q H2S Supervisor

q Driller

q 3 Floormen

q Corehand

q Geologist

q Mud LoggerOne person should monitor the H 2S levels around the core immediately after recovery usingportable H 2S detectors.

If H2S in air has been detected, personnel must wear BA at all times prior to the core barrelreaching the rotary table and until the core has been recovered and boxed. All core boxesshould be labelled that H 2S contamination may be present.

8.4 H 2S Detection During Logging

If H2S is detected during open hole logging runs, ensure that tools and cable are washed withscavenger when pulling out of a hole. When handling RFT or side wall core samples, BA

should be worn until samples are recovered and tools thoroughly washed.





8.5 H 2S Procedures During Wireline Work

1. The wireline crew must be trained in H 2S operations. All equipment to be rated andcertified for H 2S service (NACE-MR001-75).

2. A pumping sub must be positioned in the swab valve. The sub must have a facility toenable venting and connection of the kill mud line. Both lines must have double isolationvalves and a check valve on the kill line.

3. Testing personnel will don BA "under air" prior to operating valves or opening equipmentthat has contained H 2S (e.g. changing chokes, operating valves, sampling etc).

4. All non-essential personnel must keep clear of restricted areas and remain in theaccommodation. All personnel essential to the operation working within the restrictedarea must use the "BUDDY SYSTEM", i.e. always work in pairs.

5. All essential personnel relative to the breaking out of wireline tools or carrying outoperations on wireline tools on surface should wear BA.

6. Prior to opening the master valve, the mud kill line must be connected ready foroperation; all lines having been pressure tested prior to proceeding with the operation.

7. The Drilling Supervisor is to maintain an adequate and readily available supply of killfluid during wireline operations. The kill line must be tested prior to commencingoperations.

8. The venting/flow line must be tied via the rig choke manifold or test system to the flare.

9. A suitable H 2S scavenger and corrosion inhibitor must be applied to all downholeequipment, and the wireline.

10. No open tanks will be used for collecting well fluids. Surge tanks and separators will beequipped with over-board vent lines to the flare.

11. There will probably be a background level of H 2S during testing coming from a variety ofsources (incomplete combustion, vented gas from choke changes etc).

12. The lubricator must be fitted with flushing capabilities. Injection grease return lines mustreturn to a waste drum located in an assigned hazardous area. On completion of theoperation, the waste drum will be sealed and clearly marked as being exposed to H 2S.

13. At the end of the test, reverse circulate tubing contents to the flare, circulateconventionally until mud sulphide level is stable and the pH is 10.5 to 11. Prior to thepulling out, slug tubing with inhibitor.

14. On completion of the wireline phase, all equipment will be extensively flushed beforerigging down. All downhole and surface equipment will be labelled as having been

exposed to H 2S so that the correct precautions are taken when servicing the equipment.15. It is important to be aware of any increases in background levels and to take appropriate

precautions.





9 WELL TESTING WITH H 2S

9.1 Introduction

This phase of the drilling programme is likely to be the first time at which H 2S is produced tosurface and consequently the situation requires careful management.

Well testing must be performed with the minimum number of personnel in the immediatevicinity of the testing equipment to carry out the operation as safely and as efficiently aspossible.

It is essential to ensure all personnel are briefed prior to commencing the test.

The briefing should cover inherent hazards of the operation, precautions for non-essentialpersonnel, and familiarisation of the available breathing apparatus and its location on theinstallation.

9.2 Precautions

The following precautions will be followed for testing operations involving H 2S:

1. Initial hydrocarbons to surface must only take place in daylight unless the risks involvedare fully assessed by the Well Testing Supervisor, Well Operations Engineer and RigSuperintendent and approved by the OIM/Site Manager.

2. All testing equipment and tubulars shall comply with NACE MR-01-75 H 2S.

3. On initial opening of the tool string, breathing apparatus shall be worn by all rig floorand well test personnel until such time that the level of H 2S being produced has beenestablished. Depending on the level, personnel may at this time be allowed to de-maskwhere the levels fall to less than 10 ppm.

4. Burners will be equipped with a continuous pilot light system.5. All non-essential personnel shall be restricted to the accommodation during flow

period. The control of all personnel movement is the responsibility of the OIM/SiteManager in consultation with the Drilling Supervisor.

6. No open tanks shall be used for collecting well fluids. Surge tanks and separators shallbe equipped with over-board vent lines to flare.

7. There will probably be a background level of H 2S during testing, coming from a varietyof sources, e.g. incomplete combustion; vented gas from choke changes; etc.

8. At the end of the test, tubing contents shall be reverse circulated to the flare, circulateconventionally until mud sulphide level is stable and the pH is 10.5 to 11. Prior topulling out, slug tubing with inhibitor.

9. On completion of the testing phase, all equipment shall be extensively flushed beforerigging down. All downhole and surface equipment shall be labelled as having beenexposed to H 2S so that the correct precautions are taken when servicing theequipment.

9.3 Standard Service Calculation

Although most temporary well testing equipment is certified for sour service, there will be anoperational limit (in terms of H 2S concentration) imposed on the well test if any of thetemporary test equipment is certified for standard service only. The cross over point fromstandard to sour service, in terms of concentration of H 2S in the produced hydrocarbonsstream, is defined by NACE Standard HR-01-75. Equipment should be sour serviceclassification. "If gas being handled is at a total pressure of 65 psia or greater and if the





partial pressure of H 2S in the gas is greater than 0.05 psi".

For example, if the maximum surface pressure is 1665 psig (1680 psia) so that the limit ofstandard service conditions is given by:

0.05 psia = mols x Total Pressure (psia)

0.05/1680 = 0.0000298 mols

= 29.8 ppm of H 2S

9.4 H 2S Concentrations "In-Stream" During Well Testing Operations

This section refers to H 2S concentrations "in-stream" during well testing operations. If levelsof H2S are observed “in air” whilst testing, the well should be shut in and the sourceidentified. For procedures during wireline work see Section 9.5 .

9.4.1 (H 2S <10 PPM)

Well Condition : Normal Operations.Alarm H2S indication < 10 ppm.

Operational status Normal testing operations taking place.

Actions

q All personnel to be notified of condition by PA announcement

q H2S technician to ensure that all emergency equipment is available

This level will remain in force until the in-stream level reads zero, or goes above 10 ppm

9.4.2 (H 2S > 10 < 20 PPM)

Well Condition : Normal Operations.

Alarm H2S indication > 10 < 20 ppm.

Operational status Normal testing operations taking place.

Where necessary warning signs to be displayed on all sides of the rig, illuminated at nightand at times of poor visibility.

Actions All procedures for Level A apply, plus:

q Drill crew, well logging personnel and mud crew to don breathing apparatus"under air"

q Buddy up, observe wind indicators

q In the event of failure of, or leakage from the system and gas has escapedinto the atmosphere, conditions 1 through 4 shall apply

Level B will remain in effect until H 2S concentrations fall below 10 ppm, or increase abovethe standard service.

9.4.3 H 2S 20-150 PPM

Personnel who are wearing BA (at initial opening) may now de-mask if the in-streamconcentrations has stabilised below 150 ppm and ambient air concentrations remain below10 ppm.

PA announcements will be made.q Testing personnel will mask up prior to carrying out any procedure likely to





vent H 2S (e.g. changing choke, operating valves, sampling)

q Flow periods will be kept to a minimum duration

q Monitor continuously for any leaks

q Buddy system initiated

9.4.4 H 2S 150-250 PPM

q All personnel on the rig floor will wear BA "under air"

q PA announcements will be made restricting all non essential personnel to theaccommodation module


q No helicopter movements whilst flowing

q Flow periods may proceed into the night. However, no opening of the well

may be made at night9.4.5 H 2S 250-500 PPM

q All personnel outside the accommodation will wear BA "under air"

q No helicopter movements while the well is flowing


q Flow well in daylight hours only

9.4.6 H 2S OVER 500 PPM

q All personnel outside accommodation will wear BA "under air"

q Unless in-stream levels have been previously prognosed to be greater than500 ppm and all necessary recommendations and precautions previouslyagreed to enable safe testing of the well, the test shall be suspended until allnecessary precautions are in place

q Report to office Drilling Manager and safety advisor. Discuss whether testshould be recommenced and precautions to be taken





10 TEST STRING RUNNING AND PULLING PROCEDURES

q Continuous control of mud level will be carried out with the trip tank

q If the well flows from the annulus (i.e. kick occurs) the drillstring is to bepicked up and the pipe rams or the annular to be closed

q Stab in safety valve (4.5" IF PIN/BOX) with appropriate cross-over to thetubing string premium thread must be available on the rig floor in case of flowfrom tubing

q A mud pump will be lined up to fill the annulus in case of premature openingof the downhole tester valve, while running in the hole

q Reverse circulation will only occur during daylight hours unless specificallyauthorised in case of emergency

q While pulling out of hole, continuous control of the annulus level will bemaintained. A flow check will be made when the test string is pulled from theliner. Prior to pulling out of hole, the surface testing equipment and tubing willbe flushed with suitable scavenger

q Five stands before the first test tool reaches surface, ALL rig floor personnelwill go "under air". BA will be worn until all test tools are broken out and laiddown, sample chambers emptied and slip joints broken





11 MARINE OPERATIONS

11.1 General

It is essential that all standby vessels working the installation have a copy of the installationH2S procedures.

Standby vessels and supply vessel crews should be familiar with the dangers of H 2S. Theyshould be made aware that it can accumulate at low levels in dangerous concentrations.

The OIM must keep the Masters of stand-by vessels and supply vessels advised of H 2Soperations and the ongoing status of work. Vessels should only approach the rig afterdiscussion with the OIM.

All vessels should have a fixed gas detection system fitted. This system must be operationalat all times when a vessel is inside a 500 metres zone.

Every vessel should carry portable H 2S monitors and an SO 2 monitor. Designated crew

members should be trained in their use.

11.2 Procedures

q When contacted by the installation OIM, all vessels within the 500 metre zonemust depart to a minimum 1000 metres upwind of the installation

q On reaching the 1000 metres range vessels must report their location to theinstallation radio room

q The standby vessel will remain at the ready for any further instructions fromthe OIM

q If requested to come into the 500 metre zone at close stand-by, the Master

shall:- Remain upwind observing windsock/flags on the installation

- Ascertain from the OIM the exact details of the emergency and details ofairborne concentrations

- If flaring is taking place during well tests, observe smoke direction andmonitor any liquid carry-over

- Ensure the designated person on board the vessel has checked theportable detectors and made them ready for use





12 DIVING PRECAUTIONS

q Do not contaminate diving equipment with crude oil

q Do not bring any contaminated tools into the diving bell or chamber

q Do not locate bell over an area where gas bubbles are rising from the sea bed

q At the first sign of any contamination all divers should go onto the Built InBreathing System (BIBS) and breathe from the mask until test provecontamination is clear

q Control cabins should where possible be fitted with a system to give positiveinternal air pressure. Where no system is fitted, BA must be worn

q When the diver’s primary air supply is ambient air, a secondary system mustbe supplied.

q Procedures will be in place to recover the divers

q All areas of the dive system must be covered by audible alarms and areas ofhigh noise must also have warning lights.





13 FIRST AID TREATMENT

13.1 Procedure

q Remove casualty to fresh airq If breathing has ceased or is laboured, begin artificial respiration immediately

(NOTE - this is the quickest and preferred method of clearing the casualty'slungs of contaminated air)

q However, during a major escape of H 2S, it may not be possible to move thecasualty to fresh air. In such instances, those personnel rendering first aidmust continue to wear breathing apparatus. A resuscitator must be used forcasualty

q The resuscitator must be used for purging H 2S from the bloodstream

q The casualty must be evacuated to hospital as soon as possible

q Any person who has been overcome by H 2S should be seen by a doctorregardless of any apparent recovery

13.2 Notes for Medical Personnel

H2S does not combine with the haemoglobin of the blood; its asphyxiant action is due toparalysis of the respiratory centre. With repeated exposures to low concentrations,conjunctivitis, photophobia, corneal bullae, tearing pain and blurred vision are thecommonest findings. High concentrations may cause rhinitis, bronchitis, and occasionallypulmonary oedema.

Exposure to very high concentrations results in immediate death. Chronic poisoning results

in headache, inflammation of the conjunctivae and eyelids, digestive disturbances, loss ofweight and general debility.





14 H 2S CHECKLIST

The H 2S checklist should be used prior to drilling operations in formations where H 2S may beencountered.

Items Yes/No Remarks

(a) Are all personnel (including visitors) informed of hazards of H 2S and SO 2

(b) Are all personnel (including visitors) informed of proper use of safetyequipment?

(c) Are weekly H 2S safety meetings and drills being held, and attendancerecords being kept?

(d) Have all personnel been given basic H 2S First Aid Training?

(e) Are the following available?

Protective breathing apparatus for all personnel (including stand-by vesselscrew)

Resuscitators, complete with face masks, oxygen bottles and spare oxygenbottles

Breathing air manifolds, hoses and masks on the rig floor

Cascade air-bottle system to refill individual BA bottles

First aid kit

Stokes litter or equivalent

Portable H 2S detectors

Retrieval ropes with safety harnesses

Chalk boards and note pads on rig floor, in shaker area and cement pumproom

H2S detector ampoules(f) Are wind direction indicators installed?

(g) Are operational danger signs and red flags available for use?

(h) Are H 2S detection and monitoring equipment with sensing points at thefollowing location?:

Bell Nipple

Shale Shaker

Mud pits

Drilling stand

Living quarters

Other areas where H2S might accumulate

(i) Have safe briefing areas been designated?

(j) Are all ventilation devices explosion proof?

(k) Are all drill string, casing, wellhead, BOP and related equipment designedfor use in all H 2S environment?

(l) Does tool joint compound in use contain free sulphur?

(m) Is the pH of water-based mud systems maintained at 10.0 or greater?

(n) Are sufficient additives for neutralisation of H 2S available?

(o) Is gas from the mud degasser piped to a closed flare system for burning ata suitable remote stack?

(p) Is the H 2S flare system equipped with a pilot, automatic igniter and back-upigniter?

(q) Will the disposal of well influx fluids from a kick be either by pumping fluids





16 PHYSIOLOGICAL RESPONSES TO HYDROGEN SULPHIDE

H2S Concentration in Air(PPM by Volume)

Response Classification

10

15

Can smell minimal effect over 8 hours Occupational exposure standard:

- Long term exposure limit

- STEL

10

15

70 – 150

Minimal eye irritation

Minimal lung irritation

Kills smell in 3 – 15 mins

Irritates eyes, throat

Irritation

150 – 400 Loss of smell, dizziness difficult respiration,coughing, irritation of eyes, throat and lungs.

Need prompt removal to fresh air if respiratoryparalysis is to be avoided

Dangerous – may lead to seriousinjury or death.

400 – 700 Coughing, collapse unconsciousness, death.

Breathing will stop and death will result if notgiven artificial resuscitation immediately.

Dangerous – may produce seriousinjury or death.

700 – 1000 Rapidly produces unconsciousness –permanent brain damage possible. Immediateunconsciousness death in a few minutes.

Immediate threat to life.

Notes on the above table:

1 Occupational Exposure Standard as defined in the UK HSE Guidance Note EH40.

2 Note that the above values are ppm (parts per million) "in air" not "in stream".3 Above values are averages only. Susceptibility varies significantly betweenindividuals exposed.





17 PROPERTIES OF SULPHUR DIOXIDE

Sulphur Dioxide (SO 2) is a colourless gas, or liquid, with sharp pungent odour in commonorganic solvents and water. It forms a corrosive acid in aqueous solutions. It is not

combustible.q T E L =TWA 8 HRS = 2 ppm

q STEL 10 mins = 5 ppm.

q Chemical Symbol SO 2

q Melting Point -72ºC (-99ºF)

q Boiling Point -10ºC (14ºF)

q Colour Colourless

q Odour and Taste Pungent

q Specific Gravity 1.434 (liquid) @ 0ºC (32ºF)q Vapour Density 2.264 (air = 1)

q Solubility 22.8g in l00cc of water at 0 o,

0.58g in l00cc of water at 90 o

soluble in alcohol, Acetic and Sulphuric Acid

q Corrosivity Anhydrous sulphur dioxide is non corrosiveto steel or other common metals





18 MEDICAL EFFECTS

q Very highly toxic and corrosive

q Ingestion, unlikely to cause problems

q Skin, unlikely to cause problems. Frostbite injury if liquid

q Eye, pain, redness, watering and blurred vision

q Respiratory tract, irritant, cough. Shortness of breath, possible systemiceffects

q Inhalation, mild poisoning causes irritation of the throat and nose withshortness of breath, coughing and choking, and occasionally wheezing. Acutepoisoning causes severe shortness of breath due to congestion of the lungs

IN ALL CASES SEEK URGENT MEDICAL AID

18.1 Notes For Medical Personnelq Pulmonary oedema; treat with positive pressure, ventilation

q Asthma; treat with bronchidilators and steroids

q Corneal ulceration; obtain immediate ophthalmological opinion




19 GLOSSARY OF TERMS

Auto Ignition Temperature: The temperature at which a flammable substance when it comes into contact with a hotsurface will auto ignite. (The surface temperature be above the ignition temperature offlammable substance)

Buddy System To pair up and work together

Competent Person A person who has obtained the necessary knowledge, training and skills to do the job

Critical Temperature Temperature above which a gas cannot be liquefied

Critical Pressure Pressure at which a gas may be liquefied at its critical temperature

Highly Flammable Any flammable substance with an ignition temperature of 32 c or below

Ignition temperature The temperature at which a flammable substance will support combustion on the introductionof a source of ignition

Long Term Exposure Limit The maximum concentration of a (ltel) substance to which a person can be exposed byinhalation 8 hrs a day, 5 days a week over a 40 year working life without the risk of adversehealth effect

Molecular Weight The weight of a molecule compound to the weight of an oxygen atom weighing 16 units(formula weight)

N A C E National Association Of Corrosion Engineers (USA)

P P M: Parts Per Million

P S I G: Pounds Per Square Inch (Gravity)

P S I A Pounds Per Square Inch (Air)

Range of Flammability The fuel air ratio volume / volume that any flammable substance must be within beforecombustion can occur. If there is too much air the mixture will be too weak. If too much fuelthe mixture will be too rich

S C B A Self Contained Breathing Apparatus

Spontaneously Combust The ignition of a substance as a result of internal oxidation processes without the applicationof external heat

Short Term Exposure Limit: This is the maximum concentration to which a worker can be exposed by inhalation for aperiod of up to 10 minutes continuously without suffering adverse health effects

T L V: Threshold limit value, refer to airborne concentrations of substances to depict conditionsunder which nearly all workers may be repeatedly exposed without adverse health effects

environment manual

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