Explosives Safety

• Common Explosive Operations– Perforating

– Pipe Cut-off (chemical, explosive, Split Shot, Collider Tools)

– String Shots

– Gas Generator charges

– Any tool or equipment with an explosive component

Accidents with Explosives

• In entire US industry (mfg, mining, demolition, construction and oilfield) – there are about 50 deaths per year.

• In US oilfield – there are about 12 serious accidents per year. 8 deaths in worst year.– In 20 year study of 3 major service providers, there

were 94 incidents, 49 injuries, and 28 deaths.

• All preventable.

When did the accidents occur?

• 1980 to 89: 14 injuries 8 fatalities

• 1990 to 94: 18 injuries 10 fatalities

• 1995 to 00 16 injuries 9 fatalities

• These are just from the three major service providers, they do not cover the independents.

Incidents Injuries FatilitiesPower on Panel 15 19 15Stray Power 6 0 1Pinched Explosives 13 7 6Pressure 5 0 0Unknown Problems 9 7 2

Causes of Oilfield Accidents with Explosives

Source – James Brooks, Schlumberger, Jan 2002

48 33 24

Oilfield Accidents with Explosives

• Most accidents are the results of missed runs– Retrieved guns

• Power left on panel – 56%• Pinched explosives – 29%• Unknown – 12%

• Cause of detonation by cell phone, radio, radar, etc., is a very remote possibility.

• Anything that raises the incidence of missed runs significantly raises the possibility of accidents. One thing that has raised missed runs (from 2% to 10% or more) is the use of “radio safe” firing heads.

Stray Power

• RF, static, impressed current, cathode protection, and any other source that uses the well as a ground.

• Procedure – measure stray voltage with equipment isolated from well – if less than 0.25 volt, connect ground strap and proceed.

• If 0.25 to 1 volt, a RF safety cap capable of handling the problem must be used.

• Over 1 volt – identify the problem and repair/shut down while perforating..

Missed Runs with Perforating Guns

• A general information E-line sequence:1. Double check panel off and firing key removed.2. Pull gun up hole, if possible, to a shallow, safe location (tight zone) and wait min. 15 minutes3. Pull gun into lubricator, wait minimum of 15 minutes. Gun must cool down.4. Lay lubricator down, disconnect head and remove detonator (Examine for signs of low order detonation. Care must be taken for trapped pressure.) DO NOT GO NEAR THE GUN. Inspection of the gun can occur only after it is torn down.

5. Some guns may not be re-run. (Some explosives develop a “memory” for temperature and pressure)

Explosive Components

• Detonator or cap (most dangerous)

• Detonating Cord

• Charges– High explosive – TNT, Nitro, RDX, etc.– Low Explosive – gas generators – black powder

Radio Silence

• Why is it needed?

• When is it needed?

• When can it end?

• What other devices are involved?

Radio Silence

• Why? – there is a very remote chance that radio transmissions will set off a detonator (actually, it is almost unknown in the Petroleum Industry).

• When to use a radio silence policy – When using any detonator that has not been certified as radio safe.

• When is it over – when the gun is 1000 ft below the ground level. Re-institue radio silence when gun is pulled until it has been confirmed to have all fired.

• However, be cautious. Radio safe detonators are less reliable than other detonators on firing and most industry perforating accidents are from work around missed runs (guns did not fire). “Radio Safe” detonators actually increase the incidence of missed runs.

Final Word

• See the BU or Asset policy on the arming and running of explosive devices. If they don’t have a policy or defer to the service provider – MAKE SURE THEY HAVE AND FOLLOW A SAFETY POLICY.

• Any doubts? – Call me (from off well location).

George E. King 1 281 366 4083 (office), 1 281 851 8095 (Cell), 1 281 693 0371 (home)

Support Documents

• Every Service provider that deals with explosives must have a safety document – ask to see it.

• 70% of the explosive accidents occur with 30% of the companies involved in perforating. A consistent safety program and strict adherence to that program makes the difference.

Arming Sequence

• A device must always be electrically armed before being ballistically armed.

• If this sequence is followed, accidental initiation of the detonator, blasting cap, when the electrical connection is made, will not cause the rest of the explosive train to detonate such as primer cord, shaped charges, cutters and setting tools.

Arming

• Electrical arming : electrically connecting the detonator to the E-line.

 • Ballistic arming : connecting the

armed detonator to the rest of the explosive system, (primer cord and shaped charges)

Arming

• No gun shall be armed ahead of time. A gun will ONLY be armed just prior to RIH at the jobsite.

• Subsequent gun runs will be armed only after being attached to the E-line head.

Arming – (This is for information only – it is not a procedure)

1. Place cap in safety tube before removing shunt.2. Remove shunt after securely closing safety tube cover.3. Check cap electrically for insulation and continuity.4. Cut one wire lead to desired length at a time. Do not simultaneously

cut both lead wires.5. Prepare conductor wire lead and check for sparking.6. Splice and insulate conductor wire to one blasting cap lead.7. Prepare ground wire lead and splice to remaining cap lead and

insulate.8. Make a fresh square cut on detonating cord using a sharp blade and

a block of wood for back-up.9. Remove cap from tube and insert open end on detonating cord.10. Push cap until it seats on cord.11. Hold cap and cord firmly together with one hand and double crimp

cap using a standard crimping tool only.12. Secure detonator and cap end of gun or arming porthole as required.13. Pick up armed gun, carefully, and stab into the lubricator or BOP’s.

Make up lubricator to BOP's.

Some Other Identified (Problem?) Electrical Signals

• Marine radios on passing ships• Radar• Electrical storms (within 5 miles, hearing or sight –

whichever is further)• Mobile phones and radios• Electric welders• Thaw machines• Electrical circuitry that may be in contact with the well

(data gathering, cathodic protection, etc.)• Static and differential voltage potential of the well site.

Static is the more important problem.

Disarming Unfired Guns

• All these and other perforating operations to be carried out ONLY by the service company.

• During recovery, the E-line unit and other well operations must be in same safe condition as it was when the gun was armed.

• Always assume the gun has not detonated properly, misfired, when recovering it at surface no matter what the indications were.

• Check for shots fired while gun is exiting lubricator. If no shots have fired, the most dangerous situation, then the blasting cap must be disarmed as soon as possible. The odds of the gun having trapped pressure inside are also much higher when it has not fired.

Recovery and Disarming an Unfired Perf Gun or Cutter

• 95% of perforating accidents occur with misfired (retrieved) guns.

• The main problem that causes missed runs is electrical connection problems.

• Can the device be dropped and cemented over without creating problems later?

• Absolute fewest people on location – recommend service company specialists only.

Recovery and Disarming

• Can the detonator be removed before the gun is pulled? (some TCP and CT devices provide this opportunity).

• During recovery, the pad, E-line and well must be safed-out (same as running).

• Always assume that the gun being pulled is live, regardless of indications.

Recovery and Disarming

• Check for shots fired as gun is pulled from lubricator.

• If no shots fired:– Most dangerous problem – suspend operations, let the

gun sit, below ground preferably or out of the way, until it cools. Check heat with a remote sensor – don’t approach gun.

– Incidence of trapped gas pressure also higher (low order firing or burning of charges)

• If shots fired:– Expect trapped pressure (don’t assume venting)

Missed Runs - Disarming

• Disconnect ballistically, then electrically (detonators placed in safe tubes) before electrical checks.

• Re-Run?– Flooding – do not re-run charges– Electrical problem – gun can be re-run if total

cumulative time at temperature allows.– If any damage seen, do not re-run

Explosives Problems

• Detonators – very sensitive and dangerous• High Explosives – typically not a safety problem.

Problem is shock load and shattering.• Propellent - large amounts - have lost holes and

done casing/wellhead damage (BP, Arco, Oryx)• Small Propellant drivers w/perf guns - very good

mini-breakdowns

Explosives

• Two types: high and low explosives– High explosives: generates a shock, shatters

rock if not focused (focused means a shaped charge). Older examples are TNT and Nitro. Newer products are RDX, HMX, etc. Preferred explosives are usually very stable.

– Low explosives: gas generators pressure up a localized area quickly. Useful for pulses, etc.

Unusual Problems

• Loading tube misalignments –

• Loading tube failures

• Explosions at surface – rare – usually from human error. Also – watch pressure testing lubricator to very high pressures with pressure fire switches or very rapid pressuring of electrically fired guns.

Using Explosives

• Gas pulse tools – useful for breaking up scale bridges and some harder paraffin blockages. May create very short (1 meter) fractures.

• Shock tools – can rubblize a zone (may be good or bad). Useful for cavity initiation.

• Focused explosives – perforators and pipe cut-off.

Explosive Problem Areas

• Expert application only

• Watch pipe loads and forces

• Secondary problems with hole collapse, etc.

• Offers little lasting benefit if original problem is not fixed.