06 Explosives For Perforating

Quartz School for Well Site Supervisors Module – 12 Well Completions

Section – 6 Explosives for Perforating

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 1/20

ORIENTATION TO EXPLOSIVES Session Objectives: • • •

Explain the classification of explosives and give at least one example of each. List the temperature ratings of the most commonly used explosives. Describe the extra precautions that need to be taken with HMX explosives.

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 2/20

Overview of Explosives • Nature of Explosives • Classifications of Explosives • Characteristics of Specific Explosive Compounds

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 3/20

Nature of Explosives • Explosive — any substance or device that will suddenly release its energy i.e., it is a form of pressure release. No Second Chance with Explosives

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 4/20

Difference- High and Low Explosives Physics Nature Of Ignition Time To Gas Velocity Of Reaction Pressure (psi)

High Explosive

Low Explosive

Detonates Microsecond ~5 miles/sec ~4 million

Ignites Millisecond ft/sec ~50 thousand

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 5/20

Classification of Explosives Chemical Chemical Explosives Explosives Flammable Flammable Solids Solids Baker Charges

Low Low (Rapid (Rapid Burning) Burning) Black Powder American HT (Igniter needles, CST cartridges, and CPST charges)

High High (Detonating) (Detonating)

Primary Primary High High

Lead Azide (Detonators)

Secondary Secondary High High

RDX, HMX, HNS, PETN (Shaped Charges and Detonating Cords)

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 6/20

High and Low Explosives Low Explosives

High Explosives

Deflagrating Explosives: Slower reaction time and less pressure build-up.

Detonating Explosives: High rates of reactions and pressure build-up.

Primary High or Initiating Explosives

Secondary High Explosives

Extremely sensitive. Detonation can be initiated by any small disturbance.

Normally requires a detonator to set off. May detonate if heated in confinement.

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 7/20

Low Explosives • Black Powder

• American High Temp

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Composition: – Saltpeter KN03, Sulfur, Charcoal

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Characteristics:

– 86% Ammonium Perchlorate/14% Carbazole

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– Fine black powder – Flash point 500oF approx. – One hour rating: 450oF

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Applications: – Primer igniters, squibs – BST/CPST power cartridges

Composition:

Characteristics: – White Powder – Flash point: 550oF – One hour rating: 450oF

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Applications: – Sample Taker (CST)

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 8/20

Primary High Explosive - Lead Azide • Composition: Pb(N3)2 • Characteristics: – Very sensitive to friction – Self-detonates when heated sufficiently at atmospheric pressure – Flash Point: 625oF Æ point at which it starts to become gas – Temp. rating depends on purity and confinement effects

• Application: – Detonators only

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 9/20

Secondary High Explosive - RDX •

Composition: – Cyclotrimethylene trinitramine (C3H6NG6O6)

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Characteristics: – – – – – – – –

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White crystalline solid (dyed pink) Melting point of 388oF, crystal density 1.82 g/cc Detonation velocity of 8,400 m/sec Outgasses or decomposes harmlessly when heated or burned at atmospheric pressure Self-detonates if heated in confinement above 180oC or 365oF Rated at 340oF for the one hour rating at atmospheric pressure Rated at 330oF for the one hour rating when exposed to well pressure Insoluble in water or alcohol

Application: – Detonating cord – Shaped charges (all except high temperature)

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 10/20

Secondary High Explosive - PETN • Composition: – Pentaerythritol tetranitrite (C5H8N4O12 )

• Characteristics: – – – – – –

White crystalline substance More sensitive than RDX Rated temperature of 250oF for one hour Melting point 284oF Self-detonating above 400oF at atmospheric pressure. Insoluble in water, detonates when wet

• Application: – Detonating cord and shaped charges (HEGS)

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 11/20

Secondary High Explosives - PSF • Composition: – Picryl-Sulfone

• Characteristics: – Yellow powder – Flash Point 585oF – Rated at 470oF for one hour

• Application: – Shaped charges – High temperature detonating cord

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 12/20

Secondary High Explosives - HMX • Composition: – Cyclotetramethylene Tetranitramide (C4H8N8O8)

• Characteristics: – – – –

White crystalline solid, crystal density 1.90 g/cc Melting point of 275o C. Detonation velocity 9,124 m/sec Self-detonation of pure HMX when heated to 327o C at atmospheric pressure – Generally rated to 400o F for one hour. – Increased impact sensitivity when exposed above 330o F • Need to handle with care

• Application: – Detonating cord – Tubular goods cutter – Shaped charges

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 13/20

Secondary High Explosives - HNS • Composition: – Hexonitrostilbene (C14H6N6O12)

• Characteristics: – – – –

Crystalline solid, crystal 1.74 g/cc Melting point of 317o C Detonation velocity 7,000 m/sec. Outgasses or decomposes when heated or burned at atmospheric pressure – One hour rating 500o F

• Application: – Metallic covered cords – Loaded string cutters Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 14/20

Temperature Ratings Summary - 1 hr. HNS/HTX

Detonating Cord, Shaped Charges

PSF

Detonating Cord, Shaped Charges

HMX

Detonating Cord, Shaped Charges

RDX

Det. Cord, Shaped Charges HEGS-highly efficient gun system

PETN 0

100

200

300

400

500

Temperature (°F) Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 15/20

Time vs. Temperature

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 16/20

Relative Sensitivity To Mechanical Shock

HMX Above 330°F

Sensitivity

Lead Azide

PETN

RDX

HMX

American HT

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HMX and Temperature > 330 deg F •HMX at 330 ºF has a phase change which increases its impact sensitivity •If unshot guns need to be pulled from the well: –For 48 hrs do not unload the guns –After 48 hrs HMX is safe to handle

Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 18/20

Temperature Effects Overview •Ratings: –Temperature: RDX < HMX < HNS/HTX –Performance: HNS < HTX < RDX < HMX

•When Time-Temp limits are exceeded: –HMX or RDX –< 300 ºF –Reduced Performance –Charges likely to burn not autodetonate –> 300 ºF –Charges may burn or autodetonate –HMX > 330 ºF becomes sensitive (wait 48hrs before pulling out of hole) –HNS/HTX is not known to autodetonate •Might lose performance or burn Quartz School. Module 12: Well Completions / Section 6: Explosives for Perforating 19/20