Perforation

PERFORATION 

Perforation helps create a hole in the casing through the cement and into the formation to form a channel for the oil and gas to flow from the producing formation into the wellbore.

Purposes of Perforation 

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Creating a channel between the pay zone and the wellbore. Cause oil and gas to flow to the wellbore easily. future stimulation. example: Hydraulic fracturing

Perforating Guns 

 A device used to perforate oil and gas wells in preparation for production.

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It has different shapes of explosive charges

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Different range of sizes and configurations.

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 The diameter of the gun used is determined by the presence of wellbore restrictions or limitations imposed by the surface equipment.

Perforation geometry

Perforating Guns   

Casing gun Expendable gun High-shot density gun

Casing gun  

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Create holes in a casing string . Casing guns are typically 3- to 5-in. in diameter and carry up to four perforating charges per foot  Allow perforation through production casing using larger diameter gun assembly.

Expendable gun 

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 A perforating gun assembly that disintegrates upon firing, creating finer debris. It is used where wellbore restrictions allow only limited access, as in through-tubing applications. It is relatively light and simple in design with phased expendable guns.

Expendable gun

High-shot density gun 

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 A perforating gun have more than four shots per foot. Improves the phasing, or distribution of perforations, around the wellbore. Enables improved distribution of the perforations around the circumference of the casing or liner.

High-shot density gun

Perforation methods   

Bullet Perforation Perforation using laser technology Horizontal oriented perforating system  –  HOPS

Bullet Perforation 

Bullets lose velocity when gun clearance >0.5 in.

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Often use in a unconsolidated formations Cheaper to use, rarely been used today

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Bullets plug the end of the flow channel

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Perforating with Laser 

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Conventional explosive charge perforation method reduces the rock permeability Laser perforation increase the rock permeability, hence, increase the oil or gas production rate of a well.

Perforating with Laser

Perforating with Laser

Horizontal oriented perforating system  –  HOPS Performs oriented perforating  Incorporating a series of swiveled gun connectors containing internal, explosive transfer devices and an internally contained gun  weighting system.   This system incorporates a series of short gun sections that rotate to the desired orientation, providing the optimum shot pattern and maximizing reservoir production. 

Horizontal oriented perforating system  –  HOPS

Problem with Perforation 

 The main problem is the plugging after Perforation, these caused by: Charge liner residue slugs  Mud solids & crushed/compacted rock particles 

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Solution to the problem: Cleanout of Plugged Perforations, these include: 

Back surge perforations if consolidated formations

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Use ‘wash tools’ if unconsolidated formations

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Breakdown with fluid or acid, and ball sealers