Perforating guns are crucial tools used in oil and gas well completions to create channels or perforations in the wellbore casing and cement sheath. These perforations enable the flow of reservoir fluids, such as oil or gas, into the wellbore for production.
Key Facts
- Purpose: Perforating guns are used to create channels or perforations in the wellbore casing and cement sheath, enabling the flow of reservoir fluids into the wellbore for production.
- Explosive Shaped Charges: Perforating guns carry explosive shaped charges downhole, which are detonated to create the perforations in the wellbore.
- Types of Carriers: There are two basic carriers for shaped-charge perforators: retrievable hollow carriers and expendable or semiexpendable carriers.
- Hollow-Carrier Guns: Hollow-carrier guns can be run on wireline or tubing and may carry large charges, minimizing casing damage. They can be of small size for through-tubing applications or larger sizes for casing conveyance.
- Expendable Guns: Expendable guns have charges that are exposed to well fluids and pressures. They are popular for through-tubing applications and can use larger charges than hollow-carrier guns.
- Detonator Systems: Detonator systems have been redesigned to improve safety and prevent perforating problems. Specialized detonators prevent firing if the gun is filled with water and offer other safety benefits.
- Conveyance Systems: Perforating guns can be conveyed using electric line, tubing, coiled tubing, pumpdown, or slickline, depending on factors such as wellbore geometry, inclination, and well control requirements.
Explosive Shaped Charges
Perforating guns carry explosive shaped charges downhole, which are detonated to create the perforations in the wellbore. These shaped charges consist of a metal casing, a primer igniter, explosive material, and a conical liner. The detonation of the shaped charge generates a high-pressure jet of energy that penetrates the casing, cement, and formation, creating the perforation tunnels.
Types of Perforating Gun Carriers
There are two basic types of carriers for shaped-charge perforators: retrievable hollow carriers and expendable or semiexpendable carriers.
Hollow-Carrier Guns
Hollow-carrier guns can be run on wireline or tubing and may carry large charges, minimizing casing damage. They can be of small size for through-tubing applications or larger sizes for casing conveyance. Hollow-carrier guns are often used in wells with completion hardware or reservoir properties that require a specific perforating system.
Expendable Guns
Expendable guns have charges that are exposed to well fluids and pressures. They are popular for through-tubing applications and can use larger charges than hollow-carrier guns. Expendable guns are typically used in wells where debris left in the wellbore after detonation is not a concern.
Detonator Systems for Perforating Guns
Detonator systems have been redesigned to improve safety and prevent perforating problems. Specialized detonators prevent firing if the gun is filled with water and offer other safety benefits, such as resistance to stray currents and pressure switches that prevent accidental surface firing or re-safe the gun when pulled from a well.
Conveyance Systems for Perforating Guns
Perforating guns can be conveyed using various methods, including electric line, tubing, coiled tubing, pumpdown, or slickline. The choice of conveyance system depends on factors such as wellbore geometry, inclination, and well control requirements.
Conclusion
Perforating guns play a critical role in the completion of oil and gas wells by creating perforations that allow reservoir fluids to flow into the wellbore. The selection of the appropriate perforating gun system depends on various factors, including the wellbore conditions, reservoir properties, and desired production objectives.
Sources:
- https://www.slb.com/resource-library/oilfield-review/defining-series/defining-perforating
- https://petrowiki.spe.org/Perforating_equipment
- https://petrowiki.spe.org/Perforating_methods
FAQs
What is a perforating gun used for?
Perforating guns are used to create perforations or channels in the wellbore casing and cement sheath, allowing reservoir fluids to flow into the wellbore for production.
What are the main types of perforating gun carriers?
The two main types of perforating gun carriers are retrievable hollow carriers and expendable or semiexpendable carriers.
How do perforating guns create perforations?
Perforating guns carry explosive shaped charges downhole, which are detonated to generate a high-pressure jet of energy that penetrates the casing, cement, and formation, creating the perforation tunnels.
What are the key factors to consider when selecting a perforating gun system?
Factors to consider include wellbore conditions, reservoir properties, desired production objectives, and the type of conveyance system required.
What are the different methods used to convey perforating guns?
Perforating guns can be conveyed using electric line, tubing, coiled tubing, pumpdown, or slickline, depending on the wellbore geometry, inclination, and well control requirements.
How do detonator systems contribute to the safety of perforating operations?
Detonator systems have been redesigned to improve safety by preventing firing if the gun is filled with water and offering other safety features such as resistance to stray currents and pressure switches for accidental surface firing prevention.
What are the advantages of hollow-carrier perforating guns?
Hollow-carrier guns minimize casing damage, can carry large charges, and are suitable for both wireline and tubing conveyance.
When are expendable perforating guns typically used?
Expendable guns are often used in through-tubing applications where debris left in the wellbore after detonation is not a concern.