Defining Perforating

Date: 08/30/2013

Connecting to the reservoir

Perforating—the act of blasting holes through steel casing, cement, and formation rock—lasts only an instant, but the long-term viability of most oil and gas assets depends upon it. The technique involves carrying explosive charges downhole, where they are detonated to create tunnels that act as conduits through which reservoir fluids flow from the formation into the wellbore and up to the surface.

In the 1920s, E&P companies began cementing metal pipe in the wellbore to better support the casing and to isolate producing intervals from other zones. Although effective, the practice made it difficult to reach hydrocarbons on the outside of the pipe. Bullet guns were originally used to mechanically punch through the pipe and cement, but their penetration and effectiveness were limited. When shaped-charge technology was introduced to the oil field in 1948, it revolutionized well completions.

Perforating guns come in a variety of sizes and configurations, and the two primary categories are through-tubing guns and hollow-carrier, or casing, guns. Hollow-carrier guns are larger than through-tubing guns and facilitate bigger charges, more phasing options, and higher shot density. Phase is the angle between individual charges and is expressed in degrees, and shot density is the number of holes per unit of length. Completion hardware in place and reservoir properties usually dictate the type of gun system used. However, operators may install a particular type of completion to accommodate a perforating system that is suitable for a specific reservoir.

Perforating defined

“Defining Perforating,” the fifth in a series of introductory articles by the Oilfield Review, provides a concise overview of the perforating process.

Whether you are new to the industry or just looking to review the basics, this short article is a resource for understanding the fundamental concepts around perforating in the E&P industry.

Download the “Defining Perforating” article here.

Discover other introductory articles about concepts and technologies in the E&P industry at the Oilfield Review Web site.

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High shot density casing gun after perforating.