The Annular Port Air Gun












The Annular Port Air Gun is a new design for a marine air gun that provides significant improvements in both the operating efficiency and acoustic output of marine seismic source arrays. The principal feature of the Annular Port Air Gun design is an annulus containing the air chamber and shuttle valve surrounding a hollow passage through which air supply hoses and electrical control cables are routed. The new air gun design features a number of advantages:
  • Gun plates, air manifolds, and exposed air hose and electrical cable jumpers are eliminated.
  • Air fittings and electrical connectors are protected from the effects of the air blast.
  • Less drag results from smaller subarray profiles.
  • Towing symmetry results in less energetic gun movements.
  • Bubble geometry results in increased acoustic output per unit volume of air.

The improvement in peak output is attributable to the increased surface area of the toroidal-shaped bubble compared to the spherically shaped bubble generated by a conventional 4-port air gun.

The annular configuration of the new air gun also permits the use of simplified multi-gun arrays that generate less towing drag. Linear air gun clusters replace horizontal or vertical clusters found in conventional source arrays. Arrays comprising Annular Port Air Guns will be easier to deploy and retrieve, consequently these arrays will more effectively withstand the damage sustained by conventional arrays caused by frequent deployment and retrieval. Arrays configured with conventional air guns require individual tow plates, airline and electrical jumpers for each gun element. This configuration is cumbersome and exposes the air and electrical jumpers to the energetic air blast from the guns. Arrays configured with the new Annular Port Air Gun do not require tow plates, cluster spreader bars or exposed air and electrical jumpers.

An array of Annular Port Air Guns is shown at right configured with linear cluster elements. The air hose and electrical cables are routed through the core inside the annulus of the gun where they are protected from the effects of the air blast. An added design feature of the new air gun is the placement of a "zero-field" hydrophone inside the ports of the air gun, which can be used both as a precise time break sensor and as a near field hydrophone. The zero-field sensor measures the pressure field at a position inside the oscillating air bubble.


Annular Port Air Gun


Mechanical Layout


Towed Long Life Subarray


Towed APG Subarray