Airgun array design techniques

Abstract

Since airguns were introduced to the oil exploration industry in the late 1960's, they have replaced dynamite as the primary acoustic source for marine seismic profiling. Arrays of airguns compare favorably in the seismic bandwidth to dynamite for depth of penetration and resolution. Multi‐element arrays capable of peak‐to‐peak pressures exceeding 50 bars (at 1 meter) are presently being used in the industry. Independent control of chamber pressure and volume, operating depth and distance between airguns allows the design of airgun arrays which can meet particular resolution or depth of penetration objectives. Array design techniques are reviewed and data from a Shell array is presented to illustrate the degree to which success in meeting the design objectives of a high peak pressure, a high primary‐to‐bubble ratio and broad bandwidth is achieved. Far‐field signatures from the array are shown to possess the necessary shot‐to‐shot stability required of modern signal enhancement techniques when proper care is taken in deploying and towing the array. Boundary effects (ghosting) are shown to reduce shot stability. Some mechanical deployment and towing considerations are discussed.