Airgun marine seismic survey streamer method and apparatus

The method of employing airguns each having a plurality of neighboring discharge ports for discharging high pressure compressed air therethrough for generating seismic impulses in the water and wherein the firing of each airgun is controlled by electrical signals fed thereto comprising the steps of:

• positioning a plurality of such airguns of generally elongated cylindrical configuration in axial alignment along a line at spaced positions,
• interconnecting the respective successive axially aligned airguns in the line to each other by respective successive flexible sleeves extending between successive airguns while leaving all of the neighboring discharge ports of each airgun exposed to the ambient between the successive flexible sleeves,
• providing a plurality of rigid by-pass passageways extending adjacent to exterior portions of a plurality of airguns by-passing the neighboring discharge ports of such airguns,
• mounting said rigid by-pass passageways to resist the tremendous momemtary forces involved during the abrupt discharge of high pressure air through the neighboring discharge ports,
• towing the line of interconnected airguns endwise through the water with one airgun positioned behind another,
• feeding the electrical control signals for the succeeding airguns in the towed line of airguns through preceding by-pass passageways in the line, and
• supplying the high pressure compressed air for the succeeding airguns in the towed line of airguns through preceding by-pass passageways in the line for discharging the high pressure air through the exposed ports in the line of towed airguns for generating seismic impulses in the water.

The method of simultaneously employing a plurality of marine seismic survey airguns while enabling them to be conveniently controlled and handled comprising the steps of:

• providing a plurality of airguns of generally elongated cylindrical configuration each having the same diameter and each having a plurality of circumferentially spaced discharge ports located intermediate its ends,
• positioning the airguns along a line spaced apart one from another and arranged in spaced axially aligned relationship,
• providing a plurality of cylindrical flexible sleeves and interconnecting the sleeves in axially aligned relationship between each successive airgun along said line in watertight relationship therewith forming buoyancy chambers between the respective airguns while leaving their discharge ports exposed to the ambient, and thereby forming a long streamer with the airguns located at spaced points therealong,
• providing a plurality of rigid by-pass passages extending along the outside of each airgun in the region between the circumferentially spaced discharge ports for interconnecting the respective buoyancy chambers in watertight relationship through passages extending along the outside of the respective airguns and located between the respective discharge ports of each airgun,
• arranging each such rigid by-pass passage to withstand the tremendous momentary forces involved during the sudden discharge of high pressure compressed air through said discharge ports,
• providing a plurality of flexible high pressure air lines for the respective airguns for supplying high pressure compressed air thereto and extending said hose lines through the rigid by-pass passages and buoyancy chambers preceding the respective airguns supplied thereby,
• towing the streamer endwise through a body of water, and
• feeding high pressure compressed air through said air lines to the respective airguns in the streamer for discharge thereof through their discharge ports for generating seismic impulses in the water.

Airgun apparatus adapted for towing behind a survey vessel for generating seismic impulses in a body of water comprising:

• a plurality of airguns spaced along a line, said airguns each having discharge ports,
• flexible sleeve means interconnecting said airguns forming a flexible streamer in which said airguns are located at spaced positions along said streamer and in which said discharge ports are exposed to ambient,
• towing means on said streamer for towing the streamer endwise through the water,
• said flexible sleeve means being adapted to provide for buoyancy in said flexible streamer,
• means for feeding high pressure compressed air along said streamer to the respective airguns therein for charging said airguns, and
• means for feeding electrical control signals along said streamer to the respective airguns therein for firing the airguns for discharging the high pressure compressed air through said discharge ports into the body of water for generating the seismic impulses,
• thereby providing a flexible airgun streamer containing a plurality of airguns which is convenient for handling and towing behind a survey vessel.

Airgun apparatus for towing behind a survey vessel for generating seismic impulses in a body of water comprising:

• a plurality of airguns, said airguns each having a generally elongated cylindrical configuration with discharge ports located intermediate the ends of the airgun,
• said airguns being arranged in spaced positions along a line in axially aligned relationship with the front end portion of each successive airgun along the line facing the rear end portion of each precedng airgun along the line,
• a plurality of flexible sleeves,
• one of said flexible sleeves extending between each airgun and the next successive airgun along the line,
• connector means for connecting the opposite ends of the respective sleeves to each airgun and to the next successive airgun with the ends of the respective sleeves encircling the rear end portion of each airgun and the front end portion of the next successive airgun for forming a flexible streamer, and
• high pressure compressed air feeding means extending along the streamer for supplying high pressure compressed air to each of the airguns for charging the airguns with such compressed air to be discharged through said discharge ports for generating the seismic impulses.

Airgun apparatus for towing behind a survey vessel for generating seismic impulses in a body of water comprising:

• a plurality of airguns, said airguns each having a generally elongated cylindrical configuration with discharge ports located intermediate the ends of the airgun,
• said airguns being arranged in spaced positions along a line in axially aligned relationship with the front end portion of each successive airgun along the line facing the rear end portion of each preceding airgun along the line,
• a plurality of flexible sleeves,
• one of said flexible sleeves extending between each airgun and the next successive airgun along the line,
• connector means for connecting the opposite ends of the respective sleeves to each airgun and to the next successive airgun with the ends of the respective sleeves encircling the rear end portion of each airgun and the front end portion of the next successive airgun for forming a flexible streamer,
• high pressure compressed air feeding means extending along the streamer for supplying high pressure compressed air to each of the airguns for charging the airguns with such compressed air to be discharged through said discharge ports for generating the seismic impulses,
• said connector means for each sleeve comprising two cylindrical barrels inserted within the opposite ends of the sleeve and having the sleeve clamped thereto in watertight relationship,
• said cylindrical barrels having flanges projecting beyond the ends of said sleeves,
• the cylindrical barrel at one end of each sleeve being slidable onto the rear end portion of one airgun and the cylindrical barrel at the opposite end of that sleeve being slidable over the front end portion of the next successive airgun along the line,
• a pair of removable clamp rings for each airgun each engageable with one of said flanges,
• one of said clamp rings of each pair encircling the front end portion of the airgun in clamping engagement with the flange of the cylindrical barrel thereon for connecting one end of a sleeve to the front end portion of the airgun, and
• the other clamp ring of each pair encircling the rear end portion of the airgun in clamping engagement with the flange of the cylindrical barrel thereon for connecting one end of a sleeve to the rear end portion of the airgun.

Airgun marine seismic apparatus adapted for towing in a body of water behind a vessel for generating seismic impulses in the water comprising:

• multiple airguns each having a generally elongated cylindrical shape and being positioned in spaced axially aligned relationship,
• said airguns each having their discharge ports for suddenly releasing high pressure compressed air into the water located in the airgun intermediate the front and rear ends of the airgun,
• multiple flexible sleeves, one of said flexible sleeves extending between each of said airguns,
• connection means for connecting each of these flexible sleeves in watertight relationship near the rear end of the preceding airgun and near the front end of the succeeding airgun with the discharge ports exposed between the ends of said sleeves,
• said flexible sleeves each defining a flexible chamber positioned between the respective airguns for forming a flexible streamer including multiple airguns arranged along the length of the streamer in spaced apart end-toward-end relationship,
• mechanical connection means mounted on one end of said streamer for towing the streamer through the water,
• a plurality of rigid tubular transfer members,
• at least one of said transfer members extending along beside each of said airguns past the discharge ports thereof for interconnecting the preceding and succeeding chambers in watertight relationship for providing communication between said chambers,
• a plurality of high pressure hose lines extending through a plurality of said chambers and passing through the transfer members for feeding high pressure compressed air along the streamer from the end where said mechanical connection means is mounted to the respective airguns for supplying the high pressure compressed air thereto, and
• a plurality of electrical control lines extending from said end of the streamer through a plurality of said chambers and passing through the transfer members for feeding electrical firing control signals to the respective airguns for causing them to discharge the high pressure compressed air through their discharge ports.

Airgun apparatus for towing behind a survey vessel for generating seismic impulses in a body of water comprising:

• multiple pluralities of airguns, each airgun having a discharge port,
• multiple pluralities of flexible sleeves,
• the flexible sleeves of each plurality interconnecting the airguns of each plurality for forming multiple elongated flexible airgun streamers each containing a plurality of airguns spaced therealong with their discharge ports exposed to the ambient,
• towing connection means mounted at the front end of each of said streamers,
• flexible air lines extending along each airgun streamer for feeding high pressure compressed air from the front end thereof to the respective airguns therein,
• flexible electrical lines extending along each airgun streamer for feedng electrical control signals from the front end thereof to the respective airguns therein for controlling their discharge of high pressure compressed air through said ports,
• a plurality of rigid passage means extending along beside respective airguns of each streamer past the discharge port thereof and being mounted for withstanding the tremendous momentary forces involved during the abrupt discharge of high pressure compressed air therethrough,
• said flexible air lines and flexible electrical lines extending through the respective preceding rigid passage means in each streamer to the respective airguns, and
• towing means for supplying high pressure compressed air and electrical control signals to the front ends of the respective air lines and electrical lines in each of the multiple streamers, said towing means including towing cables for simultaneously towing said multiple airgun streamers behind a survey vessel positioned in spaced relationship along a line one-after-another with said multiple streamers extending along said line for a total distance of at least one kilometer for providing strong peak pressure in the water in the far field seismic signal generated by the effect of firing all of said multiple pluralities of airguns spaced apart along said distance.

The method for employing a plurality of airguns having discharge ports through which high pressure compressed air is suddenly discharged into a body of water for generating powerful seismic energy therein, said method enabling the plurality of airguns to be conveniently towed through the water and to be conveniently handled and comprising the steps of:

• providing a plurality of airguns of generally elongated cylindrical configuration and each having a plurality of circumferentially spaced discharge ports located intermediate the ends of the airgun,
• positioning the airguns in axially aligned relationship with their respective rear ends being spaced from the respective front ends of succeeding airguns,
• providing a plurality of flexible sleeves,
• positioning respective ones of said sleeves between the respective successive airguns and with the respective ends of each sleeve encircling the rear end and the front end of the airguns between which the sleeve is positioned,
• connecting the respective ends of each sleeve in encircling relationship to the rear end and to the front end of the airguns between which it is positioned, while leaving the circumferantially spaced discharge ports of each airgun directly exposed to the ambient between the respective successive flexible sleeves,
• thereby forming a flexible streamer adapted to be towed through the body of water,
• supplying the high pressure compressed air to the successive airguns in said streamer by feeding the compressed air through rigid by-pass passageways extending along the outside of the preceding airguns and located between the circumferentially spaced discharge ports thereof for by-passing the preceding airguns in the streamer, and
• arranging said rigid by-pass passageways to resist the tremendous momentary forces involved during the sudden discharge of the high pressure compressed air through said discharge ports.

Method of employing airguns having discharge ports for discharging high pressure compressed air therethrough for generating seismic impulses in the water and wherein the firing of each airgun is controlled by electrical signals fed thereto comprising the steps of:

• positioning a plurality of airguns along a line at spaced positions,
• interconnecting each airgun in the line to the next successive airgun by a flexible sleeve for forming chambers within the sleeves extending between successive airguns while leaving the discharge ports of each airgun exposed to the ambient between the successive flexible sleeves,
• providing a plurality of by-pass passageways by-passing the discharge ports of each airgun and extending between the successive chambers in the line of interconnected airguns,
• towing the line of interconnected airguns endwise through the water with one airgun positioned behind another,
• feeding the electrical control signals for the succeeding airguns in the towed line of airguns through preceding by-pass passageways in the line,
• supplying the high pressure compressed air for the succeeding airguns in the towed line of airguns through preceding by-pass passageways in the line for discharging the high pressure air through the exposed ports in the line of towed airguns for generating seismic impulses in the water,
• sensing the depth of the front and rear ends of the line of towed airguns,
• feeding low pressure air through by-pass passages in the line into the chambers within the sleeves for equalizing the pressure thereof in each of said chambers, and
• controlling the pressure of said low pressure air for controlling the effective buoyancy of said chambers.

Airgun apparatus adapted for towing behind a survey vessel for generating seismic impulses in a body of water comprising:

• a plurality of airguns spaced along a line, said airguns each having discharge ports,
• flexible sleeve means interconnecting said airguns forming a flexible streamer in which said airguns are located at spaced positions along said streamer and in which said discharge ports are exposed to ambient,
• towing means on said streamer for towing the streamer endwise through the water,
• said flexible sleeve means being adapted to provide for buoyancy in said flexible streamer,
• means for feeding high pressure compressed air along said streamer to the respective airguns therein for charging said airguns,
• means for feeding electrical control signals along said streamer to the respective airguns therein for firing the airguns for discharging the high pressure compressed air through said discharge ports into the body of water for generating the seismic impulses,
• thereby providing a flexible airgun streamer containing a plurality of airguns which is convenient for handling and towing behind a survey vessel,
• said flexible sleeve means being lengths of expandable hose having an internal diameter of approximately eight inches with layers of reinforcing strands embedded in the wall of said expandable hose, said lengths of expandable hose being more heavily reinforced near their ends for withstanding the seismic impulses as they are generated in the water near said discharge ports, and
• the middle portions of said lengths of expandable hose being less heavily reinforced for increasing the expandability of said middle portions in response to the feeding of compressed air into the interior of said lengths of expandable hose for controlling the effective buoyancy of said sleeve means.

The method for employing a plurality of airguns having discharge ports through which high pressure compressed air is suddenly discharged into a body of water for generating powerful seismic energy therein and wherein the firing of each airgun is controlled by electrical signals fed thereto said method enabling the plurality of airguns to be conveniently towed through the water and to be conveniently handled and comprising the steps of:

• providing a plurality of airguns of generally elongated cylindrical configuration and each having a plurality of circumferentially spaced discharge ports located intermediate the ends of the airgun,
• arranging for firing chamber volumes of the respective airguns to be changeable while maintaining the overall weight of each airgun the same,
• positioning the airguns in axially aligned relationship with their respective rear ends being spaced from the respective front ends of succeeding airguns,
• providing a plurality of cylindrical flexible sleeves,
• positioning respective ones of said sleeves between the respective successive airguns,
• connecting the respective ends of each sleeve in concentric relationship to the rear end and to the front end of the airguns between which it is positioned, while leaving the circumferentially spaced discharge ports of each airgun directly exposed to the ambient between the respective successive flexible sleeves,
• providing a plurality of rigid passage members extending exterior of the respective airguns by-passing the circumferentially spaced discharge ports of the respective airgun for interconnecting the interior of the respective flexible sleeves connected thereto,
• providing a plurality of flexible high pressure air lines for the respective airguns for supplying high pressure compressed air thereto and extending said air lines through the rigid passage members and flexible sleeves preceding the respective airguns supplied thereby, and
• providing a plurality of flexible electrical lines for controlling the respective airguns and extending said electrical lines through the rigid passage members and flexible sleeves preceding the respective airguns controlled thereby.

Airgun apparatus adapted for towing behind a survey vessel for generating seismic impulses in a body of water comprising:

• a plurality of airguns spaced along a line, said airguns each having discharge ports,
• flexible sleeve means interconnecting said airguns forming a flexible streamer in which said airguns are located at spaced positions along said streamer and in which said discharge ports are exposed to ambient,
• towing means on said streamer for towing the streamer endwise through the water,
• said flexible sleeve means being adapted to provide for buoyancy in said flexible streamer,
• means for feeding high pressure compressed air along said streamer to the respective airguns therein for charging said airguns,
• means for feeding electrical control signals along said streamer to the respective airguns therein for firing the airguns for discharging the high pressure compressed air through said discharge ports into the body of water for generating the seismic impulses,
• the rear end portion of each airgun comprising a cylindrical housing for providing a firing chamber,
• said cylindrical housing being open at the rear end thereof,
• a plurality of cylindrical spacers removably positioned in said cylindrical housing and being slidable into said housing through said open rear end,
• a removable circular bulkhead slidable into said cylindrical housing through said open rear end and being held in position in said cylindrical housing by said spacers,
• said bulkhead having sealing means around the perimeter thereof for engaging the interior of said cylindrical housing in airtight relationship for holding high pressure compressed air in said firing chamber,
• a retainer member removably secured over said open end for retaining said spacers and said bulkhead in position in said cylindrical housing,
• whereby the volume of said firing chamber can be changed by interchanging the relative positions of said spacers and said bulkhead, and
• thereby providing a flexible airgun streamer containing a plurality of airguns having changeable firing chamber volumes and which is convenient for handling and towing behind a survey vessel.