초록

Marine seismic data is acquired with a system of steerable seismic streamers that are intentionally maintained in a flared configuration while the streamers are towed through a body of water.

대표청구항 ▼

1. A method of acquiring seismic data in a marine environment, said method comprising: (a) towing a system of 4 to 50 laterally-spaced steerable seismic streamers through a body of water, wherein each of said seismic streamers has a front portion and a rear portion wherein the front portion of each

1. A method of acquiring seismic data in a marine environment, said method comprising: (a) towing a system of 4 to 50 laterally-spaced steerable seismic streamers through a body of water, wherein each of said seismic streamers has a front portion and a rear portion wherein the front portion of each streamer is laterally spaced from the front portions of other streamers in the system each streamer comprises a series of longitudinally-spaced marine seismic receivers characterized by:(b) simultaneously with step (a), steering said system of seismic streamers into a flared configuration where (i) all the streamers have a length of between 2 kilometers and 20 kilometers, (ii) the lateral distance between the outer-most, rearward-most marine seismic receivers at the rear portions of the streamers is at least 2 percent greater than the lateral distance between the outer-most, forward-most marine seismic receivers, (iii) the average spacing between adjacent seismic receivers of the rearward-most group of seismic receivers is in the range of 15 to 250 meters;(c) simultaneously with steps (a) and (b), recording reflected and/or refracted seismic data with said marine seismic receivers; and(d) towing the system of laterally-spaced seismic streamers in the flared configuration as described in step (b) through a survey area that is divided into a number of adjacent acquisition passes wherein gaps are avoided between adjacent passes in the seismic data collected by the marine seismic receivers. 2. The method of claim 1 wherein where said system of seismic streamers is said flared configuration the lateral distance between the outer-most, rearward-most marine seismic receivers is at least 5 percent greater than the lateral distance between the outer-most, forward-most marine seismic receivers. 3. The method of claim 1 wherein when said system of seismic streamers is in said flared configuration the average lateral spacing between said seismic streamers in a flared section of said system of seismic streamers increases rearwardly at a rate of at least 0.001meters per meter, wherein said flared section of said system of seismic streamers has a length that is at least 20 percent of the total length of said system of seismic streamers. 4. The method of claim 1 wherein at least two of said seismic streamers include a series of longitudinally-spaced steering devices capable of controlling the lateral position of said seismic streamers during said towing of step (a). 5. The method of claim 4 wherein each of said seismic streamers comprises at least three of said steering devices. 6. The method of claim 4 wherein said steering devices are capable of simultaneously controlling both the lateral position and the depth of said seismic streamers in said body of water. 7. The method of claim 1 wherein said system of seismic streamers comprises in the range of 3 to 100 individual streamers. 8. The method of claim 1 wherein each of seismic streamers comprises in the range of 10 to 300,000 of said marine seismic receivers. 9. The method of claim 1 wherein said towing of step (a) is carried out at a speed in the range of 2 to 10 knots. 10. The method of claim 1 wherein at least one-half said seismic streamers comprise a series of longitudinally-spaced steering devices capable of controlling the lateral position of said seismic streamers during said towing of step (a), wherein said system of seismic streamers comprises in the range of 4 to 50 individual streamers, wherein each of said seismic streamers has a length in the range of 2 to 20 kilometers, wherein each of said seismic streamers includes in the range of 100 to 10,000 of said marine seismic receivers, wherein the average lateral spacing between a forward-most group of said marine seismic receivers is in the range of 1 to 100 meters, wherein the average lateral spacing between a rearward-most group of said marine seismic receivers is at least 10 percent greater than the average lateral spacing between said forward-most group of said marine seismic receivers. 11. The method of claim 1 wherein said system of seismic streamers is continuously maintained in said flared configuration over a controlled flaring distance of at least one kilometer, wherein over said controlled flaring distance the average lateral distance between the outer-most, rearward-most marine seismic receivers is at least 10 percent greater than the average lateral distance between the outer-most, forward-most marine seismic receivers. 12. The method of claim 11, wherein said controlled flaring distance is at least five kilometers, wherein over said controlled flaring distance the average lateral distance between the outer-most, rearward-most marine seismic receivers is at least 20 percent greater than the average lateral distance between the outer-most, forward-most marine seismic receivers. 13. The method of claim 12 wherein each of said seismic streamers comprises a series of longitudinally-spaced steering devices capable of controlling the lateral position of said seismic streamers during said towing of step (a), wherein said system of seismic streamers comprises in the range of 5 to 25 individual streamers, wherein each of said seismic streamers has a length in the range of 4 to 12 kilometers, wherein each of said seismic streamers includes in the range of 200 to 1,000 of said marine seismic receivers, wherein the average lateral spacing between a forward-most group of said marine seismic receivers is in the range of 4 to 50 meters. 14. A method of acquiring seismic data for a subsea region of the earth, said method comprising: (a) using a marine vessel to tow at least one marine seismic source and a system of at least four laterally-spaced seismic streamers through a body of water, wherein each of said seismic streamers comprises a series of at least 100 longitudinally-spaced marine seismic receivers, wherein at least one-half of said seismic streamers include steering devices capable of controlling the lateral position of said seismic streamers during towing and wherein each streamer has a front portion and a rear portion wherein the front portion of each streamer is laterally spaced from the front portions of other streamers in the system;(b) simultaneously with step (a), maintaining said system of seismic streamers in a flared configuration over a controlled flaring distance of at least five kilometers, wherein when said system of seismic streamers is in said flared configuration the average lateral spacing between said seismic streamers in a flared section of said system of seismic streamers increases rearwardly at a rate of at least 0.001 meters per meter, wherein said flared section has a length that is at least 5percent of the total length of said system of seismic streamers and wherein the average spacing between adjacent seismic receivers of the rearward-most group of seismic receivers does not exceed 250 meters;(c) simultaneously with steps (a) and (b), exciting said at least one marine seismic source to thereby causing wave energy to travel through said body of water and into said subsea region of the earth;(d) simultaneously with steps (a) and (b), detecting reflected and/or refracted wave energy with said marine seismic receivers, wherein the detected wave energy contains seismic information about said subsea region of the earth; and(e) towing the system of laterally-spaced seismic streamers in the flared configuration as described in step (b) through a survey area that is divided into a number of adjacent acquisition passes wherein gaps are avoided between adjacent passes in the seismic data collected by the marine seismic receivers. 15. The method of claim 14 wherein said flared section has a length that is at least 40 percent of the total length of said system of seismic streamers. 16. The method of claim 14 wherein the average lateral spacing between said seismic streamers in said flared section includes rearwardly at a rate of at least 0.01 meters per meter. 17. The method of claim 14 wherein said flared section has a length that is at least 60 percent of the total length of said system of seismic streamers, wherein the average lateral spacing between said seismic streamers in said flared section increases rearwardly at a rate of at least 0.002 meters per meter. 18. The method of claim 14 wherein when said system of seismic streamers is in said flared configuration the lateral distance between the outer-most, rearward-most marine seismic receivers is at least 5 percent greater than the lateral distance between the outer-most, forward-most marine seismic receivers. 19. The method of claim 14 wherein said steering devices are capable of simultaneously controlling both the lateral position and the depth of said seismic streamers in said body of water. 20. The method of claim 14 wherein a plurality of said seismic streamers have a length in the range of 2 to 20 kilometers. 21. The method of claim 14 wherein the average lateral spacing between a forward-most group of said marine seismic receivers is in the range of 1 to 100 meters, wherein the average lateral spacing between a rearward-most group of said marine seismic receivers is at least 10 percent greater than the average lateral spacing between said forward-most group of said marine seismic receivers. 22. The method of claim 14 wherein said towing of step (a) is carried out at a speed in the range of 4 to 8 knots. 23. The method of claim 14 wherein said system of seismic streamers comprises in the range of 4 to 50 individual streamers, wherein each of said seismic streamers has a length of at least four kilometers, wherein each of said seismic streamers includes at least 200 of said marine seismic receivers. 24. The method of claim 14, wherein said controlled flaring distance is at least 15kilometers, wherein over said controlled flaring distance the average lateral distance between the outer-most, rearward-most marine seismic receivers is at lest 10 percent greater than the average lateral distance between the outer-most, forward-most marine seismic receivers. 25. A method of acquiring marine seismic data, said method comprising: (a) determining a desired flared configuration for a system of between 4 and 50 marine seismic streamers wherein the streamers have a length of between 2 kilometers and 20 kilometers and the average spacing between adjacent seismic receivers of the rearward-most group of seismic receivers is in the range of 15 to 250 meters;(b) towing said system of marine seismic streamers through a body of water;(c) simultaneously with step (b), steering said system of marine seismic streamers from a non-flared configuration into said desired flared configuration wherein each streamer has a front portion and a rear portion wherein the front portion of each streamer is laterally spaced from the front portions of other streamers in the system in both the flared and non-flared configurations;(d) simultaneously with step (b), maintaining said system of marine seismic streamers in said desired configuration for a controlled flaring time of at least 5 minutes through a survey area that is divided into a number of adjacent acquisition passes wherein gaps are avoided between adjacent passes in the seismic data collected by the marine seismic receivers in adjacent acquisition passes; and(e) using said system of marine seismic streamers to acquire marine seismic data during said controlled flaring time. 26. The method of claim 25 wherein during said controlled flaring time said system of marine seismic streamers is towed through said body of water at an average speed in the range of 2 to 10 knots. 27. The method of claim 25 wherein said controlled flaring time is at least 30minutes, wherein during said controlled flaring time said system of marine seismic streamers is towed through said body of water at an average speed in the range of 4 to 8knots. 28. The method of claim 25 wherein each of said marine seismic streamers comprises a series of seismic receivers, wherein when said system of seismic streamers is in said desired flared configuration the lateral distance between the outer-most, rearward-most marine seismic receivers is at least five percent greater than the lateral distance between the outer-most, forward-most marine seismic receivers. 29. The method of claim 28 wherein when said system of seismic streamers is in said desired flared configuration the lateral distance between the outer-most, rearward-most marine seismic receivers is at least 10 percent greater than the lateral distance between the outer-most, forward-most marine seismic receivers. 30. The method of claim 25 wherein when said system of marine seismic streamers in said desired flared configuration a flared section of said system of marine seismic streamers exhibits an average lateral spacing between said marine seismic streamers that increases rearwardly at a rate of at least 0.001 meters per meter. 31. The method of claim 30 wherein said flared section has a length that is at least 20 percent of the total length of said system of marine seismic streamers. 32. The method of claim 30 wherein said flared section has a length that is at least 60 percent of the total length of said system of marine seismic streamers. 33. The method of claim 30, wherein said flared section exhibits an average lateral spacing betweens aid marine seismic streamers that increases rearwardly at a rate of at least 0.002 meters per meter. 34. The method of claim 30 wherein said flared section has a length that is at least 40 percent of the total length of said system of marine seismic streamers. 35. The method of claim 1 wherein gaps in the seismic data between adjacent acquisition passes at the outer-most seismic receivers at the front portions of the system are avoided at the same time that gaps in the seismic data between adjacent acquisition passes at the outer-most seismic receivers at the rear portion of the system are avoided by a flared streamers that extend wider to cover portions of the survey area that due to cross currents might have been missed. 36. The method of claim 1 further comprising steering the system of laterally-spaced steerable seismic streamers into the flared configuration during successive adjacent passes so as to avoid gaps in the seismic data between adjacent acquisition passes at the outer-most seismic receivers at the front portions of the system and so as to avoid gaps in the seismic data between adjacent acquisition passes at the outer-most seismic receivers at the rear portion of the system. 37. The method of claim 1 wherein the recorded seismic data is processed to create a model of the subsurface geological formations in the seismic survey area.