Communications – electrical: acoustic wave systems and devices – Seismic prospecting – Offshore prospecting
Patent
1980-07-24
1982-10-05
Moskowitz, Nelson
Communications, electrical: acoustic wave systems and devices
Seismic prospecting
Offshore prospecting
367 16, 367 24, 367 48, 367 59, 364421, G01V 136, G01V 138
Patent
active
043531210
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention pertains to marine seismic stratigraphic systems and more particularly to an improved combined system of marine data gathering and data treatment for achieving high resolution, high penetration and high directivity.
BACKGROUND ART
In a typical marine seismic gathering system, it is customary that a vessel be equipped with both an acoustical energy source, usually on a submerged carrier towed by the vessel with certain control apparatus therefor being located on the vessel itself, and an acoustical detector array, usually in the form of a complex cable also towed by the vessel. Such a detector cable is typically towed at a shallow depth behind the vessel and is best characterized as a streamer or an extended cable including a plurality of seismic detectors or hydrophones. It is also usual for such detectors to be spaced along the streamer in multiple arrays, rather than singly. The towed streamer of the prior art is ideally neutrally buoyant and seeks a uniform depth beneath the surface of the water, usually in the vicinity of from one to three meters. The primary reason that the streamer is towed below the water surface is to avoid, insofar as possible, the effects of surface wave action or turbulence.
The returns detected by the hydrophone arrays are a result of the acoustic impulses from the source being reflected from the various subsurface seismic interfaces. One such interface is the interface between the water and the land, or in other words, the lake or ocean bottom. Other interfaces occur wherever there is a lithological variation or change. Knowledge of such interfaces or reflecting surfaces is extremely valuable in evaluating for the presence of hydrocarbon deposits and the like.
The gathered acoustic return data using such a streamer of hydrophone arrays is subjected to several natural phenomena which interfere with a clear interpretation of the data collected unless avoided or minimized and/or corrected for. One of these phenomena is surface noise. It is well-known that a hydrophone located at or near the water surface will pick up surface wave motion. Therefore, it has been found convenient to locate the hydrophone detectors below the water surface, typically on the order of one to three meters (although such below-surface location introduces ghost returns, which are discussed below).
Another recognized phenomena that must be considered before the collected data is clearly interpretable is the phenoemna known as correcting to a common depth point (CDP) file. Data may ideally be gathered to a common depth point; however, as will be explained, it is not normally practical to do that, particularly in a marine configuration setting. But, for an understanding of the concept, consider a horizontal reflecting interface with a point thereon as the "CDP". Along a parallel "datum" line above the interface, and to one side of a normal drawn to the CDP, are evenly spaced detectors. (Actually, there is normally a detector array, but for discussion herein "detector" is used to signify an associated arrayed group of individual detectors.) Along the datum line and to the other side of the normal drawn to the CDP, are equally evenly spaced sources. A first data trace would be the result of an impulse from the closest source being reflected off the interface and received at the closest detector. A second data trace would be the result of an impulse from the next closest source being reflected off the interface and received at the next closest detector. Similarly, data traces developed from successive sources to successive detectors, each resulting from a reflection off the interface at the CDP, would develop a "common depth point file".
However, there is normally only one source in a typical marine seismic system, which source is towed at a predetermined rate. Assuming that the detectors were stationary and evenly spaced, when the source was at a position corresponding to the first source in the above example, then the second, and so forth, an ideal CDP file could be developed
REFERENCES:
patent: Re23552 (1952-09-01), Babb et al.
patent: 3012223 (1961-12-01), Begun et al.
patent: 3226967 (1965-12-01), Lash
patent: 3299399 (1967-01-01), Bowers
patent: 3350683 (1967-10-01), Sengbush
patent: 3406777 (1968-10-01), Bemrose
patent: 3436722 (1969-04-01), Strange
patent: 3441902 (1969-04-01), Savit
patent: 4101866 (1978-07-01), Ruehle
patent: 4136756 (1979-01-01), Manin
patent: 4208732 (1980-06-01), Ruehle
patent: 4209854 (1980-06-01), Ruehle
Moore Neil A.
Ray Clifford H.
Bednar Emil J.
Fairfield Industries, Inc.
Moskowitz Nelson
Vaden III Frank S.
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