Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
1999-05-06
2001-04-10
Vo, Cliff N. (Department: 2772)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
C367S037000, C367S038000
Reexamination Certificate
active
06215499
ABSTRACT:
This invention relates to a method and apparatus for projecting spatially correct seismic data onto a large three-dimensional (3D) curved display surface, to aid in interpretation of geological characteristics of the earth. More specifically, this invention relates to a method for projecting computer graphic video images of seismic data onto a large curved 3D display surface, allowing viewers to interact with the 3D display, and to use their peripheral vision, and thus perceive the displayed imagery with a sense of realism comparable with natural viewing of a 3D physical reality.
BACKGROUND OF THE INVENTION
For many years seismic exploration for oil and gas has involved the use of a source of seismic energy and its reception by an array of seismic detectors, generally referred to as geophones. When used on land, the source of seismic energy can be a high explosive charge electrically detonated in a borehole located at a selected point on the terrain, or another energy source having capacity for delivering a series of impacts or mechanical vibrations to the earth's surface. Offshore, air gun sources and hydrophone receivers are commonly used. The acoustic waves generated in the earth by these sources are reflected back from strata boundary and/or other discontinuities and reach the earth's surface at varying intervals of time, depending on the distance traversed and the characteristics of the subsurface traversed. On land these returning waves are detected by the geophones, which function to transduce such acoustic waves into representative electrical analog signals, which are generally referred to as traces. In use on land an array of geophones is generally laid out along a grid covering an area of interest to form a group of spaced apart observation stations within a desired locality to enable construction of three-dimensional views of reflector positions over wide areas. The source, which is offset a desired distance from the geophones, injects acoustic signals into the earth, and the detected signals at each geophone in the array are recorded for later processing using digital computers, where the analog data is generally quantized as digital sample points, e.g., one sample every two milliseconds, such that each sample point may be operated on individually. The geophone array is then moved to a new position and the process is repeated to obtain a 3D data volume for a seismic survey.
After exploration of an area is completed, data relating to energy detected at a plurality of geophones will have been recorded, where the geophones are located at varying distances from the shotpoint. The data is then reorganized to collect traces from data transmitted at various shotpoints and recorded at various geophone locations, where the traces are grouped such that the reflections can be assumed to have been reflected from a particular point within the earth, i.e., a common midpoint. The individual records or “traces” are then corrected for the differing distance the seismic energy travels through the earth from the corresponding shotpoints, to the common midpoint, and upwardly to the various geophones. This step includes correction for the varying velocities through rock layers of different types and changes in the source and receiver depths. The correction for the varying spacing of shotpoint/geophone pairs is referred to as “normal move out.” After this is done the group of signals from the various midpoints are summed. Because the seismic signals are of a sinusoidal nature, the summation process serves to reduce noise in the seismic record, and thus increasing its signal-to-noise ratio. This process is referred to as the “stacking” of common midpoint data, and is well known to those skilled in the art. Accordingly, seismic field data undergoes the above-mentioned corrections, and may also undergo migration, which is an operation on uninterpreted data and involves rearranging of seismic information so that dipping horizons are plotted in their true location. Other more exotic known processing techniques may also be applied, which for example enhance faults and stratigraphic features or some other attribute, before the continuously recorded traces are reduced to vertical or horizontal cross sections or horizontal map views which approximate subsurface structure, and are usually in color.
Despite significant progress in interactive 3D seismic interpretation systems, seismic workstations continue to rely on vertically and horizontally displayed planar slices of recorded data to provide almost all of the “working surfaces” for horizon and fault picking, and correlation. These planar slices provide only a limited perspective of the full three dimensional picture. Often animation of successive slices is required to provide information about the third dimension. However, animation intrinsically forces a three-dimensional interpretation based on the interpreters memory of the changing picture through time, rather than on direct comparison and correlation of the data.
Once the seismic data is satisfactorily processed to incorporate necessary corrections and desired enhancements, the geophysicist interprets the 3D seismic information. In general terms, interpretation involves deriving a simple plausible geological subterranean model that is compatible with the observed data. This model is never unique, and discovering it involves a sequence of somewhat arbitrary choices.
Accordingly, it is an object of this invention to create a truly three-dimensional interactive graphic workstation to aid in geological interpretation of seismic data.
A more specific object of this invention is to visualize spatially correct seismic data on a large concave screen that facilitates horizon and fault mapping of seismic data.
Still another object is to provide a projection system for computer graphic images of seismic data that includes a portable self-supporting rigid screen with a concave inner display surface, which is economical in cost, and includes about fifty times more viewing area compared to conventional seismic workstation monitors.
Another more specific object of this invention is to provide a desk-top-based projection system having a concave screen, and a projector located about nine feet in front of the curved screen for use in interactive desk top viewing environments.
A further object is to provide a projection display system which can be used to view large scale monoscopic as well as stereoscopic color imagery of three-dimensional seismic data.
SUMMARY OF THE INVENTION
According to the present invention the foregoing and other objects and advantages are attained in a method and apparatus for extracting, mapping and projecting 3D seismic data to its spatially correct location on a relatively large concave 3D display surface. The method is based on computer software, and involves storing a volume of digitally formatted seismic data in memory of a suitable computer as a first step. A mathematical model is then created corresponding to the shape of the concave 3D display surface, and the mathematical model is inserted in the computer memory so as to at least partially intersect the seismic data volume. The intersecting seismic data is extracted and mapped onto an image plane. Next the extracted data is processed using digital computational techniques so as to maintain correct spatial position for the varying projector to screen distances associated with the concave 3D display surface, and is then projected onto the concave display surface in its spatially correct dimensions. This means that the displayed seismic data is not a vertical slice of seismic data projected onto a curved screen, but is data carved out of the 3D data volume corresponding to the shape of the concave display surface.
Accordingly, the apparatus of this invention includes a relatively large 3D display surface compared to a typical CRT monitor screen, and which is suitable for positioning on a desk or tabletop. The presently preferred 3D display surface facilitates viewing on four commonly used screen types including: a
Grismore John R.
Layton Jesse E.
Neff Dennis B.
Singleton Jacquelyn K.
Bogatie George E.
Phillips Petroleum Company
Vo Cliff N.
LandOfFree
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