Alistair R. Brown, 1985. "The Role of Horizontal Seismic Sections in Stratigraphic Interpretation", Seismic Stratigraphy II: An Integrated Approach to Hydrocarbon Exploration, Orville Roger Berg, Donald G. Woolverton
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Horizontal (or SeiscropTM) sections sliced from a three-dimensional seismic data volume normally intersect structural horizons and are effective for structural interpretation. A feature not interpretable as structure may have stratigraphic significance and is often recognizable by characteristic shape. Sink-holes, for example, appear on individual horizontal sections as discrete circular objects.
Seiscrop sections have even greater value for stratigraphic interpretation if sliced along individual seismic horizons, thus removing the effects of structure. Such a section, defined as a horizon Seiscrop section, displays the spatial distribution of seismic amplitude, or other attribute, over a single bed. Horizon Seiscrop sections have been shown to have a powerful ability to reveal subtle depositional features such as bars and channels, particularly in Tertiary clastic rocks like those of the Gulf of Mexico. A horizon Seiscrop section can be regarded effectively as the reconstitution of a depositional surface.
The extent of a gas reservoir may be revealed directly by the shape of the bright spot on a horizon Seiscrop section. A study of reflection amplitude as a function of recording offset can help validate a bright spot as resulting from hydrocarbon content. A horizon offset section displays the amplitude of one horizon as a function of offset andhorizontal position along a seismic line.
A seismic data volume may be inverted to a volume of seismic logs displaying the acoustic velocity in the subsurface. A slice following one structurally interpreted horizon through this volume is a horizon Seiscrop velocity section and has further application for delineating depositional features and the extent of hydrocarbon reservoirs.
Amplitude, displayed in the form of horizon Seiscrop sections over the top and base reflections of a known gas reservoir, has been used to assess the proportion of producible gas sand within a mapped seismic interval. This has led to net gas sand isopach maps which tie the thickness of producible gas sand in the wells. Integration of these maps has yielded total net reservoir volumes.
The interpretive approaches discussed above involve the manipulation of large quantities of seismic data. Much of this is now done interactively, as this helps the interpreter greatly with his data management. Alsoflexible color display increases visual dynamic range, and the construction of composite views helps in the appreciation of data complexities. Most important of all, the interactive interpreter can m aintain a rapid flow of ideas because of the short response time of the system.
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The publication of AAPG Memoir 26 opened up a whole new field to the exploration community. The material contained in that publication demonstrated the relationship of seismic data to the geology of the subsurface in greater detail than previously thought possible. In the years that have followed great effort has gone into refining and advancing the principles and methods of seismic stratigraphy. The goal of this Memoir 39 publication is to provide 15 papers which present and document the advances and refinements in seismic stratigraphic princples and methods that have occurred since the publication of Memoir 26. These articles help the geologist, geophysicist, and manager to keep abreast of this rapidly developing field and provide some guidelines for the evaluation of stratigraphically controlled prospects.