Changes

  | isbn    = 0891816607

  | isbn    = 0891816607

}}

}}

Subsurface geological features of interest in hydrocarbon exploration are three-dimensional (3-D) in nature. Examples are salt diapirs, overthrust and folded belts, major [[Unconformity|unconformities]], reefs, and deltaic sands. A two-dimensional (2-D) seismic section is a [[cross section]] of a 3-D seismic response. Despite the fact that a 2-D section contains signal from all directions, including out-of-plane of the profile, 2-D migration normally assumes that all of the signal comes from the plane of the profile itself. Although out-of-plane seismic signals (sideswipes) are often recognizable by the experienced seismic interpreter, the sideswipe signal causes 2-D migrated sections to mistie. These misties are due to inadequate imaging of the subsurface resulting from the use of 2-D rather than 3-D migration<ref name=pt07r13>French, W. S., 1974, Two-dimensional and three-dimensional migration of model-experiment reflection profiles: Geophysics, 39, 265–277. [http://library.seg.org/doi/abs/10.1190/1.1440426 DOI:10.1190/1.1440426]</ref> (see [[Seismic data - mapping with two-dimensional data]]).

Subsurface geological features of interest in hydrocarbon exploration are three-dimensional (3-D) in nature. Examples are salt diapirs, [[overthrust]] and folded belts, major [[Unconformity|unconformities]], reefs, and deltaic sands. A two-dimensional (2-D) seismic section is a [[cross section]] of a 3-D seismic response. Despite the fact that a 2-D section contains signal from all directions, including out-of-plane of the profile, 2-D migration normally assumes that all of the signal comes from the plane of the profile itself. Although out-of-plane seismic signals (sideswipes) are often recognizable by the experienced seismic interpreter, the sideswipe signal causes 2-D migrated sections to mistie. These misties are due to inadequate imaging of the subsurface resulting from the use of 2-D rather than 3-D migration<ref name=pt07r13>French, W. S., 1974, Two-dimensional and three-dimensional migration of model-experiment reflection profiles: Geophysics, 39, 265–277. [http://library.seg.org/doi/abs/10.1190/1.1440426 DOI:10.1190/1.1440426]</ref> (see [[Seismic data - mapping with two-dimensional data]]).

==Performing 3-D surveys==

==Performing 3-D surveys==

==Processing of 3-D data==

==Processing of 3-D data==

The basic principles of 2-D seismic data processing still apply to 3-D processing. In 2-D processing, traces are collected as common midpoint (CMP) gathers, while in 3-D processing, traces are collected as common-cell gathers (bins). These gathers are used in velocity analysis, and common-cell stacks are generated. Typical cell sizes are 25 by [[length::25 m]] for land surveys and 12.5 by [[depth::37.5 m]] for marine surveys.

The basic principles of 2-D [[seismic data]] processing still apply to 3-D processing. In 2-D processing, traces are collected as common midpoint (CMP) gathers, while in 3-D processing, traces are collected as common-cell gathers (bins). These gathers are used in velocity analysis, and common-cell stacks are generated. Typical cell sizes are 25 by [[length::25 m]] for land surveys and 12.5 by [[depth::37.5 m]] for marine surveys.

Conventional 3-D recording geometries often complicate the process of stacking the data in a common-cell gather. Cable feathering in marine 3-D surveys can result in traveltime deviations from a single hyperbolic moveout within a common-cell gather. For land 3-D surveys, [[azimuth]]-dependent moveout within a common cell gather is an issue.

Conventional 3-D recording geometries often complicate the process of stacking the data in a common-cell gather. Cable feathering in marine 3-D surveys can result in traveltime deviations from a single hyperbolic moveout within a common-cell gather. For land 3-D surveys, [[azimuth]]-dependent moveout within a common cell gather is an issue.

[[Category:Geophysical methods]]

[[Category:Geophysical methods]]