Seismic data analysis. Processing, inversion and interpretation of seismic data. Volume 2 / Анализ сейсмических данных. Обработка, инверсия и интерпретация сейсмических данных. Том 2

Subsurface geological features of interest in hydrocarbon exploration are three dimensional in nature. Examples include salt diapirs, overthrust and folded belts, major unconformities, reefs, and deltaic sands. A two-dimensional (2-D) seismic section is a cross-section of a three-dimensional (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 the signal comes from the plane of the profile itself. Although out-of-plane reflections (sideswipes) usually are recognizable by the experienced seismic interpreter, the out-of-plane signal often causes 2-D migrated sections to mistie. These misties are caused by inadequate imaging of the subsurface resulting from the use of 2-D rather than 3-D migration. On the other hand, 3-D migration of 3-D data provides an adequate and detailed 3-D image of the subsurface, leading to a more reliable interpretation.
A typical marine 3-D survey is carried out by shooting closely spaced parallel lines (line shooting). A typical land or shallow water 3-D survey is done by laying out a number of receiver lines parallel to each other and placing the shotpoints in the perpendicular direction (swath shooting). <...>