EFFICIENT 3-D METHODS FOR OIL EXPLORATION

Abstract

Since their beginnings in the mid-1970s, 3-D seismic surveys have been used in conjunction with development drilling for hydrocarbon production. When Detail 3-D data were available, there was little further use for the 2-D data collected earlier for prospect delineation and drilling of a wildcat well. The 2-D data collected in the exploration stage was nearly always on a grid.

The Exploration 3-D method is applicable at this same stage, but it is based on collecting a suite of parallel lines; not grids. These lines can be spaced up to four times the spacing used for Detail 3-D surveys, which makes collection costs comparable to 2-D grid programs. After performing stack on the wider-spaced lines, an intelligent interpolation process is used to recover data at closer line spacings. These data are then suitable for 3-D migration. Compared to 2-D, Exploration 3-D data are migrated to true subsurface positions and times, and become the basis for interpretation as a 3-D data volume.

Exploration 3-D provides a framework of data that is consistent with all 3-D requirements. Should the Exploration 3-D data not provide the resolution needed for development purposes, additional data can be collected by infill between the original lines, but they are used again for migration of the more detailed data set.