Two-Dimensional Design Basics
The design of 2-D surveys has a history of more than 60 years. Most of the basic concepts of 2-D design apply to 3-D surveys and indeed are part of the preparation necessary to begin the 3-D design. In 2-D design, the logic is controlled by in-line mostly linear paths, whereas in 3-D design planar concepts must be considered. Costs are greater in 3-D design, so more care should be taken in optimizing costs versus resolution.
The guiding principle should be to design a seismic survey that will image the selected target. There are many ways to accomplish this, so the second criterion is to image the target in the most economical way for costs and time. There are many important input parameters, but the target depth may be the most influential. Offset range, dynamite charge size or vibration power, sample rate, filters, geophones, and subsurface coverage are all directly related to target depth. Resolution parameters, such as the frequency required to also image the target, are starting design factors. In most cases, the interpretation is based on more than the target horizon. Shallow horizons of interest and deeper horizons may be interpretational needs; thus, the definition of the representative horizons is the beginning of design.