ABSTRACT

3-D seismic surveys can significantly reduce the risks associated with drilling for hydrocarbons by improving our knowledge of the details of the earth's subsurface. This is best accomplished by acquiring well-designed surveys where every change in seismic amplitude, frequency, character, time, etc. might be attributed, with confidence, to real changes in reservoir characteristics. 3-D surveys are neither a panacea nor a commodity however. For example, poorly-designed surveys can increase the risk that changes in the seismic signal are due more to design irregularities than to changing stratigraphic properties. This increased risk can lead to more dry holes being drilled.

Unfortunately, it is often difficult for the explorationist or reservoir engineer to determine whether or not a particular 3-D survey design will do a good job and return good value for the investment. For example, there is general disagreement in the seismic industry over whether wide recording patches are better or worse than narrow patches. Do you, or do you not need "all azimuths" in order to do 3-D? Should a survey geometry provide coupling for the residual statics solution? What survey property is much more important than uniform multiplicity? Getting the wrong answer to these questions can both increase the cost of your survey and degrade the quality of the results. Yet, the right answers are often counter-intuitive. This paper suggests a context for making the right decisions.