Principles of Onshore 3-D Seismic Design
The basic geometry of an onshore three-dimensional (3-D) seismic recording grid is based on five parameters: source-station spacing, receiver-station spacing, source-line spacing. receiver-line spacing, and recording swath size. At each onshore prospect considered for 3-D seismic imaging, these key design parameters can be specified by answering four simple questions: 1. What is the narrowest lateral dimension of the geologic targets that are to be imaged? 2. What is the depth of the shallowest target that must be imaged? 3. What is the depth of the deepest target that must be imaged? 4. What stacking fold is required to create an acceptable image at the depth of the principal target? The first three questions can be answered once the geology of the prospect is reasonably well known. The fourth question can be answered by (1) examining two-dimensional (2-D) seismic profiles that traverse the prospect area to estimate reflection signal quality, (2) examining 3-D seismic data recorded near the prospect, or (3) making a best guess, which is a risky and less desirable approach. Once these four questions are answered, the methodology described herein allows many onshore 3-D seismic recording grids to be designed without having to use complex computations or commercial design software. Some of the more technical aspects of 3-D seismic design, such as ensuring that there is a proper azimuth distribution of source-receiver offsets or creating a continuous numerical range of source-receiver offsets across the entire acquisition grid, are not considered in this simple treatise on first principles. The intent is to provide a procedure that allows nongeophysicists to plan simple 3-D surveys and to recognize flaws in proposed 3-D programs. This design procedure should be helpful to people who wish to verify the imaging capabilities of a particular 3-D seismic design but who do not access to, or wish to use, extensive computational resources.
Hardage, B. A., 1997, Principles of Onshore 3-D Seismic Design: The University of Texas at Austin, Bureau of Economic Geology, Geological Circular 97-5, 23 p. doi.org/10.23867/gc9705D.
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The University of Texas at Austin, Bureau of Economic Geology