Shot Profile Hand Migration in Three Dimensions

Dipping events are usually from three dimensional reflectors. Figure  21 shows one possible approach to figuring out the 3D nature of reflections from dipping events by recording into orthogonal receivers. The idea is to measure and use apparent dips in crossline and inline directions as we did in Figure  6 to estimate the distance and direction of the migrated position from the current one.

Figure 21: Using a "tee" to detect dip in three dimensions.

Figure  22 shows two late 1940's vintage Amerada Petroleum seismic records showing a "single-end shot record" and what they called a "tee" record for determining the parameters for the calculations described in previous figures. The right-hand side of each record is the single ender while the left-hand side represents the "tee". This kind of cross-spread shooting foreshadowed acquisition of seismic data using orthogonal shot and receiver lines.

Figure 22: A "tee" on the left and a single-ended spread on the right in both panels. The "tee" was a string of receivers orthogonal to the direction of the shot line.

Figure  23 shows the simple mathematics of locating the source of the reflected event when there is dip in the x and y directions. This is a 1940's vintage description of how Amerada Petroleum's scientists approached the problem. This kind of solution was considered a top-secret technology in all oil companies of the day.

Figure 23: Amerada Petroleum's solution to using the "tee" to resolve 3D dip.