Data Acquisition

During World War I (1914-1918), sound waves from exploding bombs and other ordinance were detected many miles from the explosion point. Noise from the operation of submarines was detected over even greater distances. These two observable events are thought to have lead to the speculation that one could detect geologic bedding planes by recording the sound energy from a surface explosion. Oil companies around the world began to research whether or not such an idea might be possible. One of the early investigators into this idea was a physicist named Reginald Fessenden. Figure  1 describes Fessenden's scheme for locating geological formations using a sound source. The source in this case was essentially a vibrator not unlike what we call a vibroseis today. The technique is also virtually identical to what would ultimately became sonar for locating submerged submarines.

Figure 1: A graphic describing the essence of R. Fessenden's 1917 patent for devices to generate and record seismic energy.

While I am quite sure that Fessenden was completely convinced that his device would work, his belief was not shared by all. Thus, it was necessary to prove empirically that a surface sound source would generate reflections from geologic formations, and that such reflections could be recorded at the surface and mapped or interpreted to find hydrocarbon bearing traps.

At this point in time, making a microphone, or what we now call a geophone, was very expensive and each such device was very heavy. Thus, in the very early days, very few receivers were used to record the response of each shot. Figure  2 shows a typical four microphone recording from 1928. It is believed to be one of the first seismic recordings to empirically verify that reflections from subsurface formations occurred and could be detected. The large oscillations at the beginning of this shot profile indicate the first arrival of energy from the source. The arrival indicated by the arrow as well as those above it are all reflections from the Cimarron anhydrite in central Kansas on the Seminole Plateau. The fact that these amplitudes were actually reflections was verified by drilling a well at the end of a line of four receiver shots.

Figure 2: A single trace recording.