The first petroleum discovery in the world made using seismic exploration methods was the Orchard field in 1924. That year the German Seismos Party No. 1 moved from Mexico to Texas under contract to Gulf Oil Corporation (now absorbed into Chevron).
During 1924-25 the crew made numerous discoveries of shallow salt domes, initially using an inline technique proposed by Mintrop, but by 1925 using the fan refraction technique. This technique, suggested by L.P.Garrett of Gulf, used a large explosive charge with a small number of detectors aranged along an arc centered on the shot point, with a radius of several miles. The air wave arriving at the detector was used to determine the shot instant (surveying measured the distance from source to receiver, so assuming constant velocity for the air wave allowed computation of shot instant), and the refracted first arrival was timed. For each area, a "normal" time-distance curve was established. Earlier than normal arrivals indicated salt between source and receiver, so fans in two directions could pin down the approximate location of a salt dome. Later in the fan-shooting campaign radios were introduced to record the shot instant at each geophone.
Seismos used mechanical geophones, which recorded directly at each receiver location. These were more reliable than the earliest electronic detectors, but were rapidly replaced by them.
Seismos was a company founded by Ludger Mintrop, building on technology developed in Germany
during the First World War to locate enemy artillery by timing the arrival of seismic energy
from a gunshot. The company merged later with the other German seismic contractor, Prakla,
and the merged company was bought during the 1980's by the Norwegian company Geco.
Geco is now part of Schlumberger.
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