Recognizing Hydrocarbon Signatures
In the 1970s, the realization that hydrocarbons could be directly detected by seismic data caused a major revolution in seismic processing and interpretation. The main drivers were digital recording and digital processing. The digital world led to the preservation of “true” or “relative” amplitude from acquisition through interpretation. The routine application of automatic gain control (AGC) was being reevaluated by all processing centers. Outstanding differences between processing with and without AGC were being displayed around the industry. Figure 4.A.1 contains an early 1970s example. What is surprising about this figure is that the data were acquired with a marine vibro-seis source in the offshore Gulf of Mexico. One can’t miss the gas anomaly at 1.6 s. Thus was bright-spot technology.
Figure 4.A.2 depicts the cry heard throughout the oil industry during the early 1970s: “Hydrocarbon reservoirs can be detected as seismic events that have significantly higher amplitude than surrounding reflections.” This thesis, once realized by an oil company, became the leading-edge technology to be exploited with internal research on new interpretation applications. The economic benefits for a company that had bright-spot technology were staggering when it came to evaluating potential prospects for upcoming lease sales, farm-ins, and the like.
Thirty years after the advent of the bright-spot technology, one has to wonder if there are any other interpretation techniques waiting to be developed that will change the oil industry as drastically as bright spots did. Probably not! However, there have been numerous incremental advances in amplitude interpretation since that time.