High-resolution marine seismic reflection profiling: Systems and capabilities

Abstract

Seismic reflection profiling is the most effective and commonly used geophysical tool for sub‐seafloor geologic investigations. A broad variety of seismic data acquisition systems are available, depending on the imaging depth and resolution required. High‐resolution methods utilize controlled sound sources that generate signals in the frequency range of approximately 1,000 to 10,000 Hz. Data acquired with piezoelectric swept‐frequency (chirp) transducers, mini‐sparkers, and boomer‐plate sources routinely image up to 100 m subbottom in marine sediments, with vertical resolution better than 50 cm. Small air‐gun systems with frequencies between 100 Hz and 500 Hz achieve as much as 1 km of penetration and resolution of a few meters. Imaging depths are highly dependent on the geologic environment; surveys in fine‐grained marine sediments usually produce the best results. Free gas from decaying organic matter in shallow sediments can dramatically degrade data quality. High‐resolution methods are contrasted by current hydrocarbon exploration industry systems that utilize large arrays of air guns to generate high‐energy signals between l0 Hz and 100 Hz recorded by multiple hydrophone streamers as much as 10 km in length. The resulting three‐dimensional data volumes can provide detailed images to depths greater than 15 km.