A Broadband Seismic Acquisition and Processing Solution to Improve Imaging in a Complex Shallow Water Environment, Malaysia

Abstract

Abstract There have been several recent advances in the last few years in marine broadband acquisition and processing technologies and shallow gas imaging. They have enabled new life to be breathed into old datasets through reprocessing and from completely new seismic surveys to be acquired in place of legacy conventional datasets that can lead to a step change in data quality and subsequently reservoir understanding. This paper will look at these new technologies and give an example of a shallow water dataset with complex near surface shallow gas bodies where a combination of new acquisition, processing and reprocessing techniques have been able to provide significant uplift over pre-existing legacy conventional datasets targeting thin bed pay zones. Careful consideration of the geophysical challenges and implementing targeted solutions has been a key to producing a successful output. A complimentary paper discusses in more detail the interpretational benefits of the new acquired broadband data versus the legacy conventional data. Introduction Until recent years marine seismic datasets have had to contend with the source and receiver ghost notch effect in the output frequency spectrum whereby the outgoing upward travelling source side sea-surface reflection and the returning receiver side sea-surface reflection constructively and destructively interfere with the directly down going source reflections and up going receiver side reflections to give band limited datasets. Geophysicists have had to design their surveys to enhance a given part of the bandwidth at the detriment to another part e.g. tow shallow to enhance higher frequencies or tow deep to enhance low frequencies. With the advent of broadband acquisition techniques (Hill et al., 2006; Carlson et al., 2007; Soubaras and Dowle, 2010) this no longer has to be the case and the recorded ghosts can be addressed in acqusition based solutions to give frequency rich broadband datasets that can almost reduce the wavelet to a near spike. As a by-product streamers can be towed deeper to reduce the effects of noise from sea state generated noise to provide datasets with higher signal to noise and aiding better lower frequency penetration deeper into the section. The result is rich bandwidth shallow data and better imaged deeper sections.