Real-Time Digital Signal Processing for High-Resolution Seismic Survey

Abstract

ABSTRACT Specially designed for very hi9h resolution seismic survey, DELPH1 allows digital recording and real time processing and display of the data. The system is based on an IBM-PC computer and on specific acquisition and processing board with a digital signal processor. The same equipment can be use for replay or post-processing. Il INTRODUCTION The new DELPH1 system presented here, is a digital recording and real time processing system, specially designed for very high resolution single channel seismic. Digital recording in conventional multi-channel seismic has demonstrated highly improved resolution while allowing more sophisticated processing, therefore providing far better quality of the seismic profiles. Real time processing and plotting of the seismic data allow controlling the quality of the acquisition parameters as well as on-site interpretation, thus avoiding the formerly necessary delays and increased cost due to remote processing DELPH1 is implemented on an IBM/PC like computer which provides display and storage of the data and uses a digital processor for the real time data processing. II) DIGITAL RECORDING Digital recording provides several advantages over analog recording although the latter is still currently used in high resolution single channel seismic. Primarily, digital recording improves the dynamic range of the recorded data and gives a truer reproduction of the frequency contents of the seismic signal. The greatest advantage of digital recording lies in the ability to apply powerful digital processing. The original data can undergo multiple processing using different parameters leading to far better quality final data and thus, interpretation. SOllie processing such as disconsolation and multiple removal which can not be implemented with analog techniques, are possible with digitally recorded data. Available analog processing is limited to very few possibilities (e.g. band-pass filter, swell filter, Time Variable Gain). Lastly, immediate and convenient replay of the data is then possible, thanks to modern mass-storage devices (tape, optical disk, hard disk), As a result, the use of digital recording offers the opportunity to use modern up-to-date workstations. I) REAL TIME PROCESSING Real time digital processing is an opportunity to reduce the delay and cost of processing. Furthermore, it provides the availability of fully processed data on the acquisitions site. This feature can be used to optimize the organization of the survey and/or to start the interpretation work on the site. The concept of real time processing refers here to the processing done during the time available between the acquisition of two consecutives samples, and during any non-recording time between two consecutive shots. This is done onboard the vessel, simultaneously while recording the seismic profile. The processed seismic section, presented in variable area, is available at the end of the profile. The raw data is saved onto hard disk.