Recording Technologies for High-Rate Marine Seismic Data

Abstract

ABSTRACT Developments in marine seismic data acquisition technology have made available streamer systems with 1000 channels and high sampling frequency. The resulting data rates and volumes are above the capacity of the current magnetic tape recording systems. The recording requirements of high rate seismic systems could be met through developments in laser disc technology, in the area of magnetic tape systems or through online pre-processors reducing the amount of data. New recording technologies are essential for the feasibility of high rate seismic systems. INTRODUCTION Industry demand for increased resolution of offshore seismic surveys has resulted in development of more sophisticated acquisition systems. Digital streamers have made possible significant increases in spatial and temporal sampling rates. Some streamer systems provide the possibility of recording up to 1000 channels in addition to high temporal sampling rates. These developments have led to significantly higher data rates than common in marine seismic data recording today. Standard computer readable magnetic tape, which is well known to the seismic industry, is still the state-of-the-art medium for recording of seismic data. Even though this technology has remained essentially the same for several years, it has so far proved to be reliable and sufficient. Unchanged, however~ it will not be adequate for the kind of high rate seismic data recording indicated above. Implementation of new recording technologies is therefore essential to the feasibility and cost effectiveness of high rate seismic acquisition systems The increased recording density and speed requirements of high rate acquisition systems can be met in several ways; through new developments in laser disc technology, in magnetic computer tape technology resulting in magnetic tape systems with higher data rate and density, or through the use of high density digital recorders to seismic data acquisition. Another attractive alternative is to use online pre-processors to perform data reduction to match the recorded data volume to the capabilities of current magnetic tape systems. However, online pre-processing is a large subject which we will leave out of this paper. In this paper we will discuss the use of these recording systems for high rate seismic recording and the status of their development. However, we will begin with a review of some geophysical and operational reasons for using high rate seismic recording. SOME GEOPHYSICAL ASPECTS. Increasing production and development costs of off-shore oil fields have forced many oil companies into careful evaluation of new fields and reevaluation of existing fields currently in production. To meet the required data quality may in some areas require fine spatial sampling intervals of the seismic data, in some cases significantly less than 10 m. The Delphi Survey respondents (Hewitt, 1983) predicted that 25 percent of recording systems in use by 1990 will have at least 1000 channel capability and that this percentage could increase to 50 by 1995.