DESIGN PRINCIPLES FOR SEISMIC REFLECTION AMPLIFIERS*

Abstract

ABSTRACTDuring the last two years the Exploration and Production Research Laboratory, Shell Development Company, Houston, Texas, had occasion to evaluate a number of seismic amplifier channels submitted by various seismic contractors and manufacturers. From this study, material for the present paper has been collected.The modern trends to be found in the electrical design of up‐to‐date equipment are reviewed, and opinions of the E & P Research Laboratory, not necessarily shared by the industry, are expressed. No specific designs are mentioned, the material being presented in a general way.The over‐all elementary channel is discussed briefly and the various components are described functionally.Filtering is mentioned from a point of view of minimum requirements for an average reflection survey, and absolute sensitivity, minimum useful signal voltage from a geo‐phone, and noise are discussed.Gain control is treated in two regions–the automatic control region and the initial control region. For the former, static and dynamic control characteristics are discussed, and the factors influencing the control range are brought out. For the latter, it is pointed out when a system is said to require obligatory or optional initial suppression.Harmonic distortion, originating in the inductive components of the input circuit due to low‐frequency roller energy, is presented in a manner facilitating understanding of the distribution of low‐frequency filtering along the channel.