高分辨率地震勘探智能程控型前置放大器的设计

The design of programming pre-amplifier in high-resolution seismic exploration

根据大庆长垣北地区的地震参数(V0、β),建立视等厚层状吸收介质模型,选择200 Hz(主频)的雷克子波由浅至深计算地震反射波.计算结果表明,地层吸收衰减和球面扩散导致地震反射波振幅存在巨大差异,随深度增加振幅迅速衰减,地震仪记录信号的有效动态也迅速降低,但振幅的衰减主要发生在1.5 s前的中浅层.本文对地震仪采集站的前置放大器进行改进,设计一种智能程控型前置放大器,它的增益随深度自动增大,地层深度从0.5s^3.0 s,放大器的增益依次为0 dB、18 dB2、4 dB、30 dB3、6 dB和42dB,能够比较好地弥补地震反射波的振幅衰减.经该放大器放大以后,地震仪记录信号的有效动态均达到或超过110 dB,基本满足了高分辨率地震勘探对采集仪器记录动态的需要.

Based on parameters （V0、β） of Daqing, the uniform thickness models are setup. The reflected waves from shallow to deep are calculated on the condition that the main frequency of exiting wave（Ricker wavelet） is 200 Hz. The result shows that there is large difference among the amplitudes caused by the absorption and attenuation of earth and spherical diffusion. With the increment of depth the amplitude attenuates rapidly and the main attenuation happens in 1.5 s （medium depth）. To improve the amplifer a kind of intelligent programming pre-amplifier is designed whose plus can increase with the increment of depth. The plus is 0dB, 18 dB,24 dB,30 dB,36 dB and 42dB responding to 0.5 s to 3. 0 s. It can make up the decrease of amplitude in a way. The dynamic ranges of signals recorded by seismic instrument are over 110 dB which can meet the demand of high--resolution seismic exploration.