反射波振幅谱特征与地震仪前置放大器设计
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摘要
由于地层吸收衰减及球面扩散,使得深层地震反射波的振幅衰减严重,导致地震仪记录信号的有效动态范围远小于120dB,满足不了高分辨率地震勘探对记录信号动态范围的要求。从视等厚层状吸收介质模型入手,理论计算了地震反射波的振幅谱。其特征分析表明:反射波振幅随深度的增加按指数规律衰减,但衰减主要发生在1.5s前的中浅层。设计了智能程控型前置放大器,它的增益随深度增加自动增大,其值依次为0dB、18dB、24dB、30dB、36dB和42dB,使深浅层地震反射波的振幅在记录前均得到适当补偿,确保了地震仪记录信号的有效动态范围接近120dB,这对高分辨率地震勘探理论和开发新一代地震仪具有重要意义。
By the absorption of earth and the spherical diffusion the attenuation of amplitude in deep layer is serious,so the actual dynamic range of seismic instrument is much lower than 120dB which can't meet the needs of high resolution seismic exploration.Starting from the layer absorbing media model,the amplitude spectrum is calculated theoretically.By analyzing those characters it can be known that the amplitude of reflected wave attenuates according to the rule of exponent and the attenuation happens mainly in the medium depth.The intelligent programming pre-amplifier is also designed whose gain(0dB,18dB,24dB,30dB,36dB and 42dB) can increase with the increment of depth automatically.Thus the amplitude of reflected wave can be compensated before recording and the actual dynamic range of seismic instrument is close to 120dB which bears important meaning to the theory of high resolution and to developing new generation of seismic instrument.
By the absorption of earth and the spherical diffusion the attenuation of amplitude in deep layer is serious,so the actual dynamic range of seismic instrument is much lower than 120dB which can't meet the needs of high resolution seismic exploration.Starting from the layer absorbing media model,the amplitude spectrum is calculated theoretically.By analyzing those characters it can be known that the amplitude of reflected wave attenuates according to the rule of exponent and the attenuation happens mainly in the medium depth.The intelligent programming pre-amplifier is also designed whose gain(0dB,18dB,24dB,30dB,36dB and 42dB) can increase with the increment of depth automatically.Thus the amplitude of reflected wave can be compensated before recording and the actual dynamic range of seismic instrument is close to 120dB which bears important meaning to the theory of high resolution and to developing new generation of seismic instrument.
引文
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[2]俞寿朋.高分辨率地震勘探[M].北京:石油工业出版社,1993:35 76.
[3]唐建人,李勤学.高分辨率地震勘探理论与实践[M].北京:石油工业出版社,2001:12 14.
[4]董敏煜.地震勘探[M].山东东营:石油大学出版社,2000:180-183.
[5]李庆忠.走向精确勘探的道路[M].北京:石油工业出版社,1993:81-85.
[6]钱绍瑚,刘来祥.零相位子波的垂向分辨率[J].石油物探,1988,27(2):1-9.
[7]袁子龙,左黄金,李婷婷.激发信号的主频、振幅衰减及分辨率[J].石油物探,2004,43(6):537-540.
[8]凌云.大地吸收衰减分析[J].石油地球物理勘探,2001,36(1):1-8.
[9]钱绍瑚.高分辨率勘探与地震仪器[J].物探与化探,1995,19(2):114-121.
[10]李庆忠.地震高分辨率勘探中的误区与对策[J].石油地球物理勘探,1997,32(6):751-783.
[11]康华光,邹寿彬.电子技术基础(数字部分)[M].北京:高等教育出版社,2000:95-105.
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