系统参数对海洋油气可控源电磁勘探的影响

Effect of system parameters on the marine hydrocarbon reservoir exploration by controlled-source electromagnetic method

对海洋油气可控源电磁探测仪器研发和勘探方案设计中影响测量结果的主要参数,如收发距、发射天线长度、发射天线高度、发射电流、发射频率、接收天线长度和接收天线高度等进行了理论仿真研究。研究结果表明,无论在深海环境还是在浅海环境,探测系统参数对测量结果均有相似的影响特点,只是影响程度有所差异。发射电流和接收天线长度仅决定信号幅度,两者呈正比关系,收发距和发射频率对测量结果影响最为显著,过大过小都不能得到明显的油气异常,需取中等值。发射天线长度、发射天线高度和接收天线高度对测量结果影响较小,油气引起的电场异常幅度随这3个参数值的增大而逐渐降低,通常这3个参数取值不大,可忽略其影响。在浅海环境下,发射和接收天线可贴近海面布置,此时天线高度仍然较小,这种方式不适用于深海环境。

Marine controlled-source electromagnetic method has become the research focus in subsea hydrocarbon exploration overseas.This paper studies the parameters of its survey system,which are important during instrument development and survey design.The simulations indicate whether in deep sea or in shallow sea,the system parameters affect the measurement results by the same way.The current of transmitter and the length of receiver antenna only affect the amplitude of electromagnetic signals,which is in direct proportion to them.The offset and the frequency of transmitter have remarkable effects on the measurement results.When they are too small or too big,no obvious hydrocarbon anomalies can be observed.So mid values should be allotted to them.The influences on the measurement results from the length and height of transmitter antenna and the height of receiver antenna are small.The hydrocarbon anomalies gradually become small with the increase of the three parameters.Since the values of these parameters are usually not big,their influences can be neglected.In shallow sea,both the transmitter antenna and the receiver antenna could be set close to the sea surface,where small antenna height is still kept.However,this distribution manner can not be used in deep sea.