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由于一系列的原因,在陆上油气勘探中已得到广泛应用的电磁测深方法,在我国海洋石油勘探中的应用还是一个空白。当前,我国海洋石油勘探正在向一些新领域拓展,这为电磁测深方法的应用与发展提供了机遇。海洋大地电磁测深是应用于油气勘探的最有前景的电磁测深方法。与陆地大地电磁测深一样,海洋大地电磁测深也是利用天然电磁场。在海上工作时,通常将磁信号接收器(磁探头)和电信号接收器(电极)布设在海底。海上使用的磁接收器与陆地使用的无多大差别。电极的布设,由于在海底布设大极距电极有困难;同时,与陆地相比,海底的电干扰要微弱得多,因此,在海上目前采用一种称为斩波式盐水电桥的装置,它的电极距只有几米,可以与仪器箱体连在一起。
Due to a series of reasons, the widely used electromagnetic sounding method in onshore oil and gas exploration is still a blank in our country’s offshore oil exploration. At present, China’s offshore oil exploration is expanding to some new areas, which provides opportunities for the application and development of electromagnetic sounding methods. Marine magnetotelluric sounding is the most promising electromagnetic sounding method used in oil and gas exploration. As with the terrestrial electromagnetic sounding, marine electromagnetic sounding is the use of natural electromagnetic field. When working at sea, the magnetic signal receiver (magnetic probe) and the electrical signal receiver (electrode) are usually laid on the sea floor. Magnetic receivers used at sea are not much different from those used on land. The layout of the electrodes is difficult due to the large pitch electrodes laid on the seabed; at the same time, the electrical interference on the seabed is much weaker than that on land, so a device called a chopped salt water bridge is currently used at sea, Its electrode is only a few meters away from the instrument box.