Time synchronization for marine controlled source electromagnetic recorder

Abstract

Fund: "11• 5" 863 major projects subject -the submarine gas hydrate electromagnetic detection technology (2006AA09A201) Central university funding basic research Abstract-As an effective method to improve the successful rate of marine oil and gas drilling, marine controlledsource electromagnetic method requires acquisition of many marine controlled-source electromagnetic receivers which record electromagnetic data on the same time axis. However, receiver works on the seabed where GPS signal is shielded and relatively constant temperatures, this will bring about a consequence that the land synchronization method could not be implemented. To get the marine receivers which are time synchronization, we combine the GPS and OCXO (Oven Controlled Crystal Oscillator), and then calculate time drift. This method makes time drift down minimum by time drift compensation between different receivers.

Three-Level DC-DC Controlled-Source Circuit of Marine Electromagnetic Detection Transmitter

“…e operation principle of marine controlled-source electromagnetic detection (MCSEM) is that electromagnetic transmitter is towed to offshore bottom and transmits high-power electromagnetic waves through transmitting dipole, field source signals are collected back by electromagnetic receiving equipment, and through signal processing and inversion, electro-conductive structural features of media below seafloor can be analyzed; it is one of the methods which can effectively explore natural gas hydrate (NGH) resources [2]. Due to attenuation of electromagnetic waves by seawater, the greater the current signals transmitted by the electromagnetic transmitter, the greater the detectable depth, and elevation of transmitting power will bring about problems of heat dissipation and energy loss in seafloor electromagnetic transmission system [3]. It is necessary to reduce internal resistance, reduce internal loss, and improve transmitting efficiency of the transmitter, and research and development of highefficiency and large-current electromagnetic transmitter system are of great significance to deep-sea detection.…”