For the past few years, marine CSEM (Controlled Source Electromagnetic) exploration has been applied for direct hydrocarbon detection after three dimensional seismic survey and before drilling. More recently, it has been applied after two dimensional seismic survey to delineate possible high resistive target in order to save the exploration cost.
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3JTech has developed a new marine CSEM technology using Solenoid transmitter or a Combination of Wire and Solenoid transmitter (for more information: wwj@3jtech.com.tw 

Table of Contents:

VEL Numerical Modeling 
Solenoid Numerical Modeling 
Conclusion 



VEL Numerical Modeling:

The following three figures are numerical modeling results using vertical electrical line source (VEL). The transmitting current through the VEL is at 500 amperes with 10 milseconds ramp time and 5 seconds duration. The length of VEL is one kilometer. The separation between the transmitter and receiver is one kilometer. The depth to the seabed is two kilometers. The resistivity of the first layer below the seabed is one ohmmeter. The resistivity of the target layer is 200 ohmmeter while the thickness of that is 100 meters. Figure 2 and figure 3 show the vertical electric field and the azimuthal magnetic field respectively after the current is turned off for different thickness of the first layer for the marine earth model and VEL system configuration shown in Figure 1.



Figure 1: Marine earth model and VEL system configuration for numerical Modeling.




Figure 2 shows the vertical electrical field after the current is turned off for different thickness of the first layer for the marine earth model and VEL system configuration shown in Figure 1.




Figure 3 shows the azimuthal magnetic field after the current is turned off for different thickness of the first layer for the marine earth model and VEL system configuration shown in Figure 1. 

Solenoid Numerical Modeling 

The following four figures are numerical modeling results using horizontal solenoid source. The transmitting current through the Solenoid is at 500 amperes with 10 milseconds ramp time and 5 seconds duration. The length of the solenoid is two hundred meters. The marine earth model is the same as the one for VEL modeling. Figure 5, 6 and 7 are the inline magnetic field for the different TX and RX separations at 8, 6 and 4 kilometers respectively after the current is turned off for different thickness of the first layer. The marine earth model and Solenoid system configuration is shown in Figure 4.




Figure 4: Marine earth model and Solenoid system configuration for numerical Modeling.




Figure 5 represents the inline magnetic field for the TX and RX separation at 8 kilometers after the current is turned off for different thickness of the first layer. The marine earth model and Solenoid system configuration is shown in Figure 4.




Figure 6 represents the inline magnetic field for the TX and RX separation at 6 kilometers after the current is turned off for different thickness of the first layer. The marine earth model and Solenoid system configuration is shown in Figure 4.




Figure 7 represents the inline magnetic field for the TX and RX separation at 4 kilometers after the current is turned off for different thickness of the first layer. The marine earth model and Solenoid system configuration is shown in Figure 4.


Conclusion 
From the above modeling results, the solenoid configuration shows more distinguishable signal to the target layer compared to that from VEL.


Contact: 
wwj@3jtech.com for Tech Questions. 
info@3jtech.com for system leasing or purchasing. 