Magnitude Verses Offset Study with EM Transmitter in Different Resistive Medium

Abstract

Seabed Logging (SBL) is new technique to detect hydrocarbon reservoir under the sea bed. EM transmitter is used to transmit low frequency electromagnetic signals into the subsurface layers of the sea bed to detect different resistive layers. However, detection of resistivity contrast in different resistive layers for a deep target is still a challenge in SBL. Due to economical point of view a scaled tank with a scale factor of 2000 was built to study the resistivity contrast. In the scale tank experiment aluminium rod EM transmitter of length 50 cm is towed at 35 cm height from the bottom of the tank. Three receivers are placed at 25 cm from the bottom of the tank. A series of experiments were conducted with different resistive mediums such as (tap water, salt water and salt water with oil packets). The oil packets were placed at certain positions in the water tank. The electromagnetic field responses from different resistive layers were recorded by the receivers. Different response in the magnitude of magnetic field was observed by different resistive medium. It was also observed that the magnetic field strength had increased 50% for salt water and 150% for oil which clearly shows the resistivity contrast. Our preliminary results have shown that high resistive layers in a conductive medium can be detected by using the experimental set up. © 2011 Asian Network for Scientific Information.