f Reservoir Characterization and Monitoring Using Multi-Transient Electromagnetic (MTEM)

The Multi-Transient Electro-Magnetic (MTEM) method implements a current bi-pole source with a sequence of receiver stations that measure the resulting voltage. Source and receiver stations are located in a straight line similar to 2-D seismic. Onshore and offshore acquisition systems have been developed providing continuous coverage of the subsurface including the transition zone. The earth’s impulse response is obtained for each source receiver pair by deconvolving the received voltage for the input current. The source signal is a Pseudo Random Binary Series (PRBS) that combined with vertical stacking allows us to maximize S/N. The subsurface resistivity is evaluated from the very shallow sediments down to the target depth by continuously optimizing the acquisition parameters. This involves adjusting the length of the source bi-pole, the bandwidth of the source PRBS, and the sampling rate of the recorded signal to be optimal for each offset range. The method allows for real time monitoring of the signal and real time assessment of the subsurface resistivity. The final deliverables are 2-D depth sections inverted to resistivity along 2-D profiles.