Experimental Study of Induced Polarization Effect in Unconventional Reservoir Rocks

For time domain transient electromagnetic measurement, the negative sign often appears in the polarization region, which contains the induced polarization information. It is considered that the polarization effect is caused by the capacitance charge of the earth. Extending the turn-off time of the emission current means increasing the charging time, and reducing the charging voltage, which makes the polarization effect easier to observe. Therefore, a double trapezoidal wave transmitting system with a controllable turn-off edge is designed in this paper. In the process of current transmitting, the turn-off time can be controlled by changing the clamping voltage depending on the passive clamping technology. By cutting into the absorption resistance, the current oscillation can be eliminated under the condition of ensuring linearity. To verify the effectiveness of the system, we designed a polarized wire loop based on the filament model simulating the polarized earth. Comparing the response of the wire loop, the emission current with short and long turn-off times contributes to inducing the induction and polarization fields respectively. The double trapezoidal wave transmitting system with a controllable turn-off edge is suitable for measuring the induced polarization effect.

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Electrical-prospecting method for hydrocarbon search using the induced-polarization effect

Geophysics ◽

10.1190/1.2217367 ◽

2006 ◽

Vol 71 (4) ◽

pp. G179-G189 ◽

Cited By ~ 36

Author(s):

Sofia Davydycheva ◽

Nikolai Rykhlinski ◽

Peter Legeido

Keyword(s):

Polarization Effect ◽

Induced Polarization ◽

Controlled Source ◽

3D Environment ◽

Electrical Prospecting ◽

Displacement Currents ◽

Source Excitation ◽

Induced Polarization Effect ◽

Hydrocarbon Deposits ◽

Regions Of Russia

We propose a method of surface and marine electrical prospecting using controlled-source excitation. The method is designed to detect hydrocarbon deposits at depths of a few kilometers and to map their boundaries. The technique is based on imaging the induced-polarization (IP) parameters of the geologic formation. We use the fact that, because of the imaginary part of the electric conductivity, polarized media support wave propagation processes whose nature is similar to displacement currents induced by the dielectric permittivity. However, unlike displacement currents, these processes reveal themselves at much lower frequencies and, therefore, at greater depths. It is established that the ratio of the second and the first differences of the electric potential does not decay after the current turn-off in polarized media, whereas it decays quickly if the IP effect is absent. Thus, the IP response can be observed directly and separated from the electromagnetic (EM) response. We use a vertical focusing of the electric current to decrease the effect of laterally adjacent formations to apply a 1D layered model in a 3D environment. This method obtained promising results in several regions of Russia.

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