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Unformatted text preview: ver (Rx). High frequency alternating current (20 kHz) of constant amplitude is applied to the transmitter coil. This gives rise to an alternating magnetic field around the sonde that induces secondary currents in the formation. These currents flow in coaxial loops around the sonde, and in turn create their own alternating magnetic field, which induces currents in the receiver coil of the sonde. The received signal is measured, and its size is proportional to the conductivity of the formation. Calibration: Induction logs are calibrated at the wellsite in air (zero conductivity) and using a 400ms test loop that is placed around the sonde. The calibration is subsequently checked in the well opposite zero conductivity formations (e.g., anhydrite), if available. 1- The 6FF40 Induction-Electrical Survey Log (IES-40) It is a 6 coil device with a nominal 40 inch Tx-Rx distance, a 16 inch short normal device and an SP electrode. 2- The 6FF28 Induction-Electrical Survey Log (IES-28) It is a smaller scale version of the IES-40. It is a 6 coil device with a nominal 28 inch Tx-Rx distance, a 16 inch short normal device and an SP electrode. 3- The Dual Induction-Laterolog (DIL) It has several parts: (i) a deep penetrating induction log (ILd) that is similar to the IES-40, (ii) a medium penetration induction log (ILm), a shallow investigation laterolog (LLs) and an SP electrode. The ILm has a vertical resolution about the same as the ILd (and the IES-40), but about half the penetration depth. 4- The Induction Spherically Focused Log (ISF...
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- Spring '10