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Unformatted text preview: rically Focused Log: (SFL) The spherically focused log (SFL) has an electrode arrangement that ensures the current is focused quasi-spherically. It is useful as it is sensitive only to the resistivity of the invaded zone. 62 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration Micro-Resistivity Logs Micro Log: (ML) It is a rubber pad with three button electrodes placed in a line with 1 inch spacing The result from this tool is two logs called the 2”normal curve (ML) & the1½“inverse curve (MIV). The difference between the two curves is an indicator of mudcake (so it is used in making sand counts). Micro laterolog: (MLL) It is the micro-scale version of the laterolog. The tool is pad mounted, and has a central button current electrode. The depth of investigation of the MLL is about 4 inches. Proximity Log: (PL) This tool was developed from the MLL. It is used to measure RXO. It has a depth of penetration of 1½ ft., and is not affected by mudcake. It may, however, be affected by Rt when the invasion depth is small. Micro Spherically Focused Log: (MSFL) It is commonly run with the DLL on one of its stabilizing pads for the purpose of measuring RXO. It is based on the premise that the best resistivity data is obtained when the current flow is spherical around the current emitting electrode The current beam emitted by this device is initially very narrow (1”), but rapidly diverges. It has a depth of penetration of about 4” (similar to the MLL). 63 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration 2- Induction Tools: These logs were originally designed for use in boreholes where the drilling fluid was very resistive (oil-based muds or even gas). It can, however, be used reasonably also in water-based muds of high salinity, but has found its greatest use in wells drilled with fresh water-based muds. The sonde consists of 2 wire coils, a transmitter (Tx) and a recei...
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