FIELD: physics.
SUBSTANCE: microresistivity logging tool (100) includes a shield electrode (180) placed between a guard electrode (160) and a return electrode (170). A measuring electrode (190) is placed in and electrically isolated from the guard electrode (160) and first and second potential electrodes (212, 214) are placed in and electrically isolated from the shield electrode. The tool (100) further includes at least one switch (250) configured to switch the tool (100) between distinct first and second microresistivity measurement modes. The first measurement mode is configured for taking microresistivity measurements in conductive (water based) drilling fluid and the second measurement mode is configured for taking microresistivity measurements in non-conductive (oil based) drilling fluid, thereby enabling the tool (100) to be used in any type of drilling fluid.
EFFECT: enabling microresistivity measurement in conductive and non-conductive fluids.
19 cl, 10 dwg
