Micro-Electrode Logging

Basic Information

Description

Micro-electrode logging uses a very small electrode array, with an electrode spacing of only a few centimetres. It includes both micro-potential and micro-gradient electrode arrays. To avoid mud effects, electrodes mounted on an insulating pad are pressed firmly against the borehole wall by a mechanical device.

Micro-electrode logging can measure both micro-gradient and micro-potential electrode arrays. The micro-gradient array has a shallower investigation depth than the micro-potential array. In permeable formations, the micro-gradient array is more strongly affected by the mud cake; because the mud cake has a lower resistivity, the micro-potential curve reads higher than the micro-gradient curve, producing a “positive separation”. In non-permeable formations the separation is insignificant. From the positive separation of the micro-electrode curves, permeable intervals can be identified. Meanwhile, micro-electrode logging is highly effective for distinguishing thin beds, making it an important method for determining the net pay thickness of oil and gas reservoirs.

Specification