Tool for imaging a downhole environment

摘要

The invention is concerned with a tool and method for determining standoff from a formation though mud. The tool comprising a first electrode located at a distance from the formation for measuring a first impedance. A second electrode is located at a second distance from the formation for measuring a second impedance. A processing unit measures a difference between the first impedance and the second impedance, uses the difference to determine a conductivity of the mud and based thereon, determines the standoff of at least one of the first and the second electrode.

主权项

1. A tool for determining standoff from a formation though mud, the tool comprising:
a first electrode located at a distance from the formation for measuring a first impedance; a second electrode located at a second distance from the formation for measuring a second impedance, wherein the at least one of the first and the second electrode is an imaging button; and a processing unit for measuring a difference between the first impedance and the second impedance, using the difference to determine a conductivity of the mud and based thereon, and determining a first standoff the first electrode and a second standoff of the second electrode wherein the first standoff dm is a distance by which the imaging button is recessed from the formation and is determined from:
dm=Am·|Zm·σ*|where Am is the effective area of the button, σ* is the complex conductivity and Zm is the impedance of the mud.