Wear resistant electrodes for downhole imaging

Patent metadata

Field	Value
Publication number	US-9880311-B2
Application number	US-201514699053-A
Country	US
Kind code	B2
Filing date	Apr 29, 2015
Priority date	Apr 29, 2015
Publication date	Jan 30, 2018
Grant date	Jan 30, 2018

Abstract

Devices and methods for well logging using a wear resistant electrode are provided. A downhole device may include a drill bit, a gauge pad mounted on the drill bit, and a first electrode mounted in the gauge pad. An insulating polycrystalline diamond (PCD) material may surround at least a portion of the first electrode. Additionally, the first electrode may include an electrically conductive wear resistant contact point that maintains constant contact with a wall of a wellbore. Additionally, the first electrode may measure an impedance of a geological formation during a drilling operation.

First claim

The invention claimed is:

1. A method, comprising:
placing a downhole tool in a wellbore in a geological formation, wherein the downhole tool comprises at least one electrode comprising:
a face of electrically conductive wear-resistant material;
a layer of insulating polycrystalline diamond material surrounding at least a portion of the at least one electrode;
at least one transmitting toroidal transformer coupled to the at least one electrode; and
at least one measure toroidal transformer coupled to the at least one electrode;

injecting alternating current into the geological formation via the at least one transmitting toroidal transformer of the at least one electrode;
receiving return current from the formation via the at least one measure toroidal transformer of the at least one electrode;
determining a formation resistance from the return current; and
determining a formation resistivity from the formation resistance.

2. The method of claim 1 , wherein the alternating current is injected into the geological formation at a frequency between 100 kHz and 100 MHz in an oil based mud (OBM) environment, and the alternating current is injected into the geological formation at a frequency between 1 kHz and 100 MHz in a water based mud (WBM) environment.

3. The method of claim 1 , wherein the downhole tool is mounted on a gauge pad of a drill bit.

4. The method of claim 1 , wherein the downhole tool is mounted on a drill collar.

Assignees

• Schlumberger Technology Corp

Inventors

• Clark Brian O
• Orban Jacques
• Marshall Jonathan D
• Woolston Scott R
• Hendricks Daniel
• Cannon Neil

Classifications

• G01R3/00

  Apparatus or processes specially adapted for the manufacture {or maintenance} of measuring instruments {, e.g. of probe tips} · CPC title

• G01V3/24 Primary

  using AC · CPC title