Optical window assembly for an optical sensor of a downhole tool and method of using same

A downhole tool positionable in a wellbore penetrating a subterranean formation, the downhole tool comprising:

• a housing with a flowline to receive downhole fluid in the flowline;
• a light source to pass light through the flowline;
• a pair of optical sensors positioned in the housing to measure the light passing through the flowline;
• and
• a pair of optical window assemblies operatively connectable to the pair of optical sensors, each of the pair of optical window assemblies comprising:
• a tubular sensor body positioned in the housing, the sensor body having a sensor-end and a flanged signal-end with a passage through the sensor body;
• an optical window is positioned in the passage of the sensor body to pass the light from the flowline to the at least one of the pair of optical sensors;
• a seal disposed about the sensor body;
• and
• a backup ring disposed about the sensor body between the flanged signal-end and the seal to support the seal about the sensor body whereby the downhole fluid is prevented from leaking between the seal and the sensor body.

A method of sensing downhole parameters of downhole fluid about a wellbore penetrating a subterranean formation, the method comprising:

• deploying a downhole tool into the wellbore, the downhole tool comprising a housing with a flowline through the housing, a light source, a pair of optical sensors positioned in the housing, and a pair of optical window assemblies operatively connectable to the pair of optical sensors, each of the optical window assemblies comprising:
• a tubular sensor body positioned in the housing, the sensor body having a sensor-end and a flanged signal-end with a passage through the sensor body;
• an optical window positioned in the passage of the sensor body;
• a seal disposed about the sensor body;
• and
• a backup ring disposed about the sensor body between the flanged signal-end and the seal;
• and
• measuring light passing through downhole fluid in the flowline and through the optical window with the pair of optical sensors;
• and
• preventing the downhole fluid from leaking between the seal and the sensor body by supporting the seal about the sensor body with the backup ring.