Sonde

Abstract

A sonde deploys a sensor against a well casing. The sonde has an expandable and/or resilient C-shaped member and at least one sensor. The C-shaped member has an annular configuration with a single gap that defines two ends facing each other. The member is compressible, and once compressed, its ends close together. A device releasably compresses the C-shaped member so as to allow positioning of the sonde inside the well and subsequent deployment.

1 .- 19 . (canceled)  
   
   
       20 . A sonde comprising an expandable and/or resilient C-shaped member and at least one sensor, the member having an annular configuration with a single gap that defines two ends facing each other, the member being compressible, or having been compressed, to bring its ends closer together.  
   
   
       21 . A sonde according to  claim 20 , wherein the sonde is for installation in or installed in a well casing and wherein the said C-shaped member is clampable or clamped against the inner wall of the well casing.  
   
   
       22 . A sonde according to  claim 20 , wherein the or each sensor comprises a seismic or microseismic sensor.  
   
   
       23 . An apparatus for deploying a sensor against a well casing, said apparatus comprising: 
 a sonde, adapted to be lowered into a well, the sonde comprising a split annular member and at least one sensor mounted thereto, the annular member being resilient and radially movable between a contracted and an expanded position; and    a tool for releasably retaining the annular member in the contracted position so as to allow positioning of the sonde inside the well and subsequent deployment.