Pressure sensor assembly for wellbore

Abstract

In the context of a casing-conveyed downhole pressure sensor assembly, there is provided a perforating charge which can be detonated from ground surface to open a perforation providing a pathway between the exterior formation and the pressure sensor.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:  
     
         1 . A downhole pressure sensor assembly for conveyance on the exterior surface of a string of casing to a subterranean formation to measure pressure in the formation, comprising: 
 housing means, for attachment to the exterior surface of the casing string, forming a sensor chamber;    a sensor, mounted within the sensor chamber, for measuring formation pressure; and    a shaped explosive perforating charge, associated with the housing means and oriented to form an outwardly extending perforation, when detonated, for penetrating the formation and enabling transmission of pressure from the formation to the sensor.    
     
     
         2 . The downhole pressure sensor assembly as set forth in  claim 1  wherein: 
 the perforating charge is contained within the housing means;  
 the housing means has an external surface and forms a passageway, connecting the external surface with the sensor, for transmitting formation pressure to the sensor; and  
 the charge is oriented so that the perforation will intersect the passageway when the charge is detonated.  
 
     
     
         3 . The downhole sensor assembly as set forth in  claim 2  wherein: 
 the housing means forms a second chamber, separate from the sensor chamber, wherein the perforating charge is positioned.  
 
     
     
         4 . A method for connecting a subterranean formation with a sensor for measuring a formation condition, comprising: 
 providing a downhole sensor assembly, externally conveyed on a string of casing cemented in a wellbore so that the sensor assembly is located opposite the formation, the sensor assembly comprising housing means containing a sensor for measuring the formation condition and means for forming, when activated, an outwardly directed perforation penetrating into the formation for enabling the formation condition to reach the sensor for measurement thereof; and    activating the perforation-forming means from ground surface, when required, to form the perforation.    
     
     
         5 . A method for connecting a subterranean formation with a pressure sensor, comprising: 
 providing a downhole pressure sensor assembly, externally conveyed on a string of casing cemented in a wellbore so that the sensor assembly is located opposite the formation, the sensor assembly comprising housing means containing a pressure sensor and means for forming, when activated, an outwardly directed perforation, the housing means having an external surface and forming a passageway connecting the sensor with the housing means external surface, the perforation-forming means being oriented so that the perforation, when formed, will intersect the passageway and penetrate into the formation so that formation pressure may be transmitted through the perforation and passageway to the sensor; and    activating the perforation-forming means from ground surface, when required, to form the perforation.    
     
     
         6 . A method for connecting a subterranean formation with pressure sensor means comprising: 
 providing perforation-forming means in association with a casing-conveyed downhole pressure sensor assembly, said sensor assembly having housing means containing pressure-measuring sensor means and being mounted to the exterior surface of a cemented casing string in a wellbore penetrating the formation; and    activating the perforation-forming means from ground surface to form a perforation extending into the formation, the perforation being in communication with the sensor means to enable pressure transmission between the formation and the sensor means.    
     
     
         7 . A downhole formation condition measuring sensor assembly for conveyance on the exterior surface of a string of casing to a subterranean formation to measure a condition in the formation, comprising: 
 housing means, for attachment to the exterior surface of the casing string, forming a sensor chamber;    a sensor, mounted within the sensor chamber, for measuring the formation condition; and    an explosive perforating charge, associated with the housing means and oriented to form an outwardly extending perforation, when detonated, for penetrating the formation and enabling transmission of the condition from the formation to the sensor.