Borehole temperature monitoring

Abstract

The disclosure provides a detonator which includes an oscillator, and a memory unit in which is stored a first measurement which is based on the frequency of oscillation of the oscillator at a first temperature and a second measurement which is based on the frequency of oscillation of the oscillator at a second temperature. The disclosure further extends to a method of monitoring a temperature in a borehole which includes the steps of using the first and second frequency measurements and the first and second temperatures to establish a frequency versus temperature relationship for the oscillator, placing the oscillator into the borehole, obtaining a third measurement of the frequency of oscillation of the oscillator while it is in the borehole, and using said frequency versus temperature relationship and the third frequency measurement to determine the temperature of the oscillator at the time the third frequency measurement was obtained.

1 - 17 . (canceled) 
     
     
         18 . A method of monitoring the temperature in a borehole ( 42 ) in which a detonator ( 40 ) is deployed in order to determine the existence of a hot hole condition, wherein the method includes the steps, prior to such deployment, under controlled temperature conditions, of using an oscillator ( 16 ) which functions at frequency which is temperature-dependent to determine a first measurement which is based on the frequency of oscillation (f 1 ; F 1 ) of the oscillator at a first temperature (T 1 ) and a second measurement which is based on the frequency of oscillation (f 2 ; F 2 ) of the oscillator at a second temperature (T 2 ), using said first and second frequency measurements and said first and second temperature measurements to establish a frequency versus temperature relationship for the oscillator and storing said relationship in a memory unit ( 14 ) in the detonator ( 40 ), deploying the detonator in the borehole ( 42 ), placing an emulsion explosive ( 52 ) into the borehole surrounding the detonator, subsequent to such placement, obtaining a third measure of the frequency of oscillation (f 3 ; F 3 ) of the oscillator and using said frequency versus temperature relationship to determine the temperature of the oscillator (“the third temperature”) (T 3 ) and using the third temperature to assess whether the temperature in the borehole is indicative of a hot-hole condition. 
     
     
         19 . A method according to  claim 18  wherein the second and first temperatures (T 1 ; T 2 ) span a temperature at which assembly of all or a part of the detonator ( 40 ) is done under temperature controlled conditions. 
     
     
         20 . A method according to  claim 18  which includes the step of extracting data on the stored frequency measurements from the memory unit ( 14 ) by means of a controller ( 50 ) which is in communication with the detonator ( 40 ). 
     
     
         21 . A method according to  claim 20  which includes the step of using the controller to implement a curve-fitting technique to establish said frequency versus temperature relationship from at least the first and second frequency measurements and from the first temperature and the second temperature. 
     
     
         22 . A method according to  claim 20  wherein the controller ( 50 ) is physically separate from the detonator ( 40 ) but in communication therewith.