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System for detecting blow out and lost circulation in a borehole

  • US 4,527,425 A
  • Filed: 12/10/1982
  • Issued: 07/09/1985
  • Est. Priority Date: 12/10/1982
  • Status: Expired due to Term
First Claim
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1. A method of detecting the commencement of blowouts and lost circulation in a borehole in which a drilling fluid is being circulated, comprising the steps of:

  • transducing at a selected location within the borehole the rate of f1ow of the drilling fluid into the borehole into a first electrical signal proportiona1 thereto;

    accumulating said first electrical signals over a selected interval of time;

    transducing, at said selected location within the borehole, the rate of flow of the drilling fluid out of the borehole into a second electrical signal proportional thereto;

    accumulating said second electrical signals over a selected interval of time;

    comparing the accumulation of said first electrical signals with the accumulation of said second electrical signals to determine the differences in value therebetween, a preselected difference between the compared values being indicative of the commencement of one of a blow out and lost circulation, wherein said transducing steps comprise generating at a selected point within the borehole a sonic signal within the flowing streams of drilling fluid;

    receiving the sonic signals at a first point located a selected distance above said selected point and at a second point located the same selected distance below said selected point;

    measuring the time difference between reception of the sonic signal at said first and second points in the incoming fluid stream and transducing said first electrical signal in proportion thereto and in the outgoing fluid stream and transducing said second electrical signal in proportion thereto, and wherein said measuring step comprises triggering the generation of a ramp function simultaneously with the generation of said first sonic signal;

    accumulating the value of said ramp function in response to reception of said first sonic signal at said first point and accumulating the value of said ramp function in response to reception of said first sonic signal at said second point;

    comparing the value of said ramp functions after accumulation of each; and

    producing a first time difference signal proportional to the difference in the compared values of said accumulated ramp function values.

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