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System for controlling the operating pressures within a subterranean borehole

  • US 6,575,244 B2
  • Filed: 07/31/2001
  • Issued: 06/10/2003
  • Est. Priority Date: 07/31/2001
  • Status: Expired due to Term
First Claim
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1. A method of controlling one or more operating pressures within a subterranean borehole that includes a tubular member positioned within the borehole that defines an annulus between the tubular member and the borehole, a sealing member for sealing the annulus between the tubular member and the borehole, a pump for pumping fluidic materials into the tubular member, and an automatic choke for controllably releasing fluidic materials out of the annulus between the tubular member and the borehole, comprising:

  • sensing an operating pressure within the tubular member and generating an actual tubular member pressure signal representative of the actual operating pressure within the tubular member;

    comparing the actual tubular member pressure signal with a target tubular member pressure signal representative of a target operating pressure within the tubular member and generating an error signal representative of the difference between the actual tubular member pressure signal and the target tubular member pressure signal; and

    processing the error signal to generate a set point pressure signal for controlling the operation of the automatic choke, wherein processing the error signal comprises;

    multiplying the error signal by a gain Kp;

    integrating the error signal and multiplying the integral of the error signal by a gain Ki; and

    differentiating the error signal and multiplying the differential of the error signal by a gain Kd.

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