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Systems and methods for improving drilling efficiency

  • US 8,939,234 B2
  • Filed: 09/21/2010
  • Issued: 01/27/2015
  • Est. Priority Date: 09/21/2009
  • Status: Active Grant
First Claim
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1. A method for drilling a borehole in an earthen formation, comprising:

  • (a) providing a drilling system including a drillstring having a longitudinal axis, a bottom-hole assembly coupled to a lower end of the drillstring, and a drill bit coupled to a lower end of the bottom-hole assembly;

    (b) rotating the drill bit at a rotational speed;

    (c) applying weight-on-bit to the drill bit and advancing the drill bit through the formation to form the borehole;

    (d) pumping a drilling fluid down the drillstring to the drill bit, wherein the drilling fluid has a flow rate down the drillstring;

    (e) selecting a predetermined rotational speed set point value for the drill bit;

    (f) selecting a predetermined maximum rotational speed that is greater than the set point value and a predetermined minimum rotational speed that is less than the set point value;

    (g) oscillating the rotational speed of the drill bit asymmetrically and non-uniformly about the set point value during (c), wherein the oscillations of the rotational speed of the drill bit have a random period or a random amplitude between the predetermined maximum rotational speed and the predetermined minimum rotational speed;

    (h) maintaining the rotational speed of the drill bit between the predetermined maximum rotational speed and the predetermined minimum rotational speed during (g); and

    (i) generating non-steady state conditions in the borehole during (g).

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