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Determination of virgin formation temperature

  • US 6,905,241 B2
  • Filed: 03/13/2003
  • Issued: 06/14/2005
  • Est. Priority Date: 03/13/2003
  • Status: Expired due to Term
First Claim
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1. A method for determining virgin formation temperature of earth formations surrounding a borehole that is drilled using drilling fluid, comprising the steps of:

  • keeping track of the time duration of drilling fluid circulation at borehole depth regions of interest;

    keeping track of the time after cessation of drilling fluid circulation at said borehole depth regions of interest;

    at a depth of interest, causing flow of fluid from the formations into a device in the borehole, and measuring the temperature of said fluid as a function of time with respect to initiation of said fluid flow;

    modeling the thermal history of formations surrounding the depth of interest, said modeling including a cooling phase during drilling fluid circulation, a temperature build-up phase after cessation of drilling fluid circulation, and a formation fluid flow phase after initiation of fluid flow;

    using said model and said temperature measurements for determining a trend of temperature evolution at said depth of interest; and

    determining the virgin formation temperature by extrapolation from said trend.

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