Determination of virgin formation temperature
First Claim
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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Accused Products
Abstract
A method for determining virgin formation temperature of earth formations surrounding a borehole is provided. The time duration of drilling fluid circulation and the time after cessation of drilling fluid circulation at the borehole depth regions of interest are tracked. At a particular borehole depth region of interest, fluid flows from the formations into a device in the borehole, and the temperature of the fluid as a function of time with respect to initiation of fluid flow is measured. The thermal history of formations surrounding the particular borehole depth region is modeled for 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. The model and temperature measurements are used to determine a trend of temperature evolution and the virgin formation temperature by extrapolation from the trend.
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Citations
20 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. In a method for determining virgin formation temperature of earth formations surrounding a borehole that is drilled using drilling fluid, that includes 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, and, 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;
the improvement comprising;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. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
- keeping track of the time duration of drilling fluid circulation at borehole depth regions of interest;
Specification