Patent ID: 6905241
Filing Date: 2005-06-14
Classification: E21B

Abstract:
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.