Patent ID: 6585044
Filing Date: 2003-07-01
Classification: E21B

Abstract:
A method for evaluating a formation characteristic in a well having a wellbore for intersecting a subsurface formation and being drilled from a wellbore surface with a drill bit carried at the end of a drill string, comprising:establishing a measuring system having measuring instruments for measuring a fluid flowing into and out of said wellbore, forming a closed fluid flow system extending from said wellbore surface through said drill string and returning through an annulus between said wellbore and said drill string back to said wellbore surface whereby fluids injected into said drill string at said wellbore surface travel into and out of said wellbore through a confined flow passage defined in part by said drill string and annulus, measuring the flow of the fluid injected through the drill string into said closed fluid flow system with said measuring instruments, measuring the flow of the fluid returning through said annulus from said closed fluid flow system with said measuring instruments, making a calibration comparison of the measured flow of the fluid injected into said closed fluid flow system with the measured flow of fluid returning from said closed fluid flow system, calibrating said measuring system as a function of the calibration comparison to form a calibrated measuring system, measuring, with said calibrated measuring system, the fluid injected into said drill string from the wellbore surface, measuring, with said calibrated measuring system, the fluid returning to the wellbore surface from said annulus, establishing, at a first subsurface wellbore location, a first formation parameter value associated with said formation, and correlating the calibration measurements of fluid with said first formation parameter value for determining a characteristic of said formation at said first subsurface wellbore location.