Patent ID: 7845429

Claim:
A method for determining an effective weight of a drillstring in drilling a borehole, the method comprising: (a) receiving depth-time log data for drilling the borehole with the drillstring using a computer, the depth-time log data including data related to a torque and drag factor and data related to a hydraulic factor; (b) determining the hydraulic factor, at a time point during the drilling using the computer, based on a Effective density, which is defined as: Effective Density=y*Cutter Density+(1−y)*Mud Density, wherein y represents a relative ratio of drilled cuttings to the fluid volume in an annulus between the drillstring and the borehole, and y is defined as: y=(Tbu*(dD/dt)(PI*dbit*dbit/4))/Vbu, wherein Tbu and Vbu represent a respective bottoms up time for a selected pump flowrate and annular volume, dD/dt represents a rate of penetration, and dbit represents a bit diameter; (c) determining the effective weight of the drillstring, wherein the effective weight of the drillstring is defined as: Weff=Wair(1−Effective Density/Metal Density), wherein Wair represents weight of the drillstring in the air; and (d) factoring in the determined effective weight when continuing drilling operations.