US Patent 7845429 Determining drillstring neutral point based on hydraulic factor

A solution for determining a neutral point of a drillstring in drilling a borehole is disclosed. The solution includes receiving depth-time log data for drilling the borehole with the drillstring, the depth-time log data including data related to a torque and drag factor and data related to a hydraulic factor; and determining the neutral point of the drillstring at a time point during the drilling based on the torque and drag factor and the hydraulic factor.