TIEFENMESSSYSTEM UNTER VERWENDUNG DER PARAMETER-ABSCHAETZUNG FUER EIN UNTERTAGE-BOHRLOCH-PROFIL-MESSGERAET.

摘要

Due to irregularities associated with the borehole of an oil well, a depth determination system for a well logging tool, suspended from a cable in the borehole of the oil well, produces a correction factor, which factor is added to or subtracted from a surface depth reading on a depth wheel, thereby yielding an improved indication of the depth of the tool in the borehole. The depth determination system includes an accelerometer on the tool, a depth wheel on the surface for producing a surface-correct depth reading, a computer for a well logging truck and a depth determination software stored in the memory of the computer. The software includes a novel parameter estimation routine for estimating the resonant frequency and the damping constant associated with the cable at different depths of the tool in the borehole. The resonant frequency and damping constant are input to a kalman filter, which produces the correction factor that is added to or subtracted from the depth reading on the depth wheel thereby producing a coherent depth of the well logging tool in the borehole of the oil well. Coherent depth is accurate over the processing window of downhole sensors, but not necessarily over the entire depth of the well. Thus over the processing window (which may be up to 10 m) as required by the tool software to estimate formation features, the distance between any two points in the processing window is accurately determined. No claim of depth accuracy relative to the surface of the earth is made.