Use of axial accelerometer for estimation of instantaneous ROP downhole for LWD and wireline applications

A method of determining a parameter of interest of a downhole drilling assembly conveyed in a borehole during drilling of the borehole by a drillbit on the drilling assembly, the method comprising:

• (a) making measurements with at least one accelerometer on the downhole assembly at a plurality of times, said measurements indicative of at least an axial component of motion of the downhole assembly with an accelerometer thereon;
• (b) determining at at least one of said plurality of times from said accelerometer measurements an average acceleration magnitude and an instantaneous frequency of said measurements;
• and
• (c) determining the parameter of interest from said average acceleration magnitude and said instantaneous frequency at the at least one of said plurality of times.

A method of determining a depth of a logging tool conveyed on a wireline in a borehole during the method comprising:

• (a) making measurements with at least one accelerometer on the logging tool at a plurality of times, said measurements indicative of at least an axial component of motion of the logging tool;
• (b) determining from said accelerometer measurements an axial velocity of the logging tool at the plurality of times;
• (c) identifying a plurality of maxima or a plurality of minima of said axial velocity;
• and
• (d) determining a rate of penetration from said plurality of maxima or plurality of minima.