Method and apparatus for determining oriented density measurements including stand-off corrections

A method of logging of an earth formation comprising:

• (a) using a drill collar for conveying a logging tool into a borehole in the earth formation;
• (b) using nuclear sensors on the logging tool for making a plurality of long spaced (LS) and short spaced (SS) measurements of a parameter of interest of the earth formation, said measurements being made during continuing rotation of the drill collar;
• (c) using an acoustic caliper on the logging tool for determining a standoff corresponding to each of said LS and SS measurements;
• (d) partitioning the LS and SS measurements into a plurality of spatial bins, each said spatial bin corresponding to one of a plurality of azimuthal sectors and one of a plurality of standoff bins;
• and
• (e) using a downhole processor for partitioning said LS and SS measurements into said spatial bins and determining therefrom an azimuthal bulk density corresponding to each of said plurality of sectors, said azimuthal bulk density corrected for standoff errors using a correction determined at least in part by said standoffs.

An apparatus for logging while drilling of a borehole in an earth formation comprising:

• (a) a drill collar carrying a drill bit for drilling the borehole;
• (b) at least two nuclear sensors carried by the drill collar for making measurements of a parameter of interest of the earth formation;
• (c) a caliper on the drill collar for measuring a standoff of the at least two sensors relative to a wall of the borehole;
• (d) a processor for using measurements made by the at least two nuclear sensors and determining therefrom an azimuthal variation of the parameter of interest corrected for standoff of the sensors by applying, a correction based at least in part on said standoff.

A method of logging of an earth formation comprising:

• (a) conveying a logging tool into a borehole in the earth formation and rotating the tool therein;
• (b) making a plurality of long spaced (LS) and short spaced (SS) measurements of a parameter of interest of the earth formation using nuclear sensors on the logging tool over a time interval during continuing rotation of the tool;
• (c) measuring a standoff associated with each of said LS and SS measurements;
• (d) determining an azimuth associated with each of said LS and SS measurements;
• (e) defining a plurality of azimuthal sectors around said logging tool;
• and
• (f) determining from said plurality of LS and SS measurements and their associated standoff and azimuth, an azimuthal bulk density corresponding to each of said plurality of sectors, said azimuthal bulk density corrected for standoff using a correction determined at least in part by said standoff.