Stand-off compensation for nuclear MWD measurement

A system for stand-off compensation of nuclear measurement data received by at least one detector in an MWD system operating in a bore-hole comprising:

• a) a nuclear source capable of emitting radiation to be received by the at least one detector;
• b) means for receiving data from the at least one detector and determining a peak value for the data designating a count;
• c) means for converting the data to a digital address identifying a channel corresponding to the determined peak value,
• d) a stand-off transducer located between said nuclear source and the at least one detector, for determining distance of the at least one detector from the bore-hole wall, the transducer providing a digital bin address corresponding to one of a plurality of stand-off distances represented by bins corresponding to the bin address;
• e) a memory addressed by a combination of the channel address and bin address, said memory incremented for each data count;
• and
• f) calculation means connected to the memory to retrieve the count values corresponding to each channel and bin for comparison to predetermined parameter data calibrated at stand-off distances representative of the bins.

A method for stand-off compensation of nuclear measurement data resulting from radiation generated by a nuclear source comprising:

• a) receiving nuclear response data in a detector;
• b) determining a peak value of the data;
• c) converting the peak value to a channel address;
• d) determining the stand-off distance of the detector from the bore-hole wall with a transducer located between the nuclear source and the detector;
• e) creating a bin address based on the stand-off distance;
• f) addressing a memory by combining the channel address and bin address to form a memory address;
• and
• g) incrementing the memory for each nuclear response detected at the bin and channel identified by the memory address.

A system for stand-off compensation of nuclear measurement data resulting from radiation generated by a nuclear source and received by a plurality of detectors in an MWD system operating in a bore-hole comprising:

• a) means for receiving data from each detector;
• b) means for determining the detector receiving a count;
• c) means for establishing a detector address responsive to the determined detector;
• d) means for determining a spectrum channel responsive to the detected count;
• e) means for establishing a channel address responsive to the determined channel;
• f) means for determining a stand-off distance of the detectors from the bore-hole wall, said means located between the nuclear source and the plurality of detectors;
• g) means for establishing a bin address corresponding to the stand-off distance;
• h) a memory addressed by the detector address, bin address, and channel address in combination creating a memory address;
• i) a memory location corresponding to the memory address incremented when addressed;
• and
• j) calculation means for comparing the data at each memory address with predetermined parameter data for the detector receiving the count calibrated at stand-off distances corresponding to stand-off distances identified by the bin address.