Logging tool motion error reduction for nuclear magnetic resonance logging via pulse sub-sequences

A system comprising:

• a downhole tool to be conveyed in a wellbore formed in a subsurface formation, wherein the downhole tool comprises,
• a transmitter to emit into the subsurface formation at least a first pulse sub-sequence and second pulse sub-sequence;
• and
• a nuclear magnetic resonance (NMR) sensor to detect at least a first transversal NMR relaxation dataset and at least a second transversal NMR relaxation dataset generated in response to emission of at least the first and second pulse sub-sequences;
• a processor;
• and
• a machine-readable medium having program code executable by the processor to cause the processor to,
• determine at least one of a mean value of motion noise in a simulated signal and a standard deviation of the motion noise in the simulated signal;
• generate at least the first pulse sub-sequence comprising a number of refocusing pulses at a first flip angle;
• generate at least the second pulse sub-sequence comprising a number of refocusing pulses at a second flip angle that is lower than the first flip angle, wherein the second flip angle is selected based on at least one of the mean value and standard deviation of the motion noise of the simulated signal to reduce a lateral motion effect on acquired transversal NMR relaxation data;
• detect, by the NMR sensor, NMR spin-echo signals generated in response to at least the first pulse sub-sequence to acquire the first transversal NMR relaxation dataset;
• detect, by the NMR sensor, NMR spin-echo signals generated in response to at least the second pulse sub-sequence to acquire the second transversal NMR relaxation dataset;
• and
• determine a property of the subsurface formation based on at least the first and second transversal NMR relaxation datasets.

One or more non-transitory machine-readable media comprising program code executable by a processor to cause the processor to:

• determine at least one of a mean value of motion noise in a simulated signal and a standard deviation of the motion noise in the simulated signal;
• generate at least a first pulse sub-sequence comprising a number of refocusing pulses at a first flip angle;
• generate at least a second pulse sub-sequence comprising a number of refocusing pulses at a second flip angle that is lower than the first flip angle, wherein the second flip angle is selected based on at least one of the mean value and standard deviation of the motion noise of the simulated signal to reduce a lateral motion effect on acquired transversal NMR relaxation data;
• detect, by a nuclear magnetic resonance (NMR) sensor of a logging tool positioned in a wellbore formed in a subsurface formation, NMR spin-echo signals generated in response to at least the first pulse sub-sequence to acquire a first dataset of transversal NMR relaxation data;
• detect, by the NMR sensor, NMR spin-echo signals generated in response to at least the second pulse sub-sequence to acquire a second dataset of transversal NMR relaxation data;
• and
• determine a property of the subsurface formation based on at least the first and second datasets of transversal NMR relaxation data.