NUCLEAR MAGNETIC LOGGING METHOD AND NUCLEAR MAGNETIC LOGGING DEVICE Russian patent published in 2009 - IPC G01V3/32 

FIELD: physics; measurement.

SUBSTANCE: invention can be used for investigating properties of rocks in oil and gas wells using nuclear magnetic resonance method. Formation fluid in a well is polarised, thereby creating a magnetic field. A calibration signal is stimulated from the calibration substance. At the end of polarisation the calibration signal is measured using a surface measuring device. That signal is then compared with a free precession signal of a standard sample and sensitivity of the logging device is then determined. Magnetic field is repeatedly created and the formation fluid and calibration substance inside the logging device are polarised. At the end of polarisation before measuring the free precession signal from the layer using the surface measuring device, a non-uniform constant magnetic field is applied to the calibration substance. Excluding effect of the calibration signal on the measured signal from the layer and taking into account the value of sensitivity of the logging device, the free fluid index value is obtained, from which effective porosity of the layers is determined.

EFFECT: more accurate determination of free fluid index of layers in a well.

8 cl, 4 dwg