Method of and apparatus for determining cement strength and extent of setting with a pulsed nuclear magnetic resonance spectrometer

DETAILED DESCRIPTION OF THE INVENTION Briefly, the practice of the present invention involves a method of and apparatus for analyzing a cement sample to determine both the extent of setting of the cement and the strength of the cement as it sets, by utilizing a pulsed nuclear magnetic resonance spectrometer to conduct tests on the cement samples.
The curing or setting of cement can be related to the chemical reaction occurring between the free water in the cement slurry and the chemical constituents of the cement.
The consumption of water in this reaction, and hence the extent of curing or setting of the cement can be determined by making amplitude and thermal relaxation time measurements on the sample of cement with a pulsed nuclear magnetic resonance spectrometer.
It should be noted that the term "cement" as used in this application refers to the mixture of cementatious material formed by combining water with hydraulic cement, from the time water is first combined with the hydraulic cement and the mixture is in a transportable form through to the time the mixture cures or sets to a hard product.
Portland cements are the basic hydraulic cements now being used for oil well type cementing and are often mixed with such things as accelerators, retarders, dispersants, and loss circulation agents to meet specific well conditions.
The pulsed nuclear magnetic resonance spectrometer apparatus required to conduct such an analysis on a cement sample is shown in FIG.
1.
The sample of cement is placed in sample holder 14.
The sample holder 14 fits inside the center of a wire coil 16 which in turn is mounted between the poles of magnet 12.
The central axis of the wire coil 16 is oriented perpendicular to the permanent magnetic field of magnet 12.
The sample holder 14, the wire coil 16, and the magnet 12 comprise the anaylsis zone 10 of the pulsed nuclear magnetic resonance spectrometer.
The remaining part of the pulsed nuclear magnetic resonance spectrometer is the controller 18 comprising timing, oscillator, reciever amplification circuitry, and a microcomputer