The paper describes the first spin echo Magnetic Resonance Imaging Logging (MRIL*) system. The system makes measurements while logging and does not require special borehole treatment. The tool employs static and radio-frequency magnetic fields to perform downhole the spin-echo magnetic resonance measurements with short "dead time" that previously have been possible only in the laboratory.

Logs of lithology independent porosity, irreducible water saturation and fluid diffusion coefficient are provided from real-time analysis of the spin-spin relaxation time (To) decay of the fluids contained within the pore space of the formation. Spin-lattice relaxation time (T1) behavior is directly measured by the MRIL system.

Engineering prototypes have undergone several field tests, including two tests at the Conoco Borehole Test Facility well in Newkirk, Oklahoma. Field data, including the demonstration of accuracy and repeatability are discussed. The magnetic resonance logs correlate well with measurements of porosity and irreducible water saturation made on core samples and with porosity data from standard density and neutron logging tools.

Such data, from magnetic resonance logs, can be applied to the determination of porosity and irreducible water saturation, and thus to the estimation of permeability.

Keywords:
relaxation time, porosity, permeability, frequency, amplitude, magnetization, magnetic field, diffusion coefficient, well logging, borehole fluid
Subjects:
Formation Evaluation & Management, Open hole/cased hole log analysis
Copyright 1990, Society of Petroleum Engineers
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