Electricity: measuring and testing – Particle precession resonance – Using well logging device
Patent
1994-10-20
1996-03-05
O'Shea, Sandra L.
Electricity: measuring and testing
Particle precession resonance
Using well logging device
324300, G01V 308, G01V 314
Patent
active
054970873
ABSTRACT:
A lithology-independent method of well logging to estimate the pore size within a formation containing natural gas. The method makes use of a pulsed NMR logging tool utilizing a recovery time that is greater than the relaxation time of hydrocarbon gas within the formation. In a preferred embodiment, two different NMR logs are obtained: one with a recovery time significantly shorter than the longitudinal relaxation time, T1, of the gas and one with a recovery time equal to or longer than T1. The amplitudes of the two logs are subtracted to determine a restricted diffusion coefficient of the gas. The restricted diffusion coefficient can then be used to estimate pore size and permeability of the formation by means of a relationship between measured restricted diffusion coefficient, surface to volume ratio, and estimated bulk diffusion ratio of the gas.
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SPE Paper 22723, "The Magnetic Resonance Imaging Log Characterized by Comparison With Petrophysical Properties and Laboratory Core Data," Oct. 8, 1991.
Akkurt Ridvan
Tutunjian Pierre
Vinegar Harold J.
Christensen Del S.
Haynes Maele
O'Shea Sandra L.
Shell Oil Company
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