Radiant energy – Geological testing or irradiation – Well testing apparatus and methods
Patent
1990-05-01
1991-09-24
Fields, Carolyn E.
Radiant energy
Geological testing or irradiation
Well testing apparatus and methods
250262, 250269, G01V 510
Patent
active
050515810
ABSTRACT:
The porosities of subsurface earth formations surrounding a borehole are investigated using a logging tool run in the wellbore by repeatedly irradiating the formations with discrete bursts of high energy neutrons, measuring the populations of epithermal neutrons at near and far locations from the neutron source, and also measuring the rate of decay of the epithermal neutron population at a third location following each neutron burst and deriving therefrom a measurement of the epithermal neutron slowing down time. Formation porosity values derived from the near-and-far location population measurements are corrected for detector standoff effects by use, in accordance with a predetermined empirical relationship, of the epithermal slow down time measurement. Alternatively, formation porosities may be derived both from the near-and-far location measurements and from the epithermal slowing down time measurement, and the two differently-derived porosity values may be used independently to provide enhanced information of formation porosity or they may be compared to derive a standoff-corrected porosity value.
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"Pulsed Neutron Porosity Logging", SPWLA 29th Annual Logging Symposium, Jun. 5-8, 1988, Mills et al.
"Pulsed Neutron Porosity Logging Based on Epithermal Neutron Die-Away", IAEA Research Coordination Mtg., Ottawa, Canada, Nov. 2-6, 1987, Mills et al.
Hertzog Russell C.
Loomis William A.
Wraight Peter
Berkley Richard G.
Fields Carolyn E.
Pojunas Leonard W.
Schlumberger Technology Corporation
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