New techniques and improved instrumentation have resulted in increasing uses for nuclear logs. The oxygen activation log employing an accelerator-type nuclear source is the most important new development. This log is made by quantitatively measuring the amount of artificial radioactivity produced by fast nuclear bombardment of formation oxygen. Since differences in oxygen content of common rocks are largely due to differences in porosity, the log is a sensitive indicator of oil saturated pore volume. Water filled porosity tends to respond like more dense rock due to the oxygen content of the water.,
Les techniques nouvelles et l'amélioration des instruments de mesure ont eu pour résultat d'augmenter l'emploi des sondes nucléaires. La sonde à activation d'oxygène, employant une source nucléaire du type accélérateur, est le plus important parmi les nouveaux développements. Cette sonde est basée sur une mesure quantitative de la radioactivité artificielle produite par un bombardement de noyaux rapides sur l'oxygène de la formation. Puisque les différences en quantité d'oxygène dans les roches ordinaires sont causées, dans une large mesure, par les différences en porosité, cette sonde est un indicateur très sensible pour déterminer les pores saturés d'huile. Une roche poreuse remplie d'eau a tendance à répondre de la même façon qu'une roche plus compacte à cause de l'oxygène contenu dans l'eau.
New techniques and instrumentation have been developed for nuclear logging since the last World Petroleum Congress. It is the purpose of this paper to briefly review these and to discuss in some detail the newest and most promising development-the accelerator neutron source and its application to oxygen activation logging.
When nuclear logging was first commercially offered about 20 years ago it represented the greatest advance in the industrial application of nuclear instrumentation up to that time. The speed with which precise measurements of the natural radioactivity of rocks could be made was far superior to the capabilities of equipment in most university laboratories. And making the measurement at the end of a cable two or three miles long, at the temperatures and pressures common in oil wells, was truly a triumph of instrumentation.
Since that date the well logging art has kept pace with the advance of nuclear science and engineering. Today, after some quarter million nuclear logs have been run commercially, no one stands in awe of the task of running increasingly more complex nuclear apparatus in the deepest and hottest boreholes. The accuracy and reproducibility of measurements have steadily increased, and there has been a growing demand for logs which can be interpreted even more precisely in terms of poros
