This review contains the fundamentals of radiation logging, as known today. After a brief history of nuclear physics and radiation logging, the general theories of nuclear physics and their application to the interpretation of particular radiation logs are discussed. A general description of the instruments required for radiation logging is given. The types of logs being used and field tested today are indicated. For those interested in a more complete review of radiation logging, the references will provide further information.
In the 55 years since Villard of France discovered the effects of gamma rays on a photographic plate, this form of electromagnetic radiation has been put to many practical uses. A considerable fund of information has been accumulated regarding the nature of gamma rays and means for their measurement.
0nly 25 years have elapsed since Bothe and Becker first observed the effects of neutrons in the laboratory. Today the technology of neutron application is being brought to bear on problems of both peace and war.
This paper is concerned with the interactions of both gamma rays and neutrons with earth strata penetrated by boreholes. For purposes of convenience, this discussion will be restricted to these interactions as they apply to formations encountered in oil exploration and development. Under suitable conditions, the interpretation of the recorded effects of these reactions are useful for:
The location of porous zones which might contain petroleum.
The correlation between wells of similar lithologic structures.
The determination of gas-oil interfaces in known petroleum reservoirs.
The evaluation of the porosity of particular beds.
The determination, in conjunction with a collar locator, of the location of casing with respect to beds of interest.
The logging of wells which were drilled and cased without obtaining an electric log.
The evaluation, in conjunction with an induction log, of oil or gas content of beds drilled with oil base mud.