Geological Application of Nuclear Techniques

Ahmed Badruzzaman
Chevron Texaco Exploration & Production Technology Company
Tuesday, February 25, 2003

Abstract:

Nuclear techniques form a key part of a suite of down-hole measurements used to interrogate the geological media. The techniques allow characterization, assessment, and monitoring of geological reservoirs, monitoring of wells and stored radioisotopes, identification of elements, and measurement of fluid movements and flow characteristics. Thus, the technology offers unique advantages in its ability to determine key geological, petrophysical, and borehole parameters that are unattainable by other techniques, and often with a single device. It is being contemplated for use in other planets. Depending on the application, nuclear techniques either utilize the radiation emanating naturally from the media or from dedicated sources of neutrons or photons in a device. In the latter, one measures the scattered radiation or the radiation induced by interaction of neutrons with the media. All nuclear logging devices contain pressure housing, detectors, shielding, electronics, etc.
Originally, nuclear logging devices were designed in the laboratory, tested first in well-characterized in test formations, and then in field formations. The process is iterative and time consuming, often requiring years from design to acceptance for commercial applications. Recently, computational methods, based on either Monte Carlo simulation of the radiation transport and associated nuclear interactions, or based on numerical solution of the Boltzmann transport equation, have been used with considerable success in modeling the response of these devices in order to optimize design concepts and develop calibration more quickly, and test them in complex field-like conditions that are often difficult to duplicate in the laboratory.
In the presentation, we review basics of subsurface nuclear measurements, discuss recent developments in the technology, including the author's own research, and identify challenges that require further advances in the technology.