Peer Reviewed Journal via three different mandatory reviewing processes, since 2006, and, from September 2020, a fourth mandatory peer-editing has been added.
Nuclear logging is one of most important logging services
provided by many oil service companies. The main parameters
of interest are formation porosity, bulk density, and natural
radiation. Other services are also provided from using complex
nuclear logging tools, such as formation lithology/mineralogy,
etc. Some parameters can be measured by using neutron
logging tools and some can only be measured by using a
gamma ray tool.
To understand the response of nuclear logging tools, the
neutron transport/diffusion theory and photon diffusion theory
are needed. Unfortunately, for most cases there are no analytical
answers if complex tool geometry is involved. For many years,
Monte Carlo numerical models have been used by nuclear
scientists in the well logging industry to address these
challenges. The models have been widely employed in the
optimization of nuclear logging tool design, and the
development of interpretation methods for nuclear logs. They
have also been used to predict the response of nuclear logging
systems for forward simulation problems. In this case, the
system parameters including geometry, materials and nuclear
sources, etc., are pre-defined and the transportation and
interactions of nuclear particles (such as neutrons, photons
and/or electrons) in the regions of interest are simulated
according to detailed nuclear physics theory and their nuclear
cross-section data (probability of interacting). Then the
deposited energies of particles entering the detectors are
recorded and tallied and the tool responses to such a scenario
are generated. A general-purpose code named Monte Carlo N–
Particle (MCNP) has been the industry-standard for some time.
In this paper, we briefly introduce the fundamental principles of
Monte Carlo numerical modeling and review the physics of
MCNP. Some of the latest developments of Monte Carlo
Models are also reviewed. A variety of examples are presented
to illustrate the uses of Monte Carlo numerical models for the
development of major nuclear logging tools, including
compensated neutron porosity, compensated density, natural
gamma ray and a nuclear geo-mechanical tool.
