DIRECTIONAL SURVEY . DRILLING PRODUCTS
CORE & BOREHOLE LOGGING . GEOSCIENCE . GEOTECH
HYDRO . PETROPHYSICS . PREDICTIVE ASSAY
GLOSSARY
Accuracy
Refers to the closeness of a measurement to the true value.
Acoustic impedance
The product of density and seismic velocity which indicates the ability of a boundary to reflect seismic energy.
Acoustic wave
A sound wave that is transmitted through material by elastic deformation.
Activation log
A record of radiation from radionuclides that are produced in the vicinity of a well by irradiation with neutrons; the short half-life radioisotopes usually are identified by energy of their gamma radiation or decay time.
Amplitude
The maximum height of a wave from its average value.
Atomic number
The number of protons in a nucleus.
Atomic weight
The combined weight of protons, neutrons and electrons in atoms.
Azimuth
An angular measurement that uniquely determines the orientation of a feature on the surface of Earth.
BMR
Borehole Magnetic Resonance ? a geophysical method that is used to analyse hydrogeological properties in ground rocks. It involves sending electromagnetic pulses into the ground through a borehole, which excites the hydrogen atoms, as they align with the induced magnetic field. Measuring the response and relaxation time of the hydrogen atoms as they return to their original orbit. BMR provides information on porosity and permeability in ground rocks.
Bulk density
The mass of material per volume, which indicates the density in grams per cubic centimetre of the rock with pore volume filled with fluid.
Calibration
A determination of the log values that correspond to the environmental units, such as porosity or bulk density; calibration isÿusually carried out it pits or by comparison with laboratory analyses of core.
Caliper Logging
A well logging tool which determines the diameter of a borehole along its depth.
Cased Hole Logging
Loging that occurs in a wellbore that has been cased with steel or cement to protect the open hole from fluids, pressures, wellbore stability problems, or a combination of these.
Chargeability
The normalised area under an induced polarisation (IP) decay curve, between two times, after the transmitted current is stopped in a time domain survey. Usually expressed in millivolt-seconds per volt.
Clay
A type of soil that is plastic in nature and has fine particle sizes, that are closely packed together. Clay has limited air spaces and adsorbent properties.
Compton scattering
The inelastic scattering of gamma photons by orbital electrons, Compton scattering is related to electron density and is a significant process in density logging.
Confined aquifer
An aquifer (water-bearing rock) that is overlain by an impermeable rock.
Contamination Plume
A body of contaminated groundwater flowing from a specific source.
Correlation
Locating stratigraphically equivalent rock units in different wells by matching geophysical logs.
Density log
Is well logging that provides a continuous record of a formation's bulk density along the length of a borehole.
Directional survey
A log that provides data on the azimuth and deviation of a borehole from the vertical.
ESG
ESG stands for environmental, social, and governance. It is a framework or a set of standards that evaluates how a company performs on sustainability issues.
Elastic Moduli
The unit of measurement of an object's or substance's resistance to being deformed elastically when a stress is applied to it.
Electrical field
The measurable sphere of influence in which electric forced are exerted, and which electric charge acts.
Environmental Impact Assessment
A study conducted in a region to examine the impact of various development projects on the natural environment in a region.
Fault
A zone of weakness in the Earth?s crust where failure results in cracks in rock formations.
Ferrimagnetic
Substances having a relatively large magnetic susceptibility.
Field
The space in which an effect such as gravity, magnetism or electricity is measurable.
Formation Evaluation
The process of interpreting data obtained from a wireline log for reserve estimation.
GPR
Ground penetrating radar ? is a geophysical method that uses pulses (radio and microwaves) to image the subsurface.
Gamma Ray Logging
A technique that measures natural gamma radiation emitted by rocks to characterise lithology.
Geophysical Interpretation
Analysing and visualising geophysical data to create subsurface models and make informed decisions about drilling.
Geothermal Gradient
The rate of change in temperature with respect to increasing depth in Earth's interior.
Hydraulic Conductivity
A measure to indicate how easily water can pass through rocks.
Induced Magnetisation
Magnetisation caused by an applied magnetic field.
Induced Polarisation
Induced polarisation is a geophysical imaging technique used to identify the electrical chargeability of subsurface materials, such as ore.
Interpolation
A method to determine intermediate values from the surrounding known values.ÿ
Lag
The distance a nuclear logging probe moves during one time constant.
Lithology
The general physical characteristics of rocks.
Magnetic susceptibility
A measure of how much a material will become magnetized in an applied magnetic field.
Mineral Assemblage
The variation in minerals occurring rocks.
Open Hole Logging
Logging that occurs in an uncased section of a borehole. All wells are initially open hole wells when they are initially drilled.
P-wave
A longitudinal seismic wave which is the first type of seismic wave to reach a receiver and is propagated in liquids and solids.
Permeability
The ability of rocks to allow water to move through them.
Porosity
The degree of available voids in rocks through which water can pass.
Precision
How close measurements are to each other.
Probe
Also called sonde or tool, a downhole well-logging instrument package.
Rose plot
Diagrams used to plot the orientation of joints and dykes.
S-wave
A transverse seismic elastic wave that is propagated through solids only.
Shear zone
A zone of localised weakness in the Earth?s crust that accommodates higher strain, resulting in differential movement in the Earth?s crust and mantle. Shear zones occur in regions where higher temperatures prevent faults and fractures from forming.
Sonic Logging
A type of acoustic log that displays travel time of P-waves versus depth. Sonic logging uses sonic tools to measure the speed of sound in rocks and fluids to determine rock properties.
Stratigraphy
The structure of layered rocks.
TDS
Total dissolved solids are a measure of the combined organic and inorganic contents in a liquid.
Target
The object at which a survey sighting is aimed.
Turbidity
A measure of how clear a water sample is.
Unconfined aquifer
An aquifer with its water table open to the atmosphere.
Vadose zone
Is the undersaturated portion of the subsurface that lies above the groundwater table.
WellCAD
Processing and interpretation software for borehole logs.ÿ
Wireline Cable
A steel cable used to lower and raise geophysical instruments and tools in a borehole.
Wireline Logging
A method of collecting geological data by lowering instruments down a borehole to measure various rock properties.
Wireline truck
A specialised vehicle equipped with winches for deploying and retrieving wireline logging tools.
Z/A effect
Ratio of the atomic number to atomic weight, which affects the relation between the response of gamma-gamma logs and bulkÿdensity logs.