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.
Amplitude Image
Image created using the measured amplitude of the reflected acoustic pulse propagated by an acoustic televiewer.
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.
Borehole Breakout
Vertically or near vertically elongated features / cavities in the borehole wall created by the interaction of horizontal stresses on the open hole. Used to determine maximum horizontal stress orientations in the rock mass.
Bulk Modulus
A measure of the ability of a substance to withstand changes in volume when under compression on all sides.
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.
CPS
Counts Per Second. Raw log data is acquired in CPS prior to conversion to calibrated units by the application of calibration equations.
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.
Cavity
An opening in the borehole wall that extends beyond the nominal borehole diameter.
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.
Core Analysis
Analyzing physical rock samples in the laboratory to determine key properties.
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.
Dip
Similar to Tilt, dip is the angular measurement with reference to the horizontal.
Dip Azimuth
The horizontal direction corresponding to the down dip (borehole or plane) vector orientation with reference to magnetic north, true north or borehole high-side.
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
Interval Data
Data consisting of a discrete value applied to a set depth interval down the hole, defined within “from” and “to” depths.
LAS File
Log Ascii Standard. A form of ascii file particular to the logging industry. Can be opened in any text file editor.
Lag
The distance a nuclear logging probe moves during one time constant.
Lithology
The general physical characteristics of rocks.
Log Depth
The distance from the borehole collar along the path of the borehole, increasing from zero at the collar to the end of hole.
Log Mneumonic
An abbreviated log title with no spaces in the name. Used to facilitate data import into databases with the need for data preconditioning.
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.
Point Data
A data format consisting of a discrete data value for a given depth down the hole. Also called profile data.
Poisson's Ratio
The ratio of transverse contraction (or expansion) strain to longitudinal extension strain in the direction of stretching force. Tensile deformation is considered positive and compressive deformation is considered negative.
Polar Plot
A stereo net projection of planar features intersecting the borehole where the poles to the plane are plotted instead of great circles.
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.
RQD
Rock Quality Designation is a rough measure of the degree of jointing or fracturing in a rock mass, measured as a percentage of the drill core in lengths of 10 cm or more.
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 Modulus
A measure of the ability of a material to resist transverse deformations and is also known as the rigidity.
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.
Tilt
Measurement of the borehole deviation away from vertical with zero degrees being vertical.
Travel Time Image
Image created using the measured two-way travel time of the reflected acoustic pulse propagated by an acoustic televiewer.
True Vertical Depth
Depth below surface measured vertically and not along the borehole path with increasing value going downwards.
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.
Washout
A general widening of the borehole beyond the nominal drilled size caused by mechanical and fluid effects from the drilling process.
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.
Young's Modulus
is a property of the material that tells us how easily it can stretch and deform and is defined as the ratio of tensile stress (σ) to tensile strain (ε).
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.