Field Investigations

  1. API Units
    A unit of measurement of gamma rays. API stands for American Petroleum Institute
  2. ASTM
    American Society for Testing and Materials International. ASTM develops numerous standards by consensus and published them annually.
  3. Auger
    A screwlike boring tool used in relatively unconsolidated near-surface materials.
  4. Borehole Geophysics
    The science of recording and analyzing measurements of physical properties made in wells or test holes.
  5. Caliper Log
    A well log that shows the variations with depth in the diameter of an uncased borehole.
  6. Casing
    A heavy metal pipe lowered into a borehole and cemented in place to prevent cave-in, loss of drilling fluid, and unwanted fluids from entering the borehole.
  7. Cone of Depression
    A depression in the potentiometric surface of groundwater that has the shape of an inverted cone and develops around a well from which water is being withdrawn. It defines the area of influence of a well.
  8. Cone Penetrometer
    A tool consisting of a cone-shaped tip on the end of a hollow steel rod that is pushed into the ground to record resistance to insertion.
  9. CPT
    Cone Penetration Test. The test measures the resistance of the cone to penetration and the friction of the rod. The test is used widely in the engineering and environmental industries.
  10. Drawdown
    The amount the water level in a well is lowered due to withdrawal of water.
  11. Dutch Cone
    A specific type of Cone Penetrometer
  12. Gamma Ray Log
    The radioactivity log curve of the intensity of natural gamma radiation emitted from the rocks in a borehole. It is commonly used to differentiate between shale (with a high gamma reading) and other sedimentary rocks.
  13. GPS
    Global Positioning System. A radio sensor that records the exact position on earth.
  14. Gravity Survey
    A series of measurements made by a gravimeter at a number of different locations in the field to determine the density distribution by evaluating the gravitational pull.
  15. Ground-Penetrating Radar
    The application of radar or radio waves to the subsurface using a radar impulse as the source and a receiver. Ground penetrating radar can see as deep as 100 feet. Low frequency antennas examine the subsurface at great depths while the higher frequencies are used near the surface
  16. InSAR
    Interferometric Synthetic Aperture Radar. A remote sensing method that is used to study ground deformation, particularly in subsidence, volcanic and fault studies.
  17. Invaded Zone
    A transitional zone in a borehole located between the flushed zone and the uninvaded zone. It refers to the degree to which the mud filtrate penetrates the formation fluids, resulting in a transition from the mud filtrate saturation to the formation water saturation.
  18. LiDAR
    Light Detection and Ranging. A remote sensing method using laser beams to record topographic changes.
  19. Lysimeter
    A device for collecting water from the pore spaces of soils to determine the soluble constituents removed by drainage. It is used to sample water chemistry in the vadose zone, measure deep percolation and evapotranspiration.
  20. Neutron Log
    A radioactivity log curve of the intensity of radiation produced when the rocks in a borehole are bombarded by neutrons. It indicates the presence (but not type) of fluid. It is often used in association with the gamma ray log to distinguish porous and non-porous formations.
  21. Normal Resistivity Log
    A log that makes measurements of the resistivity of formations using 4 electrodes set up in a standard 16- or 64-inch spacing.
  22. Packer Test
    An aquifer test in which two inflatable seals (or packers) are set in an open borehole to prevent movement of groundwater in the test section while the permeability of the isolated rock is determined.
  23. Percolation (perc) test
    An in-situ test that determines the suitability of a soil for a sewage disposal system (leachfield). This test is made by digging a hole, filling it with water, and measuring the rate of decline of the water table.
  24. Piezometer
    A device that measures in-situ pore water pressures, often an open standpipe to measure water levels in permeable materials, or an enclosed electronic pressure transducer used in impermeable soils.
  25. Pumping Test
    A test made by pumping a well for a period of time and observing the change in hydraulic head in the aquifer.
  26. Resistivity Log
    A log that makes quantitative measurements of the specific resistance of a material to the flow of and electric current.
  27. Rippability
    The ease with which soil or rock can be excavated mechanically.
  28. Rotary Drilling
    The chief method of drilling deep wells. A drill bit grinds a hole in the rock, and lubrication and cooling are provided by continuously circulating drilling mud which brings the well cuttings to the surface.
  29. Rock Quality Designation (RQD)
    A measure of the intactness of rock core, relating to the percentage of intact core to the total core run.
  30. Seismic Reflection
    A survey method that utilizes the travel times of seismic waves that are reflected back from deep formations giving a detailed picture of subsurface structures.
  31. Seismic Refraction
    A survey method based on the travel times of seismic waves that pass through materials of differing densities, in order to map the layers.
  32. Shelby Tube
    A thin-walled, push-tube sampler that obtains undistrubed samples of cohesive soils.
  33. Single-point resistivity log
    A log that measures the resistivity using 2 electrodes and having a limited area of investigation of from 5 to 10 times the electrode diameter.
  34. Slug Test
    An aquifer test made by either pouring a small charge of water into a well or by removing a slug of water from the well. The removal of water from a well is also called a bail-down test.
  35. Split-spoon sampler.
    A thick-walled barrel sampler that obtains disturbed soil samples and that is used in the Standard Penetration Test
  36. Spontaneous Potential (SP) Log
    A log of the difference in DC voltage between an electrode in a well and an electrode at the surface. The difference in voltage is mostly a result of the electrochemical potentials that develop between dissimilar borehole and formation fluids.
  37. Standard Penetration Test (SPT)
    A standardized soil sampling procedure in which a 140 pound hammer is dropped 30 inches, driving a two-inch split spoon sampler 18 inches. The blow count to drive the sampler through the last 12 inches is correlated with the soil conditions.
  38. Tensiometer
    A device used to measure soil matric potential (soil water suction, or the ability to draw water into pore spaces. Used to determine irrigation needs and water consumption by plants.
  39. Test Pits
    A pit easily dug with a backhoe to obtain bulk samples and to identify subsurface materials in-situ.
  40. Well Efficiency
    The ratio in percent of theoretical drawdown to actual drawdown measured in a well.
  41. Well Log
    A graphic record of the measured physical characteristics of the subsurface encountered in a well plotted as a function of depth.
Card Set
Field Investigations
Geo field investigation terms