Common Log Types and Uses

Log Type	Fluid	Casing	Parameters Measured
Natural Gamma	Not Required	Any Type or Uncased	Stratigraphic correlation Permeability
Electric (Spontaneous Potential and Single Point Resistance)	Required	Uncased	Locating top and bottom of formation Relative water quality Differentiating clean from dirty sand Character and thickness of various strata Apparent resistivity
Short Normal Long Normal Resistivity	Required	Uncased	True resistivities of the aquifer
Fluid Resistivity	Required	Uncased	Apparent resistivity minus fluid resistivity yields formation resistivity
Neutron	Not Required	Any Type or Uncased	Indicator of total porosity Amount of moisture in unsaturated zones
Gamma-Gamma	Not Required	Any Type or Uncased	Bulk density (density log) Porosity
Sonic	Required	Any Type or Uncased	Presence or absence of cement bonded to the casing Relative porosities Determining fracture patterns Detect perched water tables
Acoustic Televiewer	Required	Any Type or Uncased	Orientation and distribution of fractures Borehole and casing inspections Orientation and width of borehole features
Caliper	Not Required	Any Type or Uncased	Hole Diameter
Temperature	Required	Any Type or Uncased	Locate small or sinuous aquifers Estimate the contribution of separate zones Location of cement grout
Flow Meter	Required	Any Type or Uncased	Determination of production rate from any zone Lost circulation zones Holes in the casing
RVC Video (Radial View Color Video)	Not Required	Any Type or Uncased	Verification of as-built condition of new wells Holes in the casing Sand producing zones Location of lost hardware
Spectral Gamma	Not Required	Any Type or Uncased	Investigate the mineralogy of thin-bedded sedimentary sequences Identify radionuclides that may pose an environmental threat Uranium exploration

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