Geophysical Well Logger



        Borehole Geophysics

Geophysical Well Logging

Geophysical well logging provides valuable information about rock and soil properties adjacent to wells. Multiple logs measuring different material properties are used to define material types adjacent to the well. Information collected in many wells is used to extrapolate geology throughout a site. Often particular formations yield log curves with distinctive patterns making it possible to correlate specific lithologic units between wells. Geophysical well logging defines:

  • Geology
  • Interfaces between geologic units
  • Rock and soil types
  • General geologic structure                                Click here for E-logging details
  • Thin highly transmissive sand layers
  • Important clay barriers
  • Bentonite seals

Borehole Television

Borehole television verifies the integrity and construction of existing ground water supply and monitoring wells. The borehole camera provides sharp images of actual downhole conditions. Video tapes are made for permanent records. Borehole video visually inspects and locates:

  • Casing joints
  • Offset and cracked well casing
  • Screen interval and condition
  • Downhole geology
  • Fracturing

Borehole Seismics

Borehole seismic surveys measure geologic boundaries and rock velocities in the vicinity of boreholes. They are most commonly used to measure various types of rock moduli in situ. P and S-waves are transmitted from the source on the surface to receivers in an adjacent borehole (downhole) or from a source located in one borehole to receivers located in another (crosshole). Borehole seismic surveys provide information about:

  • Dynamic rock moduli
  • Vibratory loading response
  • Rock velocities and quality
  • Geologic layering


Seismic tomography is applied to situations where detailed pictures of the subsurface are needed. Tomography utilizes both borehole to surface and borehole to borehole shooting. Sophisticated computer programs invert the field data into a tomographic image showing a very accurate two dimensional diagram of the velocity structure in the surveyed areas. Tomography is employed to detect or map:

  • Discontinuous low velocity zones
  • Fracture zone orientation
  • Fault orientation and thickness
  • Dynamic rock moduli and quality
  • Grout curtains

At J R Associates we stand ready to apply our geophysical expertise to your particular requirements. Please contact us to discuss how our combination of techniques, knowledge, and experience can provide you with a window on what's underground.

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J R Associates, PO Box 459, Santa Clara, CA 95052-0459

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