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
Tomography
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.
J
R Associates,
Ph: (408) 293-7390 EMail: jra@GreatGeophysics.com