Office of Ground Water Borehole Geophysics Advisor and availability of a portable borehole geophysical logging system


In Reply Refer To:                             July 8, 1993
Mail Stop 411


OFFICE OF GROUND WATER TECHNICAL MEMORANDUM NO. 93.05

Subject:  Office of Ground Water Borehole Geophysics Advisor and
          availability of a portable borehole geophysical
          logging system

As part of Office of Ground Water (OGW) plans to support the
integrated application of geophysical techniques to hydrologic
investigations within the Water Resources Division (WRD), the
OGW has selected an individual to serve as the OGW Borehole
Geophysics Advisor, and secondly, acquired a portable borehole-
logging system.

The OGW has selected John Williams, New York District, to serve
in a part-time position, as the OGW Borehole Geophysics Advisor.
John has been serving as the Northeastern Region (NR) Borehole
Geophysics Advisor since 1991.  He is a member of the OGW and NR
Borehole Geophysics Advisory Groups (BGAG) and has taught at
both Division and Region workshops and courses as well as at
commercial courses.  He will remain in Albany, New York and
continue to serve the District as their ground-water
specialist.  John will work closely with personnel of the OGW
Branch of Geophysical Applications and Support in Hartford,
Connecticut and with the Borehole Geophysics Research Project in
Denver.  John also will be responsible for coordination of the
use, scheduling, and maintenance of the OGW borehole geophysics
equipment.

The portable geophysical-logging system is available to District
and other offices throughout the WRD for training, evaluation of
geophysical needs, and technology-transfer activities.  Loan of
the geophysical-logging system for a period of up to a month
will be scheduled in order of request with priority given to
first-time users. Training on the use of the logging equipment,
evaluation of logging needs, and the application of the
equipment to ground-water studies, will be provided or
coordinated by the OGW Borehole Geophysics Advisor.


DESCRIPTION OF EQUIPMENT

The geophysical logger is a downhole-digitized system
manufactured by Century Geophysical Corporation and includes a
field-rugged computer with inkjet printer, drawworks with 500
feet of cable, and multi-parameter probes.  The computer is an
80386 laptop and has menu-driven logging and analytical
software.  The software allows the user to collect, edit, store,
and display digital-log data with user-specified scales and
lithologic information.  The computer has a DC/AC inverter that
plugs into a cigarette lighter.  The logging drawworks is
lightweight and has a DC motor that operates on a 12-volt
battery.  The logging cable is Kevlar reinforced and has a
chemically resistant outer cover that is smooth for easy
decontamination.

The logging probes include short- and long-arm caliper;
electromagnetic-induction and natural gamma; single-point
resistance, self potential, and natural gamma; and fluid-
resistivity, temperature, and natural gamma.  The probes are
slimhole design, 5 to 7 feet long, and can be used in 2-inch or
greater diameter holes.  The logging system can be operated from
a van or carryall or, if necessary, hand carried to inaccessible
sites.  The computer and logging probes can be interfaced with
conventional 4-conductor loggers if additional depths are
required.


APPLICATIONS

The geophysical-logging system has potential applications to a
wide range of ground-water studies.  Gamma logs are useful for
determination of subsurface lithology and stratigraphic
correlation.  Gamma logs can be collected in open, steel-cased,
or PVC-cased holes that are air, water, or mud filled.  Single-
point resistance and self-potential logs provide lithologic
information in mud- or water-filled open holes. Electromagnetic-
induction logs, which can be collected in open or PVC-cased
holes that are air, water, or mud filled, are useful for
delineation of freshwater-saltwater interfaces and three-
dimensional mapping of electrically-conductive contaminant
plumes.  Caliper logs provide information on hole conditions and
well construction.  Caliper logs, in combination with single-
point resistance, fluid resistivity, and temperature logs, can
be used to delineate water-bearing fractures in open-hole
bedrock wells.  Additional applications of the geophysical logs
are presented in the Techniques in Water Resource Investigations
(TWRI), "Borehole Geophysics Applied to Ground-Water
Investigations" by Keys (1990, Book 2, Chapter E2).


LOGISTICAL ARRANGEMENTS

Requests for use of the geophysical-logging equipment and field
assistance for training will be made to the OGW Borehole
Geophysics Advisor.  Costs for transport of the geophysical-
logging equipment and for training will be borne by the user.
Shipment of the equipment must be by air freight.  The user will
be responsible for the repair and replacement of damaged or lost
equipment.  Due to the complexity of the equipment, repair may
involve shipment back to the manufacturer.  All repairs will be
coordinated through the OGW Borehole Geophysics Advisor.


SUMMARY

A coordinated borehole-geophysics program to help meet immediate
and long-term needs in geophysical applications and support is a
part of the OGW strategy to support ground-water programs
throughout the Division.  On the basis of periodic review of the
borehole-geophysics program during its evolution, needs for
adjustment may be required in order to maintain viable support
to the Division.  This periodic review and possible adjustment
can be implemented only with help from those in WRD who are
actively involved in or who supervise borehole-geophysical
activities.  Feedback from the "field" is critical and is
encouraged so that the OGW can fine tune and improve the
borehole-geophysics technical support to the Division.  Comments
and suggestions can be given to your BGAG representative (listed
in attachment 1) or sent directly to Ken Hollett or to me in the
OGW.



                             Chief, Office
                             of Ground Water

Attachment

WRD Distribution:  A, B, S, FO, PO