Subsurface Geologic Investigation of Fountain Hills - AZGS ...

changes. Short-normal and long-normal logs are used to determine the resistivity close
to the borehole and away from the borehole, respectively, and presumably beyond the
influence of the drilling fluid. The spontaneous potential curve (SP) measures the
naturally occurring borehole potential, or voltage, that arises due to differences between
the borehole fluid and the formation fluid. Because water is a good conductor of
electricity, where the water is high, the conductance is high; if the water content is low,
the conductance is low. The resistivity and spontaneous potential curves are usually read
together and are compared. The geophysical logs for the four ASR wells and five
monitor wells are found in Figures A-2 through A-II.
CROSS SECTIONS
Three geologic cross-sections shown in figure A-I were constructed based on the
lithologic logs derived from borehole drilling samples and geophysical logs collected
during the drilling process. Geologic cross-section A-A' (Figure A-I2) was constructed
from north to south, west of Fountain Lake. This cross-section includes, from north to
south, wells ASR-4, FHMW-2, ASR-I, and FHMW-S.
Cross-section B-B' (Figure A-l3) lies from north to south, east of Fountain Lake.
This cross section includes from north to south wells, ASR-2, FHMW-4, FHMW-I and
FHMW-3.
Cross-section C-C' (Figure A-I4) spans west to east and includes wells FHTW-3,
FHMW-2, ASR-I, and FHMW-4.
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