BOREHOLE GEOPHYSICAL LOGGING IN UNCONSOLIDATED SEDIMENTS -AN AID TO 3-D 3 D MAPPING. J.A. Hunter Geological Survey of Canada

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1 BOREHOLE GEOPHYSICAL LOGGING IN UNCONSOLIDATED SEDIMENTS -AN AID TO 3-D 3 D MAPPING J.A. Hunter Geological Survey of Canada

2 QUALITATIVE PARAMETERS - grain size - sediment type - porosity - density - pore-water salinity - elastic moduli - heavy mineral content

3 BOREHOLE : OGS3-1 Natural Gamma (cps) Inductive Conductivity (ms/m) 3 4 Magnetic Susceptibility (ppt SI) Neutron Gamma-gamma Spectral (cps) (cps) Density Temperature <---porosity density increasing Ratio (deg. C) P-Wave Velocity (m/sec) increasing > T1a Driller's Log Till-sandy,silt T1b T1c T1 water level in casing CLAY Depth (m) 3 T2a T2b T3 P S Till-sandy,silt T2 Till-sandy,clayey T3 GRAVEL -pebble -cobble 3 T G Till,silty sandy 4 T4 SILT T4 4 Till,silty,sandy DOLOSTONE 5 Near Far 5 % SMOOTHING Grad.(C deg./km) S-Wave Velocity (m/s) DOLOSTONE 5

4 Groundwater Investigations Fredericton, New Brunswick An aid to understanding the detailed stratigraphy of the confined aquifer system

5 CONDUCTIVITY (ms/m) base of coarsegrained interbeds DEPTH (m) 3 MS Cond MS Cond 3 MS Cond MS Cond? MAGNETIC SUSCEPTIBILITY (X -3 SI) BH: A BH: B BH: C BH: D <<-- ~4 km --> <-- ~5km --> <-- ~15km --> Correlation of geophysical marker horizons in Leda Clay, Eastern Ontario / Western Quebec

6 Presence of Newmarket Till in N-S N S borehole transect across ORM (as indicated by high P-wave P velocities) South Velocity (km/s) Top of Newmarket Till Oak Ridges Moraine North Elevation (masl) 3 25 Bottom of Newmarket Till Velocities between 25 and 35 m/s 15 P1-BH27 OGS OGS OGS GSC-94-MC1 OGS-93-14

7 1.9 POROSITY vs Vs POROSITY = *ln(Vs) # of Observations: 1148 R-coefficient:.82 2 sigma = +/ FRACTIONAL POROSITY Holocene Pleistocene SHEAR WAVE VELOCITY (m/s) -note separation of data based on geological age

8 SHEAR WAVE VELOCITY V S (m/s) 5 15 SHEAR WAVE VELOCITY (m/s) 5 15 SHEAR WAVE VELOCITY (m/s) 5 15 V S Ø V S Ø V S Ø 3 DEPTH (m) 4 5 DEPTH (m) 3 DEPTH (m) OGS FRACTIONAL "TOTAL" POROSITY Ø OGS FRACTIONAL "TOTAL" POROSITY 6 OGS FRACTIONAL "TOTAL" POROSITY DOWNHOLE SHEAR WAVE VELOCITY and TOTAL POROSITY WATERLOO MORAINE

9 Neutron (cps) Neutron (cps) 4 3 DEPTH (m) 3 DEPTH (m) OGS FRACTIONAL "TOTAL" POROSITY 5 OGS FRACTIONAL "TOTAL" POROSITY OGS BHs,, Waterloo Moraine

10 GAMMA-GAMMA (cps) 4 3 OGS - 1 OGS - 2 OGS - 3 OGS - 4 OGS - 5 OGS - 6 OGS - 7 OGS - 8 OGS NEUTRON (cps) Waterloo Moraine BH s 1 to 9

11 NEW SONDES (what s coming down the pipe at the GSC?) The Borehole Logging Methods Group under the leadership of Jonathan Mwenifumbo are researching the following: -spectral gamma signatures of unconsolidated overburden from passive monitoring of radio-isotopes isotopes of U, Th,, and K -capacitive-coupled coupled resistivity equipment and techniques

12 Spectral Gamma Signatures (high sensitivity 512 channel B.H. spectrometer) Gamma (cps) Count rate (cps) A Spectrum OGS-3-1 (-14m) K window U window Th window Depth (m) 3 A B Count rate (cps) B Spectrum OGS-3-1 (26-29m) C Count rate (cps) C Spectrum OGS-3-1 (34-41m) Energy (kev) 3

13 Differing U/Th ratios between Zones A and B suggest possible differing provenances

14 Capacitive-coupled coupled Resistivity Sonde designed by V. M. Timofeev,, U.S.S.R. (Canadianized by Q. Bristow, GSC) 55 mm 14 mm Capacitive Resistivity Probe Receiver Transmitter l MN = 4 mm l AB = 263 mm Spacer 175 mm 33 mm 55 mm switch battery 28 mm mm 1 mm 74 mm 8 mm 1 mm mm 123 mm T-R Spacing 414 mm 599 mm 744 mm 919 mm 4 mm 2 mm T-R Spacing 414 mm + Spacer Electrodes N, M, B, A are thin-walled hollow cylinders ~ 4 mm in dia.

15 Why capacitive-coupled? coupled? -operates in plastic casing no fluid contact needed - enhanced vertical resolution at higher resistivities Gamma (cps) Resistivity ( Ω-m) Depth (m) 3

16 ANCHORING THE 3-D 3 D FRAMEWORK WITH GOLDEN SPIKES Strategically placed, well documented boreholes in unconsolidated sediments which have been: - continuously cored and have detailed geological descriptions - cased with plastic casing and grouted c/w vandal-proof surface completions - geophysically logged with most standard slim-hole tools - sampled for geological, geotechnical and geophysical properties THESE BECOME INVESTMENTS IN THE FUTURE NATIONAL TREASURES

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21 Borehole Geophysical Logs in Surficial Sediments of Canada -a a (downloadable) PDF format collection of geophysical log suites with geological descriptions, from boreholes across Canada drilled and a cased in (mainly) Holocene and Pleistocene strata. Digital data available from: jhunter@nrcan.gc.ca