,i '

....

~.

.. . f

I

; ~f-.' ,j

'"':.

~COMMONWEALTH OF AUSTRALIA

DEPARTMENT OF NATIONAL DEVELOPMENT

BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS

. RECORD No. 1966/114

KOO-WEE-RUP RESISTIVITY SURVEY.

~

VICTORIA 1965

by

M . . WAINWRIGHT

.. , ~.,,;. I,

RESTRICTED This. Recor.d contains prelimin~"'y information' only and is subject to amendment before final issue. It is intended for the private use of title holders or authorities who can make immediate use of the data and is not to be made available to anyone othefthan the original recipients without the Director:s approval. The data after further review may be issued as an unrestricted Record.

...

•

CON T EN T S,

SUMMARY

1 j INTROnum'ION

2. GEOLOGY

3. --THEORY

. 4. METHODS AND EQUIPMENT

5. RESULTS

6. CONCLUSIONS

7. REFERENCES

APPENDICES 1 • Borehole data

_ 2.

3.

Water resistivity

Interpretations of depth probes I

Plate 1 •• Locality Map showing locations of resistivity depth probes, water sampling points; boreholes and water quality contours.

Plate 2 .0 Comparison of Wenner and Schlutnberger field curves,;

Plate 3 •• Resistivity depth probe curves K1 .. K4.

Plate 4 Resistivity depth probe curves K5 .. K,7i

Plate ,5 •• Interpretation histograms of ERR3, Geophysical megger, 'Yew i

megger and'Terrameter field curves; depth probe K3.

Piate 6, •• Calibration of Resistivity meters vs. Standard Resistanc'e •

Plate 7 Cross-sections K7 ... K6; and K7 ... K4.

Plate 8 •• Changes in field curves inland fl.'om intertidal zone.

Plate 9 ,;. Characteristics of rocks as a functioil of graiti size. (G369-1)

•

•

SUMMARY

A resistivity survey was undertaken at Kooweerup to compare the performances of resistivity meters under varying geological conditions. A new power supply was tested, but in the absence of a suitably sensitive potential meter, did not yield'reliable information. Curves obtained using the Wenner andSchlumberger ele.ctrode configurations provided fairly good correlation with -available ,borehole information. Calibration and field-tests of five resistivity meters~'have indicated their relative merits. Wat&­quality and porosity studies have been made of the widespread aquifers lying beneath clay formations at a depth of 100 feet or more ~ No signif'icant ~altwater intrusion has been found in the survey area •

'\

\

\

1. INTRODUCTION

, "\

A number of resistiVity meters are ~ommonly used by the Bureau of Mineral Resources 9 Gewlogy,'and Geophysics, Geophysical Branch. These meters have been used'on many geophysical surveys under a variety of field

• conditions. Experience has shown that there is usually a difference between field curves obtained by using different resistivity meters to;rI).ake depth probes at the same site. "The- survey was designed to establish a compartson between" , five of these instruments under varying c,onditions, and so to rel.,ate the performance of each to particular geological and hydrological conditions.

\ ,

The survey also provided an opportunity for testing a more powerful d.c. supply unit, and for comparing different electirode configurations. It

The survey was carried out over a small area in the vicinity of Koo-wee-rup, a small township roughly 44 miles south-east of M.elbourne, and about two miles inland from Western Port ,Bay (see Plate 1).

It was carried out in conjunction with the State Rivers and Water Supply Commission, between 7th and 28th September, 1965. The party consisted of M. Wainwright, party leader, and three field hands provided by the Commission. A. Radeski, technical officer, assisted the party for four. days. The State Rivers and Water Supply Commission provided assistance in many ways, and their help is gratefully acknowledged.

2. GEOLOGY . ...

The geology and hydrogeology is described by Jenkin (1962). The ,survey was conducted over an area of about 12 sq. miles in the vicinity of the township of Koo-wee-rup, which is situated,9n an alluvial plain bounded by upland areas to tlle north and east. The Bilnyip river flows into; ;Western Port Bay about two miles,"~outh~west of the township through a system of I

drainage channe).s. At the time of the survey, the standing water table was generally o~y a few feet from the surface, and drainage channels were active. A number of boreholes in the vicinity of Koo~wee-rup ae.monstrate that clay formations extend from the surface to a depth of 100 feet or more p (see Appendix 1). Beneath are deposits of sands, gravels and clays, which overlie a similar succession of Pliocene,to',Eocene sediments. The Oligoce)l,e and Eocene beds contain marls, thin coal bands, and basaltic lava and tu~fso Deep bores haye been drilled by the Department of Mines, Victoria, and §xtensive drilling o~" shallow boreholes for agricultural puxposes by private contractors has added valuable stra~igraphic inf~ation.

3. THEORY

" The basic potential theory underlying the p~inciple of resistivity work ':in layered media is well known and has been discussed in various publications and reports. (See Wiebenga, 1955; ~son and Wiebenga, 1957; Dobrin, 1960; Andrew and Wiebenga, 1965; Polak, Wiebenga, Andrew, Wainwri,ght and Kevi, in preparation). B:fiefly, current is introduced into'the'ground via metal electro-des. For a given applied current, the potential drop across two intermediate electrodes is a function of the resistivity of the ground formation. The greater the spacing of electrodes, the greater ~he depth penetration.of the applied current. By expanding the electrodes about a central point and plotting the measured apparent resistivity against electrode spacing L/2 on a log diagram, a curve is obtained. Since the method depends on the measurement of a potential field, the curve could represent an infinite number of layered models (Andrew and Wiebenga, 1965).

2

The most widely used electrode arrangement is the Wenner system (Fig. 1(a)) where the four electrodes are arranged in line with equal spacing.

". In the,Schlumberger arrangemerit v (Fig. 1{b))p the electrod.e spread is expanded about a fixed centre point, as in the We~er case. However p for a constant spacing of b 9 the spacing L is expanded until the measured potential drops to such low values that the- instrument readings are no longer acourate 0 The spacing b is therr expanded to a new value 9 and the potential readings made as

....

ii

L is expanded further. Thus p b . is kept sm~ll compared with L. Formerly, b was kept no greater than L/5. However, it has been found that b m~ be as great . as L/3 (i.e. the Wenner spacing) without affecting the interpretation significantly.

A problem arising out of resistivity work on Stradbroke Island (Polak & Kevi9 1965) and in the Burdekin delta, North Queensland, (Wiebenga et al, in preparation) is that when highly conductive near~surface l~ers are present, penetration of current into the ground is limited.. In-an attempt to increase the penetration a higher amperage power supply system was constructed by the Bureau. This consists of a petr9l-driven ~otor generator together with a rectifier unit9 which is capable of supplying currents of up to 6 amps, and voltages of 230V; - the potential difference was measured by a self;"potential (S.P.) meter. It was expected that in or near the intertidal zone of Western Port b~9 the presence of a near-surfaceaaltwater wedge might· resemble the conditions previously experienced in Stradbroke Island and in the Burdekin delta.

'. . ~ .

I~ a) L ., Wenner I , I I40-L/3-

01 Pi F,2 C

,~ L- i> I

Q1 P1'E-b~P2 Cf ':1» Schlumberger L .. --J

Fig. 1 Electrode configurations '\.

It has been .observed that"'the apparent r~sistivities computed from .data collecte,d. using an' ayc. resistivity meter were rower than those obtained

,u.sing a d.c. instrument. (This was investigpted further on a resistivity survey '.ii:t'the. Markham valley New Guinea in 1964. The report on this survey (Waimvright, in preparati.on) contains a discussion on the possible causes of the dc/ac discrepancies. One such pos&:ibility is the presence of clay particles adhering to sand grains, as is generally the case with most sand formations. When an alternating voltage is applied to a water~saturated med.ium- su.ch as this, a complex impedance is set-up, of which the real part is smaller than the pureiy resistive component measured when applying a direct current voltage. This is generally described as linduced polarisation' and the clay particle theory is called 'membrane polarisation V, by' Marshall and Madden (1959). One of the practical uses of .:induced polarisation would be to relate the magnitude of the effect to cl~ content, frequency of the applied a.c. voltage, and level of water=table in the aquifer body'o At KooweeruP9 sediments containing a high percentage of clay extend to a depth of 100 feet or more, and areas satu.rated with saline water are prese:nt near the intertidal zones, on the southern edge ·of the survey area. It (W&13 not expected that the induced polarisation effect would be marked (Vac'luier"Holmes, Kitzinger and Lavergne, 1957).

....

•

4. METHODS AND E <{,UIPMENT

The locatiorls of depth probe sites in the survey area are shown in Plate 1. Wenner and Schlumberger configurations were used~ the electrodes being expanded about a fixed centre point in each case.

At each site depth probes were repeated using alternative systems of electrodes? or repeated with the same electrode system but using different resistivity meters. Table 1 (below) gives a summary of work completed in the survey area.

DATE

9.9.1965 ,','

1 o. 9.1965

l:~

13.9.1965

,,:17.9.1965

20.9.1965

.;'4 ",

STATION

K.1

K.2 o .~_ ••• "

K.~

K.4

K.5

K. 6

K.7

Wh§lre IV :::

S ::

TABLE 1

TYPE OF ELECTRODE . -ARRAN GEMJ:i1NT

W

S

S

0-

S

W

w S

S ,-

S

S

S

Wenner spread.

Schlumberger spread.

INSTRUMENTS

E9 Yo

E9 G, T.

E9 G, Y, To

" E9 T.

E, G, Y, T.

E, G, Y, T. --"--". -e.

e.

E,G.

E, G.

E, G, . Y.

E :: ERR3.d.c. reSistivity meter designed by the Bureau. (formerly designated Rm.1)

e :: ERP d.c. resisti.vity ~system.

G Geophysical megger, a.c. meter.

Y = 'Yew' a.c. .resistivity meter.

T = ABEM Terrameter, a.c. resistivity meter.

4

Water samples-were obtained in the vicinity of each depth probe site from boreholes and surface sources; the resistivity of each sample was measured ~ a standard mud"';cell? using a Megger earth tester~ and water quality wa~ expressed in ohm=metres at 200 C9 and in total dissolved salt content (popomo) (Schlumberger, 1958).

.. . Resistivity equipment used on the survey is listed below;, the Megger Earth. tester (0~;1 000 ohm) was not suitable for depth probe measurements) since the reading accuracy of the instrument in the range of 0 to 10 ohm is very poor.

TABLE 2

INSTRUMENT MAKER FRE;QUENCY RANGE

ERR 3 B.11.R. doc o 0-10 K. ohm

Geophysical Megger Evershed and Vignoles 8-10 c.p.s. 0~30 ohm

Megger Earth Tester " 50 ... 60 c.p.s. 0~3000 ohm

Terrameter A.B.E.M. 4 c.p.s. 0-10 K. ohm

'Yew' Earth Resistance 'Tester Yokagawa 65 c.p.s. O~300 ohm

ERP.1/S.P. meter B.M.R. d.c. 0-1 Volt Potential difference

The ERP/$.Po Meter equipment consists of an rOnan' p~trol driven motor generator which supplies 115 volts to a Bureau constructed E.R.P.1. rectifier. _ F:Z:'om this up to 230 volts, and currents up to 6 amps, can be applied to the current elect~c·a:es •. The potential diifere-n'ce across the potential electrodes was measured-using·a. self~potential meter (Type D) constructed by the Bureau. The current was-reversed, and the mean potential together vuth the mean current? were used to compute the mean apparent resistivity by application of Ohm's Law, ?lld multiplication by a geometrical constant (See Plate 3, K.4). This is different from the method used in the other meters, which give a direct reading of resistance without determining the current or potential separately.

\ \

5

5. RESULTS

The results are discussed under the following four headings.

(i) Comparison of electrode arrangements.

(U) Comparison of instruments.

(iii) Correlation of interpretations with geological infor.mation.

(iv) Water quality and porosity of formations.

(i) Comparison of Electrode Arrangements

For comparison the curves obtained using the Bureau constructed EnB.3 d.c. resistivity meter at stations K1 and K3 are considered (See Plate 2) •. Clearly the curves are very similar; the measured resistance, which is a function of the potential difference between potential electrodes~ lis 'in the Wenner system greater than that for the Schlumberger for any given value of L/20 For example~ at depth probe K3 for L/2 = 300 feet, the Wenner measured resistance is 0.043 ohm, whilst for the same value of L/2 the Schlumberger measured resistance is·0.0115 ohm. The accuracy of the ERR3 (discussed Part (ii) of this section see also Plate 6) deteriorates below 0.01 ohm, so that for measured resistances below 0.01 ohm the results will be increasingly less accurate; this·will be of relatively greater importance in the Schlumberger electrode arrangement than in the Wenner for any given depth prob~.

However9th~ Schlumberger method can be carried out much more raplidly~ with less field labour, and there are theoretical grounds for suggesting

.that the system produces smoother curves. The basis·of this is that the potential electrodes in the Schlumberger system are kept stationary for an expanding range of current spacings; this means that contact potential is: constant over the s~e range. The two configurations on field evidence p~~duce very similar curves, with the Schlumberger system to be preferred on . t

practical grounds. The separate interpretations\of the Wenner and Schlumberger curves for depth probes K1 and K3 are as follows :~

K1

K3

Wenner Schlumberger

where 1st and 3rd numbers etc. refer to resistivity of IBJ'er (ohm~metres) and 2nd and 4th numbers ~tc. (in brackets) refer to depth of interface (ft.).

(ii) Compa~ison of Instruments

Five resistivity meters were compared in the i€ield, (two with direct current power supplies - d.c.; and three.with alternating current power supplies - a.c.), and the field. curves are shown in Plates 3 and 4. The three meters commonly used to make depth probes, namely ERR3, Geophysical Megger and Terrameter were calibrated against' standard resistances in the range 0.001 ohm to 1000 ohm. (See Plate 6). The t~ree instruments give results in close agreement in the range 0.5 ohm to 1000 ohm, but the Geophysical Megger is markedly less accurate than the other two instruments at 0.05 ohm and below. The mean error of each instrument at varying values of standard resistances is given. Note also that for each instrument there is a variation from the mean which in the cas~ of the Geophysical Megger amounts to + 2c:t/o of standard Resistance at 0.01 ohm.

: .. ~

6

Comparing the Terrameter and Geophysical Megger curves with the ERR3' curves (which from Plate'6 appears to be the most accurate)~ the field curves are similar, and lead to similar interpretations (e.g. K1, K2 and K4 Plate 3) 0 At K3,' the 'Geophysical Megger curve is similar to the ERR3 curve, but the Terrameter curve diverges for L/2greater than 1 00 feet. This divergence cannot be attributed to an instrumental source, since at this value of L/2 the measurgd resistance is greater than 0.01 ohm (see Plate 6), and it may represent the induced polarisation effect noted in the Markham Valley survey, (Wain~ight9 in preparation). Similarly on Plate 3, at depth probes K5 and K7, (Plate 4)~ the Geophysical Megger curves diverge from the ERR3 curves. At K5, the diver~nce commences at L/2 = 150 ft,and at K7 the divergence commences for L/2 greater than 5 ft. In the latter case the measured resistances are very low and discrepancies between different instruments are to be expected. However, from Plate 6, one would expect the Geophysical Megger measured resis'tances to be greater than those Of the ERR3 for particular values of L/2. This is not the case and also suggests that the induced polarisation effect is the reason for this.

Interpretation of the separate curves at K3 are given in histogram form in Plate 5, and the interpretations of all curves are given in Appendix 30 Of the remaining instruments the BoM.R. ERR1. high power d.c. resistivity inst~ent was tested at depth probe K4 on two separate occasions (see Plate 3). The curves were of poor quality with marked scatter, and differ considerably fro~ the curves made at the same site with four other instrumentso Whi!st the power supply system operated well, the SoP. meter used to measure the potential and applied current separately for each value of L/2 is a sound one, since it enables the resulting ~ta to be studied with respect to the magnitude of the applied current. It is possible to obtain readings of resistance with the other resistivity meters when the current is very small and the accuracy is correspondingly 10w 9 without any indication that this is the case.

The Yokagawa resistivity earth tester model L-10, or 'Yew' ~~,gger, has a low power output 'whose performance in depth probe work is typified by K2, Plate 3. For L/2'greater than 50 ft, the field curve diverges markedly from that of the ERR3. ~cause of the low power characteristics of the Yew megger, the applied currents are very small, and the resulting accuracy of the meter is low except where L/2 is small. The Geophysical megger and Terrameter might also be expected to demonstrate this effect of low applied current, although to a lesser degree. Because of its low power the vYew' megger is generally unsuitable for depth ,probe work.

In Appendix 3, the interpretations of field curves obtained using different instruments are generally similar. The region of field curves at L/2 greater than 200 ft is often not c2mpletely defined (see Plates 3 and 4), and matching with master curves may be bq$ed on extrapolation of field curves. This may lead to variation of .the interpreted resistivity of the lowest layer.

(iii) Correlation of interpretations with geological informat~~

The locations of boreholes are 'shown on Plate 1, as are depth probe sites and water sampling points. The logs of the boreholes are given in Appendix 1. Unless otherwise stated depth probes are discussed with reference to the.ERR3 interpretations using the eGG master curves (see Plate 7)0

Depth Probe K1'

The rise in resistivity from 6 to 15 ohm-metres 'at a depth of 49 ft represents a clay formation saturated with saline or brackish water above, and better quality water below. The interface at 150 ft depth indicates the presence of a more sanqy formation beneath the 15 ohm-metre layer. This is in broad agreement with the sparse data from bores (f), (g) and (h), although in bores (f) and (g) the fine sand commences at 95 ft. However, since the sand contains bands of lignite, it is possible that the upper part has a lower resistivity than one would normally ~xpect for a sand formation.

7

Depth Probe K2

Fairlygood8.gTeement between resistivity interpretation and bore log· (k). At 110ft depth9the formation resistivity rises from 6 to 60 ohm metr~s9 marking a change from clay to sand.

Depth Probe K3.

The 12 ,ohm-metre layer in the depth range 9~150 ft probably indicates a clay o~ sandy clay saturated with brackish water; below this is a 28 ohm­metre layer of uncoilsolidated sand with fresh water~ which overlies a 70 ohm~ metre formation at ,225 ft depth. This latter layer may be correlated with the limestone and silty. sand zone (305~321ft depth) proved by bore (k).

Depth Probe K4

The correlation of resistivity interpretation with bore logs (f)9 (g) and (j) is ·poor; this is not unexpected if the separation of K4 from these bores is considered.(s·ee Plate 1). Thl'l 3 ohm-metre layer extending to a depth of 60· feet probably rellresents a claY formation saturated with saline.wa:t;er.

. " ~! J. ' ~ • • •

Belo~9 the resistivity is greater than 13 ohm~metres, which may represent a chan.ge from clay to sand9 or a marked decrease in ··salinity of the pore solution9 ·

or most likely a combination of bo~h. ',.'/ . ~ ;

... De,pth Probe K5. , .

The mainr~sistivity layer of 1205 ohm-metres extends from ·near the surface to 125 ft depth, and correlates with the gravel-with=claY'(0~125 ft. depth) of bore (k). The 50 ohm~metre formation beneath represents a sand;y" formation~ and also agrees witb:;the lithological ,description from bor~Jk).

Depth Probe K6

This depth;!:probe was made C;;los~ to ·~5:~~. and the interpreta~i9n is . similar.

Depth Probe K1

Below 8 ft depth the resistivity of 2.7 ohm-metres probably represents a bracki.sh or saline clay which overlies a more sandy formation at 50 ft depth. Wh,ilst this does not qorrelate vrgry closely with bores (f) and (g) one mi~e to the north=east9 it·is a reasonable interpretation.

On Plate 7 are cross-s¢ctions of the survey area :~

(i) K7~K1-K2~K3~K5-K6

(ii) K7~X4-

Histograms of ERR3 interpretations and lithological logs of boreholes are correhtted·. Section (i) illustrates clearly the junction between predominantly clay formations and underlying sands an.d gravels. At depth probe K79 the 30 ohm-metre layer commences at 50 ft at K1. Probably the former represents an old·sand-bar, inland from which developed a saltwater marsh. At K7? saltwater intrusion does not appear to have occurred in the 30 ohm-metre formation9 but this would be a good point at which to repeat the depth probe at the end of a dry period. This method of delineating areas of salt water intrusion has been used withs~ccess in the Burdekin Delta, . North Queensland. Depth probe K4 is situated in a somewhat similar position to the west of K79 but the basal layer has a resistivity of 13 ohm~metres; this probably represents a brackish sand or sandy clay ,(see resi.stivity .. classification below)9 due to minor saltwater intrusion.

Plate 8 illustrates the field resistivity curves? which are double logarithmic plots of apparent resistivity (ohm-metres) versus L/2·':(ft) 0 NOf;e that the cuH-es are broadly similar but that the apparent resistivity for any

.. ,

8

chosen value of L/2 in general increases with the distance inland of the depth probe site from the intertidal zone. This indicates that the water quality improves inland from the intertidal zone; the survey area was once a salt marsh which is seasonally flushed with fresh water running-off from the highland areas. Because of the low permeabilitY9 this- process takes place slowly. From Plate 8 9 the sands and gravels have fairly high resistivities~ and generally ther~ is no:evidence of a serious saltwater intrusion problem. Since the survey area is u.sed mainly for stock~raising purposes, the amount of sub-surface water used is relatively small? and no problem of saltwater intrusion is likely'- i'o occur except in those areas very close to the intertidal margin.

(iv) Water g~litY2 and porosity of formations

(a) Water Quality g the quality of water samples 9 determined in ~he'manner described in Section 4? is expressed in ohm~metres at 200 C9 and in terms of the total dissolved salts (p.p~m.)· ( see Appendi,x: 2). The total dissolved content of salts is obtained approximately from the fopnula use'd by Guyod (1952) G'

Rw = 5000/C

Where ,,·--,,·0-· <:; Concentration of dissolved salts in pop.m.

Rw = Water resistivity at 200 C9 in ohm metreso

The resistivity of' the "run-off" fraction of surface samples (eog. these taken from active drainage ch~els) varies between 20 and 80 ohm~

,metres (250~62 p.p.m~). This contrasts sharply with the quality of samples, : pumped from sub-surface aquifers (2.5 to 6.3 ohm~metres9 i.e. 2000~794 p.p.m.). Contours have been drawn on Plate 1, based on the resistivities of sub-,surface samples; it is assumed that the water samples are derived from aquifers which are characterised by higher resistivities (see Plate 7). Formation resistivities have been classed into three broad divisions as 'given below9 assuming a porosity of 30% for the form~tion (Wiebenga. ej; al? in preparation) 0

Formation~i-esiB:tivity, R (ohm-metres) \

20

20 ~ 6 6

Total dissolved salt content (p.p.m. )

100

1000 ~ 3000

.3000

Description

Fresh

Brackish

Saline

'" '(b) Porosity of Formations comput ed from Archie t s formula :~

the porosity of a formation can be

Where

log R - log Rw = ~m log'P

R = Formation resistivity

Rw

P ::

m

Water resistiVity

Porosity as a fraction

Cementation factor; for unconsolidated sa.diments, m = 1030

Table 3 below gives thecpmputed porosities of the higher resistivity formations based on ,the three-l~er interpretations (see Plate 7).

-

9

TABLE 3

DEPTH Rw . Log~Rw R Log R Porosity REMARKS PROBE (ohm metres) (ohm metres) (%)

. 'K1 3 0.477 36 1.556 1805

K2 5 ,00699 60 1.778 18 0 5

K3 4 0.602 f28 ~ 1.447 15 .• 7 Average taken , 70 ' 1.845, '

K4 3.2 0.505 14 1.146' 32.1 , . ,Not used,

K5 5± 0.700 50 '1.70 17.1

K6 5+ 0.700 50 L70 17.1

Ir7 295 00398 30 "

1;47'7 18.5

17.6 Mean Porosity

The mean porosity of 17.6% is rather'low, being'more typical of, a medium gravel than sand, sandstone and shelly limeston~ as indicated by borehole data. Characteristics of rocks are discussed by Wiebenga. aniFJesson (1962); Plate 9,' which relates characteristics of rocks as a functi'on of grainsize, is taken from this report. '

6. CONCLUSIONS

Resistivity depth probes made with both the Wenner and Schlumberger electrode systems show that the two produce very similar field curves; the latter is to be preferred on economic grounds.

The ERR3 9 Geophysical Megger and Terrameter give comparable performances in depth probing, except where the measured resistances fall below a certain value ascertained in calibration tests, and below which the ERR3 is to be preferred because, .. of its better accuracy. The 'Yew' megger has limited application where the 'electrode spacmg is such that the measured resistance is not less than 0.15 ohm. The power supply for the ERP.1 high power resistivity system was shown to operate wel1 9 but .the potential meter used in conjunctiori gi3.ve'-rise to anomalous field curves.

Interpr~tatio~s of depth probes agree quite well with stratigraphic information from bO'i'ehole$. ' A junction between cl8\Y overlying sand at a depth of 90-130 ft is Vfi~e:Sprea~ over the survey area. Because of the cl8\Y zone extending from the surf~ce9 but also because the survey was conducted at a time when there was "·c6ii.eiiderable rainfall "run-off" from the hills to the north and east, there is no evidence of significant saltwater intrusion in the area. It is suggested that reSistivity measurements be repeated at the end of a dry period, so as to permit a comparison with current results, in order that zones of saltwater intrusion m8\Y be defined.

:. \ ...

"", ::f

. ANDREW,J-.'T.G~-;':~d WIEBENGA, -W .A~

,IX>BRIN, M.B.

DYSON, ID.F., and WIEBENGA,' W ~A.

JENKIN, J.j.;

GrJYOD,H.

MARSHALL, D.J., and MADDEN, ToR.

. SCHLUMBERGER . : ; . ~.~

,:-:!i:

TODD, D.K.

VACQUIER, V., HOLMES, C.R., KINTZINGER, P.R., and LAVERGNE, M.

WAINWRIGHT,', M.

WIEBENGA, W.A.

WIEBENGA, W .A., and JESSON, E.E.

WIEBENGA, W .A., POLAK, E .J.; ANDREW, J .T.G., WAINWRIGHT,. M., and KEVI, L.

10

7. . REFERENCES

1965 Two layer resistivity curves for the Wenner and Schlumberger electrode

,'" c:onfiguratlona," Bur. Min. Res. Rec • . . 1956/18- .

. 1960 GEOPHYSICAL PROSPECTING. McGRAW HILL

1957 Geophysical inve'stigations of under~ound water, ,Alice,'Springs, N.T. 1.956. ~., Min. Res. Rep. 1957/89. " "~I , \' .'

-1962, The geology and. hydrogeolbgy :of the

\ Western Por~ are~ Departme~t of .' Mines. Vic~oria, Report No. ,5

1952 Electrical well logging fundamentals. Houston, Texas

1959 Induced.polarisation, a study of its causes Gebphys. 24, No.4, p. 790

1958 INTRODUCTION TO SCHL~mERGER WEL~ LOGGING, No.: 8, p. 10. SCHLUMBERGER WELL SURVEYING CORP. U.S.A.

1959 GROUNDWATER HYDROLOGY. McGRAW HILL

1957 Prospecting for groundwater by induced ,electrical polarisation Geoph.ys.

1955

22, No. 3-,' P. 660.

Markham Valley resistivity survey T.P.N.G. 1964 Bur. Min. Res. Rec. (in preparation)

Geophysical investigations of w~ter deposits,. Western Australia Bur. Min. Res.' Aust. Bull. 30 '

, Geophysical e~ploration for underground water Bur. Min. Res. Rec. 93 :

Underground water', Burdekin Delta, North Queensland .Bur. Min. Res. Rec. (in preparation)

I,

" -' , , '

APPENDIX 1 - BOREHOLE DATA

.. Th~ location of each bore is shown on Plate 1, . Bores (a) to ' .... (h) were stUuc by private contractors; mainly to obtain water supplies for

.. irrigation and livestock purp<?-se~ •.. Bores (j.), (k) and (1) were sunk by the Department of Mines, Victoria, '

. ,'" Bore (a), O~90 ft • Clay

..

Bore (b)

Bore (c)

Bore (d)

Bore (e)

Bore and

(f) (g)

Bore (h)

Bore (j)

'.,

90-240 ft. Unknown

240-250 ft. Coarse sand

,Sandy clay '. Cl8J'

5-60 ft.

60-85 f~.

85-15,0 ft. Mainly sand, but with some lignite bands I

0-48 ft. Cl8J'

48-.60 ft" Sand

60-18 ft,. Cl8J'

18-81. ft. Sand (fairly saline i.e. 2000-4000 p.p~m.)

81~110 ft. Mainly cl8J', with some thin sand l8J'ers

110-118 ft. Lignite sand

118-185 ft. Lignite

185-200 ft. Fine sand, with fresh-water

200-205 ft. Coarse sand

Similar to bore (b). Se~-shells at 225 ft. 4epth

0-32 ft.,

32-81, ft.-

Mainly cl8J'

rJIairily sandy cIa.)'"

81-110 ft. Black coal and wood

110-130 ft. Sand

130-134 ft. Cl~

134-163 it. Mainly sand

0"':95 ft.

95 +

0-128 ft.

Cl8J'

Fine sand with lignite - fresh water zone at 168 ft. depth

Cl8J' - saturated near surface with saltwater (2000- 4000p.pm.),

(Department of Mines Bore 4, Tooradin, 1959)

0-11 ft. Sand

11-31 ft.

31-36 ft.

36-48 ft.

48-218 ft.

218-304 ft.

304-318 ft.

318-341 ft.

341-346 ft.

Clay

Sand : fresh-water at base

CI8J'

Sand, -with shells-below 111 ft. depth

Sandy clay

Gravel in t~ clay

Basalt

Cl8J'

Bore (k) -. -:.'.

.::..-.'-

Bore (1)

2

(Department of Mines bore~ ,alongside water tower N.E. of Kooweerup)

0-125 ft. Mainly gravel with clay. Fresh-water at 41 ft depth

125·-185 ft. Fine sand with some lignite

185-225 ft.

225-305 ft.

Fine sandy claJ7 ...

Mainly·sand with sandstone lenses p and shells be1.ow 258 ft.

305-321 ftQ Limestone? silty sand with shells

321-333 ft. Clay

(Department of Mines? Bore 3; located by road on Allotment 1~9 Section I, Kooweerup)

0-50 ftQ . UnlalOwn

50-84 ft •. ClClJ'" ,

84-100 ft. Slmdy clay. Fresh-water at 85 ft. standing at 13 ft •. depth

100-105 ft~ C.oarse sand

105~110 ft. Clay

Geophlf~lc~a 1 Branch, : Bar~au_ o·f fllfnera·1 Iles~ources t Geo 111gya~d 6~~~y? i c~ ..

APPENDI X 2 ~-WATER RES I SHV IT! ES

MudDCell Constant D 6.38 metres x Observed Resistances (Ohms) .- -

AREA ._ KOO..wEE .. RUP. V I CTORlA OBSERVER MEGGER TYPE : YEAR -.

1"- 1'1. . .. ·Earthoiestei"o (()',,3006 Ohms) 1~65- .-

...

i01r III " Mud Cell U S P

". Underground D Surface D Probe (Constant ..•••....•• )

---~ ---::-:--. ------ ~-.,-----~---=. F--·-.~----~----~----~~~--···-~ --~-----~------- =------=~---~~~---~--------------.. . - ..

OBSERVED .. RESISTIVITY REMARKS LOCATION ..

DEPTH TEMP. CORRECTED SALIN I TY POROSITY DATE jWMBER INSmfH (feet) (GC) .. READHJG

READING -(Ohm.metres)

(p.p.m) (%) ( I~;t a t\ oils ~ Grid References, - - . (.oj at 20 0e Pump' ng Data, pf~ v~ 1 ues, Etc)

.-._--- 0;--"';"-- ------ -----.~- ... ___ &.0 ...... _

I---... --~'"-___ a.. ______ ------- -,--~ .... ---"'" __ ~~ ______ ~~ __ ~~~ ___ ~ ____ L~ __ ~ ____

.. 8-9 1 . ·111 S 13.5 1050 67 59 .. B5 . . , Surfaf;e sample at cent re K·j

-8-9 2 . -M S 13.5 . 1451) 92.5 B1.5 61 From drain. Ditch adjacent K1

8-9 3 III - S 13.8 .. ~·o 2.5 2.2 . 2480 Surface run.off. Sawte 11 's in 1 et - ' .. - -" , .... __ . _. - .. - .. - .-

B-9 . 4 - ftI S 13.8 14- 0.89 O. 79 6330 From drainage channel, Sawtell's -

, , inlet ..

10.9 . 5 M S 12.0 It 50 .28.7 24.1t 204 From settling tank. Water from drain. Adjacent water-tower, Kooweerup

10.9 6 M S 10.0 1050 67 55 91 From drainage ditch at centre of . K2

. -- --

10-9 ·7 M S 15.5 580 37 31t 147 From Bunyip River drain, fast. I

flowing

10-9· 8. 1:1 S 16.0 350 22.3 20.8 240 From ancilliary drain parallel to Bunyip

13w9 9 Id S 14.0 380 24.2 21.7 230 Fron drain adjacent centre K3

13.9 10 M U.n.a. 16.0 68 4,.34 4.04 1230 37 F rom wi ndml 11 pump, 100 yds. east of centre K3

14.9 11 III U.n.a. 13.0 58 3.7 3.2 1560 24- Sample pumped from well 50 yds. south of centre K4 (Harewood House

15-9 12 M S 13.8 375 24 21.4 233 Samp 1 e from Buny) p Ri ve r at Glove rl t Bridge. centre K5

15;.9 13 ·M S 15.0 530 33.8 , 30.8 162 From tank filled from drain - clos to K6

21 a9 14 til S 17.1 41 2.6 2.5 2000 From small drain on norih side of le'/ee wall, 500 ft. south of centr of 1<7 (Di ckensbe rg) ,

'.

21.9 15 M S 16. "I 58 3.7 3.5 1430 F rom surface pond south of levee (see 14)

22.9 16 fi1 S 16.0 1t25 27.1 25.1 199 From active drain, west side . Bunyip River

22.9 17 ~1 50 12.8 It 5 2.9 2.5 2000 Brackish· used:'only for cattle

22.9 '1B ~. 45 16.0 75 1t.8 4.4 1~ltO 56 Sample from seH1ing tank .. probably polluted

22.9 19 M S 14.5 400 25.5 23.9 209 From drain next to road .. ,

22.9 20 M 110 14.5 110 7.0 6.3 794- 1t9 From settling tank ,

-~-------------, _ .. -----"'" .----- -----_.- ~-----~~=~-~~-~--~~ .... - _______________ IoJ, ...... OUIEI_

___ O;:> __ oa3'_~

-------~~~-~-----------------------See Plate 1 for locat Ions

-. APPENDIX 3 - REPEATED TWO LAYER DEPTH PROBE INTERPRETATIONS

, 8.) .- ERR3; b) Geophysical Megger; c) Terrameter; d) 'Yew l Meggero _

l.st y 3rd figures etc. ~efer to resi:stivit,ies (ohm metres); figures in brackets refe~ .:to depths of 'interface (ft).:· ' .

. ~

',' :. INS TRUMENT . STATION' INTERPRETATION -'

K1 a) 53 (3) 6 (29) 15 (127) 24

b) 40 (3) 6 (35) 14'(130) 28

c) 38 (3) 7 (24) 12 (135) 28

d) 30 (3) 7 (40) 30 not complete

. ~. ~) 54 (1.4) 13 (9) 5 (35) 11 (135) 40

b) • 57 (1.2) 14 (7.5) 5.5 (41) ~ (130) 31

c} 68 (1.1) 17 (603) 6.5 (45)" 8.5 (125) .30

K3 a) 105 (2) 34 (8.5) 12 (85) 20 (250) 36

b) 90 (2) 30 (9) 11 (85) 17 (270) 30

c) 200 (8) 13 (80) 20 (300) 73 ,

d) 90 (2.2) 29 (9~5) 12 (85) 20

K4 a) 5 (5) 2 (70) 30 '(450±) 15

b) 5 (6) 2 (64) 30 (440) 11

c) 5.5 (5.5) 2 (72) 22±

K5 a) 90 (3.5) 12.5 (130) 40

b) 90 (3) 13 (120) 15 I

K6 a) 50 (3) 12 (130) 45 "'

b) 42 (3) 12 (132) 42

K7 a) 5 (1.5) 2.7 (4.6) 6 (8) 2.7(62) 23

b) 3.8 (1.8) 2.5 (4.6) 4.3 (9Q5) 2 (68) 18

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Clay and silt

Sandy clay

Fine sand

Fine sand

Medium sand

Coarse sand

Coarse sand

Gravelly sand

Fine gravel c: .~

Medium gravel ...... c: Q) ...... Q) ~

Medium gravel

Coarse gravel

Coarse gravel

Boulders

CHARACTERISTICS OF ROCKS AS A FUNCTION

OF GRAI N SIZE

PERCENT 30 40 50 o

----~ - -- 40% ---

>­I-en o 0:: o a...

-----------30% -

-------~-------- - --- -- ----~-- -- 20%

- -------------- - - -15 %

Clay, soft shale __

Hard sha Ie _

Sandstone, saltwater ___ _

Sandstone, fresh water __ _ ___________________ ...... !DII!!IIlIIIIIIlIIlIll

Porous dolomite and limestone ________ _

Dense limestone ________ _

2

~ o "9J -0 !

3

Coal -- ---- ------- -- -- -----. -------------- ____ UlWJlllliJlc

Igneous and metamorphic rocks ___ _

LOG RESISTIVITY IN OHM - METRES 3 4 5 6

PLATE 9

~!liIIIl!II!!lllii[[i~III!!:::i!!I!lllil!!!II[IIIIIIIIIII!!!!1!~!~!!!I![III!!III!lllllllllllllli!III[:llllllilllllII!I!I!!I

____________ .m~ell,11 1,lrllllllEWI ~~~

{jeoph'ls'CO! Branch, Bureau oP Mt"nero/ Resources, 6eoJo9'1 and (jeoph<jsic5 G369-1

TO ACCOMPANY RE.CORD No