SELF POTENTIAL (SP)

Achmad Yoshi SatriadyMuhamad Harfan

Yusuf Hadi

Self Potential Surveying Introduction

This method measures naturally occurring electrical potentials on the ground surface.

The spontaneous or natural potentials developed in the earth by electrochemical actions between minerals and subsurface fluids or by electrokinetic processes involving the flow of ionic fluids.

Basic ConceptElectrofiltration Potential The flow of fluid through a capillary or

porous medium may generate an electrical potential (called the streaming potential) along the flow path

Basic ConceptMineralization Potential

Types of natural electric potential

Types of SP anomalies and their geological source

Field ProcedureFixed-Based ConfigurationDipole Configuration (Gradient

Configuration)

Aplication of Self-Potential Method Detection of Buried TankSelf-potential signals associated with ground water flow

Lokasi Pengukuran Anomali SPDaerah survey

dilakukan di Lebaksiliwangi Sabuga Bandung

Luas daerah pengukuran 14 x 9 m2

Teknik pengukuran yang dipakai Metode Amplitudo Potensial

Pola pengukuranJumlah titik

pengukuran 150 grid

Jarak tiap titik panjang maupun lebarnya sebesar 1 meter, dengan 1 titik acuan tetap

-7

-6

-5

-4

-3

-2

-1

0

1

2

3

4

-10 -5 0 5 10

Kontur Pengukuran Hasil Survey SP

-6 .00 -4 .00 -2 .00 0 .00 2 .0 0 4 .0 0 6 .0 0-6 .00

-4 .00

-2 .00

0 .00

2 .00

-10 .0 m V

-8 .0 m V

-6 .0 m V

-4 .0 m V

-2 .0 m V

0.0 m V

2.0 m V

4.0 m V

6.0 m V

8.0 m V

10 .0 m V

12 .0 m V

14 .0 m V

16 .0 m V

18 .0 m V

20 .0 m V

22 .0 m V

-2 .80-2 .5 0-1 .80-1 .90-2 .30-2 .7 0-3 .80-2 .30-4 .60-5 .60-6 .1 0-4 .90-4 .9 0-5 .10-4 .90

-6 .00 -6 .90 -6 .5 0 -5 .50 -5 .1 0 -4 .20 -3 .40 -2 .20 -1 .90 0 .80 -0 .30 1 .2 0 -0 .50 -1 .1 0 -1 .90

-3 .00-1 .1 02 .401 .4 02.802 .30-1 .20-1 .10-0 .400 .80-1 .4 0-5 .80-3 .7 0-4 .50-4 .90

-4 .50 -4 .30 -0 .4 0 -2 .50 -2 .9 0 0 .40 2 .80 0 .00 7 .20 7 .70 8.60 7 .1 0 8 .90 3 .90 1 .10

-0 .901 .106 .705 .9 013 .007 .006 .405 .200 .60-2 .50-5 .2 0-3 .00-1 .9 0-4 .80-2 .20

-1 .40 -5 .80 -2 .5 0 -4 .80 -1 .1 0 -2 .30 1 .00 -3 .70 -4 .20 -0 .8 0 5.80 7 .7 0 5 .10 -2 .5 0 -10 .60

-3 .500 .2015 .1020 .2 06 .002 .207 .106 .500 .90-5 .0 0-9 .20-6 .9 0-9 .60-4 .50

-8 .80 -7 .30 -6 .9 0 -7 .30 -6 .5 0 3 .00 5 .10 9 .70 20.90 1 6.20 10 .80 21 .3 0 12 .40 7 .30 0 .30

6 .409 .5011 .8013 .3 09.401 0.9014.4013 .709 .307 .204 .9010 .601 0 .8 011 .1011 .7 0

9 .7 0 7 .20 1 0 .7 0 12 .30 13 .10 12 .60 13 .00 10 .50 9 .40 7 .60 8.00 12 .8 0 13 .80 11 .70 7 .20

-6 .00 -4 .00 -2 .00 0 .00 2 .0 0 4 .0 0 6 .0 0-6 .00

-4 .00

-2 .00

0 .00

2 .00

Gambar 3D dari pengukuran SP

-8 .0 m V

-6 .0 m V

-4 .0 m V

-2 .0 m V

0.0 m V

2.0 m V

4.0 m V

6.0 m V

8.0 m V

10 .0 m V

12 .0 m V

14 .0 m V

16 .0 m V

18 .0 m V

20 .0 m V

Hasil kurva anomali kordinat -4 yang di dapat setelah data processing

dari tabel dan grafik disamping diketahui :

V(0) = -2,5 mV xo = -0,122 meter L(xi) = hasil

pengukuran potensial yang dianggap anomaly

q (silinder) = 1 (sesuai referensi menurut Bhatacharya dan Roy) merupakan ordinat posisi yang pada kasus ini posisinya sedikit di geser agar mempermudah perhitungan (dengan menambahkan 4,275)

-15

-10

-5

0

5

10

15

-3 -2 -1 0 1 2 3 4 5

Hasil kurva anomali kordinat -6 yang di dapat setelah data processing

V(0) = -4,3 mV xo = -0,217 meter L(xi) = hasil

pengukuran potensial yang dianggap anomaly

q (silinder) = 1 (sesuai referensi menurut Bhatacharya dan Roy) merupakan ordinat posisi yang pada kasus ini posisinya sedikit di geser agar mempermudah perhitungan (dengan menambahkan 4,18)

-15

-10

-5

0

5

10

15

-3 -2 -1 0 1 2 3 4 5

Hasil survey Besar momen dipol yang didapat berupa

minus, dalam hal ini dapat di asumsikan bahwa kedua anomali merupakan bahan mineral berbahan konduktor, di prediksi ini merupakan sebuah drum.

Self-potential signals associated with ground water flow (infiltration test from a ditch)

Acquisition

Self Potential anomaly expected over water flowing into & out fracture zone

Self Potential anomaly expected over water flowing into fracture zone.

Self Potential anomaly expected over water flowing into fracture zone.

The Measured Self-Potential Signal (measured along profile 3)

The Self-Potential Signal (perpendicular to the ditch)

References

Sharma, Prem V., 2004, Environmental and Engineering Geophysics, Cambridge University Press, UK.

A. Boleve et al., A new formulation to compute self-potential signals associated with ground water flow, 2007, Hydrology and earth System Sciences Discussions.

Putri, Anggun K., Fenomena Self Potential dan Interpretasinya Dengan Metoda least square, 2006, Universitas Negeri Jakarta, Indonesia.