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Parameter Akuifer
Irwan Iskandar, PhD KK Eksplorasi Sumberdaya Bumi
Teknik Pertambangan
Fakultas Teknik Pertambangan dan Perminyakan ITB
Parameter Kuantitatif
Besaran (vektor ataupun) skalar yang dapat dihitung / diukur dari pengujian di lapangan (field test) ataupun di laboratorium (laboratory test) e.g.
• Permeabilitas/konduktivitas hidraulik (Transmisivitas)
• Storativitas (specific yield, specific storage, specific retention)
• Porositas, porositas efektif
Pengujian Laboratorium
Pengujian sifat intrinsik batuan (dari intact rock)
• Porositas
• Specific yield
• Ukuran butir (hazen test)
• Permeabilitas
7
Hazen Test Approximation
D10 : effective size dari partikel, diambil nilai 10% ukuran partikel terkecil
Pengujian Permeabilitas di Laboratorium
Pengujian Permeabilitas di Laboratorium Wall permeameter (dengan tekanan) ASTM D-5084
Phone: 022 250 2239 Fax: 022 250 4209
Sample Code : KPC-9
Description : soil unconsolidated material even compacted
Grain Size : clay - silt
Date of Test :
Tested by :
Checked by :
Sample Length (cm) : 6.67
Sample Diameter (cm) : 5.5
Area of Section (cm2) : 23.74625
Constant Pressure (kg/cm3) : 0.2
Head (cm) : 200
Record of Test
Vol. Coloumn Time dV dT Q
(cm3) (sec) (cm3) (sec) (cm3/sec)
50 0 0
49.5 60 0.5 60
48.95 120 0.55 60
48.4 180 0.55 60
47.9 240 0.5 60 K :
47.55 300 0.35 60
47.15 360 0.4 60
46.7 420 0.45 60 8.19252E-06 cm/sec
46.3 480 0.4 60 8.19252E-08 m/sec
45.95 540 0.35 60 0.00583333
45.6 600 0.35 60
45.25 660 0.35 60
Dr. Irwan Iskandar ST, MT.
Hydraulic Conductivity (K)
Laboratory of Hydrogeology
Mining Engineering Department, ITBAddress: Gedung Teknik Pertambangan ITB, Labtek IV, Jl. Ganesha No. 10 Bandung,
Laboratory Test of Hydraulic Conductivity ASTM Standard D-5084
25 Januari 2012 - 10 Februari 2012
00.10.20.30.40.50.6
0 100 200 300 400 500 600 700
dV
(cm
3)
Time (sec)
Calculation of K (Hydraulic Conductivity)
tHA
LqK
..
.
Dimana;
K: Konduktivitas Hidraulik (cm/det) atau
(m/det)
q: Volume minimum rata-rata (cm3)
L: Panjang conto yang diuji (cm)
A: Luas penampang conto yang diuji (cm2) DH: Tinggi tekan/ Head (cm)
Dt Waktu pengujian (det)
• Transmisivitas : Permeabilitas x zona jenuh
T = K x b*
b* dalam uji lapangan, merupakan tebal zona pengujian
Pengujian Permeabilitas (Transmisivitas) di Lapangan
• Metode Uji e.g.:
•Pumping Test, (mendapatkan nilai T (K), S, Radius pengaruh, efisiensi sumur, debit optimum)
• Packer Test, (nilai T, dan K pada zona spesifik)
•Slug test, (Nilai T (K))
Permeability in Fractured Rocks
• Dual ‘porosity’
• Secondary porosity as ‘main actor’
• Rock defects/Fracture/gouge
• Connectivity?
• Heterogeneity
• Isotropy / anisotropy
• K value from field/lab. test?
• Connectivity
• heterogeneity
-100 m
-110 m
-120 m
K105 : high
Depth Connected
K115 : low
Not Connected
-100 m
-110 m
Permeability in Fractured Rocks
Laboratory test from core
NOT RELIABLE High K value (rock mass)
K is very low impermeable
Pumping Test
Result
• Transmisivity (Permeability)
• Storativity
• Radius of Influence
Limitation and Problem
• Need construction, observation well (obs. well),
• Sometimes obs. well not at ‘right’ position
Permeability in Fractured Rocks
25 m
100 m Pumping well
Observation well 1
Observation well 2
No drawdown
5 meter drawdown
Permeability in Fractured Rocks
Permeability in Fractured Rocks
• Packer test
• Can be test at an interval depth
• No need well construction, nor obs. well
• Suitable in fracture rocks
Result
• Transmisivity (Permeability)
• Type of rock defects (filled, blocked, open)
Packer Test
-100 m
-110 m
-120 m
K105
K115
Very limited number of water can enter the rock formation
K <<<
Packer Test