Revisiting hydrostratigraphy in Bandung-Soreang Groundwater Basin: a well-logs re-analysis

Sunarwan, B.1, Irawan, DE. 1, Puradimaja, DJ. 1, Notosiswoyo, S.2,

Sadisun, IA1, Setiawan, T.3, and Anugrah, RM4

1 Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Institut Teknologi Bandung, 2 Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology, Institut Teknologi

Bandung,

Jl. Ganesa No. 10, Bandung, 40132

3 Geological Survey of Indonesia, Ministry of Energy and Mineral Resources,

Jl. Diponegoro No. 57, Bandung, 40122

4 Faculty of Geology, Padjadjaran University, Jl. Raya Bandung Sumedang Km. 21. Sumedang

The 5th International Conference on Mathematics and Natural SciencesInstitut Teknologi Bandung, 2-3 November 2014

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Background

• The groundwater condition in Bandung-Soreang Groundwater Basin (BSGwB) has been degraded over time. Indications:

• decline of water level and • decrease of water quality.

• With the existing condition there have been two main problems:

• difficulties to manage the aquifer, based on the values of hydraulic properties from pumping test result.

• biased pumping test result since there have already many wells near by tested well.

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Objective

• The objective of this paper is propose a new aquifer classification, based on well log data, instead of solely on pumping test result.

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Hydrostratigraphic Unit (HSU)

• We will use the concept of hydrostratigraphic unit (HSU). • It is defined as body of rock in a geological framework

that has a identified lateral and vertical distribution with the same or similar hydrogeological characteristics (Maxey, 1964).

• Seaber (2002) mentioned porosity and permeability values as one of quantitative criteria to classify a HSU.

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Methods

• The basic idea is to convert the resistivity value to density then to relative permeability.

• Preliminary analysis was done to well log dataset from 111 drill holes:

• All the data have been digitized, • Calibration was applied to previous lithological classifications,• Six correlated sections have been generated.

• Producing relative porosity and permeability values:• Using Chilingarian and Baker-Hughes chart, • Calibration was applied using pumping test data, • Multiple regression technique was also applied to generate regression

equation.

• Eliminating outliers to produce good fit.• Drawing boundaries of HSU to generate fence diagram.

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Results1: Regression equations

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Conversion equation

Resistivity to density

Density to relative porosity

Relative porosity torelative permeability

Results2: New proposed HSU

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Conclusions

• With this paper we propose the following has successfully proposed:

– calibrated the lithological name from well log data. – correlation equations to convert resistivity data to relative permeability.– New aquifer system classification: three HSU’s and six sub HSU’s.

• The resulting values will be useful to predict the hydraulic properties of future drilled holes in BSGwB.

• However, the relative permeability values are not intended to substitute the calculation from real pumping test data.

• Not only intended to simplify the multi-aquifer system in this basin, we also expect this new classification can assist the authority in managing the groundwater resources in BSGwB.

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Next step

• This work is part of PhD project of the 1st author.• We need to validate the classification and equations to

more dataset.

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Main reference: 1Alger, R. P. "Interpretation of electric logs in fresh water wells in unconsolidated formations.", SPWLA 7th Annual Logging Symposium (Society of Petrophysicists and Well-Log Analysts, 1966).2Geyh, Isotopic Hydrological Study in Bandung Basin, Indonesia (CTA-PU Project Report, 1990).3Koesoemadinata dan Hartono, “Sedimentasi dan Stratigrafi Daerah Bandung”, Prosiding PIT IAGI (Ikatan Ahli Geologi Indonesia, 1981).4Matahelumasi, B. and Wahyudin, Penelitian Hidrogeologi Daerah Imbuhan Air Tanah dengan Metode Isotop dan Hidrokimia, di Cekungan Air Tanah Bandung Soreang, Provinsi Jawa Barat (Tahap II) (Pusat Lingkungan Hidup dan Geologi, Badan Geologi, 2009).5Maxey, GB. "Hydrostratigraphic units." Journal of Hydrology 2.2 (1964): 124-129. 6Priowirjanto, G and Marsudi, “Fluktuasi Muka Air Tanah di Cekungan Bandung”, Prosiding Seminar Sehari Air Tanah Cekungan Bandung (Perhimpunan Ahli Airtanah Indonesia, 1995).7Roger S. Bivand, V.G.-R., Edzer Pebesma, Applied spatial data analysis with R, Second edition (Springer, New York, 2013).8Salem, Hilmi S., and George V. Chilingarian, "The cementation factor of Archie's equation for shaly sandstone reservoirs." (Journal of Petroleum Science and Engineering 23.2, 1999), pp 83-93.9Seaber, PR. "Hydrostratigraphic units." The geology of North America 2 (1988): 9-14. Serra, Oberto, Fundamentals of well-log interpretation. Vol. 1 (Amsterdam: Elsevier, 1984).10 Silitonga, Peta Geologi Lembar Bandung, Jawa Barat, Skala 1:100.000 (Pusat Penelitian dan Pengembangan Geologi, 1973).11 Sudjatmiko, Peta Geologi Lembar Cianjur, skala 1:100.000 (Pusat Penelitian dan Pengembangan Geologi, 1972).12 Sutrisno, Peta Hidrogeologi Lembar Bandung, Jawa Barat, Skala 1:100.000 (Pusat Geologi Tata Lingkungan, 1983).

Revisiting hydrostratigraphy in Bandung-Soreang Groundwater Basin: a well-logs re-analysis

Sunarwan, B.1, Irawan, DE. 1, Puradimaja, DJ. 1, Notosiswoyo, S.2,

Sadisun, IA1, Setiawan, T.3, and Anugrah, RM4

The 5th International Conference on Mathematics and Natural SciencesInstitut Teknologi Bandung, 2-3 November 2014

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Thank you for your attention

Further questions and comments should be addressed to:

Dr. Dasapta Erwin Irawan: erwin@gc.itb.ac.id Twitter : @dasaptaerwin

The resources from this project will be made available online by the end of this month at:•ResearchGate: https://www.researchgate.net/profile/Dasapta_Irawan

•Academic.edu: https://itb.academia.edu/dasaptaerwin

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To the extent possible under law, the author of this document have waived all copyright and related or neighboring rights to this work. This work is published from Sydney, Australia.