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PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage
15-16 OKTOBER 2015; GRHA SABHA PRAMANA
165
QUANTITATIVE CHARACTERIZATION OF CARBONATE PORE SYSTEMS ON
JONGGRANGAN FORMATION USING DIGITAL IMAGE ANALYSIS (DIA)
Ari Wibowo1*, Nana Higiana Hasanah2 1Department of Geological Engineering, UPN “Veteran” Yogyakarta
2Department of Geophysical Engineering, UPN “Veteran” Yogyakarta
JL. SWK 104 (Lingkar Utara) CondongCatur, Yogyakarta 55283 *corresponding author: [email protected]
ABSTRACT Jonggrangan Formation is characterized by major occurrence of reef limestone and small portion of
bioclastic limestone that were well exposed at Samigaluh Area, Kulon Progo Regency, Daerah
Istimewa Yogyakarta Province. These carbonates have a wide variety of pore systems that imprint
different petrophysical properties, which are more difficult to predict than in siliciclastics. Digital
Image Analysis (DIA) can be applied to response the carbonates complexity by calculating pore value
and also characterizing the pore shape in digital form. The method is based on images from rock thin
sections taken under an optical microscope (OM) and also core analysis results to be compared.
Sixteen rock thin section samples have been analyzed with several observation representatively in
order to mitigate the effect of area selection problems. Blue-dyed liquid also has been added to those
thin section samples, so the pore could be identified clearly. Based on further examination, both
primary and secondary pore systems are well developed. There are six pore shapes are identified
within different pore values. Crossplots of pore values indicate the pore variety depends on several
rock parameters. In summary, understanding characterization of carbonate pore system on
Jonggrangan Formation by using DIA method is fast and accurate, useful to encourage and enrich
carbonate petrophysical analysis concept.
I. INTRODUCTION
The carbonates are influenced greatly by sea
level fluctuation which recorded on rock
textures. Pore system in carbonate is much
more complex than siliciclastics, as a result of
overhelming biological origin of carbonate
sediments that reflected by the occurance of
porosity within grains, growth framework
porosity within reefs, and the common
development of secondary porosity due to
pervasive diagenetic processes (Choquette
and Pray, 1970). In addition to traditional
descriptive and qualitative porosity
evaluations, there exists a need for
quantitative methods that characterize the
various aspects of pore space and enable a
quantitative assessment of the distribution of
porosity and other physical properties
(Anselmetti et al., 1998). This Paper discussess
about evaluating pore characteristic
quantitatively on carbonates using digital
image analysis (DIA) which well-established
method of quantifying pore space from images
of thin sections. Numerous researches were
conducted over time to classify pore structure.
Anselmeti et al. (1998) quantified the pore
shape in carbonates from digital images
obtained by optical microscope and Scanning
electron microscope. Castro (2013)
determined Gamma parameter (ratio between
pore perimeter and area) and correlated it
with permeability measurements. In this study,
authors try to enlight about relationship
several parameters toward cabonate facies
and pore type based on thin section and
supported by core analysis.
Jonggrangan Formation is one of many
carbonate facies that well exposed in
Indonesia, particularly in Java island, has been
elected to be analyzed. Carbonate reef on
Jonggrangan Formation may lead us to
understand more about the development of
carbonate pore system.
II. REGIONAL GEOLOGY
The study area belongs to Kulonprogo Sub-
basin, the eastern part of South Central Java
Basin. This basin is located on the southern
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portion of modern Java Volcanic Range and
could be identified as well as Basin lies on
Magmatic Arc. Volcanic activity which is
occured was the result of subduction beneath
the Hindia Ocean. Thus, this basin is classified
as fore arc-basin since it's location is in front of
Java Volcanic mountain range. The oldest
Formation in this area is Middle Eosen
Nanggulan Fm. which is well exposed on
Nanggulan Village. This Formation is typified
by the occurance of intercalation of sandstone,
shale, claystone and lignit which is deposited
on paralic depositional environment. Lies
conformably above Nanggulan Formation is
Kaligesing Fm. consisted of volcanic breccia
and intrusion. Since no fossil could be attained
from this formation, it is assumed as Oligosen
Age formation. Another formation which is
deposited on the approximate same time with
this formation is the polymict breccia Dukuh
Fm. Dukuh Formation consists of polymict
calcareous breccia with interbedded
sandstone and claystone, interpreted as
shallow marine sediments. Dukuh Formation
and Kaligesing Formation has interfingering
stratigraphic relation. Lies unconformably
above Kaligesing Formation are two distinctive
carbonate formation, Sentolo
Fm. and Jonggrangan Fm. Sentolo
Fm, typified as clastic carbonate formation,
consist of intercalation of calcarenite,
calcilutite, and marl. The abundant fossil
content in this formation allowed a firm
depositional environment interpretation of
this formation, as well as the Age of this
formation. Sentolo is Early Miocene carbonate
formation deposited on Neritic-upper Bathyal
environment. On the other hand Jonggrangan
Fm., the focus of this study is characterized by
the occurence of reefal limestone which
depict various carbonate facies. Jonggrangan
Fm. is interpreted as a patch reef deposited on
shelf area. Sentolo and Jonggrangan have
interfingering relation. (Pringgoprawiro and
Riyanto, 1968).
III. SAMPLE AND RESEARCH METHOD
Sixteen rock thin section samples have been
analyzed with several observations
representatively in order to mitigate the effect
of area selection problems. Blue-dyed liquid
also has been added to those thin section
samples, so the pore could be identified
clearly. The DIA (digital image analysis)
method is based on images from rock thin
sections taken under an optical microscope
(OM) and also core analysis results to be
compared. The method comprises of three
steps: image acquisition, segmentation, and
calculation of pore parameters. Image
acquisition takes approximately 10 – 15
minutes per sample, with additional time
needed for image analyses and statistical
evaluations. The segmentation process is the
separation of a specific feature from the
background and it was performed on colored
digital images acquired in standard RGB (red-
green-blue) which were converted to a binary
8-bit BW (black and white) format to identify
respectively, the pore and the matrix/cement.
In this study, the object feature of
segmentation was the rock pore that was
quantified and its geometry parameterized. In
addition, the image analyses program authors
used (Image J) is freely available as public
domain software. Then calculation process
uses mathematical programs in order to
create crossplots for several parameters.
IV. DATA AND ANALYSIS
Several parameters defined in the DIA to
quantify pore space. Two DIA parameters,
Dominant pore size (DOM) and Perimeter over
area (PoA), are proved to best describe several
aspects of pore system, namely facies, pore
type, porosity (Φ) and permeability (K).
Theoretically, dominant pore size (DOM) is
determined as the upper boundary of pore
sizes of which 50% of the porosity on a thin
section composed. Half of the pore space of
an area is composed of pores as big as or
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smaller than the DOM. Whereas, Perimeter
over area (PoA) is the ratio of the sum of total
perimeter of the pores and total pore area
identified in the thin section. It describes how
complex is the porous system independent of
total porosity.
Based on further examination from outcrop,
core (polished slab) and thin section data,
eight lithofacies have been determined (Figure
1 &2). Six pore types also have been observed
which are Vuggy, Moldic, Intraparticle,
Interparticle, Channel, and Growth-Framework.
The quantitative results show that visible
porosity (Φ) varied between 1.87 – 34.7 % and
permeability (K) varied between 44.68 –
151.68 md (Table 1). Based on crossplot both
visible and measured porosity vs perm, there
is no relationship between these parameters.
DOM varied between 157 - 1100 µm2.
Crossplot of porosity vs permeability with
according to DOM values in figure 3 shows
that for a given porosity, the high DOM values
indicate the presence of large pores in the thin
section as observed in Figure 4.A, where a
grainstone facies with vuggy pore type
displays DOM 1100 µm2. At the same porosity,
the smaller value DOM, smaller pore size is
and the larger number, larger the pore size is.
The PoA varied between 75.5 - 166 mm-1.
Figure 5 shows crossplot of porosity vs
permeability with according to PoA values.
Figure 4.B shows the high PoA value, 139.5
mm-1, for a thin section of a framestone facies
with growth-framework porosity. At the same
porosity, the smaller PoA, the simpler pore
geometry is and the larger number, the more
intricate pore geometry.
V. DISCUSSION
Linkage of measured pore with visible pore
Both visible porosity and measured porosity show the different values on several samples (Figure 6). It is result of the effect of area selection for 2 cm x 2 cm thin section samples, does not represent the whole porosity characteristic of carbonate rock. The
difference value is a possibility, because on carbonate facies, the secondary porosity (eg: vuggy, moldic, and channel) are subsequently well developed on Jonggrangan Formation. Simply put, scale of observation and area selection take an important play.
Linkage of facies with porosity and permeability
Facies is known as one factor which control petrophysical values such as porosity and permeability. However the extent of facies control on porosity is constraint by several aspects. In order to prove the hypothese, the cross-plot of lithofacies toward porosity and permeability has been done (Figure 7). It shows that the lithofacies influence on porosity and permeability is not linear. Simply put, there are several samples of the same lithofacies type which possessed different petrophysical values. For example, grainstone (red symbol) present the lowest porosity and lowest permeability but the other grainstone present higher result with different value significantly. These condition, by far are controlled by diagenetic processes. A carbonate rock has its own sedimentation history both syn depositional or post depositional. The petrophysical values can be better when dissolution happen but it can be worst while recrystallization occur, such as porosity, will be enhance by dissolution process, while recrystalisation does the opposite.
Linkage of pore type with DOM and PoA
In general, grainstones with large secondary pores (vuggy) had high DOM and low PoA. Otherwise, fine grained facies which are packstones and wackestones supported by microporosity had high PoA and low DOM. Figure 8 shows a summary of these result, crossplot of DOM vs PoA plot for all thin sections analyzed and a few images of the sections indicating the respective PoA and DOM parameters.
VI. CONCLUSIONS
This study concludes that:
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Carbonate pore system is more complex than siliciclastics.
Digital image analysis method is useful to encourage and enrich carbonate petrophysical analysis concept.
The geometric DIA parameters that varied better able to quantify the differences in pore type of the thin sections study are dominant size (DOM) and perimeter of area (PoA) which could be used to identify high and low porosity.
Integration of all available data while observing carbonate pore system is a must because its vast secondary porosity development.
VII. ACKNOWLEDGEMENT
Authors would like to acknowledge to
Geological Engineering Department of UPN
“Veteran” Yogyakarta for the support and also
to Sedimentology Lab. for facilitating the
laboratory analysis.
REFERENCES Anselmetti, F.S., Luthi, S., Eberli, G.P., 1998. Quantitative Characterization of Carbonate Pore Systems
by Digital Image Analysis. AAPG Bulletin, V.82, No. 10 p. 1-15.
Castro, D.D., Rocha, P.L.F., 2013. Quantitative Parameters of Pore Types in Carbonate Rocks. Revista
Brasileira de Geofisica.
Choquette, P.W. dan Pray, L.C. 1970, Geologic Nomenclature and Classification of Porosity in
Sedimentary Carbonates. The American Association of Petroleum Geologist Bulletin, Vol. 54, No. 2,
Ferbruary, 1970. p.222 – 224.
Ditya, A., Eberli, G.P., McNeil, D., Klaus, J., 2015. Segregating Porosity-Permeability Transform Using
Velocity and Pore Structure In Carbonate Rock. Proceedings Indonesian Petroleum Association 39th
Annual Convention & Exhibition. Jakarta.
Pringgoprawiro, H and Riyanto, 1968. Geologi Regional KulonProgo. ITB, Bandung.
Ramadhan, G.C., 2013, Organism Variety Effect on Carbonate Rock Porosity of Jonggrangan
Formation: Alternative Approach To Predict Porosity Complex. MajalahGeologi Indonesia, Vol. 28, 1
April 2013. p.29-40.
Widijana, A.R.T., Latief, F.D.E., Anissofira, A., Fatkhan, Handoyo, 2015. Modelling of The Sandstone
Ngrayong Formation Using Digital Image Analysis. Proceedings Indonesian Petroleum Association
39th Annual Convention & Exhibition. Jakarta.
Zhao, L., Nasser, M., Han, D., 2013. Quantitative Geophysical Pore-Type Characterization and Its
Geological Implication in Carbonate Reservoir. European Association of Geoscientists & Engineers,
Geophysical Prospecting p. 1-15.
TABLES Table 1. The summary of analysis result
Sample
Code Lithofacies
3D Φ
(%)
Digital Image Analysis
Visible Φ (%)
Main
Pore Type
DOM (µm2)
PoA (mm-1)
Perm
(md)
Ari 1 Wackestone 5,7 15,63 Vuggy 202 144 49,98
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Ari 2 Framestone 5,07 3,44 Moldic 704 75,5 151,68
Ari 3 Packstone 3,59 8,96 Intraparticle 110 166 84
Ari 4 Framestone 3,18 22,59 Growth-Framework 366 137,5 69
Ari 5 Bafflestone 2,58 11,25 Growth-Framework 575 116.5 52,79
Ari 6 Floatstone 2,47 1,87 Intraparticle 476 136 76,55
Ari 7 Floatstone 5,1 6,28 Vuggy 353 138,75 46,29
Ari 8 Grainstone 3,16 2,50 Intraparticle 157 175 44,68
Ari 9 Marl 6,43 22,38 Interparticle 580 106,5 -
Ari 10 Packstone 6,43 13,91 Moldic 445 114,75 83,92
Ari 11 Grainstone 8,87 34,70 Vuggy 1110 105 75,43
Ari 12 Packstone 6,6 10,74 Channel 345 139,5 118,26
Ari 13 Rudstone 7,16 8,25 Intraparticle 262,5 97, 5 93,22
Ari 14 Floatstone 7,66 8,49 Intraparticle 272,5 121,5 120,56
Ari 15 Bafflestone 2,77 13,12 Interparticle 840 92,5 100,48
Ari 16 Packstone 4,94 4,87 Intraparticle 483 145,75 -
Φ: porosity; DOM: dominant pore size; PoA: perimeter over area; Perm: permeability.
FIGURES
Figure 1. (From left to right) Integration of outcrop, core (polished slab) and thin section data.
Figure 2. Core-plug sample and tools for measuring porosity analysis to support DIA result.
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Figure 3. Crossplot of porosity vs permeability with according to DOM values. The high DOM values
indicate the presence of large pore size, and lower DOM values indicate the opposite.
Lithofacies = Grainstone Main Pore Type = Vuggy Avr. Porosity = 34.7 %
DOM = 1101µm2 PoA = 105 mm-1 K = 75.43 md
Lithofacies = Framestone Main Pore Type = Growth-Framework
A
B
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Avr. Porosity = 22.59 % DOM = 366 µm2
PoA = 137.5 mm-1 K = 69 md
Lithofacies = Packstone Main Pore Type = Channel Avr. Porosity = 10.74 %
DOM = 345 µm2 PoA = 139.5 mm-1 K =118.26 md
Figure 4. Photomicrographs show three samples section of pore system (left) in which porosity is shown as blue, and digital image analysist result in BW-image (right) which porosity is shown as black and matrix is white. (A) Grainstone facies, (b) Framestone facies, and (c) Packstone facies.
Figure 5. Crossplot of porosity vs permeability with according to PoA values.
C
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Figure 6. Comparison of measured porosity values obtained from core-plug analysis and porosity
values obtained from digital image analysis for various pore type . There is no linear caused by
nonrepresentative observation area of view under optical microscope.
Figure 7. Crossplots of measured pore vs permeability (left) and visible pore vs permeability (right) for various facies. Both crossplots ilustrates that the extent of facies control on carbonate pore system is constraint by several aspect.
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Figure 8. Crossplot of dominant size (DOM) vs perimeter of area (PoA) plot for all thin sections analyzed and a few images of the sections indicating the respective DOM and PoA parameters.