Available online at ScienceDirect. Energy Procedia 63 (2014 ) GHGT-12

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1 Available online at ScienceDirect Energy Procedia 63 (214 ) GHGT-12 Potential Evaluation of CO2 Reservoir Using the Measured Petrophysical Parameter of Rock Samples in the Gundih CCS Project, Indonesia Keigo Kitamura a *, Yasuhiro Yamada b, Kyosuke Onishi c, Takeshi Tsuji a, Shun Chiyonobu c, Benyamin Sapiie d, Alfian Bahar d, Harya Danio d, Algifari Muhammad d, Aurio Erdi d Vani Mutia Sari d Toshifumi Matsuoka b, Wawan Gunawan A. Kadir d, Gundih CCS project team a WPI-I2CNER, Kyushu University, 744 Motooka, Nishi-ku, Fukuok, , Japan b Dept. of Civil and Erath Resources Engineering, Kyoto University, Kyotodaigaku Katsura, Nishikyo-ku, Kyoto, , Japan c Faculty of International Resource Sciences, Akita University, 1-1 Tegatagakuen-cho. Akita, Akita, Japan d Institut Teknologi Bandung, 1 Jalan Ganesa, Bundung, 4132, Indonesia Abstract Click here and insert your abstract text. Physical properties of reservoir and seal-layer samples are essential information to evaluate the storage and seal potential and to predict long term CO 2 behaviour in reservoir. In this study, we measure the elastic wave velocities (V p and V s ), porosity and density of sandstone, limestone and lime-mudstone samples are measured of Ngrayong Fm. and Bulu Fm, Central Java, Indonesia. The sandstones indicate low V p, V s, density and high porosity. These results suggest that sandstones on Ngrayong Fm. have large porosity and became important candidate of CO 2 reservoir. On the other hand, limemudstone indicates high velocities with low porosity and point out that they have enough potential to be sealing layer of injected CO The The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. This is an open access article under the CC BY-NC-ND license ( Selection and peer-review under responsibility of GHGT. Peer-review under responsibility of the Organizing Committee of GHGT-12 Keywords: Gundhi CCS project; Phisycal parameter of rock; ; Lime-mud stone, Storage potential * Corresponding author. Tel.: ; fax: address: kitamura@i2cner.kyushu-u.ac.jp The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( Peer-review under responsibility of the Organizing Committee of GHGT-12 doi:1.116/j.egypro

2 4966 Keigo Kitamura et al. / Energy Procedia 63 ( 214 ) Introduction The first pilot-scale CCS project in Indonesia has been done at Gundih Area in Central Java. This pilot project is conducted as an international collaboration research between Japan and Indonesia. This gas field located in the East Java Basin and accompanies rich CO 2, which is more 2% of total gas volume. Produced CO2 is now diffused to open air at this moment. In this project, we plan to inject CO 2, separated from the produced gas, into underground sand layers near the production site [1]. In this study, we characterized reservoirs of the Gundih gas field using seismic data and applied reservoir simulation in order to evaluate the potential and security of CO 2 injection site. 2. Geological setting The target geological formation of CO 2 injection is the Ngrayong formation, consists of shelf to hemipelagic sediments in middle Miocene. The Ngrayong formation is divided into three units, Unit-I, Unit-II and Unit-III (Fig.1). Unit-I and Unit-II represent a facies-change within the lower regressive part of the Ngrayong formation. Unit-I comprises cross-bedded sandstone inter-bedded with mudstone and thin limestone. Unit-II is composed Unit-I equivalent sediment including sandy turbidites and hemipelagic mud. These lower two-units are candidates for the major CO 2 reservoir. Unit-III represents the upper transgressive part of the formation and overlies the other two units. Unit-III comprises sandy turbidites, hemipelagic muds and contourites. The Ngrayong formation is overlaid by the Bulu formation (or Wonocolo formation), which mainly consists of upper massive limestone and lower calcareous silty sediments and this formation is expected as a seal layer Fig.1 Deposiinal model of Ngrayong Formation [2] 3. Sample description and Procedures We conduct a drilling campaign to obtain rock samples from the Ngrayong and the Bulu formations. The core samples from the upper Ngrayong and the Bulu formations were corrected from two drilling wells of 7 m deep Density (kg/cm 3 ) Fig.2 Relation ship between density and porosity

3 Keigo Kitamura et al. / Energy Procedia 63 ( 214 ) each, which is composed of sandstone, siltstone, and limestone. Unfortunately, no rock sample from the lower Ngrayong was obtained by drilling. In this study, we dived the sample lithology into four groups. The limestone samples are devided into lime-mud to wackestone (hereafter lime-mudstone) and bioclastic grainstone (limestone). The sandstone group contain following three rock types; fine sandstone, very fine sandstone and sandy siltstone. Siltstone and mudstone are grouped mudstone. In this study, we measure porosity, density and elastic wave velocities to estimate the storage potential of Ngrayong formation and seal-potential of upper layers. Samples are cut in cylindrical shape for 25 mm in diameter and 25-4 mm in length and oven dried over 12h. After these processes, we measure dry weight of samples. Density and porosity are measured by Nitrogen adsorption using posimeter (PORG-2TM,Core Laboratories L.P) in the Peterophysics and formation evaluation laboratory, ITB. We measure these parameters of 99 sampleplugs. We also measured V p and V s of these sample plugs by using pulse transmission methods under dry, room temperature and atmospheric pressure conditions at ITB. In this study, we use transducers with different resonant frequency, 63kHz for V p and 1MHz for V s, respectively. We succeed in the measurements of 58 V p data and 36 V s data under above-mentioned conditions a) V p b) V s Density (kg/cm 3 ) Fig.3 Relationships between density and a)v p, and b)v s

4 4968 Keigo Kitamura et al. / Energy Procedia 63 ( 214 ) Results Figure 2 illustrates the relationship between density and porosity of all sample plugs. They indicate roughly negative linear relations. samples show a cluster distribution in range of kg/cm3 and 2-48 % of porosity. On the other hand, limestone samples indicate negative linear relation clearly. samples indicate extreme low porosity (under 1%) and high density. On the other hand, siltstone does not show clear differences against sandstone. a) V p b) V s Fig.4 Relationships between porosity and a)v p, and b)v s Figure 3 shows relationships between density and elastic wave velocities (Fig. 3a for V p and 3b for V s ). Both of V p and V s have roughly positive relation with density. and indicate clear relation but sandstone dose not show clear relations. Figure 4a indicates more clear relationship between V p and porosity. V p of limestone and lime-mud show

5 Keigo Kitamura et al. / Energy Procedia 63 ( 214 ) negative correlation with porosity. On the other hand, V p of sandstone looks like that they have no correlation with porosity. There are same relation between V s and porosity (Fig.4b). We are able to confirm the clearer relation than V p. These measurements result indicates that sandstone samples are unconsolidated or too loose consolidated and over the critical porosity [3]. 5. Discussion and summary The results of V p and V s measurement of drilling samples from Well-A indicate large contrast between limemudstone and others in every physical properties. The results of porosity and density measurements also show similar trends between limestone, mudstone and sandstone (Fig.5a). This may be because upper Ngrayong samples are mainly composed sandstone. On the other hand, measured physical parameters of Well-B are mostly constant, because they are almost sandstone of the upper Ngrayong (Fig. 5b). There are several lime-mudstone samples, which indicate low-porosity, high density and high velocities in both wells. We can identify those inter-bedded limemudstone by all physical properties. We also point out that V p -V s plot is useful parameter to identify the lithology of samples (Fig. 6)., limestone and lime-mudstone are clearly divided by elastic wave velocities. a) Well-A 1 2 Depth (m) Density (kg/m 3 ) Acoustic Impedance (x1 3 kg/m 2 s) b) Well-B Depth (m) Density (kg/m 3 ) Acoustic Impedance (x1 3 kg/m 2 s) Fig.5 Physical properties profile of Both-Wells, a) Well-A and b) well-b

6 497 Keigo Kitamura et al. / Energy Procedia 63 ( 214 ) These results indicated that the upper Ngrayong has a potential to be CO 2 reservoir and the Bulu is a candidate of seal layer. These results also suggest that the inter-bedded lime-mudstone of upper Ngrayong has a capability to be a sub-seal layer Fig.6 Relation ship between V p and V s Acknowledgements We acknowledge support of the SATREPS project by JICA-JST. Kitamura and T. Tsuji also thank WPI - I2CNER of Kyushu University for their helps. We would like to express special thanks to Mr. Isamu Kuboki for his devoted helps during our research activity in Indonesia. References [[1] Takeshi Tsuji, Toshifumi Matsuoka, Wawan Gunawan A. Kadir, Masami Hato, Toru Takahashi, Mohammad Rachmat Sule, Keigo Kitamura, Yasuhiro Yamada, Kyosuke Onishi, Djedi S. Widarto, Rio I. Sebayang, Agung Prasetyo, Awali Priyono, Tutuka Ariadji, Benyamin Sapiie, Eko Widianto, Ariesty Ratna Asikin, and Gundih CCS project team, Reservoir characterization and simulation for site selection in the Gundih CCS project, Indonesia, Energy Procedia, submitted. [2] Ardhana, W. A depositional model for the early middle Miocene Ngrayong Formation and implication for exploration in the East Java Basin, Proceedings Indonesian petroleum association, 22 nd Annual convention, 1993, IPA [3] Nur, A., G. Mavko, J. Dvorkin and D. Galmudi. Critical porosity: A key to relating physical properties to porosity in rocks. The Leading Edge 1998,