Available online at ScienceDirect. Energy Procedia 114 (2017 )

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1 Available online at ScienceDirect Energy Procedia 114 (2017 ) th International Conference on Greenhouse Gas Control Technologies, GHGT-13, November 2016, Lausanne, Switzerland 3D geological model of potential CO 2 storage: Abandoned oil and gas field LBr-1in the Vienna basin Juraj Francu a *, Miroslav Pereszlényi a, Fridtjof Riis a a a, a a a Czech Geological Survey, Leitnerova 22, Brno, Czech Republic b International Research Institute of Stavanger, Prof. Olav Hanssensvei 15, 4021 Stavanger, Norway Abstract Successful CO2 storage in abandoned oil and gas fields, building the underground gas storages, and enhanced oil and gas recovery require a functional 3D static geological model of the storage complex with the real geometry and conditions. Abandoned oil and gas field Lanzhot- preparation of a pilot research project of the geological CO2 storage. It is situated in the Northern part of the Vienna Basin, close to the Czech- -model includes a separate northern part of the LBr1 field. The 3D model is designed to serve possible to experiment and test simulations of the CO2 storage in a more-or-less real geological environment. The model documents areal and vertical extent of the storage complex, geological structure formed by the Lab reservoir horizon, trap seal built by the overlying clays, overlying and adjacent strata, aquifers, faults, natural and artificial migration paths. Further information provided by the model consists of the reservoir volume, pore space, reservoir properties, fluid distribution, and saturation by the pore fluids. A simplified 3D-model of the reservoir overburden offers a basis 2017 The Authors. Published by by Elsevier Elsevier Ltd. Ltd. This is an open access article under the CC BY-NC-ND license ( Peer-review under responsibility of the organizing committee of GHGT-13. Peer-review under responsibility of the organizing committee of GHGT-13. Keywords: 3D model; CO 2 storage; well log analysis, seismics, porosity, permeability, storage capacity * Corresponding author. Tel.: ; fax: address: juraj.francu@geology.cz 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-13. doi: /j.egypro

2 Juraj Francu et al. / Energy Procedia 114 ( 2017 ) Introduction Vienna Basin is one of the most mature areas in the Central Europe in terms of the oil and gas exploration. During the past hundred years, over deep wells have been drilled in the Czech part of the Vienna basin and more gas fields were discovered, from which 3.9 million tons of oil and 3 billion m3 of gas have been recovered. The suitable ones were converted to underground gas storages. Existence of smaller and medium-sized depleted oil and gas fields raised the question whether they would be suitable for CO 2 geological storage and whether the storage can possibly be combined with CO 2 -driven enhanced oil recovery (EOR). The Czech-Norwegian REPP-CO 2 research project provides an excellent opportunity to evaluate jointly one of the depleted oil and gas fields - LBr-1, where exploration and exploitation was carried out in the 1960s 1970s (Fig.1). Fig. 1 Position of the abandoned oil and gas field LBr-1in the Northern Vienna basin. Here the 3D geological model of the LBr-1 site is discussed more in detail as a basis for assessment of site ed to the integration of the old well and other disseminated archive data with results arising from new 3D seismic survey interpretation. The process of building the 3D geological model is shown in Fig. 2. Fig. 2 Step by step process of building the static geological model

3 2774 Juraj Francu et al. / Energy Procedia 114 ( 2017 ) Interpretation of well and seismic data The model is built based on analysis and reinterpretation of 51 well logs measured prior to 1971 and their integration with rather up to date 3D seismic survey of The target LBr-1 reservoir, the so-called Lab horizon of Middle Badenian age, is a typical oil and gas bearing horizon in smaller reservoirs in the Vienna Basin. It consists of a sandstone layer with variable petrophysical properties, which is intercalated by thin shaly interlayers (Fig. 3). Fig. 3 WSW-ENE cross section with SP and RAG2 (resistivity) well logs: 1 - Middle Badenian shale seal, 3 Lab horizon, the major reservoir, and 4 - pinch-out of the sands (5). The Spontaneous potential (SP) and apparent resistivity (RAG2) were the only available archival well log data. The SP curves were used in separation of shale and sandstone bodies and in the mutual correlations of the lithological well profiles. First, the stratigraphic boundaries were used from the archival reports [1, 2 3]. Later, they were revised and adapted in order to best represent the vertical and lateral facies distribution in the LBr-1 (Fig. 3 and t in this area. That is why the integration of the well log and seismic data in time and depth domains were based on data from the neighboring fields. An example of a seismic line coupled with the well logs is in Fig. 4. It shows 3 well logs, Midle Badenian Lab reservoir pinchout toward NE overlain by logs converted from depth to TWT. Several additional sedimentological phenomena were identified in the seismic potential unconformity at the Sarmatian/Badenian boundary, and an incised channel in the Lower Sarmatian. Gradual downdip pinchout occurs in the Middle Sarmatian, i.e. oposit direction to the middle Badenian sand bodies.

4 Juraj Francu et al. / Energy Procedia 114 ( 2017 ) Fig. 4 Integration of seismic and well log data 3. Mapping horizons The Lab horizon was divided into 4 partial reservoirs L1, L2, L3, and L4 (Fig. 5). For each of them a surface map was constructed based on the interpreted data together with the base of L4, i.e. the base of the M. Badenian or top of L. Badenian shales. The storage complex is completed with a map of top of the M. Badenian seal (Fig. 6). Detailed mapping of the lateral and vertical extent of potential storage complex resulted in a 3D model of a 30 m rvoir, overlain by a 30-. A clay seal of the Middle Badenian Fig. 5 Detailed well log correlation: 1 - M. Badenian seal and L1-L4 partial layers of the Lab horizon, and 3 L. Badenian shales.

5 2776 Juraj Francu et al. / Energy Procedia 114 ( 2017 ) Fig. 6 3D model of the Lab horizon: TMB top of M. Badenian seal, L1-L4 partial layer tops, TLB top of L. Badenian, i.e. base of the Lab horizon. 4. Analysis and modelling of faults Faults and their shapes are visible in the seismic lines as abrupt termination and change in the dip of the reflections. Clear N-S fault system was identified with through of m, which fades towards N and S. Fig. 7

6 Juraj Francu et al. / Energy Procedia 114 ( 2017 ) Litho-facial analysis and seismic attributes Application of seismic attribute analysis (Fig. 7) made it possible to visualize more details in the architecture of average absolute amplitude shows the probable initial extent of the oil and gas field (Fig. 8). The reason is interpreted as residual hydrocarbon saturation of the reservoir. 6. Petrophysical properties Fig. 8 Average absolute amplitude of the Lab horizon. Because there practically no lab petrophysical analytical data of the core samples, the well log data were used to calculate the porosity and permeability. They served as basis for construction of porosity and permeability maps of the Lab horizon (Fig. 9). Fig. 9 3D model of the storage complex: permeability in the partial L1-L4 layers of the Lab horizon. Impermeable shale is shown in purple.

7 2778 Juraj Francu et al. / Energy Procedia 114 ( 2017 ) Formation water geochemistry and zonation Formation waters from the well tests were analyzed for chemical composition. The total dissolved solids (TDS) characterize the changes in depositional environment of the entire sedimentary profile of the LBr-1 field (Fig.10 and 11). The TDS values decrease from the M. Badenian upwards to the Sarmatian as the marine conditions evolved to more lacustrian. Simi - Fig. 10 Total dissolved solids of the formation waters of the LBr-1. Fig. 10 Hydrogeochemical

8 Juraj Francu et al. / Energy Procedia 114 ( 2017 ) Reserves estimation based on the 3D model Depth of reservoir below surface from 1062 m to 1115 m Porosity up to 28 %, average 20 % Permeability up to 500 md, average 250 md up to 30 m up to 15 m Initial reservoir pressure 12.5 MPa, slight overpressure Recent reservoir pressure 10.1 MPa, practically more or less hydrostatic Reservoir temperature +42 C Total dissolved solids of reservoir water 13 g.l -1 Oil/ water contact -953 m b.s.l. Gas/ oil contact -943 m b.s.l. Number of wells in the reservoir 26. An updated reserves estimation according to the 3D model of the LBr-1 storage complex provides the following values shown in Fig. 11a. For comparison the archival estimated values [3] are shown in Fig 11b and the really recovered oil and gas in Fig. 11c. Fig. 11 Reserves estimation of the LBr-1: a results according to the 3D model, b archival estimation of 1960 [3], c really recovered oil and gas. The initial extent of the gas cap, oil zone, and aquifer together with the present gas cap are shown in Fig. 12. In the vicinity of the N and NE pinchout zones the partial layers of the Lab horizon are vertically interconnected. For this reason the gas/oil and oil/water contacts are equal in all partial layers. The pinchout of the partial layers has is rather complex and is shown by purple lines in Fig. 12. Potential spill point is probable close to the northern end of the oil zone in the LBr-1 field.

9 2780 Juraj Francu et al. / Energy Procedia 114 ( 2017 ) Conclusions Fig. 12 Areal extent of initial and present gas cap, initial oil zone, and aquifer in the partial layers of the Lab horizon. Small reserves, complex lithology, variable petrophysical properties and narrow elongated shape of the reservoir are not favourable for conversion of the LBr-1 reservoir to an economic underground natural gas storage. On the other hand, the geological 3D model suggests use of the LBr-1 North as a suitable CO 2 geological storage pilot. The interpreted small- low. Potential spill points are identified; they represent 2 injection, determining the maximum quantity of possibly stored CO 2. The geological structure itself does not contain require more attention. Acknowledgements The REPP-CO2 project is supported by the CZ08 Programme of Norway Grants given to MND a.s. for provision of LBr-1 archive site data. References [1] [2] an -North field and future possibilities of the field usage. MS Archive MND Hodonín; 1998 (in Czech). [3] Šelle M., Nemec F., i 1960 Reserves estimation. MS, Archive MND Hodonin; 1960.