Towards a 4D database management system for geothermal projects: an example of the hydraulic data of Soultz

Transcription

1 Towards a D database management system for geothermal projects: an example of the hydraulic data of Soultz Markus Jahn, Eva Schill,2, Martin Breunig3 Introduction The experience of the Soultz geothermal project and the subsequent development of geothermal energy in the adjacent fields in the Upper Rhine Graben (URG) reveal the necessity to apply an experience and analogy based approach during exploration and exploitation. During 20 years of research, different options of exploitation for geothermal energy of the subsurface have been tested in Soultz. Three reservoirs with different initial hydraulic conditions (Table ) have been developed since 988 (e.g. Jung, 992; Gérard et al., 2006; Nami et al., 2008). Apart from differences in equilibrium temperature condition, the differences in depth of the three reservoir zones imply also differences in the ambient stress field (e.g. Tenzer et al., 992; Evans et al., 2005; Dorbath et al., 200). Table : Overview of the natural reservoir conditions and the number of stimulation operations in the three different reservoir levels (upper, intermediate and deep) at the Soultz-sous-Forets EGS site (France; Jung, 992; Jung et al., 995; Weidler, 200, Hettkamp et al., 200; Tischner et al., 2007). The reservoir levels are indicated as follows: I: upper, II: intermediate, III: deep. The vertical extension of the reservoir has been determined by the extension of the seismic clouds. Reservoir Depth (m) Temperature ( C) I II (GPK2) II (GPK) III (GPK2) III (GPK3) III (GPK) Productivity or injectivity Number of hydraulic before stimulation stimulations (m3 Pa- s-) (in 5097m) 0-0 Number of chemical stimulations The intense experience in hydraulic and chemical stimulation from Soultz has been transferred to projects in the adjacent geothermal fields such as Landau. A comparison between the stimulation in the deep reservoir and the reservoir in Landau (corresponding geologically to the upper, topcrystalline and from a point of view of depth to the intermediate reservoir of Soultz) reveals an improvement in stimulation technology (Schindler et al., 200). With the stimulation of the first well in Rittershofen, also the upper reservoir is coming to the fore. Université de Strasbourg, EOST, 5 rue René Descartes, F-6708 Strasbourg Cedex, France 2 GEIE "Exploitation Minière de la Chaleur", Route de Soultz - BP 0038, F Kutzenhausen, France 3 Karlsruhe Institut für Technologie KIT, Geodätisches Institut, Englerstraße 7, D-7633 Karlsruhe, Germany

2 With this in mind, recently, there is a strong interest to save and make available the scientific results from the Soultz project, since it serves as reference for the development of the URG. From a of computer sciences point of view there are several reasons to store data in a database: A database avoids redundancy and inconsistency of the data as well as high development costs for data loss. It provides data integrity automatically checked during the insertion and update of the data as well as multiple users access with security rights. Furthermore, it does not limit the possibility of linking data (REF). This approach can achieve a great deal considering the scientific productivity on geothermal data for the future. 2 Conceptual database schema of hydraulic data If possible, geothermal spatial data should be managed in a standardized way. To be compatible with today s geo-databases, we propose to use for simple geometries the General-Feature-Model which extends the Simple-Feature-Model of the Open Geospatial Consortium (OGC) among other things - by the temporal dimension and related operations. This specification which has already become an ISO standard seems to be very suitable for mapping geothermal primary data into a database representation. Geometries n n2 Temperatures Pressures m Times belongs to n3 Flowrates m2 n m3 m belongs to Figure : Conceptual database schema as Enitiy Relationship Model By a feature we mean a real-world object with a certain geometry and a series of thematic attributes. Figure shows a first draft of the conceptual database schema for hydraulic data represented as Entity Relationship Model (ERM). The real world object (feature) e.g. could be - in connection with hydraulic data - a measuring device with a unique geometry or location and the corresponding measured data which were recorded over a specific period of time at predetermined time points. For hydraulic data only simple geometries are needed such as points which define the locations of the measuring devices. The trajectories of the wells can also be defined as polylines. Furthermore, the ISO standard (ISO 907 or ISO 909) provides certain 3D operations for single geometries. A typical operation would be to calculate distances or intersections with other geometries or geometry specific attributes such as the bounding box, length or volume. Other spatial operations are given in accordance with this standard. The measurements of a measuring device can be divided into two tables. Not only one time point, but a whole time series is stored per record. An example is the series of temperature values. The intrinsic time points are also summarized in an equally long series of time values. If e.g. the Temperatures, Pressures and some Flow rates are measured synchronously, they are referenced to the same time series in the Times table and the specific geometry in the Geometries table. This structural concept is a simple workaround to manage D geo-objects in a 3D plus nd environment. A proper D management is desirable, because real D operations on complex geometries including 3D spatial operations during time intervals could significantly support the analysis of geothermal data.

3 3 Database oriented software architecture for geothermal projects To support full spatio-temporal data availability in geothermal projects over decades, geo-scientific tools (see blue box in figure 2) should have direct access to a D geo database management system (see red box in figure 2). In a first approach, the object-relational geo database management system PostGIS is used managing time series as records in the DBMS. In future, it should be examined if an object-oriented geo database management system with D operations such as DBGeO (Breunig et al. 200, Breunig et al. 203a; 203b) could be used in addition for special D operations on complex D geometric data types such as simplicial complexes (triangle and tetrahedron networks). Project Geo service layer Client Geoscientific Tools At the top level of Figure 2 the geo-scientific tools that have been used in the Soultz project over the years by the researchers are summarized. Besides software such as GOCAD, Petrol, WellCad, Tough 2, ArcGIS, Quantum GIS or ParaView, some tools have been developed from the scratch. Each software imports and exports different types of data formats, but internally it is mostly using its own data format. A two-layer model should be preferred in which a geoscientific tool has its own client as a part of itself which can D Geo DBMS connect directly to the geo database. On the basis of its own internal data structure it then is able to interpret and integrate the results of database queries. It has a number of advantages if Figure 2: Database oriented a geo-scientific tool can connect directly to a data base software architecture especially concerning data synchronization. The geo-scientific tool can then be viewed as a client of the database. Because the number of geo-scientific tools is high, it is assumed that not every software developer will program its own client. If the database does not provide specific functionalities for synchronization with these tools, the data formats have to be converted for import and export and the specific services of the database have to be made available in an intermediate step as well. The middle layer summarizes these services as a user interface to the database. The functionalities of this layer should be kept as thin as possible to be executable on different systems without major adjustments. Furthermore, special database queries can be provided to query some basic geothermal secondary data. The lower layer in the proposed architecture is the D geo database management system (D Geo DBMS). Specific requirements have to be complied with the Geo DBMS to enable efficient geothermal data handling. The Geo DBMS should support spatio-temporal geo-objects right from the beginning, because most of the geothermal data are spatially and temporally referenced. Spatial access methods such as the R*-Tree (Beckmann et al. 990) and efficient geometric algorithms such as sweep-algorithms can then be used to index, edit or access this kind of data. Furthermore, the structure of the data should be easily comprehensible to every scientist. I.e. at the conceptual level of data abstraction, those real-world contexts and entities should be relocated that are known in as many scientific fields as involved. 3. Prototypical implementation To be compatible with today s geo-databases, the prototypical database implementation uses for simple geometry types such as points and lines - standardized geometry objects of the Open Geospatial Consortium (OGC). OGC s Simple-Feature-Model is pursued by PostGIS, an extension of PostgreSQL object-relational database management system that communicates with ParaView via OpenJUMP, an easy-to-use GIS, which uses the Java-Topology-Suite (JTS) as its topology and geometry core. The spatial object types from PostGIS and JTS are largely ISO compliant, thus they are compatible and also bring some geometric calculations with them. For these reasons and the

4 straight forward ability to extend those open source products by new requirements of geothermal projects, the choice was made to use PostGIS and OpenJUMP. Figure 3 shows the location of wells at Soultz site managed by PostGIS and visualized by ParaView via the Open JUMP connection. To make some spatial and temporal analysis, this first approach is also well suited. However, for complex geometry types an extension is required, because most high-performance simulation as well as visualization tools use complex geometries such as simplicial complexes rather than simple geometric features. Conclusion and outlook From a scientific point of view, the advantage of the Soultz project over many other EGS projects is the large amount of data acquired in 20 years of research. This quantity of data among others, allows for benchmarking investigations on a number of different reservoir relevant processes. The number of experiments carried out and their diversity in terms of experimental conditions require advanced database queries. Thus, besides hydraulic data, other types of primary data will be integrated to complete the benefit of geo database management systems by linking data. Figure 3: Wells at Soultz site colored by depth, imported to PostGIS and exported to ParaView via the use of OpenJUMP and its PlugIn architecture The technical state currently offers only a spatial data management with standardized simple feature geometries. It is desirable to extend this approach to a D Geo DBMS based on simplicial complexes to perform complex and efficient spatio-temporal operations. Database tn dataset t t n+k dataset Due to the above mentioned diversity of the Simulation experimental set-up, besides the coupling of GIS and 3D/D modeling and visualization tools, certain simulation techniques shall be starting conditions offered as services of the geo database. In this way, the comparison between simulation data and field data (Figure ) would be simplified, if both kind of data would be defined with specific and known conceptual schemes to be managed in one system, only. Thus, no complex data conversions between simulation software and database would be needed and the simulation results could also resultset be made available online. Figure : Comparison of monitored field data and simulation data

5 References Beckmann, N., Kriegel, H.-P., Schneider, R., Seeger, B., 990. The R*-tree: An efficient and robust access method for points and rectangles. Proceedings ACM SIGMOD, Atlantic City, N.Y., Breunig, M., 200. On the way to Component-Based 3D/D Geoinformation Systems. Lecture Notes in Earth Sciences, No. 9, Springer, Heidelberg, 200p. Breunig, M., Schilberg, B., Thomsen, A., Kuper, P.V., Jahn, M., Butwilowski, E., 200. DBGeO, a 3D/D Geodatabase and its Application for the analysis of landslides. Geographic Information and Cartography for Risk and Crisis Management. Lecture Notes in Geoinformation and Cartography, Springer, Breunig, M., Butwilowski, E., Golovko, D., Kuper, P.V., Menninghaus, M., Thomsen, A., 202. Advancing DBGeO. Progress and New Trends in 3D Geoinformation Sciences, Lecture Notes in Geoinformation and Cartography, Springer, Breunig, M., Butwilowski, E., Kuper, P.V., Golovko, D., Thomsen, A., 203. Topological and Geometric Data Handling for Time-Dependent Geo-Objects Realized in DBGeO. Advances in Spatial Data Handling, Lecture Notes in Geoinformation and Cartographpy, Springer, -3. Dorbath, L., Evans, K., Cuenot, N., Valley, B., Charléthy, J., Frogneux, M., 200. The stress field at Soultzsous-Forêts from focal mechanisms of induced seismic events: Cases of the wells GPK2 and GPK3. C. R. Geoscience (200), doi:0.06/j.crte Evans, K., Moriya, H., Niitsuma, H., Jones, R.H., Phillips, W.S., Genter, A., Sausse, J., Jung, R., Baria, R Microseismicity and permeability enhancement of hydrogeologic structures during massive fluid injections into granite at 3 km depth at the Soultz HDR site. Geophys. J. Int., 60, 388 2, doi: 0./j X x. Gérard, A., Kohl T., Lutz Ph., Rose P., Rummel F., The deep EGS (Enhanced Geothermal System) project at Soultz-sous-Forêts (Alsace, France). Geothermics, 35, Hettkamp, T., Baumgärtner, J., Baria, R., Gérard, A., Gandy, T., Michelet, S., Deza, D., 200. Electricity production from hot rocks. Twenty-ninth Workshop on Geothermal Reservoir Engineering: Proceedings, Stanford University, Stanford, CA, January 26-28, 200 Jung, R Connecting a borehole to a nearby fault by means of hydraulic fracturing. GRC Transaction, 6, Jung, R., Willis-Richard, J., Nicholls, J., Bertozzi, A., Heinemann, B., 995. Evaluation of hydraulic tests at Soultz-sous-Forêts, European HDR Site. In: Proceedings of the World Geothermal Congress, 995, Florence, Italy, International Geothermal Association,, Nami, P., Schellschmidt, R., Schindler, M., Tischner, T., Chemical stimulation operations for reservoir development of the deep crystalline HDR/EGS system at Soultz-sous-Forêts (France). Thirty-third Workshop on Geothermal Reservoir Engineering: Proceedings, Stanford University, Stanford, CA, January 28-30, Schindler, M., Baumgärtner, J., Gandy, T., Hauffe, P., Hettkamp, T, Menzel, H., Penzkofer, P., Teza, D., Tischner, T., Wahl, G., 200. Successful Hydraulic Stimulation Techniques for Electric Power Production in the Upper Rhine Graben, Central Europe. Proceedings World Geothermal Congress 200 Bali, Indonesia, April 200 Tenzer, H., Mastin, L., Reinemann, B., 992. Determination of planar discontinuities and borehole geometry in the crystalline rock of borehole GPK- at Soultz-sous-Forêts. In Bresse, J.C., Geothermal enery in Europe: the Soultz Hot Dry Rock project, Gordon and Breach Science Publishers SA. Montreux, Switzerland, p Tischner, T., Schindler, M., Jung, R., Nami, P., HDR project Soultz: hydraulic and seismic observations during stimulation of the three deep wells by massive water injections. Thirty-second Workshop on Geothermal Reservoir Engineering: Proceedings, Stanford University, Stanford, CA, January 22-2, 2007 Weidler, R., 200. Slug test in the non-stimulated 5 km deeep well GPK2, Internal BGR report, Hannover, Germany.