Brauchler, Ralf

[["dc.bibliographiccitation.firstpage","33"],["dc.bibliographiccitation.issue","1-2"],["dc.bibliographiccitation.journal","Journal of Hydrology"],["dc.bibliographiccitation.lastpage","45"],["dc.bibliographiccitation.volume","384"],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Hu, R."],["dc.contributor.author","Vogt, T."],["dc.contributor.author","Al-Halbouni, D."],["dc.contributor.author","Heinrich, Steffen"],["dc.contributor.author","Ptak, Thomas"],["dc.contributor.author","Sauter, M."],["dc.date.accessioned","2018-11-07T08:44:03Z"],["dc.date.available","2018-11-07T08:44:03Z"],["dc.date.issued","2010"],["dc.description.abstract","In this study the potential of cross-well slug interference tests for high resolution aquifer characterization of hydraulic heterogeneity was assessed. The cross-well slug interference tests were performed at the research site \"Stegemuhle\", located in the Leine River valley near Gottingen, Germany. The geological composition of the subsurface, consisting mainly of 3.5 m silt and clay overlying 2.5 m sand and gravel, was determined by geophysical well logging and bore core data. To account for lateral changes a refraction seismic survey was conducted. Based on these data an area, characterized by an aquifer thickness of approximately 2 m and an average hydraulic conductivity of 5.0 x 10(-4) m/s (determined by pumping tests), most appropriate for cross-well slug interference tests, was chosen. Altogether 196 cross-well slug interference tests were performed using a tomographic measurement array. The cross-well slug interference tests were evaluated using type curve analysis, which provided detailed information concerning the vertical changes of hydraulic conductivity and specific storage. To assess hydraulic strata connectivity a travel time based tomographic inversion approach was utilized. The potential of the inversion approach to determine lateral changes could be successfully demonstrated by the reconstruction of the pinch out of a high diffusivity layer close to the bottom of the aquifer. The results demonstrate that the combined evaluation of cross-well slug interference tests based on type curve analysis and travel time inversion allows for the development of a detailed model about subsurface hydraulic heterogeneity. (C) 2010 Elsevier B.V. All rights reserved."],["dc.description.sponsorship","German Research Foundation [BF3379/1-2]"],["dc.identifier.doi","10.1016/j.jhydrol.2010.01.004"],["dc.identifier.isi","000276444700004"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/20118"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","0022-1694"],["dc.title","Cross-well slug interference tests: An effective characterization method for resolving aquifer heterogeneity"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","W03531"],["dc.bibliographiccitation.journal","Water Resources Research"],["dc.bibliographiccitation.volume","48"],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Doetsch, Joerg"],["dc.contributor.author","Dietrich, P."],["dc.contributor.author","Sauter, M."],["dc.date.accessioned","2018-11-07T09:12:06Z"],["dc.date.available","2018-11-07T09:12:06Z"],["dc.date.issued","2012"],["dc.description.abstract","In this study, hydraulic and seismic tomographic measurements were used to derive a site-specific relationship between the geophysical parameter p-wave velocity and the hydraulic parameters, diffusivity and specific storage. Our field study includes diffusivity tomograms derived from hydraulic travel time tomography, specific storage tomograms, derived from hydraulic attenuation tomography, and p-wave velocity tomograms, derived from seismic tomography. The tomographic inversion was performed in all three cases with the Simultaneous Iterative Reconstruction Technique algorithm, using a ray tracing technique with curved trajectories. The experimental set up was designed such that the p-wave velocity tomogram overlaps the hydraulic tomograms by half. The experiments were performed at a well-characterized sand and gravel aquifer, located in the Leine River valley near Gottingen, Germany. Access to the shallow subsurface was provided by direct-push technology. The high spatial resolution of hydraulic and seismic tomography was exploited to derive representative site-specific relationships between the hydraulic and geophysical parameters, based on the area where geophysical and hydraulic tests were performed. The transformation of the p-wave velocities into hydraulic properties was undertaken using a k-means cluster analysis. Results demonstrate that the combination of hydraulic and geophysical tomographic data is a promising approach to improve hydrogeophysical site characterization."],["dc.description.sponsorship","German Research Foundation [BR3379/1-2]; DOE-LBNL [DE-AC02-05CH11231]"],["dc.identifier.doi","10.1029/2011WR010868"],["dc.identifier.isi","000302247700001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/26872"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Geophysical Union"],["dc.relation.issn","1944-7973"],["dc.relation.issn","0043-1397"],["dc.title","Derivation of site-specific relationships between hydraulic parameters and p-wave velocities based on hydraulic and seismic tomography"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","473"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","NEAR SURFACE GEOPHYSICS"],["dc.bibliographiccitation.lastpage","483"],["dc.bibliographiccitation.volume","11"],["dc.contributor.author","Boehm, G."],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Nieto, D. Y."],["dc.contributor.author","Baradello, L."],["dc.contributor.author","Affatato, A."],["dc.contributor.author","Sauter, M."],["dc.date.accessioned","2018-11-07T09:19:24Z"],["dc.date.available","2018-11-07T09:19:24Z"],["dc.date.issued","2013"],["dc.description.abstract","In this study the potential of combining high-resolution hydraulic tomographic and geophysical tomographic measurements to define site-specific relationships between geophysical and hydraulic parameters was investigated. We exploit the high-spatial resolution of hydraulic and geophysical tomographic images to define a representative and reliable site-specific relationship, if it exists, over an area, where geophysical and hydraulic tests are performed. The parameters involved in this study were: seismic P-wave velocity derived from seismic tomography; resistivity and electrical conductivity derived from electrical tomography (ERT); diffusivity, hydraulic conductivity and specific storage derived from hydraulic tomography. We derived a site-specific correlation function between the parameters P-wave velocity and diffusivity that shows the highest correlation of all hydraulic and geophysical parameter combinations. The transformation of the P-wave velocity field into a diffusivity field using the estimated site-specific correlation function allowed us to increase the significance of hydraulic tomographic as well as seismic tomographic measurements with respect to the spatial diffusivity distribution in the near subsurface."],["dc.identifier.doi","10.3997/1873-0604.2013034"],["dc.identifier.isi","000325784100001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/28628"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","European Assoc Geoscientists & Engineers"],["dc.relation.issn","1873-0604"],["dc.relation.issn","1569-4445"],["dc.title","A field assessment of site-specific correlations between hydraulic and geophysical parameters"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","184"],["dc.bibliographiccitation.issue","3-4"],["dc.bibliographiccitation.journal","Journal of Hydrology"],["dc.bibliographiccitation.lastpage","198"],["dc.bibliographiccitation.volume","345"],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Cheng, J.-T."],["dc.contributor.author","Dietrich, P."],["dc.contributor.author","Everett, M."],["dc.contributor.author","Johnson, Brian"],["dc.contributor.author","Liedl, Rudolf"],["dc.contributor.author","Sauter, M."],["dc.date.accessioned","2018-11-07T10:57:37Z"],["dc.date.available","2018-11-07T10:57:37Z"],["dc.date.issued","2007"],["dc.description.abstract","We present a hydraulic tomographic inversion strategy with an emphasis on the reduction of ambiguity of hydraulic travel time inversion results and the separation of the estimated diffusivity values into hydraulic conductivity and specific storage. Our tomographic inversion strategy is tested by simulated multilevel. interference slug tests in which the positions of the sources (injection ports) and the receivers (observation ports) isolated with packers are varied. Simulations include the delaying effect of wellbore storage on travel times which are quantified and shown to be of increasing importance for shorter travel distances. For the reduction of ambiguity of travel time inversion, we use the full travel time data set, as well as smaller data subsets of specified source-receiver angles. The inversion results of data subsets show different resolution characteristics and improve the reliability of the interpretation. The travel time of a pressure pulse is a function of the diffusivity of the medium between the source and receiver. Thus, it is difficult to directly derive values for hydraulic conductivity and specific storage by inverting travel times. In order to overcome this limitation, we exploit the great computational efficiency of hydraulic travel. time tomography to define the aquifer structure, which is then input into the underlying groundwater flow model MODFLOW-96. Finally, we perform a model calibration (amplitude inversion) using the automatic parameter estimator PEST, enabling us to separate diffusivity into its two components hydraulic conductivity and specific storage. (C) 2007 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.jhydrol.2007.08.011"],["dc.identifier.isi","000250884600005"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/50295"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","0022-1694"],["dc.title","An inversion strategy for hydraulic tomography: Coupling travel time and amplitude inversion"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","W03503"],["dc.bibliographiccitation.journal","Water Resources Research"],["dc.bibliographiccitation.volume","47"],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Hu, R."],["dc.contributor.author","Dietrich, P."],["dc.contributor.author","Sauter, M."],["dc.date.accessioned","2018-11-07T08:59:07Z"],["dc.date.available","2018-11-07T08:59:07Z"],["dc.date.issued","2011"],["dc.description.abstract","In this study the potential of an inversion approach based on hydraulic travel time and hydraulic attenuation tomography was assessed. Both hydraulic travel time and hydraulic attenuation tomography are based on the transformation of the transient groundwater flow equation into the eikonal equation using an asymptotic approach. The eikonal equation allows the calculation of pressure propagation and attenuation along trajectories, which is computationally efficient. The attenuation and travel time-based inversion approaches are naturally complementary: hydraulic travel times are determined by the hydraulic diffusivity, a combination of hydraulic conductivity and specific storage, whereas the attenuation is determined solely by specific storage. The potential of our hydraulic tomographical approach was investigated at a well-characterized sand and gravel aquifer located in the Leine River valley near Gottingen, Germany. The database for the hydraulic inversion consists of 392 cross-well slug interference tests performed between five wells, in which the positions of the sources (injection ports) and the receivers (observation ports), isolated with double packer systems, were varied between tests. The results have shown that the combination of hydraulic travel time and hydraulic attenuation tomography allows the reconstruction of the diffusivity and storage distribution in two and three dimensions with a resolution and accuracy superior to that possible with type curve analysis."],["dc.description.sponsorship","German Research Foundation [BR3379/1-2]"],["dc.identifier.doi","10.1029/2010WR009635"],["dc.identifier.isi","000288083200004"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/23814"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Geophysical Union"],["dc.relation.issn","0043-1397"],["dc.title","A field assessment of high-resolution aquifer characterization based on hydraulic travel time and hydraulic attenuation tomography"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","91"],["dc.bibliographiccitation.journal","International Journal of Greenhouse Gas Control"],["dc.bibliographiccitation.lastpage","106"],["dc.bibliographiccitation.volume","39"],["dc.contributor.author","Hu, Linwei"],["dc.contributor.author","Bayer, Peter"],["dc.contributor.author","Alt-Epping, Peter"],["dc.contributor.author","Tatomir, Alexandru"],["dc.contributor.author","Sauter, Martin"],["dc.contributor.author","Brauchler, Ralf"],["dc.date.accessioned","2018-11-07T09:54:00Z"],["dc.date.available","2018-11-07T09:54:00Z"],["dc.date.issued","2015"],["dc.description.abstract","A time-lapse pressure tomography inversion approach is applied to characterize the CO2 plume development in a virtual deep saline aquifer. Deep CO2 injection leads to flow properties of the mixed-phase, which vary depending on the CO2 saturation. Analogous to the crossed ray paths of a seismic tomographic experiment, pressure tomography creates streamline patterns by injecting brine prior to CO2 injection or by injecting small amounts of CO2 into the two-phase (brine and CO2) system at different depths. In a first step, the introduced pressure responses at observation locations are utilized for a computationally rapid and efficient eikonal equation based inversion to reconstruct the heterogeneity of the subsurface with diffusivity (D) tomograms. Information about the plume shape can be derived by comparing D-tomograms of the aquifer at different times. In a second step, the aquifer is subdivided into two zones of constant values of hydraulic conductivity (K) and specific storage (Ss) through a clustering approach. For the CO2 plume, mixed-phase K and Ss values are estimated by minimizing the difference between calculated and \"true\" pressure responses using a single-phase flow simulator to reduce the computing complexity. Finally, the estimated flow property is converted to gas saturation by a single-phase proxy, which represents an integrated value of the plume. This novel approach is tested first with a doublet well configuration, and it reveals a great potential of pressure tomography based concepts for characterizing and monitoring deep aquifers, as well as the evolution of a CO2 plume. Still, field-testing will be required for better assessing the applicability of this approach. (C) 2015 Elsevier Ltd. All rights reserved."],["dc.description.sponsorship","EU [309067]"],["dc.identifier.doi","10.1016/j.ijggc.2015.04.013"],["dc.identifier.isi","000358627100009"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/36448"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Sci Ltd"],["dc.relation.issn","1878-0148"],["dc.relation.issn","1750-5836"],["dc.title","Time-lapse pressure tomography for characterizing CO2 plume evolution in a deep saline aquifer"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1265"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Hydrogeology Journal"],["dc.bibliographiccitation.lastpage","1274"],["dc.bibliographiccitation.volume","21"],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Boehm, G."],["dc.contributor.author","Leven, C."],["dc.contributor.author","Dietrich, P."],["dc.contributor.author","Sauter, M."],["dc.date.accessioned","2018-11-07T09:20:47Z"],["dc.date.available","2018-11-07T09:20:47Z"],["dc.date.issued","2013"],["dc.description.abstract","A tracer tomographic laboratory study was performed with consolidated fractured rock in three-dimensional space. The investigated fractured sandstone sample was characterized by significant matrix permeability. The laboratory transport experiments were conducted using gas-flow and gas-tracer transport techniques that enable the generation of various flow-field patterns via adjustable boundary conditions within a short experimental time period. In total, 72 gas-tracer (helium) tests were performed by systematically changing the injection and monitoring configuration after each test. For the inversion of the tracer breakthrough curves an inversion scheme was applied, based on the transformation of the governing transport equation into a form of the eikonal equation. The reliability of the inversion results was assessed with singular value decomposition of the trajectory density matrix. The applied inversion technique allowed for the three-dimensional reconstruction of the interstitial velocity with a high resolution. The three-dimensional interstitial velocity distribution shows clearly that the transport is dominated by the matrix while the fractures show no apparent influence on the transport responses."],["dc.identifier.doi","10.1007/s10040-013-1006-z"],["dc.identifier.isi","000323387800007"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/28959"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Springer"],["dc.relation.issn","1431-2174"],["dc.title","A laboratory study of tracer tomography"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]