Brauchler, Ralf

[["dc.bibliographiccitation.firstpage","2013"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Water Resources Research"],["dc.bibliographiccitation.lastpage","2024"],["dc.bibliographiccitation.volume","49"],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Hu, R."],["dc.contributor.author","Hu, Lening"],["dc.contributor.author","Jimenez, S."],["dc.contributor.author","Bayer, Peter"],["dc.contributor.author","Dietrich, P."],["dc.contributor.author","Ptak, Thomas"],["dc.date.accessioned","2018-11-07T09:26:16Z"],["dc.date.available","2018-11-07T09:26:16Z"],["dc.date.issued","2013"],["dc.description.abstract","A new framework is introduced for hydraulic tomography application and validation in the field. Our motivation is the need for methods that are both efficient and expressive for resolving the spatial distribution of heterogeneous hydraulic properties in aquifers. The presented strategy involves time-efficient field experiments and a computationally efficient inversion scheme. By exploiting the early travel time diagnostics of the hydraulic pressure pulses recorded during tomographic cross-well tests, and new application of attenuation inversion, only short-term pumping tests are required. Many of these can be conducted in one day. The procedure is developed by a numerical experiment with a highly heterogeneous aquifer analogue and then applied to a field case with a shallow, unconsolidated sedimentary aquifer, the Stegemuhle site in Germany. It is demonstrated that the performance of a suite of tomographic short-term pumping tests, data processing and inversion for the reconstruction of heterogeneous diffusivity and specific storage distribution is possible within one day. Additionally, direct-push injection logging is performed at the field site, and the obtained field data is utilized for successful validation of the hydraulic tomograms. We also compare both methods with respect to the necessary requirements, time demand in the field and complexity of interpretation."],["dc.identifier.doi","10.1002/wrcr.20181"],["dc.identifier.isi","000319282100018"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/30265"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Geophysical Union"],["dc.relation.issn","0043-1397"],["dc.title","Rapid field application of hydraulic tomography for resolving aquifer heterogeneity in unconsolidated sediments"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","350"],["dc.bibliographiccitation.issue","1-2"],["dc.bibliographiccitation.journal","Journal of Hydrology"],["dc.bibliographiccitation.lastpage","362"],["dc.bibliographiccitation.volume","409"],["dc.contributor.author","Hu, R."],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Herold, Maria"],["dc.contributor.author","Bayer, Peter"],["dc.date.accessioned","2018-11-07T08:50:36Z"],["dc.date.available","2018-11-07T08:50:36Z"],["dc.date.issued","2011"],["dc.description.abstract","Travel time and steady shape inversions are complementary methods for tomographic aquifer characterization. In this work, a combined procedure is presented that facilitates determination of spatial hydraulic conductivity and specific storage distributions in heterogeneous groundwater systems. The procedure is applied to a highly heterogeneous sedimentary aquifer analog that is implemented as a two- and three-dimensional case study in a numerical flow model. By interpreting the observations from multiple simulated short-term pumping tests, the main hydraulic features of the analog are successfully reconstructed. The final results demonstrate the encouraging potential of the combined procedure for identifying the dominant structural elements and composition of sedimentary aquifers. However, limits derived from the test design of hydraulic travel time tomography in our synthetic case study prevented us from resolving small scale (10 cm in size) variability of hydraulic conductivity with high discrepancies (up to 5 orders of magnitude). A better reconstruction of the aquifer hydraulic parameters is expected by utilizing a larger amount of measurements, which involve more test and observation intervals, although such a test design would be less feasible for field applications. Still, this newly combined scheme is very attractive for an up-scaled reconstruction on the sub-meter scale. For the present case study, representative parameter values could be estimated in a computationally efficient way. (C) 2011 Elsevier B.V. All rights reserved."],["dc.description.sponsorship","German Research Foundation [BR3379/1-2]"],["dc.identifier.doi","10.1016/j.jhydrol.2011.08.031"],["dc.identifier.isi","000296601600030"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/21733"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","0022-1694"],["dc.title","Hydraulic tomography analog outcrop study: Combining travel time and steady shape inversion"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","5504"],["dc.bibliographiccitation.issue","7"],["dc.bibliographiccitation.journal","Water Resources Research"],["dc.bibliographiccitation.lastpage","5520"],["dc.bibliographiccitation.volume","51"],["dc.contributor.author","Jimenez, S."],["dc.contributor.author","Brauchler, R."],["dc.contributor.author","Hu, R."],["dc.contributor.author","Hu, Lening"],["dc.contributor.author","Schmidt, S."],["dc.contributor.author","Ptak, Thomas"],["dc.contributor.author","Bayer, Peter"],["dc.date.accessioned","2018-11-07T09:54:55Z"],["dc.date.available","2018-11-07T09:54:55Z"],["dc.date.issued","2015"],["dc.description.abstract","A sequential procedure of hydraulic tomographical inversion is applied to characterize at high resolution the spatial heterogeneity of hydraulic conductivity and specific storage at the field test site Stegemuhle, Germany. The shallow aquifer at this site is examined by five short-term multilevel pumping tests with 30 pumping-observation pairs between two wells. Utilizing travel time diagnostics of the recorded pressure response curves, fast eikonal-based inversion is shown to deliver insight into the sedimentary structures. Thus, the structural information from the generated travel time tomogram is exploited to constrain full calibration of the pressure response curves. Based on lateral extrapolation from the measured inter-well profile, a three-dimensional reconstruction of the aquifer is obtained. It is demonstrated that calibration of spatially variable specific storage in addition to hydraulic conductivity can improve the fitting of the model while the structural features are only slightly changed. At the field site, two tracer tests with uranine and sodium-naphthionate were also performed and their concentrations were monitored for 2 months. The measured tracer breakthrough curves are employed for independent validation of the hydraulic tomographical reconstruction. It is demonstrated that major features of the observed solute transport can be reproduced, and structures relevant for macrodispersive tracer spreading could be resolved. However, for the mildly heterogeneous aquifer, the tracer breakthrough curves can also be approximated by a simplified homogeneous model with higher dispersivity. Therefore, improved validation results that capture specific characteristics of the breakthrough curves would require additional hydraulic measurements."],["dc.description.sponsorship","Swiss National Science Foundation [200021_140450/1]; CCES"],["dc.identifier.doi","10.1002/2014WR016402"],["dc.identifier.isi","000360080200034"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/36640"],["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","Prediction of solute transport in a heterogeneous aquifer utilizing hydraulic conductivity and specific storage tomograms"],["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"]]