Reservoir-scale transdimensional fracture network inversion

The Waiwera aquifer hosts a structurally complex geothermal groundwater system, where a localized thermal anomaly feeds the thermal reservoir. The temperature anomaly is formed by the mixing of waters from three different sources: fresh cold groundwater, cold seawater and warm geothermal water. The stratified reservoir rock has been tilted, folded, faulted, and fractured by tectonic movement, providing the pathways for the groundwater. Characterization of such systems is challenging, due to the resulting complex hydraulic and thermal conditions which cannot be represented by a continuous porous matrix. By using discrete fracture network models (DFNs) the discrete aquifer features can be modelled, and the main geological structures can be identified. A major limitation of this modelling approach is that the results are strongly dependent on the parametrization of the chosen initial solution. Classic inversion techniques require to define the number of fractures before any interpretation is done. In this research we apply the transdimensional DFN inversion methodology that overcome this limitation by keeping fracture numbers flexible and gives a good estimation on fracture locations. This stochastic inversion method uses the reversible-jump Markov chain Monte Carlo algorithm and was originally developed for tomographic experiments. In contrast to such applications, this study is limited to the use of steady-state borehole temperature profiles – with significantly less data. This is mitigated by using a strongly simplified DFN model of the reservoir, constructed according to available geological information. We present a synthetic example to prove the viability of the concept, then use the algorithm on field observations for the first time. The fit of the reconstructed temperature fields cannot compete yet with complex three-dimensional continuum models, but indicate areas of the aquifer where fracturing plays a big role. This could not be resolved before with continuum modelling. It is for the first time that the transdimensional DFN inversion was used on field data and on borehole temperature logs as input.DFG, 318763901, SFB 1294, Data Assimilation - The seamless integration of data and models, Assimilating data with different degrees of uncertainty into statistical models for earthquake occurrence (B04)TU Berlin, Open-Access-Mittel - 201

Mass gap effects and higher order electroweak Sudakov logarithms

The infrared structure of spontaneously broken gauge theories is phenomenologically very important and theoretically a challenging problem. Various attempts have been made to calculate the higher order behavior of large double-logarithmic (DL) corrections originating from the exchange of electroweak gauge bosons resulting in contradictory claims. We present results from two loop electroweak corrections for the process $g \longrightarrow f_{\rm R} {\bar f}_{\rm L}$ to DL accuracy. This process is ideally suited as a theoretical model reaction to study the effect of the mass gap of the neutral electroweak gauge bosons at the two loop level. Contrary to recent claims in the literature, we find that the calculation performed with the physical Standard Model fields is in perfect agreement with the results from the infrared evolution equation method. In particular, we can confirm the exponentiation of the electroweak Sudakov logarithms through two loops.Comment: 10 pages, 3 figures, LaTeX2e, uses epsfi

Assessment of Data Driven and Process Based Water Management Tools for the Geothermal Reservoir Waiwera (New Zealand)

AbstractThe reservoir below the village is commercially used since 1863. Due to overproduction in the 1960s and 1970s the water level declined critically. Therefore, abstraction rates were limited, monitoring deployed and models set up to manage the site sustainably. It is shown here that data driven models based on experience and observations are of higher accuracy and provide better prognoses. Process based simulations are more flexible and the foundation for system understanding of the geothermal area. The earlier are “black box” and need regular revision and the latter are the only way for future and prospective scenarios

Holocene palaeosols and aeolian activities in the Umimmalissuaq valley, West Greenland

Aeolian sand sheets and active dunefields preserve an ancient Holocene land surface represented by palaeosols that occur around the present ice margin in the Kangerlussuaq area, West Greenland. To determine the relation between Holocene aeolian activities and periods of soil formation, both substantially dependent on the deglaciation history, palaeosols, aeolian sand sheets and dunefields were analysed using field data, grain size analyses, optically stimulated luminescence dating and AMS 14C data in an area of about 15 km2 of the Umimmalissuaq valley. Palaeosols are developed close to the ice margin (&lt;2 km) in fine-grained aeolian sediment (silt loam) and covered by sandy aeolian layers. Silt contents of palaeosols (partly &gt;60 wt%) are comparable with aeolian sand sheets currently formed at greater distances (4–5 km) from the present ice margin. We propose a transport distance for fine aeolian sediments, in which the palaeosols are formed, of at least 4 km from inboard of the present ice margin. Soil formation of the palaeosols started around 2700 cal. yr b2k. Ages from the youngest parts of the palaeosols suggest a stable period of around 2400 years, allowing for pedogenesis. This period was characterised by low but constant aeolian activity. Since aeolian activity intensified after around 300 cal. yr b2k and is still resulting in active dunefields with coarse and medium sand accumulation, the ice margin must have reached its present position at that time. </jats:p

Seismic Chimney Formation Induced by Upward-migrating Methane in the Nordland Group, Southern Viking Graben

AbstractThe Nordland Group in the Southern Viking Graben hosts seismic chimneys, represented by anomalies in seismic data and resid- ual methane accumulations. These anomalies are generally interpreted as focused fluid flow structures, and thus pose the risk of potential fluid leakage by geological subsurface utilization. Our aim was to assess if excess pore pressure, resulting from buoy- ancy effects due to upward-migrating methane in the Utsira Formation may be responsible for formation of these anomalies. Our hydromechanical simulation results demonstrate that tensile failure in the Nordland Group already occurs before the maximum methane column heights develop in the Utsira Formation below

Patient-Specific Synthetic Osteochondral Resurfacing of an Extensive Shoulder OCD Lesion in a Dog

The aim of this study was to describe template-guided implantation and clinical outcome of a patient-specific resurfacing implant for an extensive humeral head osteochondritis in a client-owned dog. An 8-month-old intact female Irish Wolfhound, weighing 45 kg, exhibiting lameness in the right thoracic limb, and diagnosed with an extensive caudocentral humeral head osteochondritis. Based on computed tomography data, an anatomically contoured patient-specific implant (Ø 25 mm) was created. The implant consisted of a trabecular titanium base and a polycarbonate urethane bearing cup. For intraoperative guidance, a surgical drill guide, models of the affected humeral head, and trial implants were 3D printed. The implantation procedure was performed using the modified Cheli approach. Orthopaedic and radiographic follow-up examinations were conducted at 6 weeks and 10 months postoperatively. The examination revealed stable implant position, and some mild residual lameness at 6 weeks. Furthermore, the mild osteophytosis, initially evident on the day of surgery, showed a progression during each subsequent follow-up. Complications were not observed at any time point. At 10 months, the dog was free of lameness and exhibited no functional impairment, even after strenuous exercise. This level of activity remained unchanged up to the latest follow-up at 18 months, as confirmed during a telephonic interview. The utilization of a patient-specific resurfacing implant using a guided approach was technically feasible and resulted in excellent short- to mid-term clinical outcome in this case of extensive caudocentral humeral head osteochondritis dissecans (OCD) lesion. However, it is crucial to note that the potential influence of the implant on osteoarthritis progression requires further investigation