Impact of drilling mud on chemistry and microbiology of an Upper Triassic groundwater after drilling and testing an exploration well for aquifer thermal energy storage in Berlin (Germany)

After completion of an exploration well, sandstones of the Exter Formation were hydraulically tested to determine the hydraulic properties and to evaluate chemical and microbial processes caused by drilling and water production. The aim was to determine the suitability of the formation as a reservoir for aquifer thermal energy storage. The tests revealed a hydraulic conductivity of 1–2 E-5 m/s of the reservoir, resulting in a productivity index of 0.6–1 m³/h/bar. A hydraulic connection of the Exter Formation to the overlaying, artesian “Rupelbasissand” cannot be excluded. Water samples were collected for chemical and microbiological analyses. The water was similarly composed as sea water with a maximum salinity of 24.9 g/L, dominated by NaCl (15.6 g/L Cl and 7.8 g/L Na). Until the end of the tests, the water was affected by drilling mud as indicated by the high pH (8.9) and high bicarbonate concentration (359 mg/L) that both resulted from the impact of sodium carbonate (Na₂CO₃) additives. The high amount of dissolved organic matter (>?58 mg/L) and its molecular-weight distribution pattern indicated that residues of cellulose, an ingredient of the drilling mud, were still present at the end of the tests. Clear evidence of this contamination gave the measured uranine that was added as a tracer into the drilling mud. During fluid production, the microbial community structure and abundance changed and correlated with the content of drilling mud. Eight taxa of sulfate-reducing bacteria, key organisms in processes like bio-corrosion and bio-clogging, were identified. It can be assumed that their activity will be affected during usage of the reservoir.     

The use of tracers to assess drill-mud penetration depth into sandstone cores during deep drilling: method development and application

For the utilization of deep saline aquifers in the frame of geotechnical use, such as geological sequestration of CO₂, H₂ or energy storage, a baseline characterization of pristine reservoir rock cores is required to monitor changes in the indigenous microbial communities and pore fluids, and to study alterations in rock characteristics resulting from interaction with geological storage technologies. However, drilling procedures and technical fluids, particularly drill mud, are sources of core contamination. To measure the penetration of drill mud into the cores, three tracers (fluorescein, microspheres, and 4′,6-diamidino-2-phenylindole stained bacteria) were tested under laboratory conditions. The flow of drill mud into core samples was induced by applying uniaxial pressure differentials to the core, and the penetration depth was microscopically determined for each tracer. Fluorescein was extracted from the rock samples and quantified fluorometrically. The results indicate that all tested tracers are suitable for tracking drill-mud penetration. The actual penetration depth seems to be related to differences in mineral composition and texture as well as microfractures. Among all tested tracers, fluorescein labelling is the simplest, cheapest and most accurate method for analyzing the contamination of rock cores by technical fluids. The application of this tracer was successfully applied during two deep drilling campaigns at the CO₂ storage pilot site in Ketzin, Germany. The results highlight that the use of tracers is indispensable to ensure the quality of core samples for microbiological and biogeochemical analysis.     

Solute transport as affected by surface land characteristics in gravely calcareous arid soils

Gravely calcareous soils cover approximately most of arid lands (in percent); however, the solute transport behavior in these soils remains a current issue. This research aimed at estimating and correlating the solute transport parameters in gravely calcareous soils as being affected by different land uses through the knowledge of the soil morphological, physical, and chemical properties. Four different land use sites were selected: irrigated trees and bare, range, and alluvial sediment lands. Solute transport parameters of soil pore water velocity (V), dispersion coefficient (D), and retardation factor (R) were estimated using bromide breakthrough curve tests for surface soil columns. In addition, field Brilliant Blue FCF dye tracing experiment was conducted to determine the maximum dimensional movements. Soil morphological analysis was able to explain the heterogeneity in the solute transport parameters. Conductive solute transport mechanism with V of 17.99 m/day was favored in a high continuous pore system observed under tree lands. Presence of high gravel and CaCO₃ contents under range lands increased pore system tortuosity and thus increased D magnitude up to 1,339.88 cm²/day. Existence of thin surface crusts at both bare soils and alluvial sediments had considerably restricted V down to 1.46 m/day. Dye staining technique aided the explanation of the existing variations by providing visual evidence on the preferential flow paths and patterns governing the solute transport mechanism at each site.     

Potential Occurrence of MTBE and BTEX in Groundwater Resources of Amman–Zarqa Basin,Jordan

This study investigates potential occurrence, distribution, and sources of the newly added gasoline oxygenate, methyl‐tert‐butyl ether (MTBE) and the petroleum derivatives benzene, toluene, ethylbenzene, and xylenes called collectively, BTEX, in Jordan's heavily populated Amman–Zarqa Basin (AZB). It presents the first data on the levels of MTBE and BTEX in the aquifers of this basin. One hundred and seventy‐nine (179) groundwater wells were sampled near petrol service stations, oil refinery storage tanks, car wrecks, bus stations, and chemical industries at different locations in the basin. Headspace GC and purge and trap GC–MS were utilized to determine the target substances in the samples. Concentrations of BTEX varied between no‐detection (minimum) for all of them to 6.6 µg/L (maximum) for ethylbenzene. MTBE was found in few samples but none has exceeded the regulated levels; its concentrations ranged between no‐detection to 4.1 µg/L. However, though the contamination levels are very low they should be considered alarming.     

Semi‐active neuro‐control for base‐isolation system using magnetorheological (MR) dampers

Vibration mitigation using smart, reliable and cost‐effective mechanisms that requires small activation power is the primary objective of this paper. A semi‐active controller‐based neural network for base‐isolation structure equipped with a magnetorheological (MR) damper is presented and evaluated. An inverse neural network model (INV‐MR) is constructed to replicate the inverse dynamics of the MR damper. Next, linear quadratic Gaussian (LQG) controller is designed to produce the optimal control force. Thereafter, the LQG controller and the INV‐MR models are linked to control the structure. The coupled LQG and INV‐MR system was used to train a semi‐active neuro‐controller, designated as SA‐NC, which produces the necessary control voltage that actuates the MR damper. To evaluate the proposed method, the SA‐NC is compared to passive lead–rubber bearing isolation systems (LRBs). Results revealed that the SA‐NC was quite effective in seismic response reduction for wide range of motions from moderate to severe seismic events compared to the passive systems. In addition, the semi‐active MR damper enjoys many desirable features, such as its inherent stability, practicality and small power requirements. The effectiveness of the SA‐NC is illustrated and verified using simulated response of a six‐degree‐of‐freedom model of a base‐isolated building excited by several historical earthquake records. Copyright © 2006 John Wiley & Sons, Ltd.     

Determination of trihalomethanes and the ionic composition of groundwater at Amman City, Jordan

A water-chemistry evaluation was made of the available springs and wells in Amman and vicinity. Trihalomethanes (THM) were found in all analysed samples with concentrations ranging from 0.2–31.88 μg/L. The probable sources of trihalomethanes in the aquifers originate from three sources: (1) chlorinated Deir Alla surface water, (2) reaction of excess chlorine in the leaky, corroded water-distribution network with organic matter in the vadose zone, and (3) sewage seepage from cesspools in the area. Total organic carbon (TOC) ranged from 0.2–1.4 mg/L. Its probable source is either from the vadose zone or the treated surface water at Deir Alla. It was found that TOC was of vital importance in the formation of THM in the presence of chlorine from the water-distribution system. Major ionic composition of the analysed samples reflected the limestone lithology of the aquifer in the investigated area. Heavy-metal content was relatively low due to the high pH of the groundwater samples. Electronic Publication