Low-frequency microtremor anomalies at an oil and gas field in Voitsdorf, Austria

Results of a passive microtremor survey at an oil and gas field in Voitsdorf, Austria, are presented. The survey consists in six parallel profiles approximately 9 km long over two hydrocarbon reservoirs. For each profile the seismic wavefield was recorded synchronously at 11 in-line stations. The measurements were conducted with broadband seismometers and lasted, for each profile, at least 12 hours overnight. Data interpretation is based on a comprehensive data set and on the analysis of four different spectral attributes. These attributes quantify the characteristic features of the wavefield's Fourier spectra in the low-frequency range (<10Hz). One attribute quantifies the spectral energy in the vertical wavefield component, another attribute quantifies the maxima in vertical-to-horizontal spectral ratios and two attributes describe the frequency shifts of peaks within the spectra of vertical and horizontal wavefield components. Due to temporal variations of the signals we combine the long-term measurements (several hours of continuous records) of multiple profiles. This procedure considerably enhances the consistency of each spectral attribute and makes them suitable to quantify lateral variations of the wavefield. The results show that using a combination of several attributes significantly increases the reliability of detecting anomalies in the microtremor wavefield that are presumably caused by hydrocarbon reservoirs. A numerical study of two-dimensional seismic wave propagation is applied to investigate the peak frequency shift attributes. The results of the study indicate that the attributes may contain information on the depth of hydrocarbon reservoirs, assuming that the reservoir acts as a (secondary) source of low-frequency seismic waves.     

Monitoring the freely dissolved concentrations of polycyclic aromatic hydrocarbons (PAH) and alkylphenols (AP) around a Norwegian oil platform by holistic passive sampling

In order to assess the environmental impact of aquatic discharges from the offshore oil industry, polar organic chemical integrative samplers (POCIS) and semipermeable membrane devices (SPMDs) were deployed around an oil platform and at reference locations in the North Sea. Exposure to polycyclic aromatic hydrocarbons (PAH) and alkylated phenols (AP) was determined from passive sampler accumulations using an empirical uptake model, the dissipation of performance reference compounds and adjusted laboratory derived sampling rates. Exposure was relatively similar within 1–2 km of the discharge point, with levels dominated by short chained C1–C3 AP isomers (19–51 ng L⁻¹) and alkylated naphthalenes, phenanthrenes and dibenzothiophenes (NPD, 29–45 ng L⁻¹). Exposure stations showed significant differences to reference sites for NPD, but not always for more hydrophobic PAH. These concentrations are several orders of magnitude lower than those reported to give both acute and sub-lethal effects, although their long term consequences are unknown.     

Separation of lipid classes from marine particulate material by HPLC on a polyvinyl alcohol-bonded stationary phase using dual-channel evaporative light-scattering detection

Using gradient HPLC and evaporative light-scattering (ELS) detection, a variety of lipid classes from marine particulate material have been separated on a polyvinyl alcohol bonded stationary phase in a single run. These classes, which cover the entire polarity range, include a nonpolar group (e.g., hydrocarbons, sterol esters, wax esters), sterols, triacylglycerols, chlorophyll a, monogalactosyldiacylglycerols, digalactosyldiacylglycerols, sulphoquinovosyldiacylglycerols, phosphatidylglycerols and phosphatidylcholine. An extract from a spring bloom sample in combination with separate lipid standards were used to optimize the chromatographic parameters. Nine classes could be identified and quantified in this extract, the major classes being triacylglycerols and nonpolar lipids. Detection limits attainable were in the range 16 ng for cholesterol to 820 ng for sulphoquinovosyldiacylglycerols. In an extract of the cyanobacteria Aphanizomenon sp. the dominating classes were found to be chlorophyll a, sulphoquinovosyldiacylglycerols, monogalactosyldiacylglycerols and nonpolar lipids. In a separate study, significant differences in lipid composition and concentrations were found between samples from various depths in the water column. The accuracy of the method was tested by comparing with gravimetric determinations. It was found to be acceptable provided that the main lipid classes can be identified and quantified. The ELS detector was modified electronically in such a way that two chromatograms with different gain factors could be obtained from the same run, thus halving the time for analysis for the majority of samples since evaluation of various lipid concentration levels often require that a sample is run twice with different gain factors. The time between injections, including column equilibration, was 55 min.     

Assessment of climate change and associated impact on selected sectors in Poland

The present paper offers a brief assessment of climate change and associated impact in Poland, based on selected results of the Polish–Norwegian CHASE-PL project. Impacts are examined in selected sectors, such as water resources, natural hazard risk reduction, environment, agriculture and health. Results of change detection in long time series of observed climate and climate impact variables in Poland are presented. Also, projections of climate variability and change are provided for time horizons of 2021–2050 and 2071–2100 for two emission scenarios, RCP4.5 and RCP8.5 in comparison with control period, 1971–2000. Based on climate projections, examination of future impacts on sectors is also carried out. Selected uncertainty issues relevant to observations, understanding and projections are tackled as well.     

Application of alternative digital rock physics methods in a real case study: a challenge between clean and cemented samples

High‐resolution three‐dimensional images are used in digital rock physics to numerically compute rock physical properties such as permeability and elastic moduli. These images are not widely available, and their preparation is both expensive and time consuming. All of these issues highlight the importance of alternative digital rock physics methods that are based on two‐dimensional images and use different approaches to compute effective properties of three‐dimensional samples. In addition, the scale of study in both standard and alternative digital rock physics is very small, which applications of its results are questionable at wells or reservoir scale. The aim of this study is to use two‐dimensional images and alternative digital rock physics techniques for computing seismic wave velocity and permeability, which are compared with well and laboratory data. For this purpose, data from one well in a reservoir located in the southwestern part of Iran are used. First, two clean (carbonate) and two cemented (limy sandstone) samples were collected from well cores at different depths. Then, two‐dimensional images by scanning electron microscope and conventional microscope were captured. In the next step, two alternative digital rock physics methods, namely, empirical relations and conditional reconstruction, have been employed to compute P‐wave velocity and permeability of a three‐dimensional medium. Results showed that, in clean (mono‐mineral) samples, velocity values were reasonably close to well data. However, permeability values are underestimated compared with laboratory data because laboratory data were obtained at ambient pressure, whereas alternative digital rock physics results are more representative of reservoir pressure conditions. Nevertheless, permeability–porosity trends are valid for both samples. In the case of cemented samples, a two‐scale procedure, along with a method for two‐scale computation and grain‐cement segmentation, is presented and developed. Results showed that P‐wave velocity is overestimated probably due to random sampling in this method. However, velocity–porosity trends are in agreement with well data. Moreover, permeability results obtained for cemented samples were also similar to those obtained for the clean samples.     

Optimization of water allocation in the Shatt al-Arab River under different salinity regimes and tide impact

Wastewater effluents from irrigation and the domestic and industrial sectors have serious impacts in deteriorating water quality in many rivers, particularly in areas under tidal influence. There is a need to develop an approach that considers the impact of human and natural causes of salinization. This study uses a multi-objective optimization–simulation model to investigate and describe the interactions of such impacts in the Shatt al-Arab River, Iraq. The developed model is able to reproduce the salinity distribution in the river given varying conditions. The salinity regime in the river varies according to different hydrological conditions and anthropogenic activities. Due to tidal effects, salinity caused by drainage water is seen to intrude further upstream into the river. The applied approach provides a way to obtain optimal solutions where both river salinity and deficit in water supply can be minimized. The approach is used for exploring the trade-off between these two objectives.     

Historical overview of 2D and 3D hydrodynamic modelling of shallow water flows in the Netherlands

Ocean Dynamics - This paper contains a historical overview of 2D and 3D hydrodynamic modelling in the Netherlands from the 1960s till now. It started in the 1960s with two-dimensional...     

Forced oscillation measurements of seismic attenuation in fluid saturated sandstone

Adopting the method of forced oscillation, attenuation was studied in Fontainebleau sandstone (porosity 10%, permeability 10 mD) at seismic frequencies (1–100 Hz). Confining pressures of 5, 10, and 15 MPa were chosen to simulate reservoir conditions. First, the strain effect on attenuation was investigated in the dry sample for 11 different strains across the range 1 × 10^?6–8 × 10^?6, at the confining pressure of 5 MPa. The comparison showed that a strain of at least 5 × 10^?6 is necessary to obtain a good signal to noise ratio. These results also indicate that nonlinear effects are absent for strains up to 8 × 10^?6. For all the confining pressures, attenuation in the dry rock was low, while partial (90%) and full (100%) saturation with water yielded a higher magnitude and frequency dependence of attenuation. The observed high and frequency dependent attenuation was interpreted as being caused by squirt flow.     

Coal Cleat/Fracture Segmentation Using Convolutional Neural Networks

Natural Resources Research - Cleats/fractures play a vital role in gas extraction from coal bed methane reservoirs. As such, fractures are identified in microcomputed tomography images by...     

Energy Consumption and Greenhouse Gas Emission of Korean Offshore Fisheries

This paper presents the energy and greenhouse gas(GHG) emission assessments of Korean offshore fisheries. The consumption of energy by fisheries is a significant concern because of its attendant environmental effect, as well as the cost of the fuel consumed in fishing industry. With the global attention of reducing GHG emission and increasing energy efficiency of fuel, the seafood industry needs to further understand its energy use and reduce its GHG emission. In the present study, the amount of energy consumed and the GHG emission of Korean offshore fisheries in a period from 2009 to 2013 were examined. Offshore fisheries accounted for 24% of Korean production in 2013 and 60% of fuel consumption related GHG emission. Whereas the total GHG emission intensity of this sector improved slightly between 2009 and 2012; as such emission decreased by approximately 1.9%, which increased again in 2013. The average amount of total GHG emission in this five years period was 1.78 × 10~6 tons of carbon dioxide equivalent/year(tCO_2eq. y~(-1)). Active fishing gear was found to consume 20% more fuel than passive gear. However, the production from passive gear was 28%, lower than 72% from active gear. The reason for this is that less abundant stationary resources are harvested using passive gear. Furthermore, the consumption of fuel was significantly influenced by the fishing method. Implementation and development of new fishing technologies and methods are important for improving energy efficiency and reducing the climate impact on fisheries. To realize these purposes, the fishery management system needs to be established by centralizing on energy efficiency and climate effect.