In situ fluid dynamics and CO2 injection in porous rocks

Understanding multiphase fluid flow in porous rocks implies knowledge of fundamental properties such as wettability, relative permeability and capillary pressure. These parameters, as well as the extent of fractures and their permeability and interconnection, are vital information needed to predict oil recovery, select production scenario and initiate EOR strategies in the reservoir. In this thesis, wettability, relative permeability and capillary pressure are measured directly from in situ saturation and pressure data and the impacts on oil recovery from capillary continuity across fractures have been studied. Finally, injection of CO2 to enhance oil recovery is investigated at different wettabilities and when varying a wide range of injection scenarios. Conventionally, relative permeability curves are generated from capillary pressure curves using best-fit analyses of the production data. Experimental methods to measure relative permeability include unsteady-state methods which are based on production data and average pressure drop across entire core samples. They may thus fail to capture capillary end effects and local variations and heterogeneities. The steady-state methods claim to describe dynamic properties but rely on pressure or saturation equilibrium. Alternatively, some steady-state methods are based on simultaneous injection of one wetting and one non-wetting fluid phase but aim to describe the properties of either drainage or imbibition processes. An alternative, explicit method to calculate relative permeabilities has been reviewed and slightly modified in this thesis, and dynamic capillary pressure curves have been measured at different wettabilities based on in situ saturation and phase pressure data collected during continuous flooding. Both methods utilize dynamic measurements to describe the properties of relative permeability and capillary pressure as opposed to most conventional methods. The relative permeability curves showed consistency with wettability, and a good match with conventional curves at strongly water-wet conditions was obtained. The capillary pressure curves corroborated data obtained from centrifuge experiments at strongly water-wet, less water-wet and near neutral-wet conditions. In addition, the proposed methods for obtaining both relative permeability and capillary pressure curves are time-saving, and in situ data increased the accuracy and confidence of the input to numerical simulators used to predict reservoir fluid flow. A drawback with the conventional Amott-Harvey Index of wettability measurement method is the time consumed from obtaining spontaneous imbibition data. The possibility to capture local heterogeneities is also limited in this method, as the data collected from imbibition and subsequent water- or oilfloods are average measures obtained from whole core samples. In this work, local wettability indices are measured during continuous flooding from in situ saturation and local pressure data by identifying the separate contributions to oil recovery from spontaneous imbibition and viscous displacement. The obtained wettability indices demonstrate an excellent match with the conventional data. Previous work has shown that wetting phase bridges across an open fracture establish capillary continuity between two mixed-wet matrix blocks and increase oil recovery exceeding the end-point for spontaneous imbibition. However, the wetting phase produced from the inlet matrix block during drainage of strongly wetted systems forms a film on the outlet end and fails to establish capillary continuity across the fracture. In this work, capillary continuity in strongly wetted systems has been established during drainage processes by packing the separating fracture with micro-particles. Capillary continuity was determined by monitoring the volume accumulated by the capillary end effect during continuous injection of the non-wetting phase. The demand for enhanced oil recovery in mature oil fields combined with carbon neutral solutions and high quality in situ data is increasing. Several projects have been initiated worldwide to capture CO2 from fossil fuel-fired power plants and other industrial processes, and CO2 is thus becoming more available for EOR projects. In order to further increase the understanding of multiphase dynamic fluid flow in porous media, MRI was used to monitor in situ saturation development during injection of liquid or supercritical CO2 at different wettabilities and at miscible conditions. A series of experiments was initiated to study oil recovery potential from injection of compressed CO2 at secondary and tertiary conditions, monitor in situ fluid flow and investigate oil recovery mechanisms in low-permeable outcrop chalk. Qualitative analysis of the MRI images indicated oil swelling at the front as the CO2 propagated through the cores, and enhanced oil recovery ranging from 9.4 %PV to 67 %PV was determined from material balance calculations. During tertiary injection of liquid CO2 in a fractured core sample, MRI images suggested that the oil in the middle and outlet end of the core was bypassed due to high fracture permeability. The results obtained from the various experiments emphasize the importance of using high spatial resolution saturation imaging, providing increased understanding of multiphase in situ fluid flow in porous media, assisting in predicting recovery mechanisms and improving input data used in numerical simulators

Characterization of two transketolases encoded on the chromosome and the plasmid pBM19 of the facultative ribulose monophosphate cycle methylotroph Bacillus methanolicus

Markert B, Stolzenberger J, Brautaset T, Wendisch VF. Characterization of two transketolases encoded on the chromosome and the plasmid pBM19 of the facultative ribulose monophosphate cycle methylotroph Bacillus methanolicus. BMC Microbiology. 2014;14(1): 7.Background Transketolase (TKT) is a key enzyme of the pentose phosphate pathway (PPP), the Calvin cycle and the ribulose monophosphate (RuMP) cycle. Bacillus methanolicus is a facultative RuMP pathway methylotroph. B. methanolicus MGA3 harbors two genes putatively coding for TKTs; one located on the chromosome (tktC) and one located on the natural occurring plasmid pBM19 (tktP). Results Both enzymes were produced in recombinant Escherichia coli, purified and shown to share similar biochemical parameters in vitro. They were found to be active as homotetramers and require thiamine pyrophosphate for catalytic activity. The inactive apoform of the TKTs, yielded by dialysis against buffer containing 10 mM EDTA, could be reconstituted most efficiently with Mn2+ and Mg2+. Both TKTs were thermo stable at physiological temperature (up to 65°C) with the highest activity at neutral pH. Ni2+, ATP and ADP significantly inhibited activity of both TKTs. Unlike the recently characterized RuMP pathway enzymes fructose 1,6-bisphosphate aldolase (FBA) and fructose 1,6-bisphosphatase/sedoheptulose 1,7-bisphosphatase (FBPase/SBPase) from B. methanolicus MGA3, both TKTs exhibited similar kinetic parameters although they only share 76% identical amino acids. The kinetic parameters were determined for the reaction with the substrates xylulose 5-phosphate (TKTC: kcat/KM: 264 s-1 mM-1; TKTP: kcat/KM: 231 s-1 mM) and ribulose 5-phosphate (TKTC: kcat/KM: 109 s-1 mM; TKTP: kcat/KM: 84 s-1 mM) as well as for the reaction with the substrates glyceraldehyde 3-phosphate (TKTC: kcat/KM: 108 s-1 mM; TKTP: kcat/KM: 71 s-1 mM) and fructose 6-phosphate (TKTC kcat/KM: 115 s-1 mM; TKTP: kcat/KM: 448 s-1 mM). Conclusions Based on the kinetic parameters no major TKT of B. methanolicus could be determined. Increased expression of tktP, but not of tktC during growth with methanol [J Bacteriol 188:3063–3072, 2006] argues for TKTP being the major TKT relevant in the RuMP pathway. Neither TKT exhibited activity as dihydroxyacetone synthase, as found in methylotrophic yeast, or as the evolutionary related 1-deoxyxylulose-5-phosphate synthase. The biological significance of the two TKTs for B. methanolicus methylotrophy is discussed

Corrigendum: Genome-Based Genetic Tool Development for Bacillus methanolicus: Theta- and Rolling Circle-Replicating Plasmids for Inducible Gene Expression and Application to Methanol-Based Cadaverine Production

© 2019 Irla, Heggeset, Nærdal, Paul, Haugen, Le, Brautaset and Wendisch. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these termsBacillus methanolicus is a thermophilic methylotroph able to overproduce amino acids from methanol, a substrate not used for human or animal nutrition. Based on our previous RNA-seq analysis a mannitol inducible promoter and a putative mannitol activator gene mtlR were identified. The mannitol inducible promoter was applied for controlled gene expression using fluorescent reporter proteins and a flow cytometry analysis, and improved by changing the −35 promoter region and by co-expression of the mtlR regulator gene. For independent complementary gene expression control, the heterologous xylose-inducible system from B. megaterium was employed and a two-plasmid gene expression system was developed. Four different replicons for expression vectors were compared with respect to their copy number and stability. As an application example, methanol-based production of cadaverine was shown to be improved from 6.5 to 10.2 g/L when a heterologous lysine decarboxylase gene cadA was expressed from a theta-replicating rather than a rolling-circle replicating vector. The current work on inducible promoter systems and compatible theta- or rolling circle-replicating vectors is an important extension of the poorly developed B. methanolicus genetic toolbox, valuable for genetic engineering and further exploration of this bacterium.publishedVersio

Evaluation of echosounder data preparation strategies for modern machine learning models

Fish stock assessment and management requires accurate estimates of fish abundance, which are typically derived from echosounder observations using acoustic target classification (ATC). Skilled operators are regularly assisted in classifying acoustic targets by software and there has been an increasing interest toward using machine learning to create improved tools. Recent studies have applied deep learning approaches to acoustic data, however, algorithm data-preparation strategies (influencing model output) are presently poorly understood and standardization is needed to enable collaborative research and management. For example, a common pre-processing technique is to resample backscatter data coming from echosounder measurements from the original resolution to a coarser resolution in the horizontal (time) and vertical (range) directions. Using data values derived from the volume backscattering coefficient obtained during the Norwegian sandeel survey, we investigate which resampling resolutions are suitable for ATC using a convolutional neural network trained to classify single values of backscatter data. This process is known as pixel-level semantic segmentation. Our results indicate that it is possible to downsample the data if important information related to acoustic characteristics is not smoothed out. We also show that the classification performance is improved when providing the network with contextual information relating to range. These findings will provide input to fisheries acoustic data standards and contribute to the on-going development of automated ATC methods.publishedVersio

Transaldolase in Bacillus methanolicus: Biochemical Characterization and Biological Role in Ribulose Monophosphate Cycle

Pfeifenschneider J, Markert B, Stolzenberger J, Brautaset T, Wendisch VF. Transaldolase in Bacillus methanolicus: Biochemical Characterization and Biological Role in Ribulose Monophosphate Cycle. BMC Microbiology. 2020;20: 63.Background The Gram-positive facultative methylotrophic bacterium Bacillus methanolicus uses the sedoheptulose-1,7-bisphosphatase (SBPase) variant of the ribulose monophosphate (RuMP) cycle for growth on the C1 carbon source methanol. Previous genome sequencing of the physiologically different B. methanolicus wild-type strains MGA3 and PB1 has unraveled all putative RuMP cycle genes and later, several of the RuMP cycle enzymes of MGA3 have been biochemically characterized. In this study, the focus was on the characterization of the transaldolase (Ta) and its possible role in the RuMP cycle in B. methanolicus. Results The Ta genes of B. methanolicus MGA3 and PB1 were recombinantly expressed in Escherichia coli, and the gene products were purified and characterized. The PB1 Ta protein was found to be active as a homodimer with a molecular weight of 54 kDa and displayed KM of 0.74 mM and Vmax of 16.3 U/mg using Fructose-6 phosphate as the substrate. In contrast, the MGA3 Ta gene, which encodes a truncated Ta protein lacking 80 amino acids at the N-terminus, showed no Ta activity. Seven different mutant genes expressing various full-length MGA3 Ta proteins were constructed and all gene products displayed Ta activities. Moreover, MGA3 cells displayed Ta activities similar as PB1 cells in crude extracts. Conclusions While it is well established that B. methanolicus can use the SBPase variant of the RuMP cycle this study indicates that B. methanolicus possesses Ta activity and may also operate the Ta variant of the RuMP

Subjective satisfaction in long-term orthokeratology patients

Purpose: To AU3 evaluate the subjective satisfaction in visual stability, night vision complains, and light distortion phenomena, and also the number of hours and days per week of lens wear, in patients with myopia undergoing orthokeratology (OK) treatment for at least 1 year. Methods: A visual analog scale (VAS) questionnaire containing 18 items was administered to 44 patients, 29 women and 15 men (mean age, 24.39 6 9.11 years), with a baseline spherical equivalent refractive error of 22.40 6 0.94 diopters and astigmatism up to 20.5 diopters. Average treatment period by the time of data collection was 19 6 7 months. Patients rated their satisfaction with the correction, with complaints of visual distortion being graded on a scale of 0 to 10, where 0 indicated no discomfort at all. Results: More than 50% of patients skipped lens wear at least 1 night per week. The most common wearing pattern was 6–8 hours a day for 72.7% with 54.5% of patients wearing lenses every 2–3 nights only. Subjective vision scores after lens removal was 9.1 6 1.1 after having worn the lenses and 8.1 6 1.4 after skipping lens wear for 1 night. Subjective vision scores before lens insertion at the end of the day was 6.9 6 2.0 and 5.8 6 2.4, respectively. The number of hours until noticeable blur reduced with increased level of baseline myopia (r = 0.396; P , 0.001). Conclusion: Orthokeratology patients show an irregular wearing pattern after 1 year of treatment that has significant effects on the subjective visual performance over the next day of skipping lens wear. Light distortion under low-light conditions seems to be a transient complication of the treatment and most of the patients report an improvement after the first weeks of treatment.Supported in part by projects PTDC/SAU-BEB/098391/2008//FCOMP-01-0124-FEDER-010897 and PTDC/SAU-BEB/098392/2008//FCOMP-01-0124-FEDER-010898 funded by Fundacao para a Ciencia e Tecnologia (FCT) of Portugal

Effects of ageing on the anterior segment of the eye structure and function

[Excerpt] The world will soon have more aged people than children and more people at extreme old age than ever before [1]. Improving quality of life as well as reducing severe disability due to age-related problems has become key for the health systems worldwide. The ageing of the world population has both structural and functional consequences for the human visual system; changes due to ageing occur in all the structures of the eye causing a variety of effects. Over the last few years, great advances in ophthalmic instrumentation allow the determination of ocular parameters to a level of detail without precedent. Such advances allowresearcherstodevelopspecificdevicesforvisualcorrection and rehabilitation and at the same time guide the clinicians in their decision making and selection of treatment options to convey with the increasing demand of highquality outcomes of the ageing population. This special issue aimed at creating a multidisciplinary forum of discussion on recent advances in the knowledge of the effects of ageing in the anterior segment of the human eye’s structure and function, and improvements on early detection, treatment, and prognosis of age-related ocular conditions of the anterior segment. As a result, a remarkable compilation of ten articles cover many of these very different aspects of ocular ageing. [...]info:eu-repo/semantics/publishedVersio

Collyria seals in the Roman Empire

Roman seals associated with collyria (Latin expression for eye drops /washes and lotions for eye maintenance) provide valuable information about eye care in the antiquity. These small, usually stone-made pieces bore engravings with the names of eye doctors and also the collyria used to treat an eye disease. The collyria seals have been found all over the Roman empire and Celtic territories in particular and were usually associated with military camps. In Hispania (Iberian Peninsula), only three collyria seals have been found. These findings speak about eye care in this ancient Roman province as well as about of the life of the time. This article takes a look at the utility and social significance of the collyria seals and seeks to give an insight in the ophthalmological practice of in the Roman Empire

PEČATI ZA KOLIRIJE U RIMSKOM CARSTVU

Roman seals associated with collyria (Latin expression for eye drops /washes and lotions for eye maintenance) provide valuable information about eye care in the antiquity. These small, usually stone-made pieces bore engravings with the names of eye doctors and also the collyria used to treat an eye disease. The collyria seals have been found all over the Roman empire and Celtic territories in particular and were usually associated with military camps. In Hispania (Iberian Peninsula), only three collyria seals have been found. These findings speak about eye care in this ancient Roman province as well as about of the life of the time. This article takes a look at the utility and social significance of the collyria seals and seeks to give an insight in the ophthalmological practice of in the Roman Empire.Rimski pečati kojima su se pečatili koliriji (lat. collyrium – kapi, losioni, voda za oči) daju vrijedan uvid u postupke njege i liječenja očiju u antička vremena. U ove su se male kamene pečate obično gravirala imena očnih liječnika i naziv kolirija koji se rabio za pojedinu očnu bolest. Pečati za kolirije pronađeni su posvuda u Rimskom Carstvu, a ponajviše na okupiranim keltskim teritorijima i to u vojnim logorima. U Hispaniji (na Iberijskom poluotoku) pronađena su tek tri takva pečata. Ovi nam nalazi govore o njezi očiju u ovoj staroj rimskoj provinciji i o životu u to doba. Cilj je članka razmotriti korisnost i društvenu važnost pečata za kolirije i pružiti čitatelju uvid u oftalmološku praksu u Rimskom Carstvu

Semi-supervised target classification in multi-frequency echosounder data

Acoustic target classification in multi-frequency echosounder data is a major interest for the marine ecosystem and fishery management since it can potentially estimate the abundance or biomass of the species. A key problem of current methods is the heavy dependence on the manual categorization of data samples. As a solution, we propose a novel semi-supervised deep learning method leveraging a few annotated data samples together with vast amounts of unannotated data samples, all in a single model. Specifically, two inter-connected objectives, namely, a clustering objective and a classification objective, optimize one shared convolutional neural network in an alternating manner. The clustering objective exploits the underlying structure of all data, both annotated and unannotated; the classification objective enforces a certain consistency to given classes using the few annotated data samples. We evaluate our classification method using echosounder data from the sandeel case study in the North Sea. In the semi-supervised setting with only a tenth of the training data annotated, our method achieves 67.6% accuracy, outperforming a conventional semi-supervised method by 7.0 percentage points. When applying the proposed method in a fully supervised setup, we achieve 74.7% accuracy, surpassing the standard supervised deep learning method by 4.7 percentage points.publishedVersio