bluuebunny/crossref_metadata_2025 huggingface dataset:
Deciphering the Fundamental Controls of Flow in Carbonates Using Numerical Well-Testing, Production Optimisation, and 3D High-resolution Outcrop Analogues for Fractured Carbonate Reservoirs
Authors: Agada Simeon , Chen Fuzhen , Geiger Sebastian , Toigulova Gulnara , Agar Susan , Benson Greg , Shekhar Ravi , Hehmeyer Owen , Amour Fred , Mutti Maria , Christ Nicolas , Immenhauser Adrian
Published: June 2013

Carbonate reservoirs contain a significant portion of the world’s proven hydrocarbon reserves but are challenging to produce due to their complex lithologies, structural heterogeneities, and neutral to oil-wet nature. Increasing recovery requires a better understanding of how different recovery processes respond to the heterogeneities inherent to these reservoirs. This will contribute to the design of appropriate engineering solutions which extend the life of mature fields and develop green fields more effectively.

We use a high-resolution 3D outcrop model of a Jurassic carbonate ramp in order to perform a series of detailed and systematic flow simulations. The aim is to test the impact of small- and large-scale geological features on reservoir performance and oil recovery. The outcrop analogue model is of excellent quality comprising a wide range of diagenetic and structural features, including discontinuity surfaces, mud mounds, mollusc banks and fractures. Flow simulations are performed for numerical well-testing and secondary oil recovery. Numerical well-testing allows us to generate synthetic but systematic pressure responses for different geological features observed in the outcrops. This allows us to assess and rank the relative impact of specific geological features on reservoir performance. The outcome documents that, due to the high level of matrix heterogeneity, most diagenetic and structural features cannot be linked to a unique pressure signature. Instead, reservoir performance is controlled by sub-seismic faults and mollusc banks acting as thief zones. Numerical simulations of secondary recovery processes reveal strong channelling of fluid flow into high-permeability layers. This is the primary control for oil recovery. However, appropriate reservoir engineering solutions such as optimising well placement and injection fluid can reduce channelling and increase oil recovery.
Optimizing the Waterflooding Performance of a Carbonate Reservoir with Internal Control Valves
Authors: Carvajal G. A. , Wang F. , Lopez C. , Cullick A. S , Al-Jasmi A. , Goel H. K
Published: June 2013

Intelligent digital oilfield (iDOF) operations include the transfer, monitoring, visualization, analysis, and interpretation of real-time data. Enabling this process requires a significant investment to upgrade surface, subsurface, and well instrumentation and also the installation of a sophisticated infrastructure for data transmission and visualization. Once upgraded, the system is then capable of transferring massive quantities of data, converting it into real information at the right time.

The transformation of raw data into information is achieved through intelligent, automated work processes, which are referred to here as "smart flows." Smart flows assist engineers in their daily well surveillance activities, helping make them more productive and improve decision making. A major oil and gas operator in the Middle East has invested in such an infrastructure and is developing a set of smart flows for key activities and workflows for its production operations, with the ultimate goal of improved asset performance.

In response to early water breakthrough, a study was commissioned to investigate whether smart completions that use down-hole internal control valves (ICVs) could provide a range of fluid-flow control options to enhance reservoir sweep efficiency, reduce produced water, and increase well life.

This paper describes the strategy and process to identify production and injection wells best suited for intelligent well completions in the Sabriyah field, Mauddud reservoir. The goal is to control zonal injection and production rates to reduce uneven water fronts, sweep and produce bypassed oil, postpone water breakthrough, and extend well life, thus boosting oil production while optimizing water handling at the surface. The study demonstrates excellent potential for down-hole control to significantly improve operations in the water injection areas.
Residual Oil Saturation Determination – Case Studies in Sandstone and Carbonate Reservoirs
Authors: Teklu Tadesse Weldu , Brown Jeffrey S. , Kazemi Hossein , Graves Ramona M. , AlSumaiti Ali M.
Published: June 2013

In petroleum reservoirs only a small fraction of the original oil-in-place is economically recovered by primary, secondary, and tertiary recovery mechanisms. A considerable amount of hydrocarbon ends up unrecovered or trapped due to microscopic phase trapping in porous media which results in an oil recovery factor typically less than 50%. Waterflooding is by far the most widely used method to increase oil recovery. The oil that remains in the porous media after waterflooding is called remaining oil saturation (ROS) which is larger than the relative permeability residual oil saturation (Sorw or simply Sor). This residual oil saturation varies depending on lithology, pore size distribution, permeability, wettability, fluid characteristics, recovery method, and production scheme. The Sor represents a statistical average over a wide range of pore scale residual saturations with in a representative elementary volume (REV). Determination of the residual oil saturation of a reservoir is a key parameter for reserve assessment and recovery estimates. Further, reliable Sor data is important for investigation of potential incremental recovery under Enhanced Oil Recovery (EOR) methods.

Various residual oil saturation measurement techniques are available both at laboratory and field scale. None of the techniques can be regarded as a single best method of determining Sor. Depending on the complexity of the reservoir under study, combinations of methods are always advisable for appropriate Sor determination. This paper catalogues a number of field case studies which use different techniques of determining Sor and ROS in sandstone and carbonate reservoirs.
Beyond Expected Value: Integrated Project Valuation for Decision Making Under Uncertainty
Authors: Xu Jingzhen
Published: June 2013

Many decisions in petroleum exploration and development have to be made with significant uncertainties. Stochastic simulations are frequently used to capture the consequences of a decision in relation to the uncertain variables within reservoirs, infrastructures and economics. The results of stochastic simulations are often used in the following risk management process to optimize decisions. A big challenge in this process is to frame the outputs of stochastic simulations in a manner which makes sense to the decision-maker and provides him with clear judgemental insights into the problem and its related uncertainties. Traditional decision-tree analysis provides a good way of formulating and structuring decision problems, but one of its disadvantages is that only the expected value is used at a decision node. Most of the decision issues involve both continuous and discrete uncertainties, which can only be fully evaluated using distribution functions. By combining the decision-tree approach with stochastic simulation the term of expected value can be extended to a distribution function. Distribution functions can provide more details than expected values for understanding the influence of relevant uncertainties in the context of a full risk spectrum. Depending on the decision-maker’s risk preference, decisions can be made based on not only the expected value but also upside or downside. A simple example on Value of Information is used to demonstrate the combination of decision-tree approach and stochastic simulation, where the value of information realized by a decision is quantified by a distribution function through Monte Carlo simulation rather than an expected value. A real decision situation concerning infill drilling in a North Sea field is presented to show the procedure of stochastic modeling of a decision tree in the framework of integrated project valuation. Important decisions along the time horizon include scheduling of drilling campaign, pilot or side-track drilling of adjacent prospects, and installing of a new template.
Geology and Geohistory Contribute to Flow Assurance, Part II: Asphaltene Risk Evaluation Incorporating Geological Heterogeneity and Covering All Operating Temperature
Authors: Yonebayashi Hideharu , Tosic Slavko
Published: June 2013

In the Kashagan field, a super giant offshore carbonate field, located in the North Caspian Sea, asphaltene risks have been continuously under evaluation. The previous work done by Yonebayashi et al. (2012)1 included asphaltene risk evaluation incorporating geology and geohistory. Work showed good correlation between fluid sampling location and experimental asphaltene onset pressure (AOP) detection at reservoir temperature. However, a boundary condition of asphaltene precipitation/no-precipitation had some range of uncertainty. The previous work focused at the reservoir temperature condition only.

This paper will present more detailed discussion of asphaltene risk by updating new AOP results, and it will capture range of temperature conditions (i.e. from reservoir temperature to surface operating temperature). For integrating these updates into the Risk-Matrix-Chart proposed in the previous work, geological heterogeneity of fluid sampling location will be taken into account. A study of numerical modeling, applying Redich-Kwong-Soave (RKS) cubic equation of state, treated the geological heterogeneity as variation of asphaltene content, and reproduced asphaltene precipitation envelopes (APE) which were well matched to overall trend of experimental AOP detection. To conclude, this work achieved to reduce uncertainty of asphaltene precipitation boundary at reservoir temperature, and showed a consistent shifting of asphaltene precipitation boundary by temperature range.
Pressure Transients in a Fractal-Cluster Model of Porous Media
Authors: de Swaan A.
Published: June 2013

The reservoir is described as a "supercritical cluster"; that is, an aggregate of condutive elements that comprises a "backbone" of connected pores or fractures that span the zone of interest, and also a collection of "sub-critical clusters" or "dangling ends" joined to the backbone to a limited extent. The scheme resembles the usual fracture and matrix-blocks setting but both backbone and sub-clusters are of the same material and share similar petrophysical properties. Whereas the backbone is a homogeneous porous medium, the sub-critical clusters behave as fractal porous media. The backbone-cluster type of flow has been observed in laboratory experiments.

The sub-critical clusters were approximated as linear fractal media characterized by static and dynamic fractal exponents and also by porosity and permeability of the compound medium. One of the ends of the linear clusters is closed and the other is joined to the backbone, where the mainstream occurs. A new solution was developed for that problem. The Laplace transform in time and space was used in the mathematical scheme.

The theory developed was applied to field cases of interference between wells in aquifers. The matches of computed and observed dynamic pressures show fair fits.
A Review of the Status of Foam Applications in Enhanced Oil Recovery
Authors: Farzaneh Seyed Amir , Sohrabi Mehran
Published: June 2013

Foam has been used for controlling gas mobility during injection processes in order to mitigate the adverse effects of low gas viscosity, reservoir heterogeneity and gravity override. In addition, foam has also been employed in near-wellbore production, matrix acidizing stimulation, hydraulic fracturing, gas shut-off and water shut-off. The optimization of these operations requires a good understanding of the physical characteristics of foam and its behavior under reservoir conditions. Despite numerous experimental and theoretical studies on foam and some field applications reported in the literature, there is no comprehensive literature survey detailing the knowledge and experience gained through the application of foam. The aim of this paper is to present a critical review of the literature available on the use of foam injection for enhanced oil recovery. An extensive appraisal of the current status of foam application in EOR methods is a useful way of presenting advantages, shortcomings and limitations of the process as well as supplementary advances. Special attention has been given to the review of new research topics, such as the use of foam as a mobility control agent. Advances in more efficient foaming agents, additives and boosters are discussed. Moreover, in depth analysis of field applications of foam in EOR projects show that the main problems encountered during field-scale foam applications are related to foam stability, foam compatibility, as well as adsorption of the injected chemicals onto the rock surface. To address this, we discuss the evolution of the pilot field application and the reasons for inconsistency between laboratory results and field scale performance.
Effect of Thermally Induced Deformation of Shale on Wellbore and Caprock Integrity
Authors: Li Biao , Wong Ron
Published: June 2013

During thermal enhanced oil recovery processes such as Cyclic Steam Stimulation (CSS) and Steam Assisted Gravity Drainage (SAGD), heat is transferred from the wellbore and reservoir to the surrounding formation. The thermally induced deformation in shale can pose an impact on casing and caprock integrity. In this research, thermally induced deformation in argillaceous shale was studied by applying an anisotropic thermal-strain model. Shale's intrinsic fabric anisotropy is considered in this new model. Thermally induced strain in shale is contributed by the strain of the solid particle and the strain in clay mineral's microspace such as Stern layer (bound water) and Diffusion Double Layer (DDL). The proposed anisotropic thermal-strain model was used to study on thermally induced deformation behaviors of argillaceous shale in Western Canada Sedimentary Basin (WCSB). The modeled volumetric strain indicates that shale could contract or dilate depending on the clay content and temperature. The resultant behavior represents the combined effect from the thermal expansion of the solid particle and the bound water as well as thermal contraction of the DDL in clay mineral. Due to the oriented fabric in shale, the thermal-strains along the vertical and the horizontal directions are different. Thermally induced contraction could cause loss in confinement provided by the formation and lead to fracturing. Numerical simulations were conducted to investigate temperature distributions around a thermal well for CSS and the reservoir-caprock interface for a SAGD project. The possibility of thermally induced contraction in shale and its impact on borehole and caprock integrity were evaluated.
Numerical Assessment of Caprock Integrity in SAGD Operations
Authors: Rahmati Ehsan , Rahmati Hossein , Nouri Alireza
Published: June 2013

This paper focuses on investigating the impact of Steam Assisted Gravity Drainage (SAGD) operations on caprock stresses. Steam injection, in SAGD operations, results in significant pore pressure, temperature, stress and volumetric changes in the reservoir. One outcome is the deformation and stress variations of the overburden strata that could lead to the containment breach of the caprock through shear or tensile failure.

We developed a model based on the nucleus-of-strain method to assess the reservoir volume changes caused by the combination of reservoir shear dilation, thermal expansion, and increased pore pressure during the SAGD operations. We then developed a forward geomechanical model and used the reservoir volume changes as input data. The nucleus-of-strain model was verified by comparing the measured surface heave data with the same from the forward model.

The geomechanical model was used along with the Mohr-Coulomb failure criterion to assess the stresses and failure potential of the overburden strata. The model was applied to a SAGD reservoir for which surface heave data were available. The outcome indicates the potential for caprock integrity problems due to tensile fracturing. A parametric study was also performed to investigate the sensitivity of the predictions to various significant parameters including the Young's modulus, Poisson's ratio, in situ stress gradient, and reservoir depth, among others. The outcome of the parametric studies will be discussed in this paper.
Modeling Three-Phase Flow During Steam Chamber Rise-Impact of Water Drainage on Oil Production Rate
Authors: He Zhongxue , Murtaza Muhammad , Dehghanpour Hassan
Published: June 2013

The existing models for steam chamber rise rate ignore the effect of water drainage that can result in three-phase flow near the finger/chamber edge. We hypothesize that a steam finger can be divided into three different regions with different pore scale displacement mechanisms. We develop the flux equations for the three regions by assuming 1) negligible oil flow inside the finger, 2) three-phase flow in the transition zone, and 3) single-phase oil flow beyond the transition zone. We further assume that oil flow is coupled to water flow in the transition zone where the dominanat pore-scale mechanisms are double displacement, coalescence, and film drainage. The model results suggest that fast drainage of water in the transition region enhances the oil displacement rate due to the flow coupling. However, increase of the transition zone thickness, due to slow water drainage, decreases the chamber rise rate because of the decrease in the rate of heat conduction to the cold bitumen.
Determination of Thermal Conductivity of Carbonate Cores
Authors: Chen Joyce , Donald James , Huang Haibo , MacDonald Jeff , Jiang Qi , Rabin Mark , Yuan Jian-Yang
Published: June 2013

The difficulties of accurately measuring thermal properties, such as thermal conductivity of fractured and/or vuggy rocks are well known. Many commercially available methods are suitable only for liquids or re-packed sands. Others either require samples to be fairly uniform or are potentially destructive due to sample size limitations. In-situ measurements are possible, but can be costly. It can also be affected by in-situ distributions of fluids in the fractures and vugs, such as water, oil and possibly gas. In order to adapt the highly non-uniform nature of the carbonate cores without having to create further destruction of these cores, we developed a non-destructive method for measuring thermal conductivity of highly vuggy and moderately fractured carbonate cores in their whole diameter. In this paper, we report the theoretical background of this methodology; laboratory observations of thermal behaviours; data analysis and resulting thermal conductivity values of carbonates cores. Using this method, we measured 20 cleaned carbonate cores (88 mm in diameter) from Grosmont C and D Formation in Saleski area. Measured thermal conductivity values ranged from 1.00 to 2.87 W/m•K in Grosmont C, and 0.82 to 3.16 W/m•K in Grosmont D. These values were determined to be a strong function of porosity rather than mineralogy, as the Grosmont Formation typically consists of greater than 95% dolomite. These measurements are also shown to be in good agreement with prior studies on non-fractured dolomite reservoirs. A correlation for thermal conductivity was derived which can be used for numerical simulation models.
Experimental and Numerical Study of VAPEX at Elevated Temperatures
Authors: Haghighat Parnian , Maini Brij , Abedi Jalal
Published: June 2013

Incorporating some heat injection along with the solvent injection appears to be the most viable option for improving the drainage rate of VAPEX in extra-heavy oil formations. The obvious question then concerns the magnitude of temperature increase needed to make the drainage rate economical. The objective of this work was to examine the effect of temperature on VAPEX performance.

VAPEX experiments under different operating conditions were conducted in a high-pressure physical model. Physical model was packed with 250 Darcy sand and saturated with Athabasca bitumen (Mackay River oil). Injecting propane at 0.817 MPa, temperatures from 40 to 60ºC were tested to investigate possible improvement to oil production rates. Experimental results were numerically simulated with a commercial compositional simulator, Computer Modelling Group's (CMG) GEM. CMG's WinProp module, along with available experimental data, was employed to model the phase behavior and properties of the propane / Athabasca bitumen system.

By history matching the experimental production data, results were extended to wider ranges of temperature and VAPEX performance at elevated temperatures was investigated. According to the results, substantial improvement in the performance of VAPEX in reservoirs containing this type of oil would require increasing the reservoir temperature above 60ºC.
Phase Behaviour of CH4-C3H8-Heavy Oil Systems under Reservoir Conditions
Authors: Yang Ping , Li Huazhou , Yang Daoyong
Published: June 2013

In this paper, techniques have been developed to experimentally and theoretically study phase behaviour of CH4-C3H8-heavy oil systems under reservoir conditions. Experimentally, PVT tests are performed to measure saturation pressures and swelling factors of a C3H8-heavy oil system and a CH4-C3H8-heavy oil system under reservoir conditions, respectively. Theoretically, the volume-translated Peng-Robinson equation of state (PR-EOS) together with the modified alpha function has been used to model phase behaviour of the above solvent(s)-heavy oil systems. The binary interaction parameter (BIP) correlation is developed for CH4-heavy oil systems based on the literature data. As for the CH4-C3H8-heavy oil system with a fixed composition, both saturation pressure and swelling factor increase with temperature. The PR-EOS together with the modified alpha function and the newly developed BIP correlation is able to predict the saturation pressures and swelling factors of the CH4-C3H8-heavy oil systems with average absolute deviation of 11.89% and 2.22%, respectively.
Laboratory Study on Steam and Flue Gas Co-injection for Heavy Oil Recovery
Authors: Monte-Mor L. S. , Laboissière P. , Trevisan O. V.
Published: June 2013

The surface steam injection is the most common enhanced oil recovery (EOR) process used in heavy oil production. Nevertheless, there are limitations due to the heat loss for deep reservoirs and for offshore fields. Downhole steam generators (DHSG) are a new technology that opens a new path for recovery of heavy oil from deep reservoirs, offshore fields and extreme cold regions. Downhole steam generators eliminate the need for surface steam distribution systems, for flowlines and wellbore steam strings. The outflow of DHSG generators are a mixture of steam and flue gas. The main objective of this paper is to investigate the recovery dynamics of steam injection combined with flue gas at lab scale to recover a 16.14°API heavy oil from a sandpack. Superheated steam at 170°C was co-injected at flow rates between 5 and 4.5 ml/min (cold-water equivalent) with flue gas at flow rates between 150 and 340 ml/min in a linear cell built for the continuous injection of steam. From the results it can be asserted that co-injection reduces by 10% the amount of steam needed for an equivalent recovery. That translates in cutting steam generator costs on a per barrel of oil produced basis. The results of the tests addressed in this study provide: 1) The gas helps to keep the pressure behind the front more stable; 2) the co-injection of steam with flue gas accelerates the start of oil production when compared with steam injection alone; 3) Results indicates recovery factors up to 79%. The results favors DHSG as a promising technology for enhanced oil recovery of heavy oils, mainly for offshore fields or reservoirs at great depth.
Optimal Application Conditions of Solvent Injection into Oilsands to Minimize the Effect of Asphaltene Deposition: An Experimental Investigation
Authors: Moreno L.. , Babadagli T..
Published: June 2013

Solvent injection into heavy-oil reservoirs is quite complex on account of the asphaltene destabilization that occurs due to the changes in temperature, pressure, and solvent type dissolved in oil. As a result of this destabilization, the asphaltene precipitates, flocculates, and eventually plugs the pores in the reservoir due to the formation of asphaltene clusters. In solvent applications, light molecular weight hydrocarbon solvents are preferred because of their high diffusion coefficient; but, as the carbon number of n-alkane solvents decreases, asphaltene precipitation increases. Therefore, the selection of the solvent and application condition is highly critical in cold and thermally-aided solvent applications.

In this research, low carbon number n-alkane (propane, n-hexane and n-decane) injection into sand pack systems saturated with heavy-oil (87651 cp) was evaluated at different pressure conditions that are applicable to typical Canadian oilsands reservoirs (100-300 psi) and temperatures (25-120 °C). First, the asphaltene behavior of different solvents at different pressures and temperatures were studied through deasphalting work in a pressure-volume-temperature (PVT) cell. Based on the quantitative (amount of asphaltene precipitated) and qualitative (microscopic images of asphaltene clusters) observations, the characteristics of asphaltene were classified in terms of their shape, size, and amount for different oil/solvent types, pressure, and temperature.

Continually, the same n-alkane solvents and heavy-oil were used in gravity drainage recovery experiments on unconsolidated sands. 2-D visual (Hele-Shaw type) and 3-D (cylindrical) sand pack experiments were carried out at the same temperatures and pressure conditions used for the PVT experiments. The asphaltene precipitated in the sand pack and in the produced oil was collected, and the standard SARA analysis was applied to determine the optimal operating conditions yielding the highest recoveries with minimal pore plugging. Moreover, the pore plugging process was analyzed through the visual inspection of 3-D sand pack experiments and the 2-D visual model using microscopic visualization and cross-checked against oil recovery rate. The asphaltene characteristics and concentration were evaluated using the microscope visualization and refractive index values, respectively. Eventually, optimal application conditions for solvent and thermally-aided solvent injection were listed for a wide range of heavy-oil and solvent types.
More Realistic Four-Phase Stability and Phase Splitting Calculations for Canadian Heavy Oil and Bitumen Reservoirs Using Solvent Injection Processes
Authors: Feizabadi Seyed Ali , Abedi Jalal , Chen Zhangxin
Published: June 2013

Steam assisted gravity drainage (SAGD) is the only economical and applicable method which the majority of companies are using to extract bitumen from the Alberta oil sands. However, there are some deficiencies in this method, including a high rate of heat loss to overburden and underburden formations in narrow (less than 15 m) oil bearing strata, a high operational cost for producing and injecting steam, and the treatment of the contaminated produced water. These disadvantages have researchers searching for other methods, such as solvent injection.

Different solvents can be considered for injection into a bitumen reservoir, such as ethane and carbon dioxide (CO2). Using CO2 as the solvent has two major advantages: achievement of miscibility with the bitumen, making it mobile by reducing its viscosity, and storage of CO2 underground. The latter is the goal of many researchers addressing the challenges of climate change.

In large-scale compositional simulations, equilibrium constants for different components in a solvent/bitumen mixture are a prerequisite. When there is no initial guess or empirical correlation for K values, the only way to obtain a true equilibrium constant is through phase stability and phase splitting calculations. Since experiments have acknowledged the formation of a second liquid phase in certain ranges of pressures and temperatures when mixing Alberta bitumen samples with solvents, fast and robust four-phase stability and splitting calculations are necessary. The four phases are the liquid diluted bitumen phase, the liquid solvent-rich phase, the solvent gas phase and the water (aqueous) phase.

The Peng-Robinson equation of state and its derivatives have been used for compressibility calculations in this study. Also, a combination of successive substitution and the Newton method has been used for phase splitting calculations for robustness.

The results have been compared to those of the available PVT simulation software (WinProp, Computer Modelling Group) and also to the experimental and modeling results of Mehrotra and Svrcek (1984). These results and comparisons indicate that the second liquid (solvent-rich) and water phases remain almost unchanged with changing pressures and temperatures; however, the components of the first liquid (diluted bitumen) and gas phases do change. This supports the idea of considering water as a phase and not as a component, which is the assumption in most compositional simulations.
Cysteine-modified orange peel for removal of Cu(II) from aqueous solutions
Authors: Liu Mingdeng , Yuan Qunhui , Jia Hanzhong , Li Shouzhu , Wang Xiaohuan , Wang Chuanyi
Published: June 2013

In the present work, cysteine-modified orange peel (COP) for the removal of Cu(II) from aqueous solutions has been developed and comparatively studied with diethylenetriamine-modified orange peel (DOP). Both COP and DOP were systematically evaluated via their capabilities for adsorbing Cu(II), including the key influential parameters such as initial pH, contact time and initial Cu(II) concentration. Further studies suggest that the sorption of Cu(II) onto both COP and DOP fits well with the pseudo-second-order equation, and the corresponding sorption isotherm can be classified to a Langmuir isotherm model. COP appears more advantageous over DOP and far better than that of unmodified OP in removal of Cu(II) from aqueous system. The maximum capacities of COP and DOP for adsorbing Cu(II) are 95.23 and 83.68 mg/g, respectively, about three times higher than that of unmodified OP. The sorption efficiency of COP drops by merely about 3% after five cycles, implying a promising usage in the removal of Cu(II) from wastewater in practice.
A new disinfection system for wastewater treatment: performic acid full-scale trial evaluations
Authors: Ragazzo P. , Chiucchini N. , Piccolo V. , Ostoich M.
Published: June 2013

To evaluate the efficiency and effect of a new disinfection technology in wastewater treatment, batch and full-scale experiments were performed between winter 2005 and summer 2011. The system, developed by Kemira Oyj, produces a disinfection solution containing performic acid (PFA) by mixing hydrogen peroxide and formic acid. A preliminary study in batch reactors established the suitability for wastewater disinfection; three subsequent full-scale plant experiments conducted at two municipal wastewater treatment plants (120,000 and 32,000 equivalent inhabitants) discharging in sensitive areas demonstrated its effectiveness and reliability in this application field. The disinfection power of the system was measured using faecal coliforms, Escherichia coli and faecal enterococci; additional water quality parameters included total organic carbon, suspended solids, eco-toxicity and disinfection by-products. Full-scale experiments indicated that PFA has a high disinfection power, always ensuring over 3 log of faecal coliforms and E. coli reductions at CT over 60 mg/L min (CT: disinfectant initial Concentration (mg/L) × contact Time (min)). The final production system yielded even better performance, with E. coli and faecal enterococci reductions ranging from 2 to 4.2 and from 0.7 to 3.2 log, respectively, at CT conditions lower than 23 mg/L min. There were no eco-toxicological effects measured by Vibrio fischeri or by-product formation.
Aeration control – a review
Authors: Åmand L. , Olsson G. , Carlsson B.
Published: June 2013

This review covers automatic control of continuous aeration systems in municipal wastewater treatment plants. The review focuses on published research in the 21st century and describes research into various methods to decide and control the dissolved oxygen (DO) concentration and to control the aerobic volume with special focus on plants with nitrogen removal. Important aspects of control system implementation and success are discussed, together with a critical review of published research on the topic. With respect to DO control and determination, the strategies used for control span from modifications and developments of conventional control methods which have been explored since the 1970s, to advanced control such as model-based predictive and optimal controllers. The review is supplemented with a summary of comparisons between control strategies evaluated in full-scale, pilot-scale and in simulations.
pH variation and influence in an autotrophic nitrogen removing biofilm system using an efficient numerical solution strategy
Authors: Vangsgaard Anna Katrine , Mauricio-Iglesias Miguel , Valverde-Pérez Borja , Gernaey Krist V. , Sin Gürkan
Published: June 2013

A pH simulator consisting of an efficient numerical solver of a system of nine nonlinear equations was constructed and implemented in the modeling software MATLAB. The pH simulator was integrated in a granular biofilm model and used to simulate the pH profiles within granules performing the nitritation–anammox process for a range of operating points. The simulation results showed that pH profiles were consistently increasing with increasing depth into the granule, since the proton-producing aerobic ammonium-oxidizing bacteria (AOB) were located close to the granule surface. Despite this pH profile, more NH3 was available for AOB than for anaerobic ammonium oxidizers, located in the center of the granules. However, operating at a higher oxygen loading resulted in steeper changes in pH over the depth of the granule and caused the NH3 concentration profile to increase from the granule surface towards the center. The initial value of the background charge and influent bicarbonate concentration were found to greatly influence the simulation result and should be accurately measured. Since the change in pH over the depth of the biofilm was relatively small, the activity potential of the microbial groups affected by the pH did not change more than 5% over the depth of the granules.
Analysis of fast boundary-integral approximations for
modeling electrostatic contributions of molecular
binding
Authors: Kreienkamp Amelia B. , Liu Lucy Y. , Minkara Mona S. , Knepley Matthew G. , Bardhan Jaydeep P. , Radhakrishnan Mala L.
Published: June 2013

We analyze and suggest improvements to a recently developed
approximate continuum-electrostatic model for proteins.
The model, called BIBEE/I (boundary-integral based
electrostatics estimation with interpolation), was able to estimate
electrostatic solvation free energies to within a mean unsigned
error of 4% on a test set of more than 600 proteins¶a
significant improvement over previous BIBEE models. In this
work, we tested the BIBEE/I model for its capability to predict
residue-by-residue interactions in protein–protein binding,
using the widely studied model system of trypsin and bovine
pancreatic trypsin inhibitor (BPTI). Finding that the BIBEE/I
model performs surprisingly less well in this task than simpler
BIBEE models, we seek to explain this behavior in terms
of the models’ differing spectral approximations of the exact
boundary-integral operator. Calculations of analytically solvable
systems (spheres and tri-axial ellipsoids) suggest two
possibilities for improvement. The first is a modified BIBEE/I
approach that captures the asymptotic eigenvalue limit correctly,
and the second involves the dipole and quadrupole
modes for ellipsoidal approximations of protein geometries.
Our analysis suggests that fast, rigorous approximate models
derived from reduced-basis approximation of boundaryintegral
equations might reach unprecedented accuracy, if the
dipole and quadrupole modes can be captured quickly for
general shapes.
A Biomechanical Perspective on Physical Therapy Management of Knee Osteoarthritis
Authors: Farrokhi Shawn , Voycheck Carrie A. , Tashman Scott , Fitzgerald G. Kelley
Published: June 2013

Synopsis

Altered knee joint biomechanics and excessive joint loading have long been considered as important contributors to the development and progression of knee osteoarthritis. Therefore, a better understanding of how various treatment options influence the loading environment of the knee joint could have practical implications for devising more effective physical therapy management strategies. The aim of this clinical commentary was to review the pertinent biomechanical evidence supporting the use of treatment options intended to provide protection against excessive joint loading while offering symptomatic relief and functional improvements for better long-term management of patients with knee osteoarthritis. The biomechanical and clinical evidence regarding the effectiveness of knee joint offloading strategies, including contralateral cane use, laterally wedged shoe insoles, variable-stiffness shoes, valgus knee bracing, and gait-modification strategies, within the context of effective disease management is discussed. In addition, the potential role of therapeutic exercise and neuromuscular training to improve the mechanical environment of the knee joint is considered. Management strategies for treatment of joint instability and patellofemoral compartment disease are also mentioned. Based on the evidence presented as part of this clinical commentary, it is argued that special considerations for the role of knee joint biomechanics and excessive joint loading are necessary in designing effective short- and long-term management strategies for treatment of patients with knee osteoarthritis.

Level of Evidence

Therapy, level 5. J Orthop Sports Phys Ther 2013;43(9):600–619. Epub 11 June 2013. doi:10.2519/jospt.2013.4121
Effectiveness of Dry Needling for Upper-Quarter Myofascial Pain: A Systematic Review and Meta-analysis
Authors: Kietrys David M. , Palombaro Kerstin M. , Azzaretto Erica , Hubler Richard , Schaller Bret , Schlussel J. Mathew , Tucker Mary
Published: June 2013

Study Design

Systematic review and meta-analysis.

Background

Myofascial pain syndrome (MPS) is associated with hyperalgesic zones in muscle called myofascial trigger points. When palpated, active myofascial trigger points cause local or referred symptoms, including pain. Dry needling involves inserting an acupuncture-like needle into a myofascial trigger point, with the goal of reducing pain and restoring range of motion.

Objective

To explore the evidence regarding the effectiveness of dry needling to reduce pain in patients with MPS of the upper quarter.

Methods

An electronic literature search was performed using the key word dry needling. Articles identified with the search were screened for the following inclusion criteria: human subjects, randomized controlled trial (RCT), dry needling intervention group, and MPS involving the upper quarter. The RCTs that met these criteria were assessed and scored for internal validity using the MacDermid Quality Checklist. Four separate meta-analyses were performed: (1) dry needling compared to sham or control immediately after treatment, (2) dry needling compared to sham or control at 4 weeks, (3) dry needling compared to other treatments immediately after treatment, and (4) dry needling compared to other treatments at 4 weeks.

Results

The initial search yielded 246 articles. Twelve RCTs were ultimately selected. The methodological quality scores ranged from 23 to 40 points, with a mean of 34 points (scale range, 0–48; best possible score, 48). The findings of 3 studies that compared dry needling to sham or placebo treatment provided evidence that dry needling can immediately decrease pain in patients with upper-quarter MPS, with an overall effect favoring dry needling. The findings of 2 studies that compared dry needling to sham or placebo treatment provided evidence that dry needling can decrease pain after 4 weeks in patients with upper-quarter MPS, although a wide confidence interval for the overall effect limits the impact of the effect. Findings of studies that compared dry needling to other treatments were highly heterogeneous, most likely due to variance in the comparison treatments. There was evidence from 2 studies that lidocaine injection may be more effective in reducing pain than dry needling at 4 weeks.

Conclusion

Based on the best current available evidence (grade A), we recommend dry needling, compared to sham or placebo, for decreasing pain immediately after treatment and at 4 weeks in patients with upper-quarter MPS. Due to the small number of high-quality RCTs published to date, additional well-designed studies are needed to support this recommendation.

Level of Evidence

Therapy, level 1a-. J Orthop Sports Phys Ther 2013;43(9):620–634. Epub 11 June 2013. doi:10.2519/jospt.2013.4668
Writing Symptomatically
Authors: Hanrahan Mairéad
Published: June 2013

Hélène Cixous and Jacques Derrida position themselves very differently in relation to literature. This article analyses that difference in the light of their relation to the symptom, the fundamentally unanalysable form through which the unconscious manifests itself. While Derrida dwells more on the impossibility of ever accessing the original secret wound to whose existence the symptom opaquely attests, Cixous tends to focus more on the effect, the symptom itself. For both, the ‘chance’ of literature lies in the fact that neither the source nor the destination of letters can be determined. I argue that the difference between Derrida's relative resignation to this condition and Cixous's celebration of it helps to explain the contrast between his position at the margins of literature and her unequivocal embrace of it.
Faulty Burials: Reinventing Psychoanalysis
Authors: Regard Frédéric
Published: June 2013

Spectrality has always been a threat to order, to the logic of difference and binary opposites — a threat therefore to the classic law of ontology, which deconstructionist thinkers and writers have consistently sought to subvert, prominently among them Jacques Derrida and Hélène Cixous. While also engaging in an implicit dialogue with Louis Althusser's theory of ‘interpellation’, Cixous and Derrida have reinvented the psychoanalysis of gender-production through their reading of each other. Spectrality is for them an injunction to preserve otherness and safeguard the presence/absence of what in fact does not yet exist, the almost unnameable which pushes at the boundaries of language and thought, and whose mystery writing aspires to attend to. Burials should not thus be performed according to established practice: they must be faulty.
Quantum Contextuality with Stabilizer States
Authors: Howard Mark , Brennan Eoin , Vala Jiri
Published: June 2013

The Pauli groups are ubiquitous in quantum information theory because of their usefulness in describing quantum states and operations and their readily understood symmetry properties. In addition, the most well-understood quantum error correcting codes—stabilizer codes—are built using Pauli operators. The eigenstates of these operators—stabilizer states—display a structure (e.g., mutual orthogonality relationships) that has made them useful in examples of multi-qubit non-locality and contextuality. Here, we apply the graph-theoretical contextuality formalism of Cabello, Severini and Winter to sets of stabilizer states, with particular attention to the effect of generalizing two-level qubit systems to odd prime d-level qudit systems. While state-independent contextuality using two-qubit states does not generalize to qudits, we show explicitly how state-dependent contextuality associated with a Bell inequality does generalize. Along the way we note various structural properties of stabilizer states, with respect to their orthogonality relationships, which may be of independent interest.
Accumulations of Heavy Metals in Roadside Soils Close to Zhaling, Eling and Nam Co Lakes in the Tibetan Plateau
Authors: Yan Xuedong , Zhang Fan , Gao Dan , Zeng Chen , Xiang Wang , Zhang Man
Published: June 2013

Concentrations of four typical heavy metals (Cu; Zn; Cd and Pb) in roadside soils close to three lakes in the Tibetan Plateau were investigated in this study. The hierarchical tree-based regression method was applied to classify concentrations of the heavy metals and analyze their potential influencing factors. It was found that the Tibetan Plateau meadow soils with higher content of sand lead to higher concentrations of Cu; Zn and Pb. The concentrations of Cd and Pb increase with road traffic volume; and for the road segments with higher traffic volume; the Cd and Pb concentrations significantly decrease with the roadside distance. Additionally; the concentrations of Zn and Pb increase as the altitude of sampling site increases. Furthermore; the Hakanson potential ecological risk index method was used to assess the contamination degree of the heavy metals for the study regions. The results show that accumulations of Cu; Zn and Pb in roadside soils remain an unpolluted level at all sites. However; the Cd indices in the regions with higher traffic volume have reached a strong potential ecological risk level; and some spots with peak concentrations have even been severely polluted due to traffic activities.
Lymphocytes of Patients with Alzheimer’s Disease Display Different DNA Damage Repair Kinetics and Expression Profiles of DNA Repair and Stress Response Genes
Authors: Leandro Giovana , Lobo Romulo , Oliveira Douglas , Moriguti Julio , Sakamoto-Hojo Elza
Published: June 2013

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, characterized by loss of memory and cognitive capacity. Given the limitations to analyze brain cells, it is important to study whether peripheral lymphocytes can provide biological markers for AD, an interesting approach, once they represent the overall condition of the organism. To that extent, we sought to find whether lymphocytes of AD patients present DNA damage and repair kinetics different from those found in elderly matched controls (EC group) under in vitro treatment with hydrogen peroxide. We found that AD patient cells indeed showed an altered DNA repair kinetics (comet assay). Real-time quantitative analysis of genes associated with DNA stress response also showed that FANCG and CDKN1A are upregulated in AD, while MTH1 is downregulated, compared with the control group. In contrast, the expression of ATM, ATR and FEN1 genes does not seem to differ between these groups. Interestingly, TP53 protein expression was increased in AD patients. Therefore, we found that kinetics of the stress response in the DNA were significantly different in AD patients, supporting the hypothesis that repair pathways may be compromised in AD and that peripheral lymphocytes can reveal this condition.
Terahertz Wave Propagation in a Nanotube Conveying Fluid Taking into Account Surface Effect
Authors: Zhang Ye-Wei , Yang Tian-Zhi , Zang Jian , Fang Bo
Published: June 2013

In nanoscale structure sizes, the surface-to-bulk energy ratio is high and the surface effects must be taken into account. Surface effect plays a key role in accurately predicting the vibration behavior of nanostructures. In this paper, the wave behaviors of a single-walled carbon nanotube (CNT) conveying fluid are studied. The nonlocal Timoshenko beam theory is used and the surface effect is taken into account. It is found that the fluid can flow at a very high flow velocity and the wave propagates in the terahertz frequency range. The surface effects can significantly enhance the propagating frequency. This finding is different from the classical model where the surface effect is neglected.