bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Applications of Waterflood Optimization via Optimal Rate Control With Smart Wells
Authors: Alhuthali Ahmed H. , Datta-Gupta Akhil , Yuen Bevan , Fontanilla Jerry P.
Published: July 2010

Waterflood optimization by means of rate control is receiving considerable attention because of increasing deployments of smart well completions and i-field technology. The use of inflow control valves (ICVs) allows us to optimize the production/injection rates of various segments along the wellbore, thereby maximizing sweep efficiency and delaying water breakthrough. Field-scale rate-optimization problems, however, involve highly complex reservoir models, production and facility constraints, and a large number of unknowns. In this paper, we propose an approach that is computationally efficient and suitable for large field cases. It is based on our previous work (Alhuthali et al. 2007, 2008), which relies on equalizing arrival time of the waterfront at all producers to maximize the sweep efficiency. We use streamlines to efficiently and analytically compute the sensitivity of the arrival times with respect to well rates. We also account for geologic uncertainty by means of a stochastic optimization framework using multiple realizations. Analytical forms for gradients and Hessian of the objective functions are derived, making our optimization computationally efficient for large-scale applications. Finally, optimization is performed under operational and facility constraints using a sequential quadratic programming approach.

We demonstrate our approach using two field-scale examples. The first is a synthetic example called "Brugge" field, a benchmark case based on a North Sea Brent-type field. The production optimization of this field is carried out as part of a closed-loop process where the production history is matched prior to the production optimization. The production optimization is performed over multiple realizations for 20 years and involves 30 wells equipped with three ICVs per well. The second example is a super-giant Middle Eastern field that has more than 50 years of historical oil production. The optimization is performed for 20 years on a portion of this field that contains nearly 300 wells consisting of conventional vertical and horizontal wells and smart horizontal wells. In both examples, multiple field-related constraints are imposed, such as the maximum well injection and production rates, the maximum allowable drawdown, restriction on high-water-cut wells, and voidage replacement for pressure maintenance. The results clearly demonstrate the viability of our approach and the benefits of optimal rate control, with a considerable increase in cumulative oil production and a substantial decrease in the associated water production.
Results of the Brugge Benchmark Study for Flooding Optimization and History Matching
Authors: Peters E. , Arts R. J. , Brouwer G. K. , Geel C. R. , Cullick S. , Lorentzen R. J. , Chen Y. , Dunlop K. N. B. , Vossepoel F. C. , Xu R. , Sarma P. , Alhutali A. H. , Reynolds A. C.
Published: July 2010

In preparation for the SPE Applied Technology Workshop (ATW) held in Brugge in June 2008, a unique benchmark project was organized to test the combined use of waterflooding-optimization and history-matching methods in a closed-loop workflow. The benchmark was organized in the form of an interactive competition during the months preceding the ATW. The goal set for the exercise was to create a set of history-matched reservoir models and then to find an optimal waterflooding strategy for an oil field containing 20 producers and 10 injectors that can each be controlled by three inflow-control valves (ICVs). A synthetic data set was made available to the participants by TNO, consisting of well-log data, the structure of the reservoir, 10 years of production data, inverted time-lapse seismic data, and other information necessary for the exercise. The parameters to be estimated during the history match were permeability, porosity, and net-to gross- (NTG) thickness ratio. The optimized production strategy was tested on a synthetic truth model developed by TNO, which was also used to generate the production data and inverted time-lapse seismic. Because of time and practical constraints, a full closed-loop exercise was not possible; however, the participants could obtain the response to their production strategy after 10 years, update their models, and resubmit a revised production strategy for the final 10 years of production. In total, nine groups participated in the exercise. The spread of the net present value (NPV) obtained by the different participants is on the order of 10%. The highest result that was obtained is only 3% below the optimized case determined for the known truth field. Although not an objective of this exercise, it was shown that the increase in NPV as a result of having three control intervals per well instead of one was considerable (approximately 20%). The results also showed that the NPV achieved with the flooding strategy that was updated after additional production data became available was consistently higher than before the data became available.
Thermal Streamline Simulation for Hot Waterflooding
Authors: Zhu Z.. , Gerritsen M.G.. G. , Thiele M.R.. R.
Published: July 2010

We explore the extension of streamline simulation to thermal-recovery processes. For each global timestep, we first compute the pressure field on an Eulerian grid. We then solve for the advective parts of the mass balance and energy equations along the individual streamlines. At the end of each global timestep, we account for the nonadvective terms of the transport equations on the Eulerian grid along with gravity, using the operator splitting method. We included temperature-dependent viscosity and account for thermal expansion of the fluids. We tested our streamline simulator on 2D heterogeneous quarter five-spot problems and compared the results with those computed by a commercial thermal simulator both for accuracy and computational efficiency. We present sensitivity studies for effects of fluid compressibility, gravity, and thermal-conductivity. For the cases investigated, our thermal streamline simulator is capable of producing accurate results at a computational cost that is significantly lower than that of existing Eulerian simulators.
Natural and Conventional Tracers for Improving Reservoir Models Using the EnKF Approach
Authors: Huseby Olaf , Valestrand Randi , Nœvdal Geir , Sagen Jan
Published: July 2010

Natural tracers (geochemical and isotopic variations in injected and formation waters) are a mostly unused source of information in reservoir modeling. On the other hand, conventional interwell tracer tests are an established method to identify flow patterns. However, they are typically underexploited, and tracer-test evaluations are often performed in a qualitative manner and are rarely compared systematically to simulation results. To integrate naturaland conventional-tracer data in a reservoir-modeling workflow, we use the ensemble Kalman filter (EnKF), which has recently gained popularity as a method for history matching. The EnKF includes online update of parameters and the dynamical states. An ensemble of model representations is used to represent the model uncertainty. In this paper, we include conventional water tracers as well as natural tracers (i.e., geochemical variations) in the EnKF approach. The methodology is demonstrated by estimating permeability and porosity fields in a synthetic field case based on a real North Sea field example. The results show that conventional tracers and geochemical variations yield additional improvement in the estimates and that the EnKF approach is well suited as a tool to include in this process. The principal benefit from the methodology is improved models and forecasts from reservoir simulations, through optimal use of conventional and natural tracers. Some of the natural-tracer data (e.g., scale-forming ions and toxic compounds) are monitored for other purposes, and exploiting such data can yield significant reservoir-model improvement at a small cost.
Misconceptions Regarding the Chemical Role of Completion/Packer Fluids in Annular Environmentally Assisted Cracking of Martensitic Stainless Steel Tubing
Authors: McKennis Jeffrey S. , Sook-Bae Nam , Termine Enrico J. , Shimamoto Ken , Kimura Mitsuo
Published: July 2010

The increased use of corrosion resistant alloys (CRAs) in deep high-pressure/high-temperature (HP/HT) wells has led to production-tubing cracking failures throughout the industry. Many of these failures have occurred from the outside (annulus side) and have been attributed to environmentally assisted cracking (EAC) and, hence, are best described as annular EAC (AEAC). Examination of these failures points to a serious incompatibility of the production tubing metallurgy with the packer fluid under stress.

In 2003, combining expertise in fluid chemistry and metallurgy, the authors formed a research alliance to address the AEAC problem by examining the compatibility of a wide spectrum of completion fluids with various martensitic stainless steel (MSS) metallurgies. This unique research collaboration, involving extensive stress-cracking testing performed with different metallurgies and different fluids under simulated well conditions, has resulted in an extensive database (more than 4,000 test entries for 27 fluids and six MSS metallurgies) and a new body of knowledge regarding the causes behind AEAC failures.

Conventional wisdom holds that chloride ion and oxygen play major causative roles. The authors’ findings, however, identify other contaminants in completion/packer fluids that play the dominant role in the chemical mechanism of the crack failures. Such contaminants include sulfur-containing species, oxidants other than oxygen, and select basic ionic species. This paper addresses the effect of the new information and identifies serious misconceptions regarding the role of completion /packer fluids in the tubular failures.

The authors’ comprehensive study has advanced the industry's knowledge of the causes of AEAC by detailing the previously unrecognized importance of various contaminants present in the fluids. As a consequence, the need for quality assurance and best- practice fluid management throughout the life cycle of the fluids is now recognized. Misconceptions with respect to the chemical mechanisms and causative factors of AEAC failures are discussed. Such information should expand the industry's AEAC knowledge base and minimize the risk of tubular failure.
Quantitative Evaluation of Calcium Sulfate Precipitation Kinetics in the Presence and Absence of Scale Inhibitors
Authors: Fan Chunfang , Kan Amy T , Fu Gongmin , Tomson Mason B , Shen Dong
Published: July 2010

In this study, the nucleation kinetics of calcium sulfate scale formation in the presence and absence of scale inhibitors has been studied. The nucleation kinetics of calcium sulfates in 0–3.2 M NaCl solution was measured from 0 to 200°C at various supersaturation conditions [saturation index (SI) = 0–1.3]. The phase behavior of these various calcium sulfate phases was monitored by X-ray diffraction (XRD). The inhibition study was performed by evaluating the inhibition efficiency of calcium sulfate precipitation at the same supersaturation and temperature ranges as those of the nucleation study. Several polyphosphonate, polymeric, and environmentally friendly inhibitors were found to be effective inhibitors. The study has shown that calcium sulfate scales are very difficult to inhibit at SI > 1. Calcium sulfate scale is inhibited most effectively by hexamethylenediamine tetra(methylene phosphonic acid) (HDTMP) if the saturation index is less than approximately 1.0. In addition, a semiquantitative model to predict precipitation kinetics of calcium sulfate as a function of temperature, pH, SI, and HDTMP concentration is established with experimental results from this study. The effect of methanol and methylene glycol (MEG) on calcium sulfate precipitation kinetics and inhibition is also presented.
Design of a High-Pressure Research Flow Loop for the Experimental Investigation of Liquid Loading in Gas Wells
Authors: Fernandez J.. , Falcone G.. , Teodoriu C..
Published: July 2010

Existing models to predict and analyze liquid loading in gas wells are based on steady-state flow. Even when transient-multiphase- wellbore models are employed, steady-state or pseudosteady-state inflow-performance relationships are used to characterize the reservoir. A more-reliable approach consists of modeling the dynamics in the near-wellbore region with its transient boundary conditions for the wellbore. The development of new models to mimic the dynamic interaction between reservoir and wellbore requires a purpose-built flow loop. We have developed a design to construct such a facility.

This new facility will be the first to integrate pipe representing the wellbore with a porous medium that will fully mimic the formation surrounding the wellbore. This design will account not only for flow into the wellbore, but also for any reverse flow from the pipe into the medium.

We used integrated wellbore/reservoir system analysis to screen the parameters required to recreate liquid loading under laboratory conditions. Our results suggested using a compressed-air system with a discharge pressure between 470 and 650 psi with gas rates of 400 to 650 scf/min along with water injected at a rate of 100 gal/min. Once the range in operating conditions was defined, the equipment and mechanical components for the facility were selected and designed.

Our results showed that three reciprocating compressors working in parallel provide the smallest, most economic, and most flexible configuration for the TowerLab facility at Texas A&M University (TAMU). The design of the pressure vessel hosting the porous medium will require a cylindrical body with top- and bottom-welded flathead covers with multiple openings to minimize weight. The required superficial velocities for air and water indicate the system will need independent injection into the porous medium through two manifolds. Optimally, the system will use digital pressure gauges, coriolis or vortex technology to measure air flow, and turbine meters for water flow.

A joint-industry project (JIP) on liquid loading in gas wells was initiated in January 2009, which includes the implementation of the proposed design for the TowerLab facility to generate experimental data that will significantly improve our ability to mimic the physics of multiphase flow, and so develop and validate flow models for the characterization of liquid loading in gas wells. It is anticipated that a preliminary version of the new loop, including an inlet multiphase-flow pump, has been assembled and will be operational early in Fall 2010, with plans for the full design to be implemented in 2010-11.
Integration of Well-Test Pressure Data Into Heterogeneous Geological Reservoir Models
Authors: Li Gaoming , Han Mei , Banerjee Raj , Reynolds Albert C.
Published: July 2010

This paper presents the application of the ensemble Kalman filter (EnKF) method to the integration of well-test data into heterogeneous reservoir models generated from geological and geophysical data. EnKF does not require computing the gradient of an objective function and, hence, can be applied easily with any reservoir simulator, and more importantly, it is far more efficient than a gradient-based history-matching procedure when the forward model is represented by a reservoir simulator. In the procedure for integrating pressure-transient data considered here, the static geological/geophysical data are assumed to be encapsulated in a multivariate probability-density function (pdf) characterized by a prior mean and covariance for the joint distribution of the porosity and permeability fields. Because the prior mean of the property fields obtained from the core and log data can sometimes be erroneous, a partially doubly stochastic model is applied to account for the uncertainty of the prior mean. In the doubly stochastic model, a correction to the prior mean is adjusted together with the heterogeneous field during history matching. The method is tested with synthetic heterogeneous single-layer and two-layer reservoirs. Excellent data matches are obtained with EnKF in a small fraction of the time that would be required for a gradient-based history-matching process, and the observed data fall within the uncertainty bounds of the ensemble data predictions. In the layered-reservoir case, the uncertainty in rock-property fields is reduced further by integration of production-log data (layer flow rates). We show that problems of statistical inconsistency and poor data matches that are sometimes encountered when matching production data with EnKF do not occur when matching pressure data with the EnKF implementation used here. This undoubtedly occurs because the dynamical system (reservoir-simulator equations) is much more nearly linear for the single-phase-flow problems considered here than for multiphase-flow cases.
A Novel a-Amylase Enzyme Stabilizer for Application at High Temperatures
Authors: Samuel Mathew , Mohsen Abdul Hameed , Ejan Aziz Bin , Ooi Yean Sang , Ashraf Shameed , Nasr-El-Din Hisham A.
Published: July 2010

Cleanup of drilling-fluid filter cake in long horizontal and multilateral wells is a difficult task. Both mechanical and chemical means (acids, oxidizers, chelating agents, and enzymes) have been used in the field. However, these methods have serious limitations and can affect well performance adversely. Acids and oxidizers are very reactive, but are nonspecific. Enzymes can be used to degrade starch and xanthan polymers. The major limitation of enzymes is their inability to stay active at temperatures greater than 200°F.

The activity of enzymes at 207°F was less than 10% of their activity at 200°F. Previous studies to increase the stability enzymes were aimed at: (1) changing salinity, (2) changing the source of the enzymes, (3) using additives that alter the conformation of enzymes, or (4) modifying the enzymes chemically. These techniques did not maintain the activity of the enzymes at 200°F. For filter-cake removal, enzymes have been used globally at higher temperatures, though their activity is known to be much less than 2%.

This paper examines the use of chemicals that function as a stabilizer for enzymes up to 250°F. Optimized concentrations of this stabilizer not only inhibit the coagulation of enzymes at these high temperatures but also maintain the activity of enzymes at the high temperatures that are encountered in the oil field. Laboratory studies on the stability, compatibility, and filter-cake-damage reversal were conducted with stabilized-enzyme formulation.

Experimental results indicated that the new proprietary enzyme stabilizer was very effective in eliminating the deactivation tendency of enzymes at high temperatures. Conventionally, enzymes coagulated at temperatures greater than 140°F and charred when exposed to temperatures greater than 200°F, but in the presence of the stabilizer, precipitation and burning were not observed. When using an enzyme at high temperatures without the stabilizer, the burned residue accumulated on the surface, resulting in a thin film that reduced the permeability of the cake even further. High-pres- sure/high temperature (HP/HT) filtration studies using the enzyme stabilizer showed that this film was not formed, which resulted in a cake with much higher retained permeability.
Simulation of O/W Emulsion Flow in Alkaline/Surfactant Flood for Heavy Oil Recovery
Authors: Wang Jinxun , Dong Mingzhe
Published: July 2010

The formation and flow of emulsions during alkaline flooding process plays an important role for improving heavy oil recovery. In this study alkaline/surfactant (A/S) flood tests were performed in sandpacks to demonstrate the effectiveness of sweep efficiency improvement by the in-situ generated oil-in-water (O/W) emulsion. High tertiary oil recoveries were obtained in sandpack flood tests. Experimental results were history matched by including the mechanisms of in-situ generation and flow of O/W emulsion, as well as the chemical adsorption and the reduction of interfacial tension involved in the chemical flooding process. The decrease in local water phase permeability caused by the entrapment of emulsion droplets was modelled using the filtration theory. Both the pressure response and the oil recovery improvement were fairly matched. Field-scale simulations were conducted to investigate the potential of A/S flooding for heavy oil reservoirs. Simulations showed promising results of chemical flooding for heavy oils. It was indicated that a certain length of waterflooding time would benefit the final oil recovery, and there existed an optimum chemical slug size. These laboratory results and the simulation technique are helpful in the simulation and design of field-scale projects of chemical flooding for enhanced heavy oil recovery.
Estimation of Bitumen and Solids Content in Fine Tailings Using Low-Field NMR Technique
Authors: Motta Cabrera Sandra C. , Bryan Jonathan L. , Kantzas Apostolos
Published: July 2010

The oil sands mining and extraction processes in Canada produce large volumes of tailings that are a mixture of mainly water, clay, sand, chemicals and bitumen. This mixture is transported to tailings ponds, where gravity segregation occurs. During this process, a stable suspension called mature fine tailings (MFT) is formed, which requires many years to fully consolidate. Therefore, land reclamation and water recirculation become significant environmental issues. For this reason, it is important to understand the tailings' content and their settling properties. This study uses the low-field nuclear magnetic resonance (NMR) technique to estimate the water, bitumen and solids composition of synthetic and real tailings samples through a bimodal compositional detection method under ambient conditions. NMR measurements were conducted in 15 minutes, which is a relatively fast measurement allowing for rapid monitoring of tailings compositions. The results show that the NMR technique can be a potential on-site fast measurement of composition and settling characteristics of tailings.
Viscosity and API Gravity Determination of Solvent Extracted Heavy Oil and Bitumen
Authors: Jiang Chunqing Dennis , Bennett Barry , Larter Steve R. , Adams Jennifer J. , Snowdon Lloyd
Published: July 2010

This paper describes and discusses laboratory experiments showing that reliable determinations of viscosity usually cannot be made on high-viscosity samples of heavy oil or tar sand bitumen that have been solvent-extracted from core or cuttings samples with toluene or otherwise contaminated or diluted with this solvent. The toluene solvent cannot be quantitatively removed without damaging the bitumen sample because of the concomitant evaporation of volatile materials that act naturally as solvents in the bitumen. Only small amounts of natural or contaminant solvent are sufficient to effectively control the sample viscosity. Viscosity values determined on residual bitumen after solvent removal may be either higher or lower than the nominally correct value depending on whether excessive residual toluene solvent remains in the sample or excessive volatile material has been removed from the sample during the evaporation. On the other hand, the impact of solvent on the density (i.e., API gravity) of a sample is linear and there are several advantages to using solvent plus bitumen mixtures to determine density for high-viscosity samples.
Containment of a Vertical Tensile Region During Surfactant-Polymer Injection
Authors: Zuluaga Elizabeth , Schmidt Joseph H , Dean Rick , Pardo Carlos W.
Published: July 2010

Many studies have been completed concerning the evaluation of fracture height growth during hydraulic fracturing. While there are analytical solutions available to estimate vertical fracture growth, a more comprehensive solution requires the use of coupled geomechanics-reservoir simulators (GMRS) that could also fully incorporate the effects of fluid-flow into the analysis. This paper introduces results from a new coupled in-house GMRS to estimate the extent of vertical tensile regions developed in the sand interval that could break into adjacent shales during surfactant-polymer injection for a well located onshore Asia. The reservoir was treated as an elastic material and the injection zone was treated as a zone of higher permeability after the weakly consolidated formation reached a tensile stress state.

The geomechanical information for the simulator was obtained from triaxial tests, well-logs and minifracs. Reservoir and fluid data were extracted from the in-house reservoir simulator model available for the field.

A half unit of a seven-spot pattern was evaluated by using an unstructured grid, which provided more geometric flexibility. The results indicated that injection rates higher than 4000 B/D (0.0074 m3/s) combined with viscosities greater than 10 cp (0.01 Pa-s) will cause the fracture to break into the shales penetrating into the bottom sand. On the other hand, injection rates lower than 2000 B/D (0.0037 m3/s) were shown to be safe, even for the highest viscosity injection fluid tested, viz 30 cp (0.03 Pa-s). Viscosities greater than 20 cp (0.02 Pa-s) cause the injection fluid to break into adjacent sands if flow rates are above 2000 B/D (0.0037 m3/s). As expected, the higher the viscosity and injection rate, the higher the tendency of the fractures to grow out of containment. A chart with safe limits for surfactant-polymer injection was provided to the business unit to guide them in the design of new injectors and provide safe conditions for surfactant-polymer injection.
A Turbulent Flow Model for Use in Numerical Evaluation of Air Quality
Authors: Settari A. , Lantz R.B.
Published: July 2010

Several articles have appeared recently which describe air quality models combining a wind flow calculation with the calculation of pollutant dispersion.Most of them use simplified methods to obtain the wind field. In the presentstudy, one of these methods (termed a modified potential method) is comparedwith a turbulent flow model based on the solution of the Navier-Stokes equations. A simple model of turbulence, suitable for environmental applications, is developed.

The comparative results show that the modified potential model is adequatefor many large-scale environmental studies. Its applicability is limited wherelocal effects associated with viscous flow are extremely important. Such casescan be more realistically simulated with the turbulent flow model, although atsignificantly higher costs.

Introduction

Mathematical modeling of atmospheric dispersion has been in increasing usein the evaluation of environmental impact for both existing sources and newplants. More and more emphasis is being placed on the need to satisfyshort-term (half an hour, one hour and twenty-four hours) air quality criteria.Predictions of short-term concentrations require more accurate simulationtechniques than predictions of annual averages. Short-term standards are morelikely to be exceeded in the vicinity of large sources and are influenced moreby terrain configuration than the long term annual standards.

A computer model for simulation of pollutant dispersion requires twoimportant parts: calculation of wind field (flow model) and calculation of theconcentration field (diffusion model). Most existing atmospheric dispersionmodels concentrate on the diffusion part and make very crude assumptions aboutthe wind field. The simplest approach to diffusion, used in several computer models, is based on Gaussian plume models. The basic formula for Gaussian plumemodels is derived assuming flat terrain and a constant mean wind invariable with height. The Gaussian distribution of concentration then follows from the assumption of constant diffusion coefficients. Various corrections have beenproposed to account for the influence of terrain and meteorology on the windfield and diffusion. However, these corrections (generally involving anassumption about the behaviour of the plume centerline) are empirical. As aresult, Gaussian models cannot adequately account for complex topography andmeteorology.
Factors Affecting Coking in Heavy Oil Cores, Oils and SARA Fractions Under Thermal Stress
Authors: Verkoczy B.
Published: July 2010

In previous work we demonstrated that minerals influence coking, combustion, and oil displacement. The effect is significant and seeminglyreservoir-specific. The magnitude and specific details, however, are much lessunderstood where the factors of surface area or the catalytic nature of themineral matrix are concerned. We recently performed a systematic study of thisphenomenon as part of Phase I of Saskatchewan Research Council's multiclient Thermal Studies project. A number of native cores from several heavy oilreservoirs, along with their corresponding matrices and oil thermal properties, were investigated. The results indicated that the surface area, as well as thesurface activity of the minerals, the asphaltene contents, and the nature ofthe oil, played a major role in coke (fuel) formation, depending on thereservoir type. Exploratory isothermal low-temperature oxidation (LTO) kineticstests on core materials, however, yielded somewhat conflicting results. It wasconcluded that in the rather complex oil system, several competing oxidationreactions interfere in some of the temperature domains, rendering the rate datasuspect. We felt the need to separate the oil into simpler and chemically morerepresentative constituents which would make the studies on oxidation andthermal cracking reactions more meaningful. We have adopted the existingseparation technique to obtain such fractions, i.e., saturates, aromatics, resins and asphaltenes (SARA). In previous work on some neat SARA fractions andin current work on several synthetic SARA cores, we have shown that thechemical group types tend to pyrolyse and produce coke independently of eachother. Therefore, the solid fuel formed from pyrolysis can be predicted from SARA test data for the whole oil or core sample. A meaningful experimentalapproach for the kinetics study of SARA fractions and synthetic cores will bediscussed in the text.
Laboratory and Field Validation of a Sealant System for Critical Plug-and-Abandon Situations
Authors: Nagelhout A.C.G.. C.G. , Bosma M.G.R.. G.R. , Mul P.J.. J. , Krol G.G.. G. , van Velzen J.F.G.. F.G. , Joldersma J.S.. S. , James S.G.. G. , Dargaud B.. , Schreuder G.J.R.. J.R. , Théry F..
Published: July 2010

This paper presents case histories and discusses the laboratory validation of a sealant system for plug-and-abandon (P&A) operations in critical gas wells close to habitations. To ensure long-term isolation both inside and outside the original casing, the plan was to mill out the casing and cement and to place the plug from rock face to rock face. The milled-out section was planned so that in the worst-case scenario, the differential gas pressure would have to be supported by 25 m of cement plug, even though a greater height of cement would be placed inside the original casing above the milled-out section.

Two cement systems were designated as candidates for the plugging operation with slurry properties suitable for the application. The gas-sealing ability of the selected systems was validated with both small-scale and large-scale tests. One system, exhibiting both high flexibility and expansion, met the stringent specifications and did not leak until a differential pressure of more than four times the specification was applied. The paper will discuss the parameters of the selected system, thus providing guidelines for system selection for critical plugging operations. A detailed case history of one well (two plugs) is given along with the results from four other wells.
An Assessment of the Productivity of Multilateral Completions
Authors: Raghavan R. , Ambastha A.K.
Published: July 2010

A mathematical model is developed in order to evaluate the productivity ofmultilateral completions. The model may also be used to understand and discernthe pressure behaviour of multilateral completions. The ability to incorporatethe location of each lateral rigorously is the unique feature of the model. Asa result of the development of this model, it is now possible to calculaterapidly the efficacy of various options and to incorporate this completionscheme in numerical models to evaluate the possible influences of interference, boundaries, changes in reservoir properties, etc.

Introduction

Even a perfunctory survey of the literature indicates that, althoughmultiple lateral completions are quite common, there is a dearth of informationon methods to compute productivity, to devise procedures to evaluate thecompletion efficacy, and to forecast performance. The goal of this paper is todevelop a mathematical model to attain these general objectives. To ourknowledge, the results presented in this paper are not available in theliterature. The principal feature of the analytical model described here isthat it is possible to examine the influence of the location of the laterals ofthe multilateral system rigorously and completely. The specific contributionsof this work are as follows:to develop a model that may be used to designfor specific configurations of horizontal sections and evaluate theconsequences that follow from this choice,to screen candidates for thistype of completion scheme, andto discuss transient behaviour and outlinea methodology to analyze pressure tests with a view to determine reservoirproperties and completion efficiency. Before considering the specific detailsof this work, we note that myriad completion schemes are referred to asmultilateral wells. In this paper, we refer to a system with one or morehorizontal sections in a single zone that produce against a common pressure andproducing string as a multilateral completion. Methods are outlined to extendthe scheme discussed here to multiple, non-communicating zones.
Adsorption Equilibrium and Thermodynamic Studies of Copper (II) Ions from Aqueous Solutions by Oil Palm Leaves
Authors: Sulaiman Othman , Mohamad Amini Mohd Hazim , Rafatullah Mohd , Hashim Rokiah , Ahmad Anees
Published: July 2010

Oil palm leaf powders (OPLP), an agricultural waste material, were used as new non-conventional and low-cost adsorbents for the removal of copper (II) ions from aqueous solution. Batch studies were performed to evaluate and optimize the effects of various parameters such as contact time, pH of the solution, initial metal ion concentrations and adsorbent dosage. Langmuir, Freundlich and Temkin isotherms were used to analyze the equilibrium data at different temperatures. The experimental data fit well with the Langmuir adsorption isotherm, indicating thereby the mono layer adsorption of the copper (II) ions. The monolayer sorption capacity of OPLP for copper (II) ions was found to be 11.22 mg/g at 30 °C. The thermodynamic parameters like standard free energy, standard enthalpy, and standard entropy changes for the adsorption of copper (II) ions have also been computed and discussed. The heat of adsorption [?H° = -39.84 kJ/mol] implied that the adsorption was exothermic in nature.
Combined Effect of Inflammatory Gene Polymorphisms and the Risk of Ischemic Stroke in a Prospective Cohort of Subjects With Type 2 Diabetes: A Go-DARTS Study
Authors: Palmer Colin N.A. , Kimber Charlotte H. , Doney Alex S.F. , Proia Anna S. , Morris Andrew D. , Gaetani Eleonora , Quarta Miriam , Smith Roy C. , Pola Roberto
Published: July 2010

OBJECTIVE

We have previously observed that genetic profiles determined by the combination of five functionally significant single nucleotide polymorphisms (SNPs) (rs1800795, rs5498, rs5361, rs1024611, and rs679620) of genes encoding prototypical inflammatory molecules are associated with history of ischemic stroke. Here we tested the ability of this multigenic model to predict stroke risk in a large population-based prospective cohort of subjects with type 2 diabetes.

RESEARCH DESIGN AND METHODS

This study was conducted using a prospective cohort of individuals with type 2 diabetes participating in the Go-DARTS (Genetics of Diabetes Audit and Research in Tayside Scotland) study, which includes genetic and clinical information of patients with diabetes within the Tayside region of Scotland, U.K. The above-mentioned inflammatory SNPs were investigated in 2,182 Go-DARTS participants. We created an inflammatory risk score (IRS), ranging from 0 to 5, according to the number of “at-risk” genotypes concomitantly carried by a given individual. The primary outcome was the occurrence of fatal or nonfatal stroke of any kind. Mean follow-up time was 6.2 ± 1.1 years.

RESULTS

The incidence of stroke increased according to the IRS. The IRS was significantly and independently associated with increased stroke risk after adjustment for other conventional risk factors (hazard ratio 1.34 [95% CI 1.1–1.7]; P = 0.009). The highest hazard ratio for stroke was found in subjects concomitantly carrying >3 proinflammatory variations and in subjects without previous cardiovascular diseases.

CONCLUSIONS

This large prospective cohort study provides evidence that SNPs of genes encoding prototypical inflammatory molecules may be used to create multigenic models that predict stroke risk in subjects with type 2 diabetes.
Homogeneous Insulin and C-Peptide Sensors for Rapid Assessment of Insulin and C-Peptide Secretion by the Islets
Authors: Heyduk Ewa , Moxley Michael M. , Salvatori Alison , Corbett John A. , Heyduk Tomasz
Published: July 2010

OBJECTIVE

Glucose-stimulated islet insulin or C-peptide secretion experiments are a fundamental tool for studying and assessing islet function. The goal of this work was to develop Ab-based fluorescent homogenous sensors that would allow rapid, inexpensive, near-instantaneous determinations of insulin and C-peptide levels in biological samples.

RESEARCH DESIGN AND METHODS

Our approach was to use molecular pincer design (Heyduk et al., Anal Chem 2008;80:5152–5159) in which a pair of antibodies recognizing nonoverlapping epitopes of the target are modified with short fluorochrome-labeled complementary oligonucleotides and are used to generate a fluorescence energy transfer (FRET) signal in the presence of insulin or C-peptide.

RESULTS

The sensors were capable of detecting insulin and C-peptide with high specificity and with picomolar concentration detection limits in times as short as 20 min. Insulin and C-peptide levels determined with the FRET sensors showed outstanding correlation with determinations performed under the same conditions with enzyme-linked immunosorbent assay. Most importantly, the sensors were capable of rapid and accurate determinations of insulin and C-peptide secreted from human or rodent islets, verifying their applicability for rapid assessment of islet function.

CONCLUSIONS

The homogeneous, rapid, and uncomplicated nature of insulin and C-peptide FRET sensors allows rapid assessment of β-cell function and could enable point-of-care determinations of insulin and C-peptide.
Identification of De Novo Synthesized and Relatively Older Proteins
Authors: Jaleel Abdul , Henderson Gregory C. , Madden Benjamin J. , Klaus Katherine A. , Morse Dawn M. , Gopala Srinivas , Nair K. Sreekumaran
Published: July 2010

OBJECTIVE

The accumulation of old and damaged proteins likely contributes to complications of diabetes, but currently no methodology is available to measure the relative age of a specific protein alongside assessment of posttranslational modifications (PTM). To accomplish our goal of studying the impact of insulin deficiency and hyperglycemia in type 1 diabetes upon accumulation of old damaged isoforms of plasma apolipoprotein A-1 (ApoA-1), we sought to develop a novel methodology, which is reported here and can also be applied to other specific proteins.

RESEARCH DESIGN AND METHODS

To label newly synthesized proteins, [ring-13C6]phenylalanine was intravenously infused for 8 h in type 1 diabetic participants (n = 7) during both insulin treatment and 8 h of insulin deprivation and in nondiabetic participants (n = 7). ApoA-1 isoforms were purified by two-dimensional gel electrophoresis (2DGE) and assessment of protein identity, PTM, and [ring-13C6]phenylalanine isotopic enrichment (IE) was performed by tandem mass spectrometry.

RESULTS

Five isoforms of plasma ApoA-1 were identified by 2DGE including ApoA-1 precursor (pro-ApoA-1) that contained the relatively highest IE, whereas the older forms contained higher degrees of damage (carbonylation, deamidation) and far less IE. In type 1 diabetes, the relative ratio of IE of [ring-13C6]phenylalanine in an older isoform versus pro-ApoA-1 was higher during insulin deprivation, indicating that de novo synthesized pro-ApoA-1 more rapidly accumulated damage, converting to mature ApoA-1.

CONCLUSIONS

We developed a mass spectrometry–based methodology to identify the relative age of protein isoforms. The results demonstrated accelerated oxidative damage to plasma ApoA-1, thus offering a potential mechanism underlying the impact of poor glycemic control in type 1 diabetic patients that affects a patient's risk for vascular disease.
Exposure to the Chinese Famine in Early Life and the Risk of Hyperglycemia and Type 2 Diabetes in Adulthood
Authors: Li Yanping , He Yuna , Qi Lu , Jaddoe Vincent W. , Feskens Edith J.M. , Yang Xiaoguang , Ma Guansheng , Hu Frank B.
Published: July 2010

OBJECTIVE

Early developmental adaptations in response to undernutrition may play an essential role in susceptibility to type 2 diabetes, particularly for those experiencing a “mismatched rich nutritional environment” in later life. We examined the associations of exposure to the Chinese famine (1959–1961) during fetal life and childhood with the risk of hyperglycemia and type 2 diabetes in adulthood.

RESEARCH DESIGN AND METHODS

We used the data for 7,874 rural adults born between 1954 and 1964 in selected communities from the cross-sectional 2002 China National Nutrition and Health Survey. Hyperglycemia was defined as fasting plasma glucose ≥6.1 mmol/l and/or 2-h plasma glucose ≥7.8 mmol/l and/or a previous clinical diagnosis of type 2 diabetes.

RESULTS

Prevalences of hyperglycemia among adults in nonexposed, fetal exposed, early-childhood, mid-childhood, and late-childhood exposed cohorts were 2.4%, 5.7%, 3.9%, 3.4%, and 5.9%, respectively. In severely affected famine areas, fetal-exposed subjects had an increased risk of hyperglycemia compared with nonexposed subjects (odds ratio = 3.92; 95% CI: 1.64–9.39; P = 0.002); this difference was not observed in less severely affected famine areas (odds ratio = 0.57; 95% CI: 0.25–1.31; P = 0.185). The odds ratios were significantly different between groups from the severe and less severe famine areas (P for interaction = 0.001). In severely affected famine areas, fetal-exposed subjects who followed an affluent/Western dietary pattern (odds ratios = 7.63; 95% CI: 2.41–24.1; P = 0.0005) or who had a higher economic status in later life experienced a substantially elevated risk of hyperglycemia (odds ratios = 6.20; 95% CI: 2.08–18.5; P = 0.001).

CONCLUSIONS

Fetal exposure to the severe Chinese famine increases the risk of hyperglycemia in adulthood. This association appears to be exacerbated by a nutritionally rich environment in later life.
One-axis molecular rotation and phonon scattering in solid C2H6 and C2F6
Authors: Pursky Oleg , Konstantinov Vyacheslav
Published: July 2010

Using solid C2H6 and C2F6 as an example, the one-axis molecular rotation effect on thermal conductivity has been considered in orientationally-ordered (OO) and orientationally-disordered (OD) phases of simple molecular crystals. The influence of molecular rotation on the heat transfer processes has been studied by a modified method of reduced coordinates, which permitted separating phonon-phonon and phonon-rotation contributions to the total thermal resistance.
A theoretical model for the collective motion of proteins by means of principal component analysis
Authors: Kamberaj Hiqmet
Published: July 2010

A coarse grained model in the frame work of principal component analysis is presented. We used a bath of harmonic oscillators approach, based on classical mechanics, to derive the generalized Langevin equations of motion for the collective coordinates. The dynamics of the protein collective coordinates derived from molecular dynamics simulations have been studied for the Bovine Pancreatic Trypsin Inhibitor. We analyzed the stability of the method by studying structural fluctuations of the Ca atoms obtained from a 20 ns molecular dynamics simulation. Subsequently, the dynamics of the collective coordinates of protein were characterized by calculating the dynamical friction coefficient and diffusion coefficients along with time-dependent correlation functions of collective coordinates. A dual diffusion behavior was observed with a fast relaxation time of short diffusion regime 0.2–0.4 ps and slow relaxation time of long diffusion about 1–2 ps. In addition, we observed a power law decay of dynamical friction coefficient with exponent for the first five collective coordinates varying from −0.746 to −0.938 for the real part and from −0.528 to −0.665 for its magnitude. It was found that only the first ten collective coordinates are responsible for configuration transitions occurring on time scale longer than 50 ps.
Rhabdochona ictaluri sp. nov. (Nematoda, Rhabdochonidae) from ictalurid catfishes in Mexico
Authors: Aguilar-Aguilar Rogelio , Rosas-Valdez Rogelio , León Gerardo
Published: July 2010

A new species of Rhabdochona is described as a parasite of two endemic species of catfishes (Ictalurus dugesii and Ictalurus pricei) from two river basins in central and northern Mexico (Río Ameca and Río Tunal). Rhabdochona ictaluri sp. nov. is characterized by a combination of morphological traits that include the presence of basal teeth, bifurcated deirids, absence of a dorsal barb in left spicule and length ratio between spicules. The combination of these traits readily distinguishes the new species from all its congeners, including those species possessing 14 teeth in the prostom. The new species appears to be specific to freshwater ictalurids.
Two thousand parasites on a single ray: An infection with two species of skin monogeneans on a blotched fantail ray kept in an aquarium
Authors: Justine Jean-Lou , Grugeaud Adeline , Keller Florent , Leblanc Philippe
Published: July 2010

A blotched fantail ray, Taeniurops meyeni (Müller et Henle, 1841), was captured in New Caledonia, South Pacific, and kept in a tank for quarantine before exhibition at the Nouméa public aquarium. After 24 days, the ray exhibited a heavy infection with two species of skin monogeneans. A freshwater bath allowed the collection of 1,914 monogeneans, including 1,453 capsalids, Neoentobdella taiwanensis Whittington et Kearn, 2009, on the ventral surface, and 461 monocotylids, Dendromonocotyle pipinna Chisholm et Whittington, 2004, on the dorsal surface. More than 300 monogeneans were prepared on slides to allow precise measurements. Capsalids and monocotylids occupied about 6% and 0.2% of the total ventral and dorsal ray surfaces, respectively.
Redescription of Lemuricola (Madoxyuris) bauchoti (Nematoda, Oxyuridae) from Lemur catta in Madagascar
Authors: Rosario Robles María , Loudon James , Kinsella John , Hunter-Ishikawa Mandala , Miller David , Sauther Michelle , Cuozzo Frank
Published: July 2010

Lemuricola (Madoxyuris) bauchoti Chabaud, Brygoo et Petter, 1965 is redescribed from material collected from the ring-tailed lemur, Lemur catta, from the Beza Mahafaly Special Reserve in Madagascar using the scanning electron microscope. This is a new host record and the first oxyurid reported from the ring-tailed lemur. Previously, records of each species of the subgenus Madoxyuris have been restricted to a single host species, but the close relationship between these nematodes and their Strepsirrhini hosts will only be proven when additional records fill in the gaps in their distribution.