bluuebunny/crossref_metadata_2025 huggingface dataset:
Repair of a palmar soft tissue defect of the proximal interphalangeal joint with a transposition flap from the dorsum of the proximal phalanx
Authors: Zhang X. , Shao X. , Zhu M. , Jiang R. , Feng Y. , Ren C.
Published: December 2011

This article describes the use of a transposition flap raised from the dorsum of the proximal phalanx for coverage of the volar defects at the proximal interphalangeal joint. The flap was based on the first dorsal branch of the proper digital artery. From January 2007 to March 2009, 14 digits in 14 patients (10 males and 4 females) were treated. There were 5 index, 6 middle, 2 ring, and 1 little finger. All patients underwent surgery 2–9 hours (mean 5 hours) after injury. Soft tissue defects ranged in size from 1.2 × 1.7 cm to 2.1 × 2.3 cm (mean 1.7 × 2 cm). Flap size ranged from 1.5 × 1.7 cm to 2.4 × 2.7 cm (mean 2 × 2.4 cm). Mean pedicle length was 1.1 cm (range 0.8–1.4 cm). All flaps completely survived. At final follow-up from 24–29 months (mean 26 months), mean active motion arcs of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints were 84° (range 75–91°), 86° (range 65–100°) and 54° (range 32–80°), respectively. Our technique is useful and reliable for coverage of a palmar defect over the proximal interphalangeal joint.
Regulation and function of the E-cadherin/catenin complex in cells of the monocyte-macrophage lineage and DCs
Authors: Van den Bossche Jan , Malissen Bernard , Mantovani Alberto , De Baetselier Patrick , Van Ginderachter Jo A.
Published: December 2011

E-cadherin is best characterized as adherens junction protein, which through homotypic interactions contributes to the maintenance of the epithelial barrier function. In epithelial cells, the cytoplasmic tail of E-cadherin forms a dynamic complex with catenins and regulates several intracellular signal transduction pathways, including Wnt/β-catenin, PI3K/Akt, Rho GTPase, and NF-κB signaling. Recent progress uncovered a novel and critical role for this adhesion molecule in mononuclear phagocyte functions. E-cadherin regulates the maturation and migration of Langerhans cells, and its ligation prevents the induction of a tolerogenic state in bone marrow-derived dendritic cells (DCs). In this respect, the functionality of β-catenin could be instrumental in determining the balance between immunogenicity and tolerogenicity of DCs in vitro and in vivo. Fusion of alternatively activated macrophages and osteoclasts is also E-cadherin–dependent. In addition, the E-cadherin ligands CD103 and KLRG1 are expressed on DC-, T-, and NK-cell subsets and contribute to their interaction with E-cadherin–expressing DCs and macrophages. Here we discuss the regulation, function, and implications of E-cadherin expression in these central orchestrators of the immune system.
The least core in fixed-income taxation models: a brief mathematical inspection
Authors: Curt Paula , Litan Cristian M , Filip Diana Andrada
Published: December 2011

For models of majority voting over fixed-income taxations, we mathematically define the concept of least core. We provide a sufficient condition on the policy space such that the least core is not empty. In particular, we show that the least core is not empty for the framework of quadratic taxation, respectively piecewise linear tax schedules. For fixed-income quadratic taxation environments with no Condorcet winner, we prove that for sufficiently right-skewed income distribution functions, the least core contains only taxes with marginal-rate progressivity.
Validation of the individualised neuromuscular quality of life for the USA with comparison of the impact of muscle disease on those living in USA versus UK
Authors: Sadjadi Reza , Vincent Kelly A , Carr Alison J , Walburn Jessica , Brooks Victoria L , Pandya Shree , Kissel John T , Jackson Carlayne E , Rose Michael R ,   Muscle Study Group
Published: December 2011

Background

The Individualised Neuromuscular Quality of Life (INQoL) questionnaire is a published muscle disease specific measure of QoL that has been validated using both qualitative and quantitative methods in a United Kingdom population of adults with muscle disease. If INQoL is to be used in other countries it needs to be linguistically and culturally validated for those countries. It may be important to understand any cultural differences in how patients rate their QoL when applying QoL measures in multi-national clinical trials.

Methods

We conducted a postal survey of QoL issues in US adults with muscle disease using an agreed translation, from UK to US English, of the same questionnaire as was used in the original construction of INQoL. This questionnaire included an opportunity for free text comments on any aspects of QoL that might not have been covered by the questionnaire. We examined the responses using both quantitative and qualitative approaches. The frequency of the responses in US versus UK populations was compared using appropriate correlation tests and Rasch analysis. A phenomenological approach was used to guide the qualitative analysis and facilitate the exploration of patients' perceptions and experiences.

Results

The US survey received 333 responses which were compared with 251 UK survey responses.

We found that INQoL domains covered all the issues raised by US subjects with no additional domains required. The experiences of those with muscle disease were remarkably similar in the US and UK but there were differences related to the impact of muscle disease on relationships and on employment which was greater for those living in the United States. The greater impact on employment was associated with a higher importance rating given to employment in the US. This may reflect the lower level of financial support for those who are unemployed, and the loss of employment related health benefits.

Conclusions

INQoL is appropriate for use in US population but there may be differences in the importance that US subject attach to certain aspects of QoL that could be the basis for further study.

If these differences are confirmed then this may have implications for the interpretation of QoL outcomes in multi-national trials.
Sex-independent neuroprotection with minocycline after experimental thromboembolic stroke
Authors: Hoda Md Nasrul , Li Weiguo , Ahmad Ajmal , Ogbi Safia , Zemskova Marina A , Johnson Maribeth H , Ergul Adviye , Hill William D , Hess David C , Sazonova Irina Y
Published: December 2011

Background

Minocycline provides neurovascular protection reducing acute cerebral injury. However, it is unclear whether minocycline is effective in females. We tested minocycline in both sexes and aged animals using a novel embolic stroke model in mice that closely mimics acute thromboembolic stroke in humans.

Methods

Five groups of mice were subjected to thromboembolic stroke: adult males, aged males, adult females, aged females, and adult ovariectomized females. They were treated with phosphate saline (vehicle) or minocycline (6 mg/kg) immediately after stroke onset. Behavioral outcomes, infarct volumes and cerebral blood flow were assessed. The effect of minocycline on expression and activity of MMP-9 was analyzed.

Results

The model resulted in reproducible infarct in the experimental groups. As expected, adult females were significantly more resistant to cerebral ischemic injury than males. This advantage was abolished by aging and ovariectomy. Minocycline significantly reduced the infarct volume (P < 0.0001) and also improved neurologic score (P < 0.0001) in all groups. Moreover, minocycline treatment significantly reduced mortality at 24 hours post stroke (P = 0.037) for aged mice (25% versus 54%). Stroke up-regulated MMP-9 level in the brain, and acute minocycline treatment reduced its expression in both genders (P < 0.0001).

Conclusion

In a thromboembolic stroke model minocycline is neuroprotective irrespective of mouse sex and age.
The sampling formula and Laplace transform associated with the two-parameter Poisson-Dirichlet distribution
Authors: Xu Fang
Published: December 2011

In this paper we investigate the relationship between the sampling formula and Laplace transform associated with the two-parameter Poisson-Dirichlet distribution. We conclude that they are equivalent to determining the corresponding infinite-dimensional distribution. With these tools, a central limit theorem is established associated with the infinitely-many-neutral-alleles model at any fixed time. We also obtain the probability generating function of random sampling from a generalized two-parameter diffusion process. At the end of the paper a selection case is considered.
Ruin Probability with Parisian Delay for a Spectrally Negative Lévy Risk Process
Authors: Czarna Irmina , Palmowski Zbigniew
Published: December 2011

In this paper we analyze the so-called Parisian ruin probability, which arises when the surplus process stays below 0 longer than a fixed amount of time ζ > 0. We focus on a general spectrally negative Lévy insurance risk process. For this class of processes, we derive an expression for the ruin probability in terms of quantities that can be calculated explicitly in many models. We find its Cramér-type and convolution-equivalent asymptotics when reserves tend to ∞. Finally, we analyze some explicit examples.
On the Zagreb Index of Random Recursive Trees
Authors: Feng Qunqiang , Hu Zhishui
Published: December 2011

We investigate the Zagreb index, one of the topological indices, of random recursive trees in this paper. Through a recurrence equation, the first two moments of Zn, the Zagreb index of a random recursive tree of size n, are obtained. We also show that the random process {Zn − E[Zn], n ≥ 1} is a martingale. Then the asymptotic normality of the Zagreb index of a random recursive tree is given by an application of the martingale central limit theorem. Finally, two other topological indices are also discussed in passing.
Hettita toposzok a hieroglif luvi történetírásban. Megjegyzések a kontinuitás kérdéséhez
Authors: Simon Zsolt
Published: December 2011

Az elmúlt két évtized kutatása sokrétű politikai és kulturális folyamatosságot tárt fel a Hettita Birodalom és utódállamai között. Jelen dolgozat egy mindeddig nem vizsgált aspektust, az irodalom kérdését veszi szemügyre. Ugyan a vizsgálatnak a hagyományozódás sajátosságai miatt a historiográfiára kell korlátozódnia, a luvi szövegek motívumai és stíluseszközei segítségével mégis kimutatható, egyfelől e szövegek szerves folytatói a hettita történetírásnak; másfelől idővel számos egyedi vonást nyertek. Noha a hagyományozódás pontos technikai részletei még további kutatást kívánnak, a hettita nagykirályok monumentális feliratai, illetve a karkamiši utódállam bizonyosan központi szerepet játszottak.
Lapszéli jegyzetek Taddeo Ugoleto szótárában
Authors: Bolonyai Gábor
Published: December 2011

Taddeo Ugoleto, Mátyás könyvtárosa korának elismert humanista tudósa volt. Magyarországi tartózkodása után több latin irodalmi mű editio princepsét is sajtó alá rendezte, többek között Quintilianus, Augustinus, Ausonius és Claudianus egyes írásait. Szövegkiadói munkájával párhuzamosan készített tanulmányai azonban nem maradtak ránk. Emiatt különösen értékesek azok a bejegyzések, elsősorban pótlólagos címszók és magyarázatok, amelyeket Johannes Crastonus 1483. november 10-én Vicenzában megjelent, jelenleg Bécsben őrzött (ÖNB Ink. X. E. 9.) görög–latin szótárának egyik példányába írt bele, néhány évvel azt követően, hogy megkezdte Corvin János nevelését. A kutatásban eddig figyelmen kívül hagyott bejegyzések alapján nemcsak Ugoleto görögös műveltségére és olvasmányaira lehet következtetni, hanem új adatok nyerhetők a Királyi Könyvtár görög nyelvű könyvállományával kapcsolatban is.
Conceiving Ecoptopia
Authors: Barnhill David Landis
Published: December 2011

Clarity of terminology is important in ecotopian studies. We can de?ne an ecotopian society as one that operates in interactive harmony with ecological systems, with humans and nonhuman nature mutually ?ourishing. The functions of ecotopia include critiquing contemporary society, stimulating ecotopian desire, and creating thought experiments about possible ecotopian societies. While many have noted the limitations of producing detailed and universal blueprints for a utopia, we can and should articulate positive content in ecotopian dreaming, which would give orientation to efforts toward an ecotopian horizon. The following principles provide a framework for ecotopianism while allowing for a wide diversity of ecotopian explorations: suf?ciency, high quality of life, egalitarianism, communitarianism, libertarianism, radical democracy, decentralization, appropriate technology, an af?rmation that the natural world has intrinsic value, a sense of identi?cation with nature, and a critique of the degradation of ecological systems.
Estimação de frequência usando sensores de erro com atrasos adaptativos
Authors: Correa Diego Paolo Ferruzzo , Bueno Átila Madureira , Piqueira José Roberto Castilho
Published: December 2011

Neste trabalho é proposta uma solução para a melhoria no desempenho dos Early Error Sensing (EES) Adaptive Time Delay Tanlock Loops (ATDTL) de 1ª ordem apresentados em (Al-Zaabi et al., 2005), quanto a estimação de frequência e tempo de captura. Os EES-ATDTL são Phase-Locked Loops (PLL) digitais utilizados para implementações em hardware, devido à simplicidade da sua estrutura. Teoremas de ponto fixo são usados para se determinar condições sob as quais é possível obter uma convergência rápida no processo de captura e é obtida uma estimativa da frequência de entrada, utilizando um filtro de tipo Gaussiano para melhorar a adaptação do ganho. Os modelos matemáticos usados são os apresentados em (Al-Araji et al., 2006). São feitas simulações para avaliar os resultados teóricos.
Foaminess and Viscosity Effects in Heavy Oil Flow
Authors: Alshmakhy Ahmed , Maini Brij
Published: December 2011

Foamy oil viscosity is a controversial topic among researchers as to what happens to the apparent oil viscosity when the dispersed gas bubbles start migrating with the oil. For conventional oils, below the true bubble point pressure, the oil viscosity increases as the gas freely evolves from the oil. For foamy oils, it has been suggested that the apparent viscosity of gas-in-oil dispersion remains relatively constant, or perhaps declines slightly, between the true bubble point and a characteristic lower pressure, called pseudo bubble point, which is the pressure at which the gas starts separating from the oil. Below this pressure, the viscosity increases, reaching the dead oil value at atmospheric pressure. However, it is a well known fact in dispersion rheology that the viscosity of dispersion is higher than the viscosity of the continuous phase. Therefore, the concept of foamy oil viscosity being lower than the oil viscosity is counterintuitive. The major difference here is the extreme viscosity of the base liquid phase for foamy oil and how this interacts with the gas phase in a porous medium. The reported results appear to be very oil specific in this area, and are also a very strong function of how rapidly pressure is depleted in a given system. It is also likely that the apparent viscosity for flow of foamy oil in porous media is not the true dispersion viscosity due to the size of dispersed bubbles being comparable to the pore sizes.

This study aims to investigate this issue by measuring the foamy oil viscosity under varied conditions. The effect of several parameters, such as shear/flow rate, foaminess and gas volume fraction on foamy oil viscosity was experimentally evaluated. A slim tube packed with sand was used to measure the apparent viscosity of gas-in-oil dispersions. The results show that the apparent viscosity of foamy oils is considerably higher than the live oil viscosity. . The results obtained also showed that the presence of an added foaming agent had only a minor impact on the apparent viscosity of foamy oil, especially at higher expansion factors. Also, at the same expansion factor, the apparent viscosity was higher at higher flow rate. Overall, the presence of a foaming agent resulted in enhanced dispersed flow of gas, as evidenced from the size of bubbles being produced and the observed pressure fluctuations
Pitfalls of Superposition When Analyzing Production Data
Authors: Moghadam S. , Mattar L.
Published: December 2011

Production data are usually analyzed using typecurves. Production data are typically variable rates, whereas typecurves are typically "constant rate" solutions. Therefore, "superposition" must be used to convert the multiple rates into their constant rate equivalent, before typecurves can be used to determine the flow regime.

For linear flow the kernel of the superposition function is square-root-time, for radial flow it is log-time and for boundary-dominated flow it is material-balance-time. When superposition is used, the appropriate function must be used. In practice, the dominant flow regime dictates the choice. However, the flow regimes can be determined only after typecurve matching. This creates a self-referencing procedure.

In many situations, using square-root-time superposition makes the data look like linear flow, while using log-time makes it look like radial flow, and using material-balance-time makes it look like boundary dominated flow. This is self-defeating and can easily lead to the wrong diagnosis of flow regimes. In other situations, the choice of superposition function does NOT change the shape of the data, and the diagnosis tends to be unique. Numerous variable rates are investigated in an attempt to identify when superposition is safe, or which function distorts data the least.

Superposition functions are more forgiving for the early time data, and therefore they are less likely to change the shape of the data significantly in well test analyses, whereas in production data analysis the focus is more on the late time data. Using an inappropriate superposition function can result in the wrong diagnosis of flow regimes and the wrong interpretation of production, and very critically, the wrong forecast of reserves. The choice of superposition function must be an "informed choice" by the analyst.
Effects of High Oil Viscosity on Slug Liquid Holdup in Horizontal Pipes
Authors: Kora C. , Sarica C. , Zhang H.-Q. , Al-sarkhi A. , Alsafran E. M.
Published: December 2011

In the recent years, the increased consumption of hydrocarbon resources and the decline in discoveries of low viscosity oils increased the importance of high viscosity oils. Significant changes in flow behavior were observed with increasing oil viscosity. Determination of the liquid holdup in the slug body is essential to calculate pressure drop for multiphase flow systems.

An experimental study was performed to investigate the effect of high oil viscosity on slug liquid holdup and liquid film height. 144 tests were carried out in 50.8-mm ID horizontal pipe for different oil viscosities and superficial liquid and gas velocities. Tests were conducted at oil viscosities of 0.587, 0.378, 0.257 and 0.181 Pa-s. Superficial liquid and gas velocities varied from 0.1 to 0.8 m/s and 0.1 to 3.5 m/s, respectively. The experimental measurements were compared with the existing slug liquid holdup model predictions to investigate the performances of these models for high viscosity oil.

The predictions of the Gregory et al. (1978), the Gomez et al. (2000), the Abdul-Majeed (2000), the Al-safran (2009) correlations and the Zhang et al. (2003) mechanistic model were compared with high viscosity data. It was concluded that the slug liquid holdup predictions of these empirical and mechanistic models disagree with measurements especially above a 2 m/s mixture velocity. New slug liquid holdup correlations were developed in this study. The new correlations are expected to improve predictions of slug liquid holdup for high viscosity oil especially at high mixture velocities. No significant effect of high oil viscosity on liquid film holdup was observed within the selected oil viscosity range of this study.
A New Approach to Numerical Simulation of Fluid Flow in Fractured Shale Gas Reservoirs
Authors: Bogachev Kirill , Zhabitsky Yakov , Eydinov Dmtry , Shelkov Vasilii , Robinson Tom
Published: December 2011

This paper presents a novel approach to numerical simulations of hydraulic fractures in dynamic reservoir simulations. The fluid flow in fractures is modeled through a network of virtual perforations created in the model grid blocks intersected by the expected fracture trajectory and directly connected to the fractured well. It is demonstrated that by adjusting the productivity indexes of fracture virtual perforations on each time step, practically any static and dynamic behavior of the fracture and its proppant can be realistically modeled. The crossflow between real and virtual perforations is managed by solving a joint well equation. The algorithm takes into account effects of fracture permeability degradation due to pressure, proppant destruction, or total accumulated liquid flux. When the fracture half-length is greater than the average grid block size, the approach described in this paper provides much more realistic simulations than the conventional skin-factor approach or manual generation of high permeability channels. One of the most important advantages of the proposed method is that it can be robustly used for large full-field models with hundreds of horizontal or vertical wells with large scale hydraulic fracturing.
Pre-Treatment Options for Frac Flow Back Brines: Laboratory and Pilot Plant Testing of Oil Removal Materials
Authors: Platt F. M. , Burnett D. B. , Eboagwu U. M. , Vavra C. J.
Published: December 2011

This paper deals with the need to determine the optimum solution for the removal of hydrocarbons in frac flow back fluids on wells completed in unconventional resource areas. These include wells in the Barnett, Eagleford and Marcellus Shales. Fracture stimulation fluid volumes of up to 14 million gallons per well are becoming common. A significant portion of that water returns to the surface as a contaminated waste. To reduce cost and lower the environmental impact of managing such production, companies are seeking to treat and re-use fluids during development of the field.

This project looked at several methods to remediate the produced hydrocarbons to allow reuse of the fluids in other treatments. Our investigations included testing of removal techniques and the concomitant analytical methodology to use in field operations to ensure proper performance of the technologies. Tests were performed with actual field produced brines with five different filter medias including samples that can be regenerated as an alternative to absorbent materials that require replacement or regeneration to continue operation. Pre-treated fluids were then processed through subsequent membranes and purification to make them suitable for re-use. Results from this work have allowed our program to develop more efficient removal treatments and more reliable analytical methodology providing better field level guidelines for commercial operations.
Improving Fracture Initiation Predictions on Arbitrarily Oriented Wells in Anisotropic Shales
Authors: Prioul Romain , Karpfinger Florian , Deenadayalu Chaitanya , Suarez-Rivera Roberto
Published: December 2011

The hydraulic fracturing stimulation of unconventional shale reservoirs requires the identification of sections along the well with good reservoir and completion quality. Completion quality depends on the poromechanical properties of the reservoir. Shales are known to exhibit anisotropic elastic properties. The elastic anisotropic of shales is of first order as it affects four key geomechanical steps: the in-situ stress field, the stress concentration around the borehole, the failure properties both in tension and compression and the geometry of the hydraulic fracture. Consequently, the initiation pressure of hydraulic fractures at the wellbore predicted by data and models taking into account the anisotropy can be lower or higher by up to 100% as compared to isotropic conditions.

We performed a thorough sensitivity analysis of in-situ stress, material anisotropy and well orientation conditions for different scenarios for far field in-situ stress and near field borehole stress, under isotropic and anisotropic conditions. We consider three scenarios. Scenario-1 where both the far field in-situ stress and the near field borehole stress are computed under isotropic assumption. Scenario-2 where only the far field in-situ stress is computed using anisotropic assumption while keeping the isotropic solution for stress concentration is kept. Scenario-3 where both the far field in-situ stress and the stress concentration take into account the material anisotropy. In addition, for each scenario, we considered three different σH/σh cases. This study shows that the full anisotropic solution or scenario 3 is always the most appropriate one for predicting correct initiation pressures and the pressure is always lower for the anisotropic case. It is clear that the observed effects are magnified by the degree of anisotropy of the rock, i.e. each rock or formation will influence differently the initiation pressure. We conclude that the material anisotropy is affecting the in-situ stress model as well as the stress concentration around the borehole. Both effects need to be considered in order to account for the anisotropy. If the effect of the anisotropy is taken into account, for both the far and the near field, it will be possible to better predict the initiation pressure and better stimulate unconventional reservoirs.
Morphology and Growth of Fractures in Unconventional Reservoirs
Authors: Zhao Nan , McLennan John , Deo Milind
Published: December 2011

Understanding the morphology and growth of hydraulic fractures is essential in the development of unconventional tight gas and shale gas resources. In this paper, we report the use of a computational tool consisting of geologic data representation, geomechanical modeling and multiphase flow simulations to predict reservoir performance. A finite element-based geomechanical module is interfaced with a control-volume finite element discrete-fracture reservoir simulator. The hydraulic fracture geometry is generated by following the fluid injection pathway in the existing fracture network and in the matrix. The permeabilities in the fractures and in the matrix are adjusted dynamically in the simulator based on coupling of the geomechanical and flow attributes. The approach described is applicable to tight gas and shale gas reservoirs. There are over 3700 active wells in the Greater Natural Buttes field in Uinta Basin, Utah with a cumulative production of 1.8 trillion cubic feet of gas. Most of this production comes from several tight gas formations (matrix permeability of less than 0.01 md). The importance of hydraulic fractures and their interaction with natural fractures in shale gas reservoirs characterized by nano-Darcy permeabilities is well known. This methodology provides a means of mapping a complex (non-planar) network of hydraulically-activated/induced fractures. The initial conductivity distribution in the fractures and the relative permeability of the matrix along with the stress tensor and mechanical properties of the matrix and the fractures control the geometry of the hydraulic fracture system and the ultimate well performance. Prediction of complex hydraulic fracture morphology and injected water balance are important in the development of tight gas and shale gas resources. Multiphase flow simulations with complex fracture networks will help delineate complex effects such as water blocks, "permeability jail" phenomena, etc.
Oil Recovery Enhancement for Thamama B Lower in an Onshore Abu Dhabi Field. Using Conceptual Models to Understand Reservoir Behaviour
Authors: Carvalho Álvaro , Dias Ana , Ribeiro Maria Teresa
Published: December 2011

The Thamama B reservoirs in Abu Dhabi onshore fields represent over 50% of the total reserves of the country. Therefore, the optimization of production and the maximization of recovery are of paramount importance. While reserves are distributed uniformly in the reservoir, the permeability distribution is heterogeneous, with top layers being more permeable (100 mD to 1D than lower ones (1 to 10 mD). This has a strong impact on water flooding performance and requires a thorough understanding of the reservoir fluid flow physics and behaviour, focusing on the detailed analysis of the water hold-up and slumping mechanisms, including the origin and shape of the existing water cones in the lower zones and the bypassed oil zones.

Study results showed that the management of Thamama B reservoirs needs to be achieved through the combination of high quality field surveillance programmes, associated with detailed reservoir studies developed specifically for the modelling of the water advance in the reservoir.

A mechanistic model of a Thamama B reservoir in an Abu Dhabi onshore field was created to determine which parameters, and respective uncertainty ranges, have the greatest impact on fluid dynamics. These were identified to be: rock wettability, (and the associated capillary pressure and relative permeability curves), and the presence of high permeability and dense intervals within the reservoir, both in the upper and lower zones. Once the parameters are identified, it is then vital to reduce the associated uncertainty, by fine tuning the models and undertaking representative forecasts.

The hereby proposed way forward concentrates on monitoring the reservoir performance and build refined reservoir models that can be easily used to understand the reservoir mechanisms and to characterize and accurately predict the water movement in the Thamama B reservoirs, in order to be able to establish the most adequate field development methodologies leading to the optimization of production and to the maximization of ultimate recovery.
Steamdrive Direct Contact Steam Generation for SAGD
Authors: Betzer-Zilevitch Maoz "Moose"
Published: December 2011

In recent years there has been a shift in the Steam Assisted Gravity Drainage (SAGD) steam generation technologies from the traditional Once Through Steam Generator (OTSG) and lime based water softening towards the use of an evaporator and industrial High Pressure (HP) steam boilers. As a result, the available steam temperature and pressure exceeds the steam temperature that is required for injection into the underground formation. This excess steam enthalpy is the driver behind the steam generation method to be proposed.

The method described is a revolutionary process for generating additional steam from highly contaminated oily water with an option for zero liquid waste discharge. The industrial boiler superheated steam is used as the driving force for generating additional steam in a direct contact heat transfer with the contaminated water. Fine Tailings from tailing ponds can be also used. The presented technology generates a "tailor made" pressure and temperature steam, as required for injection into the underground oil bearing formation. This newly developed technology allows generation of additional lower temperature steam from waste water in a high efficiency energy process. The simulation results show that an additional 8% – 24% steam (on a mass basis) can be generated from highly contaminated oily water. The amount of additional steam generated increases with the temperature of the driving steam, and with the reduction of the pressure of the formation. For low pressure shallow formations, additional steam can be produced in comparison to deep, high pressure formations. Another option is to recycle a portion of the produced steam through a heater and use it as the driving steam, and by that minimizing the need for external steam as a heat energy source. A portion of the oil component in the water feed will be converted into hydrocarbon gas that is expected to show similar behavior to a solvent. Additional solvents can be added and injected with the steam to improve the oil recovery. The presented technology has a high thermal efficiency capable of consuming contaminated hot produced water, without the need to reduce their heat to allow effective water treatment. The technology "fits" in the gap between the HP superheated steam and the injection steam while allowing the producers to maximize the advantages and benefits from the use of evaporators and steam boilers for SAGD oil production and can convert the existence of oil contaminate within the feed water into an advantage by replacing the solvent. This steam generation direct contact facility can be located in close proximity to the SAGD pads to use the hot produced water and inject the produced steam into the injection wells.
Effect of Polymer Injection on the Mobility Ratio and Oil Recovery
Authors: Morelato Assunção Pablo , Rodrigues Lorennzo Marrochi , Romero Oldrich Joel
Published: December 2011

The fluids injection in oil reservoirs has the function to supplement the natural energy and in some cases is used to interact with the rock/oil system of reservoir, creating favorable conditions for oil recovery, for example lower interfacial tension, oil swelling, oil viscosity reduction and wettability modification. Polymer injection in heavy oil reservoirs is the subject of extensive studies since its implementation does not depend of major technological devices, requiring only mixing and filtration equipments in addition to those already used for common water injection. Moreover, polymers are not toxic and corrosive and can generate mobility ratios favorable in both borders of the injection seat. The adoption of this solution reduces the water/oil ratio of production, thus reducing the operational costs and consequently creating higher economic return. This work aims to evaluate the potential of polymer injection in heavy oil reservoirs. Therefore, using the reservoir simulation CMG's IMEX, it was analyzed in heavy oil reservoirs the influence of the polymer injection on the mobility ratio, advanced water front during the breakthrough, the oil recovery factor and BSW. Tests with two models of reservoir were performed: homogeneous reservoir and heterogeneous stratified reservoir. Water injection was proposed as a comparison to the polymer injection method.
Advancements in Understanding and Enhancing Biogenic Methane Production from Coals
Authors: Budwill Karen , Koziel Susan , Vidmar John
Published: December 2011

It is estimated that only 5% of Alberta’s CBM reserves are recoverable (Rieb, 2006). A variety of techniques such as horizontal drilling and new fracturing methods have allowed greater recoveries of the methane gas. Alberta Innovates – Technology Futures (formerly the Alberta Research Council) is developing a biotechnology that stimulates and enhances biogenic methane production coal seams. Biogenic methane production is believed to have occurred in the geological past, and is believed to be still occurring in deep, subsurface coal seams albeit at extremely slow rates. It is postulated that the native microorganisms are nutrient limited and, based on laboratory evidence, by adding an organic, nitrogen-rich nutrient, the methane production rate can be increased up to 30-fold over non-amended cutlures. The microbial diversity of Alberta coal seams has begun to be mapped out using state-of-the-art genomic sequencing techniques. It appears the geophysical environment has a strong influence on the types of microbes present as the microbial populations from deeper, more saline Mannville coals are significantly different than the microbes detected in Horseshoe Canyon coals. The microbial population changes upon addition of a nutrient, with shifts occurring in the types of fermenting organisms and methanogenic species. Low molecular weight monocarboxylic acids were observed to be produced and then consumed over the incubation period. These methanogenic precursor substrates accumulated in cultures with only nutrient and no coal. Much lower methane production occurred in these cultures suggesting an unbalanced nutritional state, whereas those cultures with un-limiting carbon from coal and nitrogen source from the nutrient generated large amounts of methane. The effects of surface area, bioavailability of coal moieties and coal porosity and permeability on biogenic methane production are under investigation. Results will aid in the design and deployment of an effective enhanced biogenic methane coal bed field trial.
Investigation of Liquid Loading in Tight Gas Horizontal Wells with a Transient Multiphase Flow Simulator
Authors: Jackson Donald F.B. , Virués Claudio J.J. , Sask David
Published: December 2011

Liquid loading occurs when gas production declines to a rate that is insufficient to lift the associated liquids to surface. At lower rates, gas production becomes intermittent and eventually stops entirely. However, liquid holdup in the horizontal section may impair production before loading in the production tubing becomes evident. Holdup in the horizontal section can lead to slug flow from the horizontal wellbore to the tubing and to an earlier onset of liquid loading in the tubing.

This paper presents liquid holdup data from a single onshore horizontal tight gas well, obtained through video-logging. A transient multiphase flow model is then used to match the observed conditions.

The results from the transient multiphase flow model were found to be consistent with the measured data acquired from the video-logging. Sensitivity analyses were performed with normalized trajectories representing toe-up, toe-down, undulating, and complex drilling profiles. Sensitivities to variations in the liquid-gas ratio and the distribution of the reservoir inflow were also investigated. The results of the transient multiphase flow modelling support the conclusion that complex trajectories are more prone to production losses caused by liquid holdup.

The implications of this conclusion for trajectory optimization and tubing landing depth selection are explored. Modelling liquid holdup can lead to improvements in planning new drilling projects, mitigating the impact of liquid loading on long-term performance.
Study and Application of Heat Self-Generating CO2 Flooding for EHOR
Authors: Zhou Yongbing , Qin Guowei , Fu Shuang , Wang Maosheng , Wang Lei , Zheng Xianbao , Xiao Hongwei , Bai Yanming , Liu Mingjun
Published: December 2011

Heat self-generating CO2 flooding is a new technique combining of steam flooding, gas flooding and so on. Its main mechanism is the application of steam heating self-generating gas agent solution to generate a large volume of gases (including CO2, NH3, etc) in the formation. While some of these gases acting with the crude oil to reduce the oil viscosity, some form miscible flooding to reduce oil/water interfacial tension, so as to achieve the purpose of enhancing heavy oil recovery. An optimized selection of the heat self-generating gas agents was performed. By comparison the difference before and after the reaction of the solution, the increase of alkaline is occurred after the reaction, which is helpful to reduce oil viscosity and lower interfacial tension. Studies indicate that heat-generating CO2 flooding technique can get a maximum viscosity reduction rate of 75.3%, oil/water interfacial tension decreased by 54.18%, and further improve the oil recovery by 4.6% based on the steam flooding, which shows a technical advantage to conventional enhancing oil recovery method. The pilot field shows that the technique can greatly improve the oil production, which will provide a powerful technical supporting for the efficient development of heavy oil.
Effect of Gas Dissolution on Heavy Oil Well Performance: Rheology Considerations
Authors: Dabholkar Dinesh , Mahadevan Jagan
Published: December 2011

Crude oils may exhibit shear rate dependent viscosity under reservoir temperature and pressure conditions due to many factors such as wax content, asphaltenes, solids, and water droplets. In a previous experimental study we investigated the shear rate-shear stress relationship for heavy crude oil using capillary viscometer. The study showed mildly non-Newtonian behavior of heavy oil and the rheological power-law parameters (flow behavior index and flow consistency) depend on the extent of gas dissolution and at higher gas dissolution the fluid flow behavior index approaches unity. Impact of non-Newtonian flow behavior on oil inflow performance can be significant.

In this study, a two dimensional unsteady state model is developed to represent the multiphase flow behavior of heavy oil, accounting for the non-Newtonian behavior and the model is solved using a fully implicit finite difference scheme. In essence, the approach is that of a traditional black oil type of reservoir modeling, but with the viscosity of the heavy oil represented by a power law model. Power law parameters for saturated oil at high temperature and different pressures, obtained from experiments in a companion study are used in modeling the rheology of heavy oil. Modified Darcy’s law is used to model non-Newtonian flow of heavy oil through porous media. Results of the numerical solution are validated with analytical solution of single phase non-Newtonian flow through porous media available in the literature.

Non-Newtonian behavior under reservoir conditions can increase the pressure drawdown required for production by several times and hence affect the production. The well inflow performance calculated using the simulator shows that, as the exponent of the power law model decreases, the production flow rate decreases. Thus, in comparison to a Newtonian behavior, a power law behavior results in a poorer inflow performance. The results presented here may be used to explain higher recoveries in heavy oils which display non-Newtonian behavior. Additionally, strategies for production optimization could be achieved by controlling the fluid rheology and hence the power law parameters by maintaining solution gas in the oil phase.
Monitoring of In-Situ Combustion Process in Southern Part of Balol Field Through Analysis of Produced Fluids
Authors: Dayal H. S. , Pandey Vivek , Mitra Sujit , Bhushan B. V. , Bhandari A. C. , Dwivedi M. M.
Published: December 2011

Balol field is located in the heavy oil belt of North Cambay Basin in the state of Gujarat, India. The API gravity and oil viscosity is 15° and 300 cp respectively. Low primary recovery of 13% necessitated the application of ISC (In situ Combustion). The success of ISC in the southern part of Balol field has led to more than four-fold increase in oil production. Oil rate increased from a level of 60 m3/d to about 260 m3/d together with decline in Water cut from 82 % to 40% with injection of air @ 0.18 MMSm3/d. The ISC process was first implemented on commercial scale in October 1997 and has been instrumental in achieving the recovery of about 50 % of STOIIP from southern sector.

In ISC process in Balol, air is injected through injection well which is ignited artificially, to initiate the process in high temperature oxidation mode. The combustion takes place when oxygen, crude oil react to generate heat alongwith water and combustion gases. Oil is displaced by the vaporizing action of the thermal front and sweep provided by the combustion gases, hot water and steam. Nitrogen does not take part in the reaction and makes a free trip to the producers.

The produced fluids like flue gas, oil and water were collected at regular intervals, their composition were measured for monitoring the In-situ combustion process. The increase in CO2 concentration to the level of 15 %, reduction in oil viscosity and water salinity by half, increase in Well Head temperature and SO4 ion concentration in produced water enabled in understanding of various aspects of combustion process like confirmation of ignition, front movement and burn efficiency.

This paper elaborates how monitoring has helped in re-orientation and optimisation of air injection leading to manifold increase in oil production. Currently, oil recovery is close to the envisaged recovery factor.
Optimal Application Conditions for Heavy-Oil/Bitumen Recovery by Solvent Injection at Elevated Temperatures
Authors: Leyva-Gomez H. , Babadagli T.
Published: December 2011

Steam injection is the most common technique in heavy oil/bitumen recovery. However, the emission of greenhouse gases into the atmosphere, its water requirements and excessive operational cost and problems entail finding alternative solutions. One approach is combining steam and solvent injection by taking advantage of steam injection preheating the reservoir for more effective solvent recovery application. In this case, the performance of subsequent solvent injection strictly depends on the temperature and pressure in the reservoir. Recent experimental studies on superheated solvent injection showed that solvent in the gas formed near the saturation line yields an optimal recovery minimizing the asphaltene precipitation and maximizing the recovery. This paper investigates this process through a numerical modeling exercise and formulates the optimal pressure and temperature conditions for different reservoir conditions and hydrocarbon solvents.

We first report the results of numerical simulation of laboratory experiments, in which heavy oil was exposed to solvent vapour at high temperatures. To achieve these results, a radial 3D numerical model of 15x1x63 cells was constructed using a commercial numeric simulator. The injection of either propane or butane into sand packs or consolidated sandstones at elevated temperatures was simulated. A pressure-temperature sensitivity analysis was carried out for different core sizes to understand the dynamics of the gravity drainage process associated with asphaltene precipitation. Asphaltene pore plugging behaviour was modeled and diffusion of solvent into the heavy oil was analyzed to determine both ideal solvent type and optimal operating conditions for solvent injection at high temperatures.

Our preliminary results and observations showed that the solvent should be in the gas phase and its sensitivity to temperature and sample height (for effective gravity drainage) is more critical than the pressure. There also exists a critical temperature that yields amaximum recovery and this value was determined for the rock/reservoir types and solvents considered in this study. Solvents considered, i.e., propane and butane, behaved differently in terms of asphaltene precipitation and its effects on ultimate recovery. The history matching to the experimental data was achieved primarily by considering this effect.