bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrating Nuclear Energy to Oilfield Operations -- Two Case Studies
Authors: Robertson Eric P. , Nelson Lee O. , McKellar Michael G. , Gandrik Anastasia , Patterson Mike
Published: November 2011

Fossil fuel resources that require large energy inputs for extraction, such as the Canadian oil sands and the Green River oil shale resource in the western USA, could benefit from the use of nuclear power instead of power generated by natural gas combustion. This paper discusses the technical and economic aspects of integrating nuclear energy with oil sands operations and the development of oil shale resources. A high temperature gas-cooled reactor (HTGR) that produces heat in the form of high pressure steam (no electricity production) was selected as the nuclear power source for both fossil fuel resources. Both cases were based on 50,000 bbl/day output. The oil sands case was a steam-assisted, gravity-drainage (SAGD) operation located in the Canadian oil sands belt. The oil shale development was an in-situ oil shale retorting operation located in western Colorado, USA. The technical feasibility of the integrating nuclear power was assessed. Preliminary economic analyses of each case were evaluated using a discounted cash flow, rate of return approach.

Integrating an HTGR to both the SAGD oil sands operation and the oil shale development was found to be technically feasible for both cases. In the oil sands case, integrating an HTGR eliminated natural gas combustion and associated CO2 emissions, although there were still some emissions associated with imported electrical power. In the in situ oil shale case, integrating an HTGR reduced CO2 emissions by 88% and increased natural gas production by over 400%. Economic analyses included parametric evaluations on taxes imposed on CO2 emissions, royalty rates, capital costs, etc. The magnitude of the tax on CO2 emissions was found to have a major impact on the economic results of the cases considered.

As the world moves toward limiting CO2 emissions, integrating non-CO2-emitting energy sources to the development of energy-intense fossil fuel resources is becoming increasingly important. This paper attempts to reduce the barriers that have traditionally separated fossil fuel development and application of nuclear power and to promote serious discussion of ideas about hybrid energy systems.
New Ways of Removing Cyclic Borehole Noise from Low- and High- Resolution LWD Images and Its Impact on Image Interpretation
Authors: Sugiura Junichi , Lee Rick
Published: November 2011

The use of logging-while-drilling (LWD) imaging tools in real-time decision making and post-drilling analysis has become commonplace. However, image noise and processing errors due to the inherent measurement physics can propagate errors and thus complicate interpretation of open-hole log data and images. For example, the standard density images tend to amplify image noise from small borehole irregularities. Among different borehole irregularities, spiraling is known to occur more frequently with conventional rotary assemblies, steerable motor assemblies, and rotary steerable assemblies. When the cyclic noise amplitude from spiraling becomes large relative to the measurement of the primary interest, it grossly affects measurement accuracy of bulk density, photoelectric, and neutron porosity.

This paper shows novel methods to remove cyclic noise from formation evaluation (FE) images by applying frequency-domain filtering. Although the initial attempt of fast Fourier transforms1 illustrates the straightforward concept, it is seldom used due to implementation issues requiring interactive filter design and intensive operator intervention. Recently, a new method2 has been designed to improve the filtering process. Additionally, the new adoptive filter designs automate the cyclic noise removal process from the FE images. Stand-alone software has been developed to process the entire image logs from one well, without human supervision. The software adoptively modifies the filter behavior as borehole oscillation noise characteristics change with formation, drilling assemblies, hole inclination, and depth.

To quantitatively examine its validity, the algorithm is then applied to various field data, not only on low-resolution density images but also on higher-resolution density images. The new algorithm has been proved by bringing considerable improvement to the image quality without any artificial interruptions. The rugosity effect is significantly reduced, and the apparent resolution of bed boundary features increased.

Furthermore, comparative field examples illustrate the improvement in image feature extraction. This new method is critical, for example, for small fracture detection and for accurate dip analysis in irregular boreholes. This new method is not only effectively used for density images but also applicable to any other borehole images, such as resistivity and ultrasonic images.
Horn River Basin: A Study of the Behavior of Frac Barriers in a Thick Shale Package Using the Integration of Microseismic, Geomechanics and Log Analysis
Authors: Beaudoin Bill , Allison Jeff , Khalid Salman , Faurschou Ken
Published: November 2011

Horn River Group (HRG) shales are prime exploration targets. The shales form a 200m thick package of over-pressured, organic rich, siliceous mudrocks found at drilling depths between 2400–2700m. The gross thickness of the shale interval and the observed frac barriers within the shale package present a challenge for maximizing the stimulated rock volume when completing wells. Within Devon Canada, an exploration program was designed to evaluate reservoir complexity and heterogeneity, the ultimate goal being to optimize horizontal, vertical and lateral well placement while balancing recovery factor and capital costs.

Core and log data from vertical wells were analyzed to target optimal horizontal drilling zones for hydraulic fracture initiation and ease of drilling. Geomechanical log analysis supports the observation made from microseismic data that frac height growth through the frac barriers in the shale package happens preferentially depending upon the direction from which the fracture was initiated.
Chemical Process for Improved Oil Recovery From Bakken Shale
Authors: Shuler Patrick , Tang Hongxin , Lu Zayne , Tang Yongchun
Published: November 2011

There is a new chemical improved oil recovery (IOR) process for Bakken reservoirs. In this concept a custom surfactant agent may be incorporated into standard hydraulic fracturing treatments for the Bakken to increase oil recovery. These are reservoirs from the Late Devonian to Early Mississippian age occupying about 200,000 square miles (520,000 km2) of the subsurface of the Williston Basin, covering parts of Montana, North Dakota, and Saskatchewan. The rock formation consists of three members: Lower shale, Middle dolostone/siltstone, and Upper shale. The shales were deposited in relatively deep marine conditions, and the dolostone/siltstone was deposited as a coastal carbonate during a time of shallower water. The Middle member is the principal oil reservoir, roughly two miles (3.2 km) below the surface. Both the Lower and Upper members are organic-rich marine shales.

The oil in place in the Bakken shale play is very large, with an April 2008 USGS report estimating the amount of technically recoverable oil in the Bakken Formation at 3.0 to 4.3 billion barrels. Production from the Bakken has been limited in the past, but now has become a very active area of development with the widespread advent of drilling horizontal wells and large-volume hydraulic fracturing treatments. One key to the economic production rates of oil from these formations is to create an extensive well-connected fracture system.

Laboratory experiments demonstrate that specialized surfactant formulations will interact with this mixed- to oil-wet low permeability Middle member to produce more oil. Specifically, including such a surfactant chemical formulation in an aqueous phase (e.g. hydraulic fracturing fluids) will promote the spontaneous imbibition of this fluid into the tight matrix and microfractures containing high oil saturation. This promotes expulsion of oil otherwise trapped to migrate into the fracture system and then be produced into the wellbore. Thus including an appropriate surfactant in frac fluids or in other aqueous-based treatment fluids can produce additional oil.
Case Study: Modeling the Phase Behavior of Solvent Diluted Bitumen
Authors: Agrawal P. , Schoeggl F. F. , Satyro M. A. , Yarranton H. W.
Published: November 2011

The design of solvent-based and solvent assisted heavy oil recovery processes requires accurate predictions of phase behavior as straightforward as saturation pressures and as potentially complex as vapour-liquid-liquid equilibria and asphaltene precipitation. In this case study, saturation pressures of dead and live bitumen were measured in a Jefri PVT cell at different concentrations of a multi-component solvent at temperatures from 20 to 180°C. Saturation pressures and the onset of asphaltene precipitation were also measured for the bitumen diluted with n-pentane. The onset of precipitation was determined by titrating the bitumen with pentane and periodically circulating the mixture past a high pressure microscope.

The data were modeled with the Advanced Peng-Robinson equation of state (APR EoS). The maltene fraction of the bitumen was characterized into pseudo-components based on extrapolated distillation data. The asphaltenes were characterized based on a Gamma distribution of the molecular weights of self-associated asphaltenes. The APR EoS was tuned to match the saturation pressures by adjusting the binary interaction parameter between the solvent and the pseudo-components via a correlation based on critical temperatures. Rather than adjusting the interaction parameters for each pair of components, only the exponent in the correlation was adjusted. The role of mixing rules in correctly predicting the onset and amount of asphaltene precipitation is discussed.
Numerical Simulation of SAGD with Vertical Slimholes
Authors: Chang J. , Ivory J. , Tunney C.
Published: November 2011

Steam assisted gravity drainage is the primary in-situ recovery method for bitumen from the large Athabasca deposit in Alberta, Canada. SAGD field operations encounter a significant decrease in production performance when low permeability shale barriers are present in the formation. These layers can reduce SAGD performance and impede the growth of the steam chamber. They also significantly limit the percentage of the deposit where bitumen can be economically recovered with SAGD. The concept of drilling vertical slimholes to create flow paths through barriers was conceived and investigated at Alberta Innovates - Technology Futures (formerly the Alberta Research Council). Use of slimholes has the potential to significantly increase the amount of recoverable bitumen (reserves) and the rate at which it is produced during SAGD. For shallow reservoirs, the slimholes could be drilled from the surface at relatively low cost.

2-D and 3-D field scale numerical simulations were performed using reservoir properties and operating conditions that were based on published information for the MacKay River SAGD operation in the Athabasca deposit. The reservoir depth was 135 m, the initial pressure 500 kPaa, the initial temperature 7.5 °C, and the initial oil saturation 0.8. The simulations explored the impact of vertical slimholes, which were 7 m laterally offset from the horizontal well pair (Figure 1), on reservoirs with and without shale layers or shale lenses. The effect on SAGD performance of slimhole cross-section (25 cm × 25 cm or 50 cm × 50 cm) and distance between slimholes (12 m or 24 m in the direction parallel to the well pair was investigated). The effect of reservoir and slimhole permeability and the impact of horizontal slimholes from the injector or producer were also explored.

The slimholes were represented by high permeability vertical channels using refined grids. Counter-current flow of gas and liquid through the slimholes was represented by adjusting the relative permeability in the slimholes.

For a reservoir, with a continuous shale layer, SAGD performance was improved by vertical slimholes due to the recovery of previously inaccessible oil from above the shale layer where a secondary steam chamber was formed.
A Parametric Simulation Study for Solvent Co-injection Process in Bitumen Deposits
Authors: Yazdani A. , Alvestad J. , Kjonsvik D. , Gilje E. , Kowalewski E.
Published: November 2011

In situ extraction of ultra viscous deposits from the vast bitumen resources in western Alberta requires significant water and energy usage which consequently lead to green house gas emissions. Currently proven steam-based recovery schemes include Cyclic Steam Stimulation, Steamflooding, and Steam Assisted Gravity Drainage (SAGD) processes, which are accompanied by many economical and environmental challenges. Co-injection of solvent with steam is a technology that has the potential to improve the efficiency of steam processes as well as reduce the energy use and CO2 emissions.

In recent years, researchers and industry have attempted to further develop the process by conducting fundamental research as well as field pilot trials with varying degrees of success. However, the current level of understanding of the process and knowledge around the fundamental physics and mechanisms involved are not fully satisfactory.

In this paper, a parametric simulation study was performed to address the key aspects of the solvent co-injection (SCI) process that contribute to further understanding and development of the process. Simulation observations were verified with experimental evidence where available to support the results and conclusions. Effects of several operational and geological parameters were evaluated on the performance of the SCI process and the relative performance benefits were assessed over normal SAGD operations. These parameters included solvent type, solvent concentration, initial solution gas-oil ratio, relative permeability curves, pay thickness, and presence of a low quality top layer.

The results revealed that the optimum solvent should not only be chosen on the basis of mobility improvement capability, but should also consider other operational, phase and flow behavioral and/or geological conditions that are set or present. Higher concentrations of solvents showed more energy saving upsides than rate acceleration benefits. It was also observed that the reservoir steam intake rate is still likely to be the prime performance indicator of the SCI process. In addition, it was found that the potential exists with the SCI process for accessing more resources, particularly below the producer level. Furthermore, steam trap control on the producer seems to be problematic when utilized for SCI simulation. With the current well control capacity of simulators, a higher degree of subcool is likely to be needed to avoid live vapor phase production from the producer.
Experimental and Analytical Modeling of Gravity Drainage Dominated Heavy-Oil Recovery Under Non-Isothermal Conditions: A Microscale Approach
Authors: Arguelles-Vivas F. J. , Babadagli T.
Published: November 2011

Steam assisted gravity drainage (SAGD) is a well-known example of a non-isothermal gravity dominated recovery application. It is commonly observed that field scale applications of this process yield less recovery than estimated. This requires in-depth analysis of the problem at the pore scale to account for the residual oil saturation in the swept zone.

It is still uncertain to what extent pore scale mechanisms, such as the counter and co-current nature of multiphase flow, the trapping mechanism and the distribution of phases, the formation and flow of emulsions, and heat transfer mechanisms affect the process of non-isothermal gravity drainage dominated heavy-oil recovery. Alteration of wettability due to phase change under steam heating and how wettability interacts with spreading coefficients are still enigmatic.

In this paper, we used a single capillary tube to mimic an elementary volume in the swept area during gravity dominated displacement under non-isothermal applications. We carried out two-phase (air-oil) and three phase (air-oil-initial water saturation) flow displacements in a capillary tube under isothermal and non-isothermal conditions, varying the air injection rate and the capillary properties. Detailed visualization experiments were carried out to analyze: (1) The effects of oil viscosity, wettability and the spreading coefficient on isothermal and non-isothermal displacement, (2) the interplay among capillary, gravity and viscous (steam injection rates) forces and wettability using different size capillaries, and (3) residual oil saturation and phase distribution in the capillaries (mainly the thicknesses of the wetting and non wetting phases).

The analytical calculations based on the experimental observations (measured displacement rates) suggest that at low capillary numbers, the temperature does not have a significant influence in the residual saturation of processed and crude oil. For heavy crude oil this is true for the capillary numbers less than 0.02. Above this threshold capillary number, the oil recovery (and therefore residual oil saturation) is very sensitive to the capillary number, i.e., the injection rate, interfacial tension, and wettability, and to temperature.
Unlocking Thin Beds Potential: Gas Identification Through Downhole Fluid Analysis
Authors: Loi D. , Mazzoni S. , Gigliotti M. , Baio C. , Borghi M. , Baldini D. , Italiano F. , Cantini S.
Published: November 2011

Several offshore gas fields are present in Adriatic Sea (Italy), producing since the 60s. The gas is produced from multilayer metric sand reservoirs. The declining production in these mature fields is normally offset by drilling new deviated wells. Recent technology evolution shifted the focus from metric reservoirs to thinly laminated intervals (thin beds), until now not produced due to difficulties in indentifying gas bearing zones. This paper proposes a critical review of existing thin beds evaluation techniques and shows a successful case history using wireline formation testing technology.

While gas identification in metric reservoirs can be achieved with standard petrophysical measurements, thin beds are challenging since lamination thickness is half inch or less. Even the most advanced petrophysical logging tools struggle in providing discrimination of gas from water in this environment. Conventional pressure gradient approach also does not work, since thin beds often overpressurized and pressures are supercharged due to low mobility.

A new wireline formation testing approach for thin beds to discriminate gas from water zones was proposed, using a dual packer string with downhole fluid analysis capabilities, including fluid density measurement. Twelve stations in thin beds were attempted, all resulted representative in terms of fluid identification and pressure measurement. Productivity forecast of the tested intervals was also provided using as input pressures and permeabilities derived from dual packer tests.

The possibility to verify gas presence in zones with high uncertainties saved the cost of multiple well testings, optimized the completion strategy of the different reservoirs and allowed to increase the field production and reserves.

Several gas fields today producing from metric reservoirs will be revisited in the very near future in order to start production from thin beds, until now untouched. The wireline dual packer approach described in this paper, along with enhancement of petrophysical logs applications, will certainly play a key role in optimal exploitation of thin beds gas reserves.
Experimental Study of Air Injection in SAGD Chamber
Authors: Rahnema H. , Barrufet M. , Mamora D.
Published: November 2011

Steam Assisted Gravity Drainage (SAGD) is a successful method for recovering bitumen and heavy oil that is widely used in Alberta, Canada. However as the SAGD chamber fully develops (mature chamber), the oil production rate starts to decline and the steam oil ratio (SOR) to increase, directly affecting the economic viability of the process at this stage. Air injection after SAGD is one potential option to recover residual oil inside mature SAGD chambers, and to avoid having steam migration form adjacent SAGD patterns.

In this paper, a detailed laboratory experiment is presented in order to analyze the feasibility of in-situ combustion after an SAGD process. A 3D laboratory model was designed and constructed. The combustion cell was fitted with 48 thermocouples. A horizontal pair well is placed at the bottom of the model with interwell spacing of 3 cm. The SAGD chamber occupies 26% of the model. The first 15 cm of the injection well is preheated using an electric igniter. Enriched air is used for establishing the combustion chamber. After ignition, the combustion front develops near the injection side and progresses forward while laterally limited inside SAGD chamber boundaries. Flue gases and hot oil are produced through the bottom horizontal well. A maximum temperature of 617°C was recorded, with cumulative oil recovery of 12% original oil in place (OOIP). Post experiment analysis of the sand pack shows that, besides sweeping the residual oil in the SAGD chamber, the combustion process created a hard coke shell around the chamber, which isolated the steam chamber from the surrounding media.
Effect of Natural Fracture Density on Production Variability of Individual Wells in the Tight Gas Nikanassin Formation
Authors: Gonzalez Laureano , Aguilera Roberto
Published: November 2011

A statistical model with a strong correlation has been developed to determine average fracture density on the basis of production variability of 271 individual wells producing exclusively from the Nikanassin and equivalent formations in a very large area of more than 15,000 km2 in the Western Canada Sedimentary basin (WCSB), Alberta and British Columbia, Canada.

Fractional production variability plots published by Nelson (2001) have been used successfully in the past in many naturally fractured reservoirs around the world. Up to now, the generation of such graphs has been based on empirical observations from field production data. The variability of the graphs is qualitatively interpreted as a measure of reservoir heterogeneities.

This paper presents a sequential methodology to reproduce the empirical fractional variability plots of the Nikanassin tight gas formation using real data, an empirical variability distribution model (VDM) and dual-porosity numerical simulation. Different simulation approaches and multiple sensitivities were generated from the simplest to the most detailed cases to understand what causes the curvature of the fractional production variability plot (FPVP) in Nikanassin wells. The base simulation case is a homogeneous dual porosity model where porosity and permeability are set constant for matrix and fractures. A second case accounts for a heterogeneous dual porosity model generated through statistical distributions of porosity and permeability. Finally, Discrete Fracture Network (DFN) methodology is used to generate multiple fracture models from where stochastic fracture properties are generated for the simulation model.

It is concluded that curvature of the variability plot is mainly affected by the occurrence of natural fracture density. This finding permits estimating fracture density approximately parallel to the northwest/southeast-trending thrust belt of the Canadian Rocky Mountains in both the west and east side of the deformation wedge. An unexpected result is that for a significant change in fracture permeability and porosity with constant fracture density, the fractional production variability curve is not affected significantly in the case of gas reservoirs. Although the method is applied specifically to the Nikanassin tight gas formation, the theory is developed in detail in such a way that the methodology can be applied in other tight gas reservoirs around the world. Findings from this work are in good agreement with the geological description of the Nikanassin formation and with a previous production analysis performed in the six study areas based on the cumulative number of wells versus yearly cumulative gas production.
SeTES: A Self-Teaching Expert System for the Analysis, Design, and Prediction of Gas Production From Unconventional Gas Resources
Authors: Moridis George J. , Kuzma Heidi Anderson , Reagan Matthew T. , Blasingame Thomas A. , Huang Y. Wayne , Santos Ralph , Boyle Katie , Freeman Craig M. , Ilk Dilhan , Cossio Manuel , Bhattacharya Srimoyee , Nikolaou Michael
Published: November 2011

SeTES is a self-teaching expert system that (a) can incorporate evolving databases involving any type and amount of relevant data (geological, geophysical, geomechanical, stimulation, petrophysical, reservoir, production, etc.) originating from unconventional gas reservoirs, i.e., tight sands, shale or coalbeds, (b) can continuously update its built-in ‘public’ database and refine the its underlying decision-making metrics and process, (c) can make recommendations about well stimulation, well location, orientation, design, and operation, (d) offers predictions of the performance of proposed wells (and quantitative estimates of the corresponding uncertainty), and (e) permits the analysis of data from installed wells for parameter estimation and continuous expansion of its database. Thus, SeTES integrates and processes any available information from multiple and diverse sources on a continuous basis to make recommendations and support decision making at multiple time-scales, while expanding its internal database and explicitly addressing uncertainty. It receives and manages data in three forms: public data, that have been made available by various contributors, semi-public data, which conceal some identifying aspects but are available to compute important statistics, and a user’s private data, which can be protected and used for more targeted design and decision making. SeTES can be a vital and easy-to-use tool in gas production from unconventional gas resources, and presents a new paradigm for communicating research and technology to the public and distributing scientific tools and methods. It is expected to result in a significant improvement in reserve estimates, and increases in production by increasing efficiency and reducing uncertainty.
Reservoir Quality Mapping Based on IDC Analyses and Hydraulic Frac Size
Authors: Kuppe Frank , Carlson Patrick
Published: November 2011

A three part process has been developed to generate a correlation which can be used to 1) map representative ∅h in the Kakwa Cadotte reservoir and 2) optimize the design of hydraulic fracture treatments. This same process can be applied to multi-fractured horizontal wells, completed in the Upper Montney reservoir, to generate a relationship between Estimated Ultimate Recovery (EUR), ∅h and total hydraulic fracture tonnage.

The initial stage of the process required the application of IDC (Inverted Decline Curve) technology to determine independent quantities of 1) reservoir quality (kh) and 2) hydraulic fracture placement (as measured by fracture half length = Xf). Using this IDC technique to differentiate between the better and lesser quality wells we can find a correlation between Estimated Ultimate Recovery (EUR) and some function of porosity, net pay and fracture tonnage (the second step in this process).

The physics behind this relationship essentially correlates to hydraulic fracture volumetrics and effective insitu permeability within each well’s drainage area. Wells that do not match the trend established by the "clear majority" of wells (data points) can now be readily flagged and included in the established correlation by modifying ∅h and/or frac tonnage until they match the trend. This adjustment would of course have to be rationalized by either a change in 1) possible kh, throughout the well drainage area, or 2) the effective frac tonnage displaced for the well. Given that most of the two dozen wells evaluated established an excellent correlation, this technique became very useful in narrowing the range of possible kh or effective Xf, within each well’s drainage area. After establishing the relative contribution to EUR of 1) reservoir quality and 2) hydraulic fracture effectiveness, we could map a representative kh distribution to optimize future well locations.

Finally, the process (for developing this correlation) was also tested on 46 Upper Montney horizontal wells producing from the Swan reservoir. Although producing into multiple hydraulic fractures, the linear trend of the inverted decline curve, for these wells, still yields a reliable indicator of permeability and/or fracture placement effectiveness. An excellent correlation exists between IDC slopes and independently determined EURs but more work is required to differentiate between the relative contributions of reservoir quality (kh) and hydraulic fracture effectiveness (Xf). This reservoir surveillance technique will be useful for the placement of horizontal wells, particularly unconventional Montney wells, and the optimization of hydraulic fracture treatments, along the entire Montney trend.
Simulation of Noncondensable Gases in SAGD Steam Chambers
Authors: Gittins Simon , Gupta Subodh , Zaman Maliha
Published: November 2011

Cenovus Energy has been very successfully developing the Foster Creek and Christina Lake projects using the Steam Assisted Gravity Drainage (SAGD) process. The SAGD process at both these projects has been operated at well above the initial reservoir pressure for extended periods of time and this has been adequately simulated using dead oil models which omit solution gas from the simulations.

As we move into later stages in the life of the more mature well pairs at these projects it is important to better understand the role of non-condensable gases on the development of the steam chambers in order to optimize the methane co-injection, steam ramp-down and ultimately blow-down phases of operations. Cenovus also plans on implementing reduced pressure SAGD and Solvent Aided Processes (SAP) at future projects and non-condensable gas is expected to play a significant role in these processes.

Hence, understanding the flow behavior of non-condensable gases in SAGD steam chambers could have far-reaching consequences for lowering the energy intensity and associated costs as well as reducing the environmental impact of bitumen production while potentially increasing reserves.

This paper presents the results of some recent simulations which are improving our understanding of the role of solution gas in SAGD and the impact of non-condensable gases on steam chamber development.
Microseismic Evaluation of Stage Isolation With a Multiple-Fracport, Openhole Completion
Authors: Maxwell S. C. , Chen Z. , Nizkous I. , Parker R. , Rodionov Y. , Jones M.
Published: November 2011

Multiple, mechanically-activated, sliding-sleeve fracports is a common completion used for horizontal wells in unconventional reservoirs. Characteristic seismic signals have been observed at approximately the same time as pressure spikes associated with balls dropped to open the sliding sleeves. The ‘ball drop’ seismic signals are high amplitude, low frequency, multiple discrete events with a short period of time, with each event locating at the fracport. The seismic radiation characteristics are consistent with an axial displacement along the treatment well. The seismic signals are attributed to the sleeve sliding open, which results in sufficient energy to account for the high amplitude signals. The occurance of the ball drop events can therefore be used to diagnose if the ball seated and the sleeve opened at the expected location, and along with the pressure and microseismic response can be used to validate the expected actions of the completion. Several case studies are also presented illustrating successful stage isolation with proper completion operation, response of the sleeve not opening properly and stage overlap associated with both hydraulically connected fracture networks in the reservoir and connected fracture ports.
Synthesis, structure, and luminescent properties of two novel polynuclear complexes of 1,3-di(pyridin-2-yl)propane-1,3-dione
Authors: Tan Jin-Ting , Zhao Wen-Jie , Chen San-Ping , Li Xia , Lu Ying-Li , Feng Xing , Yang Xu-Wu
Published: November 2011

Two complexes, {[Cd6(o-dppd)2(µ2-Cl)6(µ3-Cl)2(DMF)2(H2O)2Cl2]·DMF·CH3OH}n (I) (DMF = N,N-dimethylformamide; o-dppdH = 1,3-di(pyridin-2-yl)propane-1,3-dione) and [Cu4(o-dppd)2(OAc)4(OH)2]·4H2O (II), were synthesised and characterised by single-crystal X-ray diffraction, elemental analysis, IR, solid fluorescence and TGA. The results showed that complex I had a rodshaped polynuclear chain with hexacoordinating Cd atoms bridged by oxygen, µ2-Cl and µ3-Cl; complex II was a tetranuclear oligomer. In general, supramolecular architectures are constructed through hydrogen-bonding and π-π stacking interactions. I shows luminescence.
Neutralizing IL-6 Reduces Human Arterial Allograft Rejection by Allowing Emergence of CD161+ CD4+ Regulatory T Cells
Authors: Fogal Birgit , Yi Tai , Wang Chen , Rao Deepak A. , Lebastchi Amir , Kulkarni Sanjay , Tellides George , Pober Jordan S.
Published: November 2011

Perioperative injuries to an allograft exacerbate graft rejection, which in humans is primarily mediated by effector memory T cells. IL-6 transcripts in human coronary artery segments rapidly increase posttransplantation into immunodeficient mouse hosts compared with those of pretransplant specimens and fall dramatically by 30 d. Adoptive transfer of human PBMCs allogeneic to the artery 2 d postoperatively results in T cell infiltrates and intimal expansion 4 wk later. Ab neutralization of human IL-6 reduces the magnitude of intimal expansion and total T cell infiltration but increases the relative expression of CD161 while decreasing other Th17 markers. Coculture of MHC class II-expressing human endothelial cells (ECs) with allogeneic CD4+ memory T cells results in T cell activation and EC secretion of IL-6. Neutralizing IL-6 in primary allogeneic T cell–EC cocultures results in enhanced T cell proliferation of CD161+ CD4+ T cells, reduces total T cell proliferation upon restimulation in secondary cultures (an effect dependent on CD161+ T cells), increases expression of FOXP3 in CD161+ T cells, and generates T cells that suppress proliferation of freshly isolated T cells. These data suggest that IL-6 released from injured allograft vessels enhances allogeneic T cell infiltration and intimal expansion in a model of human allograft rejection by inhibiting an increase in CD161+ regulatory T cells.
IL-15 Regulates Homeostasis and Terminal Maturation of NKT Cells
Authors: Gordy Laura E. , Bezbradica Jelena S. , Flyak Andrew I. , Spencer Charles T. , Dunkle Alexis , Sun Jingchun , Stanic Aleksandar K. , Boothby Mark R. , He You-Wen , Zhao Zhongming , Van Kaer Luc , Joyce Sebastian
Published: November 2011

Semi-invariant NKT cells are thymus-derived innate-like lymphocytes that modulate microbial and tumor immunity as well as autoimmune diseases. These immunoregulatory properties of NKT cells are acquired during their development. Much has been learned regarding the molecular and cellular cues that promote NKT cell development, yet how these cells are maintained in the thymus and the periphery and how they acquire functional competence are incompletely understood. We found that IL-15 induced several Bcl-2 family survival factors in thymic and splenic NKT cells in vitro. Yet, IL-15–mediated thymic and peripheral NKT cell survival critically depended on Bcl-xL expression. Additionally, IL-15 regulated thymic developmental stage 2 to stage 3 lineage progression and terminal NKT cell differentiation. Global gene expression analyses and validation revealed that IL-15 regulated Tbx21 (T-bet) expression in thymic NKT cells. The loss of IL-15 also resulted in poor expression of key effector molecules such as IFN-γ, granzyme A and C, as well as several NK cell receptors, which are also regulated by T-bet in NKT cells. Taken together, our findings reveal a critical role for IL-15 in NKT cell survival, which is mediated by Bcl-xL, and effector differentiation, which is consistent with a role of T-bet in regulating terminal maturation.
Granzyme B Regulates Antiviral CD8+ T Cell Responses
Authors: Salti Suzan M. , Hammelev Erin M. , Grewal Jenny L. , Reddy Sreelatha T. , Zemple Sarah J. , Grossman William J. , Grayson Mitchell H. , Verbsky James W.
Published: November 2011

CTLs and NK cells use the perforin/granzyme cytotoxic pathway to kill virally infected cells and tumors. Human regulatory T cells also express functional granzymes and perforin and can induce autologous target cell death in vitro. Perforin-deficient mice die of excessive immune responses after viral challenges, implicating a potential role for this pathway in immune regulation. To further investigate the role of granzyme B in immune regulation in response to viral infections, we characterized the immune response in wild-type, granzyme B-deficient, and perforin-deficient mice infected with Sendai virus. Interestingly, granzyme B-deficient mice, and to a lesser extent perforin-deficient mice, exhibited a significant increase in the number of Ag-specific CD8+ T cells in the lungs and draining lymph nodes of virally infected animals. This increase was not the result of failure in viral clearance because viral titers in granzyme B-deficient mice were similar to wild-type mice and significantly less than perforin-deficient mice. Regulatory T cells from WT mice expressed high levels of granzyme B in response to infection, and depletion of regulatory T cells from these mice resulted in an increase in the number of Ag-specific CD8+ T cells, similar to that observed in granzyme B-deficient mice. Furthermore, granzyme B-deficient regulatory T cells displayed defective suppression of CD8+ T cell proliferation in vitro. Taken together, these results suggest a role for granzyme B in the regulatory T cell compartment in immune regulation to viral infections.
An MHC Class Ib-Restricted CD8+ T Cell Response to Lymphocytic Choriomeningitis Virus
Authors: Chen Lili , Jay David C. , Fairbanks Jared D. , He Xiao , Jensen Peter E.
Published: November 2011

Conventional MHC class Ia-restricted CD8+ T cells play a dominant role in the host response to virus infections, but recent studies indicate that T cells with specificity for nonclassical MHC class Ib molecules may also participate in host defense. To investigate the potential role of class Ib molecules in anti-viral immune responses, Kb−/−Db−/−CIITA−/− mice lacking expression of MHC class Ia and class II molecules were infected with lymphocytic choriomeningitis virus (LCMV). These animals have a large class Ib-selected CD8+ T cell population and they were observed to mediate partial (but incomplete) virus clearance during acute LCMV infection as compared with Kb−/−Db−/−β2-microglobulin−/− mice that lack expression of both MHC class Ia and class Ib molecules. Infection was associated with expansion of splenic CD8+ T cells and induction of granzyme B and IFN-γ effector molecules in CD8+ T cells. Partial virus clearance was dependent on CD8+ cells. In vitro T cell restimulation assays demonstrated induction of a population of β2-microglobulin–dependent, MHC class Ib-restricted CD8+ T cells with specificity for viral Ags and yet to be defined nonclassical MHC molecules. MHC class Ib-restricted CD8+ T cell responses were also observed after infection of Kb−/−Db−/−mice despite the low number of CD8+ T cells in these animals. Long-term infection studies demonstrated chronic infection and gradual depletion of CD8+ T cells in Kb−/−Db−/−CIITA−/− mice, demonstrating that class Ia molecules are required for viral clearance. These findings demonstrate that class Ib-restricted CD8+ T cells have the potential to participate in the host immune response to LCMV.
Hepcidin Is Regulated during Blood-Stage Malaria and Plays a Protective Role in Malaria Infection
Authors: Wang Hai-Zhen , He Ying-Xin , Yang Chun-Ju , Zhou Wei , Zou Cheng-Gang
Published: November 2011

Hepcidin is one of the regulators of iron metabolism. The expression of hepcidin is induced in spleens and livers of mice infected with pathogenic bacteria. Recent studies have indicated that serum hepcidin level is also increased in human subjects infected with Plasmodium falciparum. The mechanism of the regulation of hepcidin expression and its role in the infection of malaria remains unknown. In this study, we determined the expression of hepcidin in livers of mice infected with Plasmodium berghei. The expression of hepcidin in the liver was upregulated and downregulated during the early and late stages of malaria infection, respectively. Inflammation and erythropoietin, rather than the iron-sensing pathway, are involved in the regulation of hepcidin expression in livers of infected mice. Meanwhile, we investigated the effect of hepcidin on the survival of mice infected with P. berghei. Treatment of malaria-infected mice with anti-hepcidin neutralizing Abs promoted the rates of parasitemia and mortality. In contrast, lentiviral vector-mediated overexpression of hepcidin improved the outcome of P. berghei infection in mice. Our data demonstrate an important role of hepcidin in modulating the course and outcome of blood-stage malaria.
Leukemic Priming of Resting NK Cells Is Killer Ig-like Receptor Independent but Requires CD15-Mediated CD2 Ligation and Natural Cytotoxicity Receptors
Authors: Sabry May , Tsirogianni Maria , Bakhsh Ismail A. , North Janet , Sivakumaran Janani , Giannopoulos Konstantinos , Anderson Robert , Mackinnon Stephen , Lowdell Mark W.
Published: November 2011

Resting human NK cells require a two-stage activation process that we have previously described as “priming” and “triggering.” NK-sensitive tumor cells provide both priming and triggering signals. NK-resistant tumors evade lysis, mostly by failure to prime; however, we recently reported a tumor cell line (CTV-1) that primes resting NK cells but fails to trigger lysis. In this article, we report two additional leukemia cell lines that prime NK cells but are resistant to lysis. Tumor-mediated NK priming is via CD2 binding to a ligand within CD15 on the tumor cell. NK-resistant RAJI cells became susceptible to NK lysis following transfection and expression of CD15. Blockade of CD15 on K562 cells or on CD15+ RAJI cells significantly inhibited lysis, as did blockade of CD2 on resting NK cells. NK priming via CD2 induced CD16 shedding, releasing CD3ζ to the CD2, leading to its phosphorylation and the subsequent phosphorylation of linker for activation of T cells and STAT-5 and synthesis of IFN-γ. Blockade of C-type lectin receptors significantly suppressed the tumor-mediated priming of NK cells, whereas blockade of Ig-superfamily–like receptors had no effect at the NK-priming stage. Tumor priming of resting NK cells was irrespective of HLA expression, and blockade of HLA–killer Ig-like receptor interactions did not influence the incidence or degree of priming. However, CD15–CD2 interactions were critical for NK priming and were required, even in the absence of HLA-mediated NK inhibition. Tumor-mediated priming led to a sustained primed state, and the activated NK cells retained the ability to lyse NK-resistant tumors, even after cryopreservation.
Structural Basis of Diverse Peptide Accommodation by the Rhesus Macaque MHC Class I Molecule Mamu-B*17: Insights into Immune Protection from Simian Immunodeficiency Virus
Authors: Wu Yan , Gao Feng , Liu Jun , Qi Jianxun , Gostick Emma , Price David A. , Gao George F.
Published: November 2011

The MHC class I molecule Mamu-B*17 has been associated with elite control of SIV infection in rhesus macaques, akin to the protective effects described for HLA-B*57 in HIV-infected individuals. In this study, we determined the crystal structures of Mamu-B*17 in complex with eight different peptides corresponding to immunodominant SIVmac239-derived CD8+ T cell epitopes: HW8 (HLEVQGYW), GW10 (GSHLEVQGYW), MW9 (MHPAQTSQW), QW9 (QTSQWDDPW), FW9 (FQWMGYELW), MF8 (MRHVLEPF), IW9 (IRYPKTFGW), and IW11 (IRYPKTFGWLW). The structures reveal that not only P2, but also P1 and P3, can be used as N-terminal anchor residues by Mamu-B*17–restricted peptides. Moreover, the N-terminal anchor residues exhibit a broad chemical specificity, encompassing basic (H and R), bulky polar aliphatic (Q), and small (T) residues. In contrast, Mamu-B*17 exhibits a very narrow preference for aromatic residues (W and F) at the C terminus, similar to that displayed by HLA-B*57. Flexibility within the whole peptide-binding groove contributes to the accommodation of these diverse peptides, which adopt distinct conformations. Furthermore, the unusually large pocket D enables compensation from other peptide residues if P3 is occupied by an amino acid with a small side chain. In addition, residues located at likely TCR contact regions present highly flexible conformations, which may impact TCR repertoire profiles. These findings provide novel insights into the structural basis of diverse peptide accommodation by Mamu-B*17 and highlight unique atomic features that might contribute to the protective effect of this MHC I molecule in SIV-infected rhesus macaques.
Expansion of Functionally Anergic CD21−/low Marginal Zone-like B Cell Clones in Hepatitis C Virus Infection-Related Autoimmunity
Authors: Terrier Benjamin , Joly Florence , Vazquez Thomas , Benech Philippe , Rosenzwajg Michelle , Carpentier Wassila , Garrido Marlène , Ghillani-Dalbin Pascale , Klatzmann David , Cacoub Patrice , Saadoun David
Published: November 2011

Homeostasis of peripheral B cell subsets is disturbed during chronic hepatitis C virus (HCV) infection, leading to the occurrence of autoimmunity and B cell lymphoproliferation. However, mechanisms by which HCV causes lymphoproliferation remain controversial. We report in this article on the elevated number of clonal CD21−/lowIgM+CD27+ marginal zone (MZ)-like B cells, which correlates with autoimmunity and lymphoproliferation in HCV patients. We found an increase in autoreactive BCRs using VH1–69 and VH4–34 genes in CD21−/low MZ B cells. CD21−/low MZ B cells showed impaired calcium-mediated signaling, did not upregulate activation markers, and did not proliferate in response to BCR triggering. CD21−/low MZ B cells also were prone to dying faster than their CD21+ counterparts, suggesting that these B cells were anergic. CD21−/low MZ B cells, in contrast, remained responsive to TLR9 stimulation. Gene array analyses revealed the critical role of Early growth response 2 and Cbl-b in the induction of anergy. Therefore, HCV patients who display high frequencies of unresponsive CD21−/low MZ B cells are more susceptible to developing autoimmunity and/or lymphoproliferation. These cells remain in peripheral blood controlled by functional anergy instead of being eliminated, and chronic antigenic stimulation through TLR stimulation may create a favorable environment for breaking tolerance and activating these cells.