bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of Concomitant Infection with
Chlamydia trachomatis
IncA-Negative Mutant and Wild-Type Strains by Genomic, Transcriptional, and Biological Characterizations
Authors: Suchland Robert J. , Jeffrey Brendan M. , Xia Minsheng , Bhatia Ajay , Chu Hencelyn G. , Rockey Daniel D. , Stamm Walter E.
Published: October 2008

Clinical isolates of
Chlamydia trachomatis
that lack IncA on their inclusion membrane form nonfusogenic inclusions and have been associated with milder, subclinical infections in patients. The molecular events associated with the generation of IncA-negative strains and their roles in chlamydial sexually transmitted infections are not clear. We explored the biology of the IncA-negative strains by analyzing their genomic structure, transcription, and growth characteristics in vitro and in vivo in comparison with IncA-positive
C. trachomatis
strains. Three clinical samples were identified that contained a mixture of IncA-positive and -negative same-serovar
C. trachomatis
populations, and two more such pairs were found in serial isolates from persistently infected individuals. Genomic sequence analysis of individual strains from each of two serovar-matched pairs showed that these pairs were very similar genetically. In contrast, the genome sequence of an unmatched IncA-negative strain contained over 5,000 nucleotide polymorphisms relative to the genome sequence of a serovar-matched but otherwise unlinked strain. Transcriptional analysis, in vitro culture kinetics, and animal modeling demonstrated that IncA-negative strains isolated in the presence of a serovar-matched wild-type strain are phenotypically more similar to the wild-type strain than are IncA-negative strains isolated in the absence of a serovar-matched wild-type strain. These studies support a model suggesting that a change from an IncA-positive strain to the previously described IncA-negative phenotype may involve multiple steps, the first of which involves a translational inactivation of
incA
, associated with subsequent unidentified steps that lead to the observed decrease in transcript level, differences in growth rate, and differences in mouse infectivity.
Human α- and β-Defensins Bind to Immobilized Adhesins fromPorphyromonas gingivalis
Authors: Dietrich Deborah E. , Xiao Xiangjun , Dawson Deborah V. , Bélanger Myriam , Xie Hua , Progulske-Fox Ann , Brogden Kim A.
Published: October 2008

Human neutrophil peptide α-defensins (HNPs) and human β-defensins (HBDs) are small well-characterized peptides with broad antimicrobial activities and a diversity of innate immune functions. Although the interactions of defensins with bacteria and their membranes have been well characterized, the interactions of defensins with bacterial adhesins have not. Here we determine if HNPs and HBDs bind to the immobilized adhesins ofPorphyromonas gingivalisstrain 381, recombinant hemagglutinin B (rHagB) and recombinant fimbrillin A (rFimA), by surface plasmon resonance spectroscopy. Association of HNPs and HBDs with rHagB or rFimA was dose dependent and defensin specific. HBD3, HNP-2, and HNP-1 bound more readily to immobilized rHagB than HBD2 and HBD1 did. HNP-2, HNP-1, and HBD3 bound more readily to immobilized rFimA than HBD1 and HBD2 did. Binding of defensins to adhesins may serve to prevent microbial adherence to tissues, attenuate proinflammatory cytokine responses, and facilitate delivery of bound antigen to antigen-presenting cells with defensin receptors.
Colony-Stimulating Factor-1-Dependent Macrophage Functions Regulate the Maternal Decidua Immune Responses againstListeria monocytogenesInfections during Early Gestation in Mice
Authors: Qiu Xuan , Zhu Liyin , Pollard Jeffrey W.
Published: October 2008

The association between extreme-prematurity births and intrauterine infection emphasizes the importance of understanding the host immune responses against uterine-invading microbes during early pregnancy to the prevention of preterm births.Listeria monocytogenes, a clinically relevant intracellular bacterium, has a predilection for replication at the maternofetal interface during pregnancy. Here, using mice carrying the recessive null osteopetrotic mutation in the colony-stimulating factor-1 (CSF-1) gene, we show that CSF-1-dependent macrophage functions are required for the maternal decidua immune responses againstL. monocytogenesinfections during early gestation in mice. In the absence of CSF-1, pregnant mice were more susceptible to uterine infection byL. monocytogenes; their inability to control the expansion of colonized bacteria in the pregnant uterus led to decidual cell death, tissue disintegration, and resorption of the developing embryo. However, CSF-1-deficient mice were able to produce significant levels of both Th1 cytokines and neutrophil chemoattractants and to recruit neutrophils to the decidual tissue in response toListeriainfection. Depletion of macrophages in hormonally induced pseudopregnant mice resulted in higher uterine bacterial levels afterL. monocytogenesinfection. These data suggest that the anti-Listeriaresponses in the maternal decidual tissue are dependent on CSF-1-regulated macrophages.
Isolation, Synthesis, and Antimicrobial Activities of Naturally Occurring θ-Defensin Isoforms from Baboon Leukocytes
Authors: Garcia Angie E. , Ösapay George , Tran Patti A. , Yuan Jun , Selsted Michael E.
Published: October 2008

θ-Defensins are macrocyclic antimicrobial peptides that were previously isolated from leukocytes of a single species, the rhesus macaque. We now report the characterization of baboon θ-defensins (BTDs) expressed in bone marrow and peripheral blood leukocytes. Four cDNAs encoding θ-defensin precursors were characterized, allowing for the prediction of 10 theoretical θ-defensins (BTD-1 to BTD-10) produced by binary, head-to-tail splicing of nonapeptides excised from paired precursors. Five of the predicted θ-defensins were purified from baboon leukocytes, and synthetic versions of each were prepared. Anti-θ-defensin antibody localized the peptides in circulating neutrophils and monocytes and in immature and mature myeloid elements in bone marrow. Each of the BTDs possessed antimicrobial activity against bacterial and fungal test organisms in vitro. Peptide activities varied markedly despite a high degree of sequence conservation among the θ-defensins tested. Thus, baboons express numerous θ-defensins which appear to differentially contribute to host defense against diverse pathogens.
Infected-Host-Cell Repertoire and Cellular Response in the Lung following Inhalation ofFrancisella tularensisSchu S4, LVS, or U112
Authors: Hall Joshua D. , Woolard Matthew D. , Gunn Bronwyn M. , Craven Robin R. , Taft-Benz Sharon , Frelinger Jeffrey A. , Kawula Thomas H.
Published: October 2008

Francisella tularensiscauses systemic disease in humans and other mammals, with high morbidity and mortality associated with inhalation-acquired infection.F. tularensisis a facultative intracellular pathogen, but the scope and significance of cell types infected during disease is unknown. Using flow cytometry, we identified and quantified infected-cell types and assessed the impact of infection on cell populations following inhalation ofF. tularensisstrains U112, LVS, and Schu S4. Initially, alveolar macrophages comprised over 70% of Schu S4- and LVS-infected cells, whereas approximately 51% and 27% of U112-infected cells were alveolar macrophages and neutrophils, respectively. After 3 days, roughly half of Schu S4- and LVS- and nearly 80% of U112-infected cells were neutrophils. All strains infected CD11bhighmacrophages, dendritic cells, monocytes, and alveolar type II cells throughout infection. Macrophage, monocyte, and dendritic-cell populations were reduced during U112 infection but not Schu S4 or LVS infection. These results demonstrate directly thatF. tularensisis a promiscuous intracellular pathogen in the lung that invades and replicates within cell types ranging from migratory immune cells to structural tissue cells. However, the proportions of cell types infected and the cellular immune response evoked by the human pathogenic strain Schu S4 differ from those of the human avirulent U112.
Purification and characterization of 3,4-dihydroxyphenylalanine oxidative deaminase fromRhodobacter sphaeroidesOU5
Authors: Ranjith N. K. , Ramana Ch. V. , Sasikala Ch.
Published: October 2008

An enzyme involved in the catabolism of 3,4-dihydroxyphenylalanine (DOPA) was isolated from Rhodobacter sphaeroides OU5. The enzyme catalyzes the formation of 3,4-dihydroxyphenylpyruvic acid (DOPP) and ammonia from DOPA. Formation of ammonia by DOPA oxidative deaminase was O2dependent and the enzyme isolated to its homogeneity has 100% affinity for DOPA. DOPA oxidative deaminase is functional at low concentrations of the substrate (<100 μmol·L–1) and is independent of NADH. The molecular mass of the purified enzyme is ~190 kDa and the enzyme could be a pentamer of 54, 42, 34, 25, and 23 kDa subunits as determined by SDS–PAGE.
Oral immunization with recombinant Lactococcus lactis confers protection against respiratory pneumococcal infection
Authors: Villena Julio , Medina Marcela , Raya Raúl , Alvarez Susana
Published: October 2008

In the present work, we evaluated if oral immunization with the pneumococcal protective protein A (PppA), expressed in the cell wall of Lactococcus lactis (L. lactis PppA+), was able to confer protective immunity against Streptococcus pneumoniae . Mice were immunized orally with L. lactis PppA+ for 5 consecutive days. Vaccination was performed one (nonboosted group) or 2 times with a 2 week interval between each immunization (boosted group). Oral priming with L. lactis PppA+ induced the production of anti-PppA IgM, IgG, and IgA antibodies in serum and in bronchoalveolar (BAL) and intestinal (IF) lavage fluids. Boosting with L. lactis PppA+ increased the levels of mucosal and systemic immunoglobulins. Moreover, the avidity and the opsonophagocytic activity of anti-PppA antibodies were significantly improved in the boosted group. The presence of both IgG1 and IgG2a anti-PppA antibodies in serum and BAL and the production of both interferon γ and interleukin-4 by spleen cells from immunized mice indicated that L. lactis PppA+ stimulated a mixture of Th1 and Th2 responses. The ability of L. lactis PppA+ to confer cross-protective immunity was evaluated using challenge assays with serotypes 3, 6B, 14, and 23F. Lung bacterial cell counts and hemocultures showed that immunization with L. lactis PppA+ improved resistance against all the serotypes assessed, including serotype 3, which was highly virulent in our experimental animal model. To our knowledge, this is the first demonstration of protection against respiratory pneumococcal infection induced by oral administration of a recombinant lactococcal vaccine.
Targets for hydrogen-peroxide-induced damage to suspension and biofilm cells of Streptococcus mutans
Authors: Baldeck Jeremiah D. , Marquis Robert E.
Published: October 2008

Hydrogen peroxide (H2O2) is considered a major endogenous source of oxidative stress to oral bacteria and also is widely used in oral care products. Our study objectives were to identify specific targets for H2O2-induced damage to cells of Streptococcus mutans in suspensions and monospecies biofilms and to differentiate bacteriostatic and bactericidal actions of the peroxide. Streptococcus mutans was grown in suspension cultures and fed-batch biofilms for assessing relative sensitivities of viability, glycolysis, and protein synthesis to H2O2 damage. Biofilm cells were found to have essentially the same peroxide sensitivity as cells in suspensions. H2O2 at low concentrations of about 16.3 mmol/L was highly inhibitory for glycolysis and mainly bacteriostatic. The most sensitive target detected for glycolytic inhibition was glyceraldehyde-3-phosphate dehydrogenase with IC50 (50% inhibitory concentration) values of ca. 2.2 mmol/L for suspension cells and 2.3 mmol/L for biofilms with 15 min treatments. The phosphoenolpyruvate:glucose phosphotransferase pathway was less sensitive with an IC50 of ca. 10 mmol/L. Aldolase was not inhibited at bacteriostatic concentrations of the peroxide. For suspensions and biofilms, acidification somewhat diminished peroxide sensitivity, while increased temperature enhanced sensitivity. At concentrations above about 30 mmol/L, H2O2 became mainly bactericidal but not mutagenic for S. mutans. A major target for bactericidal damage was protein synthesis, thus rendering cells incapable of repairing or replacing oxidatively damaged proteins.
Film coating of seeds with Bacillus cereus RS87 spores for early plant growth enhancement
Authors: Jetiyanon Kanchalee , Wittaya-Areekul Sakchai , Plianbangchang Pinyupa
Published: October 2008

The plant growth-promoting rhizobacterium Bacillus cereus RS87 was previously reported to promote plant growth in various crops in both greenhouse and field trials. To apply as a plant growth promoting agent with practical use, it is essential to ease the burden of routine preparation of a fresh suspension of strain RS87 in laboratory. The objectives of this study were to investigate the feasibility of film-coating seeds with B. cereus RS87 spores for early plant growth enhancement and to reveal the indoleacetic acid (IAA) production released from strain RS87. The experiment consisted of the following 5 treatments: nontreated seeds, water-soaked seeds, film-coated seeds, seeds soaked with vegetative cells of strain RS87, and film-coated seeds with strain RS87 spores. Three experiments were conducted separately to assess seed emergence, root length, and plant height. Results showed that both vegetative cells and spores of strain RS87 significantly promoted (P ≤ 0.05) seed emergence, root length and plant height over the control treatments. The strain RS87 also produced IAA. In conclusion, the film coating of seeds with spores of B. cereus RS87 demonstrated early plant growth enhancement as well as seeds using their vegetative cells. IAA released from strain RS87 would be one of the mechanisms for plant growth enhancement.
Seed regeneration of Scots pine in boreal forest stands dominated by lichen and feather moss
Authors: Steijlen Ingeborg , Nilsson Marie-Charlotte , Zackrisson Olle
Published: October 2008

Six old-growth, late postfire Scots pine (Pinussylvestris L.) dominated forest stands of the Vaccinium–Cladina type were selected along a latitudinal gradient in northern Sweden. In two of the stands, Scots pine seedlings that had naturally regenerated during the last 40 years were surveyed in relation to field- and bottom-layer vegetation. The most abundant forest floor species, viz. Cladina spp., occupied 41% of the ground cover and dominated the microhabitat of Scots pine seedlings <10 years old. The second most common species, Pleuroziumschreberi (Bird.) Mitt., which occupied 10 and 20% of the ground cover at the two sites, was, in contrast, only found to cover less than 3% of the microhabitat of the seedlings < 10 years old. With increasing age of seedlings (>10 years), however, the cover of Cladina spp. significantly decreased and the cover of P. schreberi and various ericaceous species slightly increased. Thus Scots pine seedlings initially establish in lichen-dominated vegetation but as they develop P. schreberi and ericaceous species gradually become more abundant in the ground vegetation. The relationships between natural establishment patterns and microhabitat were further empirically tested by sowing seeds of Scots pine in patches of Cladina spp. and patches of P. schreberi. Seeding was performed in six sites during 3 consecutive years. A significant higher number of established Scots pine seedlings were found in Cladina spp. vegetation than in P. schreberi dominated vegetation, and Scots pine seedlings in P. schreberi experienced a significantly higher mortality. Laboratory studies indicated a negative chemical influence by P. schreberi on Scots pine seed germination but not on radicle growth of pregerminated seeds. The negative influence of P. schreberi on Scots pine seed germination and seedling survival in the field experiments is interpreted as an effect of moisture factors, chemical interference, and barriers of nutrient availability. Age structures of naturally established Scots pine showed evidence of continuous regeneration over the last 40 years. The study emphasizes the importance of biotically mediated regeneration patterns in explaining spatial stand structure and temporal dynamics in northern boreal Scots pine forest ecosystems during prolonged absence of fire. Tree regeneration tends not to be associated with mesoscale characteristics such as gaps and tip-up mounds, but rather with microhabitat conditions. The results have implications for predicting the effect of climatic warming.
Radial growth patterns and the effects of climate on second-growth Douglas-fir (Pseudotsugamenziesii) in the Siskiyou Mountains, Oregon
Authors: Little Ronda L. , Peterson David L. , Silsbee David G. , Shainsky Lauri J. , Bednar Larry F.
Published: October 2008

Three sites with fire-generated second-growth (70–100 years old) Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) in southwestern Oregon were examined using dendroecological techniques to determine (1) temporal patterns of radial growth and (2) the effects of variation in climate on growth. Long-term patterns of radial growth vary among sites, but similar interannual variation in radial growth indicates a common response to regional climate. Growth is positively correlated with the Palmer Drought Severity Index and precipitation during summer. Furthermore, growth is positively correlated with precipitation during autumn prior to the growth year, which suggests the benefits of soil moisture recharge for subsequent stemwood production. Annual precipitation is strongly seasonal, and soil moisture stress in summer is apparently severe enough to be the dominant climatic influence on radial growth. Positive correlations of growth with most monthly temperatures reflect the benefit of warm temperatures on photosynthesis and radial growth during periods of adequate soil moisture. Although coastal Oregon is generally considered to be a high precipitation environment, conditions are clearly dry enough during summer to limit carbon gain in second-growth Douglas-fir. If future climatic conditions result in increased soil moisture stress during summer, productivity of such second-growth stands may decrease below current levels.
Damping-off disease of pine seedlings on soils treated with simulated acidic rain
Authors: Schier George A. , Patton Roy L.
Published: October 2008

Damping-off during seed germination and early seedling growth of Pinusrigida Mill., Pinusechinata Mill., Pinustaeda L., and Pinusstrobus L. were observed for 28 days on three New Jersey (U.S.A.) Pine Barrens soils (Atsion, Downer, Lakewood) treated with simulated acidic rain solutions of pH 4.2, 3.5, or 3.0 (SO42−:Cl−:NO3−, 2.2:1.4:1.0). The soils were sandy, highly acidic, and deficient in mineral nutrients. Treatment with rain solution was started 53 days before planting the pine seeds and continued during germination. Seedling emergence and seedling mortality were affected significantly by solution pH, soils, and species. Seedling emergence of all pine species on Atsion and Lakewood soils decreased with increasing solution acidity. On Downer soil seedling emergence was unaffected by solution acidity probably because the buffering action of the soil decreased the acidity of the rain solution. Seedling mortality of all species increased with increasing treatment acidity on all soils and was significantly higher on Atsion (100% at pH 3.0) than on the other soils. Although solution acidity significantly increased the concentration of Al in the soil solution, there was no evidence of Al toxicity. Two isolated fungal species, a Trichoderma and a Penicillium, significantly reduced seedling emergence and increased seedling mortality of P. rigida in sterile, acid-washed quartz sand; however, neither seedling emergence nor seedling mortality was affected significantly by solution acidity.
Comments Synchronic large-scale disturbances and red spruce growth decline
Authors: Johnson A.H. , Cook E.R. , Siccama T.G. , Battles J.J. , McLaughlin S.B. , Leblanc D.C. , Wargo P.M.
Published: October 2008

not available
NEAR-AXIAL INTERFERENCE EFFECTS IN LONG-RANGE OCEAN ACOUSTIC PULSE PROPAGATION
Authors: GRIGORIEVA NATALIE S. , FRIDMAN GREGORY M.
Published: October 2008

In many long-range ocean propagation experiments the source and receiver are placed close to the depth of the waveguide axis. In this case, rays emerging from the source at sufficiently small angles intersect the sound-channel axis many times and form in its vicinity a large number of caustics with caustics cusps located repeatedly along the axis. In neighborhoods of cusped caustics there exists a very complicated interference pattern. Neighborhoods of interference grow with range and at long ranges they overlap. As a result, a complex interference wave (axial wave), that propagates along the waveguide axis, appears. The goal of this paper is to obtain the representation for the axial wave in the time domain and calculate its magnitude for a realistic model of a three-dimensional range-independent medium. Numerical computations are done for the average profile from the Acoustic Engineering Test (AET) experiment. The pulse center frequency of 75 Hz with 30-Hz bandwidth is used that corresponds to broadband acoustic signals which were transmitted during November 1994 in the eastern North Pacific Ocean as a part of the AET. The propagation range is 3250 km. The sound source is located on the waveguide axis, and the receiver is placed close to the depth of the axis. Through numerical simulation the dependencies of the magnitude of the axial wave on depth of the receiver and propagation range are studied.
A FORMULATION OF THE FAST MULTIPOLE BOUNDARY ELEMENT METHOD (FMBEM) FOR ACOUSTIC RADIATION AND SCATTERING FROM THREE-DIMENSIONAL STRUCTURES
Authors: CHEN Z.-S. , WAUBKE H. , KREUZER W.
Published: October 2008

Compared to the traditional boundary element method (BEM), the single level fast multipole boundary element method (SLFMBEM) or the multilevel fast multipole boundary element method (MLFMBEM) reduces the computational complexity of a job from O(n2) to O(n3/2) or O(n log 2n), respectively with n being the number of unknowns; this means a dramatical reduction in terms of CPU-time and storage requirement. Large scale problems, unsolvable with the traditional BEM, can be solved by using the FMBEM. In this paper, the traditional BEM, SLFMBEM, and MLFMBEM are formulated within the framework of the Burton–Miller Collocation BEM for acoustic radiation and scattering from 3D structures. Attention is especially paid to the practical aspects of the method in order to get a reliable and efficient computation code. The performance of the method is tested with practical examples, including one for computing the head-related transfer function (HRTF) between 1000 and 18 000 Hz.
Multidisciplinary stochastic impedance inversion: integrating geological understanding and capturing reservoir uncertainty
Authors: Rowbotham P. S. , Marion D. , Lamy P. , Insalaco E. , Swaby P. A. , Boisseau Y.
Published: October 2008

Stochastic (or geostatistical) impedance inversion techniques have great potential in addressing key questions in reservoir characterization. They work at the vertical scale of reservoir models and, therefore, at higher resolution than the seismic data. They produce multiple equiprobable results which provide an assessment of, the uncertainties, and they are ideally suited for integrating non-seismic information in the inversion process. However, two issues have slowed the acceptance of stochastic impedance inversion techniques. First, there is suspicion of‘ unconstrained random noise generators’, which appear to offer extra information for free, and, secondly, managing and extracting value from multiple realizations is difficult. For these reasons, faster deterministic inversion approaches, resulting in a single lower-resolution impedance volume, with less quantified uncertainty, are more commonly used when building reservoir models.

To address the first issue, we have developed ways of integrating 3D constraints from sedimentary modelling with the geostatistical impedance inversion method, since these two approaches bring complementary information on reservoir properties. The resulting high-resolution multiple realizations of impedance are combined with uncertainties from petrophysical regression analysis to produce multiple realizations of reservoir properties (e.g. porosity), and from each an estimate of total pore volume. We illustrate the benefits of this multiple realization work flow applied to data from a shallow marine siliciclastic reservoir. A comparison of the seismic/sedimentologically constrained reservoir models with those constrained by well data only has demonstrated more accuracy and better control on the spatial variability of reservoir properties. In this example, however, adding more constraints results in a broader range of possible reservoir models and a more meaningful uncertainty assessment. We conclude that our models constrained by well data only were derived with unrealistic simulation parameters and an over-optimistic assessment of a priori uncertainty.
Thermal history modelling in the southern Faroe–Shetland Basin
Authors: Carr A. D. , Scotchman I. C.
Published: October 2008

Hydrocarbon generation is a temperature-dependent process and the prediction of hydrocarbon generation in basin modelling requires the crustal heat flow history to be predicted. Tectonically, the Faroe–Shetland Basin (FSB) has been subjected to a number of Cretaceous rifting events, followed in the Tertiary by Balder volcanism and, finally, by Oligo-Miocene inversion. In this study the thermal history of the FSB is derived using two independent methods (rifting–volcanic–subsidence history and maturation). The methodology is described using two wells (204/19-1 and 205/22-1) in the southern FSB. The vitrinite reflectance results predicted by the PresRo
®
model, which was devised for modelling maturation in overpressured basins such as the FSB, produced predicted vitrinite reflectances that matched the measured values. The method was then applied to a pseudowell within the Foinaven sub-basin, and the predicted vitrinite reflectance values for the Kimmeridge Clay Formation source at 8 km depth indicate that the source is still mature for oil generation due to the extensive retardation induced by the highly overpressured, argillaceous Mesozoic sediments.
Insights into Cretaceous–Palaeogene sediment transport paths and basin evolution in the North Atlantic from a heavy mineral study of sandstones from southern East Greenland
Authors: Whitham Andrew G. , Morton Andrew C. , Fanning C. Mark
Published: October 2008

Major changes in sandstone provenance occurred during the deposition of the Cretaceous–Eocene succession in Kangerlussuaq, southern East Greenland. These changes can be recognized on the basis of provenance sensitive heavy mineral parameters (apatite:tourmaline and rutile:zircon ratios and garnet geochemistry) and the SHRIMP U–Pb dating of detrital zircons. The results support the subdivision of the succession into three units separated by major unconformities spanning the Late Coniacian to Late Campanian and Late Maastrichtian to Early Eocene. Rifting during the deposition of the first unit (Aptian–Late Coniacian) led to rift flank uplift and resulted in the local sourcing of sediment. Thermal subsidence during the deposition of the second unit (Late Campanian–Late Maastrichtian) led to rift flank subsidence and sediment sourcing from outside the immediate region. Renewed rifting immediately preceding the third unit (Early Eocene) resulted in a return to local sediment sourcing. The basin morphology during the deposition of the second unit would have been more conducive for the long-distance transport of sediment into the adjacent Faroe–Shetland Basin than during deposition of the first and third units. The results provide a framework for the identification of Greenland-sourced material in the Faroe–Shetland Basin.
Time-lapse seismic programme at Gullfaks: value and the road ahead
Authors: Najjar Nazih F. , Strønen Lars Kristian , Alsos Trine
Published: October 2008

Improved hydrocarbon recovery through the identification of unswept oil regions has been the primary objective of the time-lapse seismic programme at the Gullfaks Field in the North Sea. Three time-lapse seismic surveys covering the entire field have been acquired, a pre-production survey in 1985 followed by two surveys in 1996 and 1999. Input from qualitative time-lapse interpretations has resulted in the drilling of a number of successful wells, and has improved the understanding of drainage patterns. Recently, a quantitative time-lapse study was launched. The objective of the study was two-fold: to link flow simulation predictions directly to the 4D seismic response and to map changes in oil saturation and quantify associated uncertainties.
Overview of global 4D seismic implementation strategy
Authors: Waal Hans de , Calvert Rodney
Published: October 2008

For many Shell-operated fields around the world, time-lapse reservoir monitoring (4D) is now an integral part of field management and some 25 dedicated 4D surveys were acquired for this purpose by the end of 2002. This widespread application is the result of a focused implementation effort aimed at global deployment to maximize the value extracted from the surveys in terms of saved costs, increased production, increased recovery and improved HSE management, where effective implementation is achieved through a combination of global operatorship and technology capability.

Apart from ensuring global deployment, there is the challenge to extend the range of 4D applicability. To achieve this the project has three application portfolios:

today's‘ proven’ 4D technology portfolio, which is about monitoring fluid movements in thick clastic oil reservoirs offshore. Results come largely from comparing reservoir simulator output with difference maps derived from repeat 4D streamer surveys;

a‘ stretch’ portfolio where the technology is applied to gas reservoirs, land data, stacked reservoirs, carbonate fields and to the monitoring of pressure changes;

a‘ tomorrow's technology’ portfolio, which has the potential to increase the application base even further. The new technologies are about the use of permanent arrays, downhole acquisition, passive listening and ‘smart fields’ where semi-continuous 4D monitoring provides eyes and ears between the wells.

More and more value is realized as 4D becomes fully integrated with subsurface work flows and modelling tools. Benefits from 4D technology for individual fields can be in the tens or hundreds of millions of dollars. A large fraction of these come from 4D surprises, illustrating that we tend to underestimate our uncertainties and suggesting different approaches to field management.
4D using legacy seismic data on the Alwyn North Oil Field
Authors: Hubans C. , Rapin M. , Ottlé J.F. , Manin M. , Harker S.D. , Richardson G , Cooper R.
Published: October 2008

This paper presents the results of 4D (time-lapse) seismic analysis of the westerly dipping Brent Group fault blocks of Alwyn North, a TotalFinaElf oil field located in the northern North Sea. Two legacy 3D surveys were used; one shot in 1980–1981, the second in 1996 with different sources, shooting directions and other acquisition and processing parameters. The Brent reservoir is of Middle Jurassic age, Alwyn North burial depths are in excess of 3000 m and oil production commenced in 1987. Careful processing and imaging of the amplitudes from the two surveys produced a visual qualitative comparison with hydrocarbon production, water injection and fluid movement within the reservoir. The 4D results show a close correspondence to the sweep determined by reservoir simulation after nine years of production and confirmed by well results. A third 3D survey was acquired in 2001, following commencement of miscible gas injection, and further 4D work is planned to follow on from the encouraging results of the present study.
Syn-sedimentary faulting and the formation of localized reservoir sands: Carboniferous examples from the Campine Basin, Belgium and the Dutch offshore
Authors: Kosters M. , Donselaar M. E.
Published: October 2008

The Westphalian B in the Campine Basin in Belgium contains a low net-to-gross succession of fluvial channel and crevasse sandbodies embedded in lacustrine and floodplain claystone and siltstone. Study and correlation of closely spaced boreholes reveals a localized 15–25 m thick succession of stacked fluvial channel sandbodies in this overall low net-to-gross setting. This concentration of sandbodies is interpreted as the fill of a tectonically induced palaeo-valley based on the orientation of syn-sedimentary faults and the palaeogeographical setting of the Campine Basin, far away from the Westphalian sea. The depositional model was used to interpret stacks of fluvial sandstone of the Caister Sandstone (Westphalian B) in the Dutch offshore and may guide finding economic reservoirs in the overall low net-to-gross labyrinth-type fluvial architecture in this area and in comparable structural settings.
Mechanical compaction behaviour of natural clays and implications for pore pressure estimation
Authors: Goulty N. R.
Published: October 2008

In pore pressure estimation and in basin modelling programs it is often assumed that porosity in clay-rich sediments depends on the vertical effective stress. An alternative assumption is that porosity depends on the mean effective stress. Yet triaxial test data on natural clays have shown that porosity depends on both the mean effective stress and the differential stress. Triaxial test data for Winnipeg clay are re-plotted here to quantify the errors in estimated pore pressures that would result if it is assumed that porosity depends on either vertical or mean effective stress. The assumption that porosity depends on vertical effective stress may result in gross underestimates of pore pressures in compressional basins, where horizontal stresses in overpressured zones at depth are greater than the vertical stress. Sections through the yield surface of Winnipeg clay are consistent with a generalized yield locus for clays, normalized for composition as well as volume, based on data from several natural clays. Consequently, a refined equivalent depth method of pore pressure estimation that accounts for porosity dependence on both mean and effective stress could, in principle, be implemented. The method would require some knowledge of yield properties and of all three principal stresses in the subsurface.
Kela-2: a major gas field in the Tarim Basin of west China
Authors: Shilin Xu , Xiuxiang Lu , Zhonghua Sun , Xuejun Pi , Luofu Liu , Qiming Li , Huiwen Xie
Published: October 2008

Kela-2, a large gas field developed in a sub-thrust anticline within the Kuqa depression of the Tarim Basin and with reserves of 7.55×10
12
SCF, represents the largest unsegmented gas pool in China. Detailed petrographic, geochemical, structural and fluid inclusion studies show that the field is a result of a favourable interrelationship of geological events, involving several periods of compressive structuring, multiple periods of oil and gas migration and a complex diagenetic history. The Kela-2 discovery well encountered abundant oil and gas shows over a 448 m gas column within Cretaceous to Lower Tertiary Bashijiqike and Baxigai Formation sands. Gas is trapped in a large, heavily faulted, northeast-east striking fold with a décollement horizon developed along a gypsiferous horizon. The structure, with a closure of 55 km
2
, was initiated in the Late Tertiary compressive phase and was accentuated during Quaternary Xiyu compression.

The source of the gas is Triassic and Jurassic coals, which communicate with the reservoir vertically through faults. It is possible through fluid inclusion studies to identify two periods of secondary oil migration and two periods of re-migration within the reservoir. The reservoirs were deposited in a continental environment, within which secondary porosity has been developed by leaching of carbonate cement that infilled original primary pore spaces. The gypsiferous mudstones of the Lower Tertiary provide a common seal to both reservoirs, which are abnormally pressured.
Mathematical models of the distribution of geotracers during oil migration and accumulation
Authors: Yang Yunlai , Aplin Andrew C. , Larter Steve R.
Published: October 2008

Compounds which partition into water and which are adsorbed by solid phases (‘geotracers’) are lost from petroleum along migration pathways, giving important clues about the nature and length of the route from source to reservoir. Many factors influence the distribution of petroleum geotracers, including migration distance, the inherent properties of the migration systems, the chemical properties of the tracers, the volume of reservoired oil and the filling sequence. This paper constructs the mathematical models that are required to describe adequately the occurrence of geotracers in migrated and reservoired oils. The models show that for commonly used geotracers (phenol and carbazole compounds): (1) adsorption to oil-wet mineral sites is a major process removing geotracers from oil; (2) adsorption onto mineral surfaces can be treated as an equilibrium process on a geological time-scale; (3) diffusion of tracers from a migrating oil slug to the surrounding sediments can be neglected; and (4) the tracer concentration in a reservoired oil is not related uniquely to migration distance but is negatively correlated to the ratio of relative migration distance divided by the volume of reservoired oil having travelled the migration pathway. The potential applications of the models in petroleum exploration include: assessment of the route and relative distance of oil migration (with implications for the identification of undrilled prospects); estimation of the volume of lost oil by spill from a reservoir; and differentiation of migration through fractures and capillary migration through fine-grained rocks.
The Rotliegend reservoir in Block 30/24, UK Central North Sea: including the Argyll (renamed Ardmore) and Innes fields
Authors: Heward Alan P. , Schofield Paul , Gluyas Jon G.
Published: October 2008

Rotliegend Auk Formation sandstones form the second most productive reservoir in the 30/24 fields and the major source of aquifer pressure support. In the Argyll Field, where the Zechstein oversteps beyond the Rotliegend on to Devonian continental sandstones, there were initial difficulties distinguishingbetween the Rotliegend and the Devonian.

Four facies associations are present in the Rotliegend Auk Formation: aeolian slipface sands, aeolian wind-ripple sands, water-lain Weissliegend sands and other water-lain conglomerates, breccias and sands. Five reservoir zones consist of different proportions of these facies which infill topography and onlap the Argyll high. Their distribution and character reflect periods of sediment supply, subsidence and fluctuating climatic conditions towards the margin of an interior continental basin.

The Auk Formation as a whole forms a high quality reservoir at depths of 3000–4000 m. The best intervals, with Darcy permeabilities, consist of coarse-grained Weissliegend sands. Two of the four initial wells in the Ardmore (Argyll) Field redevelopment are planned to target the Rotliegend reservoir.
Characterization and zonation of a marly chalk reservoir: the Lower Cretaceous Valdemar Field of the Danish Central Graben
Authors: Jakobsen Finn , Ineson Jon R. , Kristensen Lars , Stemmerik Lars
Published: October 2008

In the Valdemar Field of the Danish Central Graben, production is from the Upper Hauterivian–Aptian succession (Tuxen and Sola formations) which comprises interlayered pelagic/hemipelagic chalks, marly chalks and marlstones. Based on core data, the reservoir chalks (6–10% insoluble residue (IR)) and marly chalks (10–30% IR) possess porosities in the 20–48% range and matrix permeabilities of 0.1–4 mD. The porosity (
ϕ
) of these chalks correlates negatively with the IR (particularly clay) content. A permeability cut-off of 0.1 mD was defined for reservoir studies, corresponding to a
ϕ
of 20–30% and an IR of
c
. 35%. A detailed reservoir zonation, based on integration of core and petrophysical data constrained within a sequence stratigraphic framework, illustrates the stratigraphical compartmentalization of the field. The distinctive nature of this heterogeneous argillaceous chalk reservoir is illustrated by comparison with Maastrichtian–Danian chalks of the Central Graben. For a given porosity, the matrix permeability of the Valdemar Field chalks is a factor of ten lower than that of an equivalent Maastrichtian chalk, the irreducible water saturation is a factor of ten higher and the capillary entry pressure of the Lower Cretaceous reservoir is 2–3 times that of the younger chalks.
The complexity of a ramp–flat–ramp fault and its effect on hanging-wall structuring: an example from the Njord oil field, offshore mid-Norway
Authors: Ehrlich Ralf , Gabrielsen Roy H.
Published: October 2008

The Njord oil field of the mid-Norwegian continental margin comprises a hydrocarbon trap structure, which is delineated by segments of master faults with complex geometry. The Vingleia Fault Complex includes the major fault segments that delineate the Njord structure to the southeast and east. Three master fault segments with a change in strike orientation are recognized. Reflection seismic sections reveal that these segments show strong variations in fault plane geometry. The central part is characterized by a pronounced ramp–flat–ramp geometry, which diminishes both southwestward and northeastward, so that the northeastern and southwestern segments have a more listric geometry. Hence, an along-strike profile shows an antiform-like culmination in the master fault surface.

To the characteristic deformation of ramp–flat–ramp faults, additional deformation in the Njord Field is obvious and marked by extensional horses, extensive roll-over folding, varying strata rotation, characteristic fault bending and variable influence of synthetic and antithetic faults. The occurrence of the style of deformation and geometrical variations in fault pattern are closely related to the structural position above the detachment fault. The following steps in the development of the Vingleia Fault Complex and the associated deformation of the hanging-wall fault block are proposed. (1) Initiation of the master faults in early Triassic. This stage was characterized by slow, extensional displacement. The positions of the master fault segments were possibly influenced by basement in homogeneities marked by a magnetic/gravity anomaly. (2) It is likely that the ramp–flat–ramp had already become established at this stage and that the master fault geometry and a proposed weak salt layer promoted this. (3) During accelerating extension in mid to late Jurassic, the master fault segments became connected by one-sided, lateral linking of fault tip and fault plane or by mutual curved linking of the fault tips. (4) Simultaneously, a roll-over anticline developed within the hanging wall of the master fault. Its relatively large amplitude is produced by a differential movement on the fault surface in combination with a dip-parallel shift of the vertical displacement maximum, which is positioned above a change in the footwall dip.
Modelling of the hydrocarbon generation history and volumetric considerations of the coal-sourced Lulita Field, Danish North Sea
Authors: Carr A. D. , Petersen H. I.
Published: October 2008

The hydrocarbon generation history of the Middle Jurassic Lulita Field in the Søgne Basin in the northeastern part of the Danish Central Graben has been predicted by modelling the Lulita-1Xc well located on-structure and a pseudowell located in the kitchen area. The Lulita Field consists of east-dipping Middle–Upper Jurassic sediments in a structural trap. Waxy oil, sourced from Middle Jurassic coals and type III kerogen (and possibly type I kerogen) shales, occurs in Middle Jurassic sandstone reservoirs sealed by Upper Jurassic marine shales. Maturity modelling (vitrinite reflectance) was carried out by using the PresRo
®
kinetic model and a heat flow history calibrated from both the tectonic-subsidence history and maturity data. An effective oil window (‘oil expulsion window’) between 0.85% and 1.8%R
o
for the Middle Jurassic coal and type III kerogen source rocks was applied. Timing for onset of oil generation differs between the Lulita-1Xc well and the pseudowell. The top of the source rocks becomes mature during the Late Cretaceous in the kitchen area and during the Oligocene in the Lulita-1Xc well. However, oil expulsion from the entire Middle Jurassic source rocks is modelled to have started from the Paleocene in the kitchen area and appears to have continued through to the present day. No, or little, expulsion is modelled in the Lulita-1Xc well, indicating that the Lulita Field was charged by updip migration of hydrocarbons from the Søgne Basin kitchen to the east. Hydrocarbon charging pre-dates the time of potential diagenetic modification of the reservoir, thus limiting reduction in reservoir porosity and permeability. Based on the known coal source rock volume and quality, calculated maximum generated and expelled hydrocarbons cannot account for the estimated in-place volumes of oil. The additional hydrocarbons were probably generated from coaly shales and shaly coals that form the lateral equivalent of the Middle Jurassic coals in the kitchen area, possibly with contributions from lacustrine to brackish type I kerogen shales.
Calibration improves uncertainty quantification in production forecasting
Authors: McVay Duane A. , Lee W. John , Alvarado Martin G.
Published: October 2008

Despite recent advances in uncertainty quantification, the petroleum industry continues to underestimate the uncertainties associated with reservoir production forecasts. This paper describes a calibration process that can improve quantification of uncertainties associated with reservoir performance prediction.

Existing methods underestimate uncertainty because they fail to account for all, and particularly unknown, factors affecting reservoir performance and because they do not investigate all combinations of reservoir parameter values. However, the primary limitation of existing methods is that their reliability cannot be verified because the testing of an estimate of uncertainty from existing methods yields only one sample for what is inherently a statistical result. Verification and improvement of uncertainty estimates can be achieved with calibration – comparison of actual performance with previous uncertainty estimates and then using the results to scale subsequent uncertainty estimates.

Calibration of uncertainty estimates can be achieved with a more frequent, if not continuous, process of data acquisition, model calibration, model prediction and uncertainty assessment, similar to the process employed in weather forecasting. Improved ability to quantify production forecast uncertainty should result in better investment decision making and, ultimately, increased profitability.