bluuebunny/crossref_metadata_2025 huggingface dataset:
Population biology of Stellifer rastrifer, S. brasiliensis and S. stellifer in Caraguatatuba Bay, northern coast of São Paulo, Brazil
Authors: Pombo Maíra , Denadai Marcia Regina , Turra Alexander
Published: October 2012

Ecosystems may reflect environmental changes in many respects, from the debilitation of individuals to alterations in community composition. Equally, population parameters may provide reliable indications of environmental changes. Members of the sciaenid fish genus Stellifer are usually very abundant where they occur, often with two or more species living in sympatry. Here, the population dynamics of three Stellifer species from southeastern Brazil were assessed. Sampling was carried out in shallow marine areas of Caraguatatuba Bay, from August 2003 to October 2004. The species evaluated were Stellifer rastrifer (n=3183), S. brasiliensis (n=357) and S. stellifer (n=116). The area under greater continental influence tended to support more, but smaller individuals. Size variations over time were similar among species and negatively correlated with Krel, which showed smooth fluctuations. The general length-frequency distribution was concentrated between 6.0 and 9.0 cm, and the great majority of females did not present mature gonads during the sampling period. The findings support the existence of a stratification by size for these species, indicating that the area is essential for the development of younger fish. Failure to consider these characteristics for the management of similar areas may have serious implications for these environments.
Export of materials along a tidal river channel that links a coastal lagoon to the adjacent sea
Authors: Ramírez Javier Aldeco , Poillon Martha Signoret , Gómez María Adela Monreal , León David Alberto Salas de
Published: October 2012

Intratidal variability and flux of salt, chlorophyll-a and suspended materials were evaluated in a shallow tropical tidal channel linking a coastal lagoon to the western Gulf of Mexico. Velocity, temperature and conductivity were used to calculate the fluxes. Data were recorded during three tidal velocity cycles (tvc) under extreme river discharge conditions. Chlorophyll-a and suspended materials were determined below the surface. In both seasons (dry and rainy), the flow was ebb-dominated and with longer duration than when in flood. Maximum current velocities were 0.30 m s-1 in May (dry season) and 0.60 m s-1 in September (rainy season). In the dry season the mean chlorophyll-a export was of 7.56 Kg over tvc while the import was of 3.32 Kg. In the rainy season mean export (47.3 Kg) was 6 times greater than the import (7.93 Kg over tvc). Phytoplankton was dominated by organisms of marine origin. The mean of exported, suspended materials in the rainy season (111.3 Kg) was 4.6 times greater (859 Kg) than that in the dry season (184.7 Kg over tvc). Tidal velocity asymmetry is an effective mechanism of exportation, introducing relatively warm and saltier water into the river through the tidal channel.
Nuclear abnormalities in erythrocytes and morphometric indexes in the catfish Cathorops spixii (Ariidae) from different sites on the southeastern Brazilian coast
Authors: Azevedo Juliana de Souza , Braga Elisabete de Santis , Ribeiro Ciro Alberto Oliveira
Published: October 2012

Nuclear abnormalities in erythrocytes (NAE) were taken as biomarkers in the catfish Cathorops spixii (Ariidae) sampled in an estuary little affected by human activity (Cananéia) and in three regions (Santos Channel: SC, Santos Bay: SB and São Vicente Channel: SVC) of the Santos-São Vicente estuary impacted by various anthropogenic activities. Increases in NAE were observed in fish from SC and SVC sampled in the summer period as compared with specimens from the Cananéia estuary. These results suggest the presence of genotoxic compounds in these regions. However, the absence of significant differences in micronuclei frequency reflects slight mutagenic effects in these individuals. It is possible that the lower NAE frequency in specimens from SB might be associated with the greater remobilization and dilution of chemicals in this region. The low frequency of NAE in C. spixii from the Cananéia estuary is in accordance with the slight anthropogenic influence in this system, and may be suggestive of the absence of genotoxic and mutagenic effects in these organisms.
Remote wind stress influence on mean sea level in a subtropical coastal region
Authors: Costa Mabel Calim , Bernardes Marcos Eduardo Cordeiro
Published: October 2012

The purpose of this study was to assess the relative influence of remote wind stress on mean sea level (MSL) variations in the coastal region of Cananeia (Sao Paulo State, Southern Brazil) during the period from 1/1/1955 to 12/31/1993. An optimized low-pass Thompson filter for the study area, and spectral analysis (cross spectrum, coherence and phase lag) of the relationship between the MSL and both parallel (T//) and perpendicular (T|) wind stress components were applied. These were extracted from four grid points of the NCEP/NCAR global model. The predominance of annual oscillations as those of greatest coherence and energy, of periods of approximately 341 days (frequency of 0.00293 cpd) and 410 days (frequency of 0.00244 cpd), respectively, were observed. Offshore NCEP/NCAR grid points were those with the highest coherence and energy throughout the study in relation to the observed MSL. This may be linked to the restriction of the NCEP/NCAR model as regards the inland limit. It is also concluded that remote wind stress may play an important role in several MSL time scales, including the annual ones. Based on criteria such as coherence and energy peaks, the wind stress component of greatest effect on MSL was the parallel one.
Population biology and diet of the southern kingcroaker Menticirrhus americanus (Linnaeus, 1758) (Perciformes: Sciaenidae) in Caraguatatuba Bay, southeastern Brazil
Authors: Turra Alexander , Santos Flávia Borges , Bessa Eduardo , Fernandez Wellington Silva , Bernadochi Ligia Coletti , Denadai Márcia Regina
Published: October 2012

This study evaluated the spatio-temporal distribution, population biology and diet of Menticirrhus americanus in Caraguatatuba Bay. Samples were taken monthly between August 2003 and October 2004, by trawling in two previously selected areas. The northern area is more exposed to wave activity and is influenced by a river, functioning as a small estuary. In contrast, the southern area is relatively sheltered from wave energy and influenced to a lesser degree by smaller rivers. The fishes' length was measured, and the sex and gonadal stage macroscopically identified. The abundance of this species was compared between areas and among months. The diet was identified and quantified. M. americanus occurred in equal proportions in the two study areas, being most abundant in April 2004, followed by December 2003 and January 2004. The population was dominated by small immature individuals. The few individuals in maturation or mature that were captured showed no seasonal pattern of distribution. This species had a varied diet, feeding on worms (nemerteans, sipunculans and echiurans), mollusks (bivalves and cephalopods), polychaetes, crustaceans and fish. The presence of intact nematodes in the intestine suggests that these are parasites. The results demonstrated that M. americanus has a homogeneous spatial and temporal distribution in Caraguatatuba Bay, being uniformly distributed between the south and north areas as well as across the months. This species can be considered a carnivorous predator, showing a preference for consuming benthic sandy-beach species such as glycerids and other polychaetes, crustaceans, and bivalve siphons.
Copepod distribution in surface waters of the Drake Passage using Continuous Plankton Recorder and a Pump-Net onboard system
Authors: Thompson Gustavo , Dinofrio Estela O. , Alder Viviana A. , Takahashi Kunio T. , Hosie Graham W.
Published: October 2012

There is no single instrument that can sample quantitatively the complete spectrum of pelagic organisms, or even all the components of zooplankton. Mesh size is the main factor affecting species selectivity in the Continuous Plankton Recorder (CPR), implying a need to use multiple net systems to fully characterize a community. The spatial distribution of copepod communities in the water masses of the western and eastern sectors of Drake Passage were studied using, respectively, a CPR and a Pump Net onboard system. For this purpose, and assuming that copepod community size structures of each of the three water masses were similar in both the sectors studied, the possibility of complementing CPR results using a Pump-Net onboard system was evaluated. The latter system allows the estimation of absolute abundances and has the advantage of solving two problems associated with CPR, namely mesh clogging and low catching efficiency. The contribution of the nauplius forms and species accurately identified with both samplers was analyzed. Although Oithona similis dominated both communities, in the western sector small species made a greater contribution than Calanus simillimus, the opposite being true for the eastern sector. Nauplii and early copepodite stages of O. similis were missing from the CPR samples and represented between 69 and 79% of total copepod communities, whereas small calanoid copepods, C. simillimus copepodites and later stages of O. similis were inaccurately sampled by the CPR and represented between 14 and 18% of the copepod community. Hence, the Pump Net sampler is useful for complementing the semi-quantitative information of the CPR and for its calibration.
A section-sampling design to assess zooplankton distribution in a highly complex hydrographic region (SW Atlantic Ocean, 34-41ºS): insights for a new time series?
Authors: Cepeda Georgina Daniela , Di Mauro Rosana , Martos Patricia , Delia Viñas Maria
Published: October 2012

Regular fish stock assessment cruises could provide a proper data platform to sample zooplankton. It is essential, however, that adequate sampling designs should be developed for each area so that zooplankton features may be accurately described with minimum sampling effort. On the Northern Argentine Continental Shelf (NACS, 34-41ºS), a sectioned-sampling design (18 samples distributed in 4 sections) associated with E. anchoita stock estimation cruises was implemented to provide a rapid and reliable survey of zooplankton distribution in relation to the physical environment. The results obtained were similar to those registered in previous studies based on exhaustive sampling. We suggest that a new zooplankton time series covering this broad área be established, based on this sampling design, to contribute to the knowledge of the variability of zooplankton populations and their relation to fishery resources.
The dynamics of a frictionally-dominated Amazonian estuary
Authors: Asp Nils Edvin , Schettini Carlos Augusto França , Siegle Eduardo , Silva Marcio Sousa da , Brito Roney Nonato Reis de
Published: October 2012

The hydrodynamics, morphology and sedimentology of the Taperaçu estuary were investigated. This is one of several estuaries located within the largest mangrove fringe in the world, bordering the Amazon region, subject to a macrotidal regime and regionally atypical negligible fresh water supply. The results reveal widespread sand banks that occupy the central portion of the estuarine cross-section. Well-sorted very fine sandy sediments of marine origin prevail. Shorter flood phases, with substantially higher current velocities, were observed in the upper sector of Taperaçu, as expected for a shallow, friction-dominated estuary. However, ebb domination can be expected for estuaries with large associated mangrove areas and substantial estuarine infilling, both of which situations occur on the Taperaçu. The tidal asymmetry favoring flood currents could be the result of the absence of an effective fluvial discharge. Furthermore, it was observed that the Taperaçu is connected by tidal creeks to the neighboring Caeté estuary, allowing a stronger flux during the flood and intensifying the higher flood currents. As a whole, the results have shown a complex interaction of morphological aspects (friction, fluvial drainage, connections with neighbor estuaries, infilling and large storage area) in determining hydrodynamic patterns, thus improving the understanding of Amazon estuaries.
Ticks on birds caught on the campus of the Federal Rural University of Rio de Janeiro, Brazil
Authors: Santolin Ísis Daniele Alves Costa , Luz Hermes Ribeiro , Alchorne Nívea Maria , Pinheiro Michele da Costa , Melinski Ramiro Dário , Faccini João Luiz Horácio , Ferreira Ildemar , Famadas Kátia Maria
Published: October 2012

The prevalence of parasitic infections, particularly those caused by ectoparasites, may influence the biology and ecology of wild birds. The aim of this study was to investigate occurrences and identify the species of ticks collected from wild birds caught on the campus of the Federal Rural University of Rio de Janeiro. The birds were caught using mist nets between October 2009 and December 2010. In total, 223 birds were caught, represented by 53 species and 19 families in nine orders. Nineteen birds (n = 7 species) were parasitized by immature ticks (prevalence of 8.5%). Forty-four ticks were collected, of which 23 were nymphs and 21 were larvae. There were associations between parasitism by ticks and non-Passeriformes birds, and between parasitism and ground-dwelling birds, which was possibly due to the presence (or inclusion among the captured birds) of Vanellus chilensis (Charadriiformes: Charadriidae). All the nymphs collected were identified as Amblyomma cajennense. In general terms, we must emphasize that wild birds in the study area may play the role of dispersers for the immature stages of A. cajennense, albeit non-preferentially.
Are We Ready To Stratify Treatment for Diffuse Large B-Cell Lymphoma Using Molecular Hallmarks?
Authors: Barton Sarah , Hawkes Eliza A. , Wotherspoon Andrew , Cunningham David
Published: October 2012

abstract

Learning Objectives:

After completing this course, the reader will be able to: Describe the oncogenic drivers in DLBCL, especially those that have recently been identified, and how they relate to the oncogenic DLBCL subtypes.Describe the prognostic and potentially predictive implications of DLBCL COO subtype for chemotherapy and rituximab.Outline the evidence for novel targeted therapies and therapeutic strategies in DLBCL, how they may be stratified by DLBCL subtype or to specific tumor molecular features, and how these strategies can be incorporated into current treatment paradigms and prospective clinical trial design.

CME This article is available for continuing medical education credit at CME.TheOncologist.com

The division of the heterogeneous entity of diffuse large B-cell lymphoma (DLBCL) into the ontogenic phenotypes of germinal center B-cell-like (GCB) and activated B-cell-like (ABC) is optimally determined by gene expression profiling (GEP), although simpler immunohistochemistry (IHC) algorithms are alternatively being used. The cell-of-origin (COO) classification assists in prognostication and may be predictive of response to therapy. Mounting data suggests that IHC methods of classifying COO may be inaccurate. GEP categorization of COO is superior in defining prognostically and biologically distinct DLBCL subtypes, but current barriers to its widescale use include inaccessibility, cost, and lack of methodological standardization and prospective validation. The poorer prognosis of ABC-DLBCL is frequently associated with constitutive activity in the NF-κB pathway and aberrations in upstream or downstream regulators of this pathway. The molecular mechanisms underlying lymphomagenesis in GCB-DLBCL are arguably less well defined, but C-REL amplification and mutations in BCL-2 and EZH2 are common. New technologies, such as next-generation sequencing, are rapidly revealing novel pathogenic genetic aberrations, and DLBCL treatment strategies are increasingly being designed focusing on distinctive pathogenic drivers within ontogenic phenotypes. This review examines emerging molecular targets and novel therapeutic agents in DLBCL, and discusses whether stratifying therapy for DLBCL using molecular features is merited by current preclinical and clinical evidence.
Power from wood gasifiers in Uganda: a 250 kW and 10 kW case study
Authors: Buchholz Thomas , Da Silva Izael , Furtado John
Published: October 2012

Wood gasification systems have the potential to contribute to rural electrification in sub-Saharan Africa. This paper presents an operational and economic analysis of two wood-based gasification systems (250 kW and 10 kW) installed in Uganda in 2007. Both systems proved their potential to compete economically with diesel-generated electricity when operating close to the rated capacity. At an output of 150 kW running for approximately 12 h/day and 8 kW running for approximately 8 h/day, the systems produced electricity at US$0·18 and 0·34/kWh, respectively. A stable electricity demand close to the rated capacity proved to be a challenge for both systems. Fuelwood costs accounted for approximately US$0·03 kWh for both systems. Recovery of even a small fraction of the excess heat (22%) already resulted in substantial profitability gains for the 250 kW system. Results indicate that replicating successful wood gasification systems stipulates the integration of sustainable fuelwood supply and viable business models.
Contrasting migration tendencies of sympatric red deer and roe deer suggest multiple causes of migration in ungulates
Authors: Mysterud Atle , Bischof Richard , Loe Leif Egil , Odden John , Linnell John D. C.
Published: October 2012

Understanding the drivers of seasonal migration among large herbivores is crucial for management and conservation. The forage maturation hypothesis predicts migration even at low population density, due to the benefits of increased access to newly emergent, high quality forage. We provide the first study comparing migration tendency of the two most widely distributed deer species in Europe, roe deer (Capreolus capreolus) and red deer (Cervus elaphus). The study was conducted in an area with a low population density of both species. We found that 94% of the GPS‐collared red deer, but only 27% of the roe deer, migrated. This supports the forage maturation hypothesis in red deer only. Our study thus provides evidence of multiple causation of migration in ungulates, and is consistent with the hypothesis that the forage maturation hypothesis might be a more important driver for migration in grazers compared to browsers.
RESISTANCE TO CHANGE AND PREFERENCE FOR VARIABLE VERSUS FIXED RESPONSE SEQUENCES
Authors: Arantes Joana , Berg Mark E. , Le Dien , Grace Randolph C.
Published: October 2012

In Experiment 1, 4 pigeons were trained on a multiple chain schedule in which the initial link was a variable‐interval (VI) 20‐s schedule signalled by a red or green center key, and terminal links required four responses made to the left (L) and/or right (R) keys. In the REPEAT component, signalled by red keylights, only LRLR terminal‐link response sequences were reinforced, while in the VARY component, signalled by green keylights, terminal‐link response sequences were reinforced if they satisfied a variability criterion. The reinforcer rate for both components was equated by adjusting the reinforcer probability for correct REPEAT sequences across sessions. Results showed that initial‐ and terminal‐link responding in the VARY component was generally more resistant to prefeeding, extinction, and response‐independent food than responding in the REPEAT component. In Experiment 2, the REPEAT and VARY contingencies were arranged as terminal links of a concurrent chain and the relative reinforcer rate was manipulated across conditions. For all pigeons, initial‐link response allocation was biased toward the alternative associated with the VARY terminal link. These results replicate previous reports that operant variation is more resistant to change than operant repetition (Doughty & Lattal, 2001), and show that variation is preferred to repetition with reinforcer‐related variables controlled. Behavioral momentum theory (Nevin & Grace, 2000) predicts the covariation of preference and resistance to change in Experiments 1 and 2, but does not explain why these aspects of behavior should depend on contingencies that require repetition or variation.
RELATIVE EFFICACY OF HUMAN SOCIAL INTERACTION AND FOOD AS REINFORCERS FOR DOMESTIC DOGS AND HAND‐REARED WOLVES
Authors: Feuerbacher Erica N. , Wynne Clive D. L.
Published: October 2012

Despite the intimate relationship dogs share with humans in Western society, we know relatively little about the variables that produce and maintain dog social behavior towards humans. One possibility is that human social interaction is itself a reinforcer for dog behavior. As an initial assessment of the variables that might maintain dog social behavior, we compared the relative efficacy of brief human social interaction to a small piece of food as a reinforcer for an arbitrary response (nose touch). We investigated this in three populations of canids: shelter dogs, owned dogs, and hand‐reared wolves. Across all three canid populations, brief social interaction was a relatively ineffective reinforcer compared to food for most canids, producing lower responding and longer latencies than food.
RELATIVE VERSUS ABSOLUTE STIMULUS CONTROL IN THE TEMPORAL BISECTION TASK
Authors: Carvalho Marilia Pinheiro de , Machado Armando
Published: October 2012

When subjects learn to associate two sample durations with two comparison keys, do they learn to associate the keys with the short and long samples (relational hypothesis), or with the specific sample durations (absolute hypothesis)? We exposed 16 pigeons to an ABA design in which phases A and B corresponded to tasks using samples of 1 s and 4 s, or 4 s and 16 s. Across phases, we varied the mapping between the samples and the keys. For group Relative, short and long samples were always associated with the same keys (e.g., Phase A: ‘1s→ Left, 4s→ Right’; Phase B: ‘4s→ Left, 16s→ Right’); for group Absolute, the 4‐s sample was associated always with the same key (e.g., Phase A: ‘1s→ Left, 4s→ Right’; Phase B: ‘16s→ Left, 4s→ Right’). If temporal control is relational, group Relative should learn the new task faster than group Absolute, but if temporal control is absolute, the opposite should occur. We compared the results with the predictions of the Learning‐to‐Time (LeT) model, which accounts for temporal discrimination in terms of absolute stimulus control and stimulus generalization. The acquisition curves of the two groups were generally consistent with LeT and therefore more consistent with the absolute than the relative hypothesis.
INDIVIDUAL DIFFERENCES IN IMPULSIVE CHOICE AND TIMING IN RATS
Authors: Galtress Tiffany , Garcia Ana , Kirkpatrick Kimberly
Published: October 2012

Individual differences in impulsive choice behavior have been linked to a variety of behavioral problems including substance abuse, smoking, gambling, and poor financial decision‐making. Given the potential importance of individual differences in impulsive choice as a predictor of behavioral problems, the present study sought to measure the extent of individual differences in a normal sample of hooded Lister rats. Three experiments utilized variations of a delay discounting task to measure the degree of variation in impulsive choice behavior across individual rats. The individual differences accounted for 22–55% of the variance in choice behavior across the three experiments. In Experiments 2 and 3, the individual differences were still apparent when behavior was measured across multiple choice points. Large individual differences in the rate of responding, and modest individual differences in timing of responding were also observed during occasional peak trials. The individual differences in timing and rate, however, did not correlate consistently with individual differences in choice behavior. This suggests that a variety of factors may affect choice behavior, response rate, and response timing.
COMMITMENT AND SELF‐CONTROL IN A PRISONER'S DILEMMA GAME
Authors: Locey Matthew L. , Rachlin Howard
Published: October 2012

Humans often make seemingly irrational choices in situations of conflict between a particular smaller—sooner reinforcer and a more abstract, temporally extended, but larger reinforcer. In two experiments, the extent to which the availability of commitment responses—self‐imposed restrictions on future choices—might improve self‐control in such situations was investigated. Participants played a prisoner's dilemma game against a computer that played a tit‐for‐tat strategy—cooperating after a participant cooperated, defecting after a participant defected. Defecting produced a small—immediate reinforcer (consisting of points convertible to gift cards) whereas cooperating increased the amount of subsequent reinforcers, yielding a greater overall reinforcer rate. Participants were normally free to cooperate or defect on each trial. Additionally, they could choose to make a commitment response that forced their choice for the ensuing five trials. For some participants, the commitment response forced cooperation; for others, it forced defection. Most participants, with either commitment response available, chose to commit repeatedly despite a minor point loss for doing so. After extended exposure to these contingencies, the commit‐to‐cooperate group cooperated significantly more than a control group (with no commitment available). The commit‐to‐defect group cooperated significantly less than the control group. When both commitment alternatives were simultaneously available—one for cooperation and one for defection—cooperation commitment was strongly preferred. In Experiment 2, the commitment alternative was removed at the end of the session; gains in cooperation, relative to the control group, were not sustained in the absence of the self‐imposed behavioral scaffold.
Integration of Microseismic Data, Fracture and Reservoir Simulation into the Development of Fractured Horizontal Wells in the Cardium Formation - A Tight Oil Case Study
Authors: Quirk David , Ziarani Ali S. , Mills Scott , Wagner Kevin , Chen Cheney
Published: October 2012

Multi-fractured horizontal wells have been used successfully to exploit tight gas and shale gas reservoirs in North America over the last decade. This technology has also been successfully implemented in tight oil reservoirs in recent years. Some of the prominent tight oil plays in Canada are the Cardium, Bakken and Viking formations. Higher oil prices and depleting conventional resources have challenged operators to exploit these tight oil resources. Some of the primary reservoir engineering challenges are the optimization of the fracture spacing along the length of a horizontal wellbore, and the spacing between the horizontal wells in a resource play.

Three-dimensional reservoir simulation is the most reliable technique for reservoir modeling from these complex completions in permeability-challenged reservoirs. For an accurate representation, reservoir simulation requires data input from different sources to be incorporated into the model. In this study, microseismic data was integrated with a fracture-pumping operation to create a calibrated fracture model in a pseudo-3D fracture simulator. This fracture simulation model was subsequently imported into a multi-layer numerical reservoir model developed for the Cardium formation. The reservoir model was production matched using the fracture conductivities from the calibrated fracture model.

The history-matched reservoir model was then used to understand production depletion in this tight oil reservoir. Sensitivity studies were conducted on the history-matched model for fracture and wellbore spacing optimization. An improvement in the recovery factor was shown when fracture spacing was reduced, and when wellbores were more closely spaced. The time to production interference between fractures and wellbores helps optimize the play. This paper presents the workflow (integrating microseismic and fracturing studies) and results of a 3D reservoir simulation study conducted on a fractured horizontal well in the Cardium tight oil formation.
Characterizing and Simulating the Non-Stationariness and Non-Linearity in Unconventional Oil Reservoirs: Bakken Application
Authors: Chu L. , Ye P. , Harmawan I. , Du L. , Shepard L.
Published: October 2012

This paper presents an innovative integrated methodology and working procedure for characterizing and simulating the strong non-linearity and non-stationariness caused by changes in confined pressure-volume temperature (PVT) properties over time related to pore-throat size, the pressure-dependent permeability, and the intervened multiple porous media created by multi-stage fracture stimulation. The complicated physics behind the observed phenomena are explored. More specifically, this paper demonstrates and discusses the following: 1) a new rate-transient analysis (RTA) procedure to infer the stimulated reservoir volume (SRV) and fracture parameters; 2) the impact of the non-stationary feature, compaction effect, and pore-throat related PVT properties on the flow regime and well performance; 3) how to incorporate the non-stationary and non-linear features into the reservoir model; 4) the integrated procedure for history matching, performance forecast, and recovery assessment; 5) several field examples in the Bakken to illustrate the procedure.

The proposed procedure has been successfully applied for the following: 1) constructing the non-stationary, non-equilibrium, and highly non-linear simulation models; 2) facilitating the history matching by addressing permeability reduction and PVT property variations caused by compaction and capillary pressure; 3) and ensuring more reliable performance forecasts and recovery assessments.

The study shows that the reduction of the bubblepoint pressure could be several hundred psi in the typical Bakken rock; moreover, such reduction continues following the depletion via the compaction effect. The compaction effect could impair the matrix permeability by up to one order of magnitude.

The study reveals the following: 1) the confined PVT properties could widen the favored operation window, whereas the compaction effect could significantly impair the ultimate recovery of the wells; 2) the RTA-inferred SRV-related parameters are the key input for capturing the non-stationary features; 3) the impact on recovery could be over 50% without addressing the aforementioned non-stationary and non-linear issues.

This paper explores several unique phenomena in unconventional oil reservoirs which have not previously been published. The proposed analysis and assessment procedure greatly enhances the understanding of the unconventional assets and we feel will improve the accuracy of long-term rate and recovery forecasts.
Impact of Porous Media on Saturation Pressures of Gas and Oil in Tight Reservoirs
Authors: Pang Jianyuan , Zuo Julian Y. , Zhang Dan , Du Liangui
Published: October 2012

The tremendous efforts have been made by the industry in tapping the recoverable resources from the unconventional reservoirs in the past ten years. Shale (tight) gas and shale (tight) oil are the two typical ones. Some research studies focused on the effect of porous media on the dew point of gas condensates in terms of experimental and theoretical work. The contradictory conclusions were reached. On the other hand, some conclusions were made for crude oil as well on the basis of the measurements of the bubble point pressure of crude oil in porous media. Therefore, it is of great importance to develop an effective method to predict the phase behavior of shale gas and shale oil in porous media and investigate the effects of some factors on the saturation pressures of gas condensate and crude oil in tight reservoirs.

In this paper, a general framework of theoretical models has been developed to predict the saturation pressures of shale gas and shale oil in tight reservoirs. The Laplace equation is used to relate to the pressures in vapor and liquid phases from the curved interface. The Parachor model is applied to determine the interfacial tensions of crude oil and gas condensate. By taking into account of porous media in the proposed models, the calculations have been performed in some case studies. The effect tendency of some properties of porous media such as permeability and porosity on the dew or bubble point of reservoir fluid is discussed in this paper.
Analysis of Flow and the Presence of Fractures and Hot Streaks in Waterflood Field Cases
Authors: Baker Richard , Stephenson Tim , Lok Crystal , Radovic Predrag , Jobling Robert , McBurney Cameron
Published: October 2012

Over a thousand well pairs in five different fields in Western Canada have been examined using communication analysis techniques. The results of this analysis strongly suggest that in addition to conventional Darcy type flow through the matrix rock, there is also strong communication between wells through induced fractures, and/or natural fractures.

Most of these five fields are not typically thought of as naturally fractured. Nonetheless this type of fracture flow exists. It is highly likely that these hot streaks are pressure sensitive and therefore have a geo-mechanical component that controls permeability. The geo-mechanical component means that permeability can vary with time and injection pressure. This work on the Western Canadian Sedimentary Basin (WCSB) is similar to work done by Heffer in the North Sea.
2D-NMR Applications in Unconventional Reservoirs
Authors: Cao Minh C. , Crary S. , Zielinski L. , Liu C. B. , Jones S. , Jacobsen S.
Published: October 2012

In conventional reservoirs, 2D-NMR fluids evaluation targets the free fluid part of the total porosity with the assumption that the bound fluid is irreducible water. As such, pulse sequences are designed for long relaxing fluids, and the interpretation commonly assumes free diffusion of hydrocarbon molecules in water-wet pores. This is clearly not appropriate for unconventional reservoirs such as shale gas and shale oil where the fast-relaxing fluids of interest reside in the bound fluid region.

We show a revised 2D-NMR model that focus on fast relaxing fluids. In unconventionals, the three causes of fast relaxation are: small pore size, heavy oils and wettability alteration. The fast relaxation has the following consequences with respect to diffusion. In small pores, fluids cannot diffuse freely, and hence, the free diffusion lines of water, gas and oil must be corrected accordingly. In heavy oils, the oil relaxation can be enhanced by a wettability change to an oil/mixed-wet system. Another case of hydrocarbon-wet systems is hydrophobic kerogen. Consequently, the oil diffusion line as a function of viscosity (T2) must also be modified before the 2D map interpretation. This can be accomplished within the framework of the restricted diffusion model previously applied to water and gas that captures both the effects of surface relaxation and geometric restriction to molecular motion.

The results of the revised 2D-NMR model are shown through modeling and log examples in a shale gas reservoir and a shale oil reservoir. In real rocks, there is also a need to take into account simultaneously two models: an unconventional model as described above and a conventional model for long relaxing fluids associated with the matrix of the rock. The 2D-NMR log results are compared with lab results. Essentially, we show that adding diffusion and T1 information to standard T2 relaxation logs improves both the understanding and evaluation of unconventional reservoirs.
On the Fracture Height Migration Under Unified Fracture Design Optimization
Authors: Yang Mei , Valkó Peter P. , Economides Michael J.
Published: October 2012

We have published already a three-layer p-3D fracture design optimization using the Unified Fracture Design (UFD) approach; fracture height, resulting from fracture geometry optimization and therefore net pressure, was matched against the value resulting from fracture height migration at the same pressure.

For a multi-layered formation a more robust and more general approach is suggested in this work. First a range of admissible reference treating pressures is prepared. For each pressure level we determine the up-down tip locations and hence we obtain the fracture height map. Thus, there is a relationship between induced height and net pressure and this relationship can be calculated from Linear Elastic Fracture mechanics before the actual design optimization is carried out.

According to the applicable fracture propagation model, for a given fracture half length, there exists a width and henceforth a net pressure. The ancillary height is a geometric byproduct. Matching the net pressure and height with the LEFM independently determined pair of height and net pressure results in a solution that satisfies both. The dimensionless productivity index, JD, is then calculated.

For the fracture half lengths, ranging from a minimum (corresponding to aspect ratio one with respect to the perforated thickness) to a laterally fully penetrating fracture, we repeat the above procedure to calculate JD and so forth, until a maximum JD is accomplished.
NPV-Based Design for Coal Seam Reservoirs
Authors: Jukes Rachael , McIntosh Carl , Amorer Gabriel , Economides Michael J.
Published: October 2012

The production of natural gas from coal seam gas reservoirs has had a long and established history in the energy industry. Due to the relatively low permeability seen in many of these reservoirs, hydraulic fracturing is sometimes required to achieve economic production rates. The economic validity of hydraulic fracturing is dependent on a number of factors, including reservoir properties (and subsequent production rates), cost of stimulation services, as well as the type and quantity of materials. The justification of hydraulic fracturing is usually performed through net present value (NPV) analysis. NPV models for hydraulic fracturing in conventional and shale reservoirs are readily available in literature; however the same cannot be said for coal seam gas.

This paper presents a NPV model adjusted to the coal seam gas environment. That is, it considers the effect of the dewatering period required before natural gas may be desorbed from the targeted formation. The model only considers the incremental production of hydraulic fracturing as well as the incremental cost to fracture, thereby demonstrating the true present value of the treatment. Included in the model is a break-even price required for sales gas.

The production data represented within this paper was forecasted utilizing a pseudo three dimensional model that integrates unified fracture design (UFD). Sensitivity analyses were performed based on variances in reservoir properties (e.g. net pay, permeability, Langmuir isotherm) and stimulation design (e.g. proppant mass, type of proppant). This allows for greater understanding of the effects of the reservoir upon the economics of the project, as well as providing a means to economically optimize stimulation design.
Pore Pressure Modeling and Stress Faulting Regime Determination of the Montney Shale in the Western Canada Sedimentary Basin
Authors: Contreras Oscar , Hareland Geir , Aguilera Roberto
Published: October 2012

This work establishes an effective approach to predict pore pressure in the overpressured Montney Shale and overburden from sonic logs by implementing normal-trend and explicit methods. The cause of the overpressure condition in the Montney is also addressed. These two methods were selected on the basis of the study carried out by Contreras et al. (2011) that worked successfully for pore pressure prediction under subpressured conditions in parts of the Western Canada Sedimentary Basin (WCSB). As a second objective, the stress faulting regime was determined in the study area by using Stress Polygons and data from diagnostic fracture injection test analysis as a quantification of the minimum horizontal stress. This is of paramount importance since there is not a generic theory about the stress faulting regime for most of the west region of the WCSB.

The Eaton method from sonic logs (Eaton, 1975) and the Bowers method (Bowers, 1995) were implemented in two vertical wells drilled through the Montney shale. The first part of the analysis considered two normal compaction trends but unreasonable pressure profiles were obtained and required a revision on the depositional environment. It was found that for the study area three normal compactions trends have to be considered. The Bowers method was initially implemented using both loading and unloading conditions in order to establish a safe range of pore pressure to allow successful well plans.

It is concluded that undercompaction could be masked as the only overpressure mechanism in the Montney shale in the study area. The formation experiences an inverse faulting regime that will lead to the creation of horizontal hydraulic fractures. The Eaton method using three normal compaction trends and an exponent equal to 0.9 works successfully in the study area. The Bowers method using the loading and the unloading conditions, and the specific correlation parameters were found to be suitable for the study area and can be extrapolated to adjacent future production and exploratory wells.
Water Distribution in the Montney Tight Gas Play of the Western Canadian Sedimentary Basin: Significance for Resource Evaluation
Authors: Wood J. M.
Published: October 2012

Water distribution in unconventional gas reservoirs is a key parameter that influences many aspects of resource exploitation including selecting geographic areas for multi-well development programs, identifying target zones for horizontal wells, calculating reserves, estimating permeability, and understanding variability in gas and water production. Insights on water distribution in the Montney tight gas play of northeast British Columbia and northwest Alberta were gained by integrating reliable bulk volume water measurements from full-diameter core samples with other core, well log and geologic data. Water distribution in the studied Montney section was found to be related to stratigraphic architecture and rock fabric (defined by degree of bioturbation), and is interpreted to have been influenced by displacement efficiency of mobile formation water updip through tight Montney siltstones during hydrocarbon charging. Low gradient clinoform units with few shaly zones in the Lower Montney section enabled efficient water displacement and led to water contents close to irreducible water saturation. Higher gradient clinoform units with common shaly zones in the Upper Montney allowed less efficient water displacement, and significant volumes of mobile water were retained in parts of the section. Water saturation varies widely and directly influences effective gas permeability. A simple method for determining effective gas permeability from well logs was developed based on empirical relationships derived from the core and log data set. Effective gas permeability logs generated by this method help with the identification of target zones with superior reservoir quality for exploitation using horizontal multi-frac technology. A Pickett plot with effective gas permeability lines was found to be a useful tool for log-based comparison of Montney rock quality by stratigraphic zone or geographic area. This work shows that understanding water distribution and its influence on effective gas permeability leads to improved delineation of "sweet spots" for resource development in unconventional gas plays.
Understanding Anomalous Phase Behavior in Unconventional Oil Reservoirs
Authors: Du Liangui , Chu Lifu
Published: October 2012

Normal pressure/volume/temperature (PVT) analysis is based on a fundamental assumption that there is no potential difference between the gas a d liquid phases. The nanometer pore throats in unconventional reservoirs could impose a phase capillary pressure up to 1,000 psi. Therefore, the observed oil viscosity and bubble point pressure (Pb) in an unconventional oil reservoir are substantially lower than those reported by the PVT lab. Such reductions are further aggravated by the compaction effect and then become variable with pressure depletion. In this work, a set of non-linear fugacity equations was constructed by bringing capillary pressure in with the phase equilibrium equations.

The corresponding PVT reports for 14 Bakken fluid samples were recalibrated by combining the newly developed non- linear fugacity equations and the pore throat reduction imposed by compaction effects. The resultant PVT tables help clarify all the inconsistent PVT observations. Examples are presented to demonstrate the significance of such PVT corrections.

The corrected PVT tables were used in the Bakken reservoir simulation model and successfully resolved not only the inconsistent gas/oil ratio (GOR) issue between the model and real production data, but also substantially facilitated the history match and widened the optimal operational pressure window.

A series of studies were completed to address the combined impact of the capillary pressure and compaction on Bakken reservoir fluid properties. The Pb could be reduced in a range from hundreds to over 1,000 psi, compared to the corresponding lab PVT report. Such reduction is more severe in the lower formation permeability and solution GOR scenarios. Furthermore, oil density and viscosity could also be reduced by up to 10% due to the lighter components migrating to the oil phase. This study reveals the cause of the delayed GOR increase and the strange stepwise GOR increases observed in unconventional oil reservoirs.

This new understanding of the PVT property variation in an unconventional oil reservoir optimizes the operations procedure and will permit more reliable performance forecasts.
A Complete Petrophysical Evaluation Method for Tight Formations from Only Drill Cuttings in the Absence of Well Logs
Authors: Ortega Camilo , Aguilera Roberto
Published: October 2012

The amount of tight formations petrophysical work conducted at present in horizontal wells and the examples available in the literature are limited to only those wells that have complete data sets. This is very important. But the reality is that in the vast majority of horizontal wells the data required for detailed analyses are quite scarce.

To try to alleviate this problem, a new method is presented for complete petrophysical evaluation based on information that can be extracted from drill cuttings in the absence of well logs. The cuttings data include porosity and permeability. The gamma ray (GR) and any other logs, if available, can help support the interpretation. However, the methodology is built strictly on data extracted from cuttings and can be used for horizontal, slanted and vertical wells. The method is illustrated with the use of a tight gas formation in the Deep Basin of the Western Canada Sedimentary Basin (WCSB). However, it also has direct application in the case of liquids.

The method is shown to be a powerful petrophysical tool as it allows quantitative evaluation of water saturation, pore throat aperture, capillary pressure, flow units, porosity (or cementation) exponent m, true formation resistivity, distance to a water table (if present), and to distinguish the contributions from viscous and diffusion-like flow in tight gas formations. The method further allows the construction of Pickett plots without previous availability of well logs. The method assumes the existence of intervals at irreducible water saturation, which is the case of many tight formations currently under exploitation.

It is concluded that drill cuttings are a powerful direct source of information that allows complete and practical evaluation of tight reservoirs where well logs are scarce. The uniqueness and practicality of this quantitative procedure is that it starts from only laboratory analysis of drill cuttings, something that has not been done in the past.