bluuebunny/crossref_metadata_2025 huggingface dataset:
Effectiveness of Rapid Prescreening and 10% Rescreening in Liquid-Based Papanicolaou Testing
Authors: Currens Heather S. , Nejkauf Katharine , Wagner Lynn , Raab Stephen S.
Published: December 2011

Although rapid prescreening (RPS) has been shown to be an effective quality control procedure for detecting false-negative conventional Papanicolaou (Pap) tests, RPS has not been widely implemented in the United States. In our laboratory, cytotechnologists performed RPS in 3,567 liquid-based Pap tests: 1,911 SurePath (BD Diagnostics–TriPath, Burlington, NC) preparations that were manually screened and 1,656 ThinPrep Pap tests (Hologic, Bedford, MA) that were imaged using the ThinPrep Imaging System (Hologic). We compared the sensitivity of RPS, 10% rescreening (R-10%), and routine screening (RS). In contrast with previously published findings, we found that RS + RPS did not improve screening sensitivity compared with RS + R-10%. These results support the following hypotheses: (1) Higher baseline RS sensitivity as a result of Pap test diagnoses standardization implemented for quality improvement purposes decreases the performance impact of RPS. (2) R-10% and RPS quality assurance methods detect diagnostic failures caused by different types of cognitive errors.
Aptameric Molecular Switch for Cascade Signal Amplification
Authors: Ma Cuiping , Zhao Chunhui , Ge Yujie , Shi Chao
Published: December 2011

BACKGROUND

High sensitivity of analysis is constantly in demand in biomedical research and clinical diagnosis. In recent years aptamer-based analytical methods have been developed for protein detection. We developed a cascade signal amplification strategy based on molecular switches and aptamers to improve protein detection.

METHODS

Our cascade signal amplification strategy based on molecular switches and aptamers consisted of 2 steps, including the recognition and the triggering of a polymerase reaction. The procedure was designed to simplify the analysis by detecting trace amounts of target isothermally, in real time, and in a homogeneous solution. We applied this method to measure thrombin in human serum samples.

RESULTS

This cascade signal amplification strategy exhibited a linear response in thrombin concentration from 0.3 to 10 nmol/L, with a detection limit of 1.7 × 10−10 mol/L within 60 min. Results of the analysis of thrombin in human serum diluted 1:1 appeared to be linear, as was observed in buffer, in the tested concentration range of 0.3–10 nmol/L.

CONCLUSIONS

The aptameric sensor provides promising potential for detecting and screening trace concentrations of biomarkers in complex matrices for clinical applications.
Are Consumers Really Willing to Pay More for a Favorable Country Image? A Study of Country-of-Origin Effects on Willingness to Pay
Authors: Koschate-Fischer Nicole , Diamantopoulos Adamantios , Oldenkotte Katharina
Published: December 2011

Price-related consequences of the country-of-origin (COO) cue have received limited attention in extant literature. In this study, the authors draw from equity theory and cue utilization theory and investigate (1) whether a brand's COO affects a consumer's willingness to pay and (2) the extent to which the consumer's familiarity with the brand moderates this relationship. The results of three complementary experimental studies reveal that COO indeed has a positive impact on willingness to pay. Furthermore, the authors find a negative moderating influence of brand familiarity on the COO effect in a high-involvement setting but not in a low-involvement setting. The authors discuss the theoretical and managerial implications of the findings, and they identify directions for further research.
Global Product Quality and Corporate Social Responsibility Perceptions: A Cross-National Study of Halo Effects
Authors: Madden Thomas J. , Roth Martin S. , Dillon William R.
Published: December 2011

Attribute ratings often contain a holistic or global impression of the brand, commonly referred to as “halo.” A halo response can occur when perceptions of a brand's performance on an attribute are influenced by performance perceptions on another attribute or by a global impression of the brand. Using cross-national survey data from consumers in Argentina, China, Spain, and the United States, the authors examine the extent to which a halo response introduces bias to product quality and corporate social responsibility perceptions of competing brands. The findings show that halo is more pervasive for product quality than for corporate social responsibility associations, varies across brands and markets, and is strongly related to brand recommendations. Examining cross-national brand performance and halo perceptions can help international marketing managers understand key perceptual similarities and differences between and across markets, which can inform strategic considerations such as whether to pursue global, panregional, or national branding, positioning, and advertising strategies.
Avatar fandom as nature-religious expression?
Authors: Istoft Britt
Published: December 2011

The article investigates spiritual trends in the fandom around the movie Avatar; in particular whether nature, represented by the "goddess" Eywa, is seen as sacred by fans and if so, if this may influence fans' environmental practices. I have used the popular net-based fan forums avatar-forums.com and naviblue.com, because these sites show a broad, non-specialized interest in the movie. The result of the investigation shows a weight on pantheistic or animistic interpretations of nature. The practices springing from this view include meditation in nature to enhance awareness as well as daily practices like recycling, vegetarianism and an ecological lifestyle. Radical environmental initiatives are few, but exists on an ideological level, but more importantly there has been a production of manifestos aimed at politicians. A comparison to already established fandoms indicates that a development in the direction of more communal and face-to-face fan activities may be on the way.
The role of religion in linking conservation and development
Authors: Bhagwat Shonil A , Ormsby Alison A , Rutte Claudia
Published: December 2011

The world’s religions have made a contribution to environmental conservation and sustainable development through faith-based non-governmental organizations. Partnerships between secular conservation and development organizations and faith-based groups, however, are not always easy. Such partnerships face various challenges, including differences in worldviews, conict between identities, and the attitudes and behavior of religious groups that may not be favorable to conservation and development. Despite a possible overlap of values, these incompatibilities can often cause tensions between secular organizations and religious groups. A number of examples, however, suggest that faith-based groups are starting to address these incompatibilities. We suggest that partnerships with faith groups might be valuable because these groups can enhance public support for conservation and development. While secular organizations need to work with faith groups on the basis of shared ethical or moral values, identifying effective ways to strengthen the linkages between secular organizations and faith groups is also necessary.
Church and climate change
Authors: DeLashmutt Michael W.
Published: December 2011

This article examines the extent to which the Church of England’s institutional environmental policies, practices, and theologies are being translated into the context of the parish church. This study uses a series of focus group interviews to gather data from six parishes around the Diocese of Truro to assess the attitudes towards, and actions regarding, environment and climate change amongst regular Church of England churchgoers. The study suggests that despite a wealth of institutional resources that have been developed to foster theologically informed environmental knowledge, very little awareness of the institutional Church’s ethos is found in the local church context.
The role of the interpreter in constructing asylum seeker’s credibility: A hearing at the Spanish Asylum and Refugee Office
Authors: Díez Isabel Gómez
Published: December 2011

The paper’s objective is to establish the interpreter’s role in the construction of the asylum seeker’s credibility during the interaction at asylum hearings. To illustrate this, I perform a discourse analysis of the interaction at an asylum hearing with a Nigerian applicant and an English-Spanish interpreter, taking place at the Oficina de asilo y refugio in Madrid (Spain) in 2005. Firstly, I identify the functions adopted by the interpreter in the hearing, the interactional sequence generated by his working method and its impact on his translation activity. Secondly, I focus on the alterations in the interpreter’s rendition which may have an impact on the applicant’s credibility and I set out to elucidate the factors explaining these alterations.
Multilingual and transnational encounters in late modernity: Linguistic practices and social processes
Authors: Martín Rojo Luisa , Márquez Reiter Rosina
Published: December 2011

This paper examines the essential role played by language in the provision of services to facilitate interchanges between persons of different origins in order to enable not just the performance of these activities, but also to make it possible for the participants, who may not share cultural assumptions or values, to (re)negotiate their relations and identities. This is precisely a key sector in the new economies, and the way in which linguistic resources are managed by the multinational firms and other institutions of the developed world is reminiscent of colonial times, particularly in Spain. Within this frame, this paper focuses on the linguistic practices in some of these newly created institutional spaces in the service sector, particularly in settings where Spanish has a role to play. The analysis of linguistic policies and interactions shows how, depending on whether they concern public/private service-providers, participants mobilise their linguistic resources to (re)construct different relations and meanings within these varying institutional settings. The paper also examines how multilingualism is managed in these institutional encounters. In this context, tensions between the reproduction of a monolingual ideology of ‘one state – one language’ and the actual multilingual practices inevitably arise, making the unravelling of these new linguistic landscapes a challenge. It is the institutions, not the users, that decides how linguistic resources have to be managed, and several pieces of evidence of the lack of adaptation to user’s needs are supplied, which can be seen as part of an ethnocentric approach corresponding to the values of the host community. Such a sociolinguistic order shapes interaction and reinforces asymmetries. The analysis also shows the active involvement of social actors who can reproduce as well as challenge this sociolinguistic order.
Espécies novas de Alpaida (Araneae, Araneidae), descrições complementares e nota taxonômica
Authors: Buckup Erica Helena , Rodrigues Everton Nei Lopes
Published: December 2011

Alpaida arvoredo sp. nov. é descrita com base em machos e fêmeas da Ilha do Arvoredo, litoral de Santa Catarina, Brasil. O macho foi descrito associado à Alpaida hoffmanni Levi, 1988. O macho correto de A. hoffmanni é descrito pela primeira vez. Alpaida caramba sp. nov., com base em ambos os sexos, é descrita do Rio Grande do Sul, Brasil. Os machos de Alpaida kochalkai Levi, 1988 e A. lomba Levi, 1988, são descritos pela primeira vez.
Nitrogen dynamics in soil management systems. I - flux of inorganic nitrogen (NH4+ and NO3-)
Authors: Sá João Carlos de Moraes , Cardoso Eduardo Garcia , Briedis Clever , Ferreira Ademir de Oliveira , Borszowskei Paulo Rogério , Santos Josiane Burkner , Massinham Aline , Ferreira Carla Fernanda , Siuta Júnior Darci , Baranek Edemar José , Piccolo Marisa de Cássia , Pavei Mariana , Urquiaga Segundo
Published: December 2011

In agricultural systems the N-NH4+ and N-NO3- contents is significantly affected by soil management. This study investigated the dynamics of inorganic nitrogen (N; NH4+ and NO3-) in an experimental evaluation of soil management systems (SMSs) adopted in 1988 at the experimental station of the ABC Foundation in Ponta Grossa, in the Central South region of the State of Paraná. The objective of this study was to evaluate the changes in N-NH4+ and N-NO3- flux in the surface layer of a Red Latosol arising from SMSs over a 12-month period. The experiment was arranged in a completely randomized block design in split plots, in three replications. The plots consisted of the following SMSs: 1) conventional tillage (CT); 2) minimum tillage (MT); 3) no-tillage with chisel plow every three years (NT CH); and 4) continuous no-tillage (CNT). To evaluate the dynamics of inorganic N, the subplots represented samplings (11 sampling times, T1 - T11). The ammonium N (N-NH4+) and nitric N (N-NO3-) contents were higher in systems with reduced tillage (MT and NT CH) and without tillage (CNT) than in the CT system. In the period from October 2003 to February 2004, the N-NH4+ was higher than the N-NO3- soil content. Conversely, in the period from May 2004 to July 2004, the N-NO3- was higher than the N-NH4+ content. The greatest fluctuation in the N-NH4+ and N-NO3- contents occurred in the 0-2.5 cm layer, and the highest peak in the N-NH4+ and N-NO3- concentrations occurred after the surface application of N. Both N-NH4+ and N-NO3- were strongly correlated with the soil organic C content, which indicated that these properties vary together in the system.
Resposta germinativa de sementes de caroá [Neoglaziovia variegata (Arruda) Mez]
Authors: Silveira Daniela Garcia , Pelacani Claudinéia Regina , Antunes Cimile Gabrielle Cardoso , Rosa Sandra Santa , Souza Fernanda Vidigal Duarte , Santana José Raniere Ferreira de
Published: December 2011

O caroá é uma Bromeliaceae nativa da Caatinga brasileira cujas fibras retiradas das folhas geram trabalho e renda para diversas famílias nordestinas com a fabricação de vários produtos artesanais. A propagação ocorre via sementes, que podem servir como alimento para muitos animais e pássaros. Diante de sua importância econômica regional, a planta do caroá tem sido coletada na caatinga de forma extrativista, já tendo praticamente desaparecido em algumas regiões da Bahia. Objetivou-se, com o desenvolvimento deste trabalho, avaliar o efeito da temperatura e da restrição de água na germinação de sementes de Caroá. A germinabilidade foi avaliada sob as temperaturas de 25, 30, 34 e 37° C, sendo que a temperatura mais favorável à germinação foi utilizada no ensaio seguinte, combinando com diferentes soluções-teste de polietilenoglicol. As maiores taxas de sementes germinadas (> 66%) ocorreram quando as temperaturas do meio eram mais elevadas, sendo que a de 30° C foi a que proporcionou a maior velocidade média de germinação (0,12 dias-1) e índice de velocidade de germinação; por sua vez a germinação decresceu com a diminuição do potencial osmótico do meio. Sob condições de restrição hídrica, as sementes de caroá mostraram capacidade germinativa até o potencial de -0,6 MPa.
Geosynthetics applications for the mitigation of natural disasters and for environmental protection
Authors: Brandl H.
Published: December 2011

ABSTRACT: The paper first describes the versatile application of geosynthetics for the mitigation of floods, landslides, rockfalls, debris flows and avalanches. It focuses on dykes or flood protection dams, on geosynthetic-reinforced stabilising fills (up to 130 m height) and barrier dams. Geosynthetic-reinforced floating embankments (up to 70 m height) in creeping slopes and seismic areas show clear advantages over rigid structures (e.g. bridges) not only from a geotechnical point of view but also regarding economy, maintenance and environmental aspects. Environmental protection is predominantly considered by gaining renewable energy from the ground via ‘energy-geosynthetics'. Several other applications are also mentioned. Compaction optimisation and control of geosynthetic–soil structures is recommended by roller-integrated CCC (continuous compaction control), thus improving their behaviour significantly.
Systems engineering: the design and operation of municipal solid waste landfills to minimize contamination of groundwater
Authors: Rowe R.K.
Published: December 2011

ABSTRACT: This paper discusses the need to adopt a systems engineering approach to the design and operation of municipal solid waste landfills. It discusses how the interaction between the different components affects the performance of the entire system, and how, because of this interaction, the performance of the system as a whole is much better than the individual contributions of each of the parts. Issues discussed in this context are: landfill covers and the role that they play; the effect of landfill operations such as the waste placement and leachate recirculation on liner temperature and leachate characteristics; leachate collection and the control of head on the liner; diffusion of contaminants through composite liners; the effect of geomembrane–clay liner interaction on leakage; the significance of wrinkles in a geomembrane; the effect of liner temperature on leakage; possible means of controlling liner temperature; geomembrane protection; the long-term performance of geomembranes and geosynthetic clay liners; and finally the contaminant transport implications of these issues. It is concluded that by taking a systems approach to design, construction and operations we can provide safer containment of waste and long term-environmental protection.
Economic‐based projections of future land use in the conterminous United States under alternative policy scenarios
Authors: Radeloff V. C. , Nelson E , Plantinga A. J. , Lewis D. J. , Helmers D , Lawler J. J. , Withey J. C. , Beaudry F , Martinuzzi S , Butsic V , Lonsdorf E , White D , Polasky S
Published: December 2011

Land‐use change significantly contributes to biodiversity loss, invasive species spread, changes in biogeochemical cycles, and the loss of ecosystem services. Planning for a sustainable future requires a thorough understanding of expected land use at the fine spatial scales relevant for modeling many ecological processes and at dimensions appropriate for regional or national‐level policy making. Our goal was to construct and parameterize an econometric model of land‐use change to project future land use to the year 2051 at a fine spatial scale across the conterminous United States under several alternative land‐use policy scenarios. We parameterized the econometric model of land‐use change with the National Resource Inventory (NRI) 1992 and 1997 land‐use data for 844 000 sample points. Land‐use transitions were estimated for five land‐use classes (cropland, pasture, range, forest, and urban). We predicted land‐use change under four scenarios: business‐as‐usual, afforestation, removal of agricultural subsidies, and increased urban rents. Our results for the business‐as‐usual scenario showed widespread changes in land use, affecting 36% of the land area of the conterminous United States, with large increases in urban land (79%) and forest (7%), and declines in cropland (−16%) and pasture (−13%). Areas with particularly high rates of land‐use change included the larger Chicago area, parts of the Pacific Northwest, and the Central Valley of California. However, while land‐use change was substantial, differences in results among the four scenarios were relatively minor. The only scenario that was markedly different was the afforestation scenario, which resulted in an increase of forest area that was twice as high as the business‐as‐usual scenario. Land‐use policies can affect trends, but only so much. The basic economic and demographic factors shaping land‐use changes in the United States are powerful, and even fairly dramatic policy changes, showed only moderate deviations from the business‐as‐usual scenario. Given the magnitude of predicted land‐use change, any attempts to identify a sustainable future or to predict the effects of climate change will have to take likely land‐use changes into account. Econometric models that can simulate land‐use change for broad areas with fine resolution are necessary to predict trends in ecosystem service provision and biodiversity persistence.
Effect of Dynamic Loading on Wellbore Leakage for the Wabamun Area CO2 Sequestration Project
Authors: Nygaard Runar , Salehi Saeed , Lavoie Rob
Published: December 2011

To permanently remove CO2 from the atmosphere large scale injection of CO2 from stationary sources such as coal fired power plant and heavy oil production into brine filled formation is seen as one of the most viable options. One of the main risks identified with storing CO2 into the subsurface is the potential for leakage through existing wells penetrating the cap rock. The wellbore system has several components which can fail and create leakage paths such as type and placement of wellbore casing and cements, completion method, abandonment and wellbore expansion or contraction by changes in temperature and pressure. Of the 1000 wells in the study area near Lake Wabamun, Alberta 95 wells penetrated the immediate cap rock above the proposed Nisku injection formation and was identified as potential leakage pathways. The leakage risk of these wells was evaluated based on the knowledge of well design, current well status and historical regulation’s in the area. For the subset of 27 well studied on only 4 wells were identified as wells requiring work over which was less of a problem than anticipated. To evaluate the risk of creating leakage paths by thermal and pressure changes caused by CO2 injection, a three dimensional finite-element model was built which used elasto-plastic material models for cement and formation. Multi-stage simulations for casing-cement and cement-formation interactions with temperature enabled elements were conducted. Because of the uncertainty on cement properties in old wells, a parametric study of cement properties was conducted. The simulation results indicated that thermal cooling might reduce near-wellbore stresses which will increase risk of integrity loss in casing-cement and cement-formation. The parametric study reviled that the risk of debonding and tensile failure will increase with increasing Young’s modulus and Poisson’s ratio of the cement under dynamic loading conditions. In addition, low mechanical cement strength will increase risk of shear failure in the cement.
Fracture Stimulation Optimization in Horizontal Cardium Completions
Authors: Woo Ving , Pope Timothy L. , Abou-Khalil Emile , Davidson John , Bonnell Andrew , Zhang Jenny
Published: December 2011

The Cretaceous Cardium formation has been produced since the early 1950’s. The Cardium is a sandstone that can exhibit a wide range in permeability. This is due to the diversity of the depositional environment creating deposits that can vary from siltstone, fine grained sandstone to conglomerate. The formation is laterally extensive across western Alberta. Secondary recovery in the form of water flooding has been ongoing in the core area since the 1960’s allowing production into the twenty first century. However, it wasn’t until the application of horizontal drilling and multi-stage completion techniques that the vast reserves in the poorer quality areas could be economically produced.

This paper discusses the initial phase of an optimization process used to increase production and net present value in Cardium completions through the application of reservoir modeling, optimized fracture spacing and the application of a solids-free viscoelastic fracturing fluid. The new approach provides higher production rates and accelerated flowback compared to the gelled oil system previously employed. In addition to the previous two points, the economics are further enhanced by the elimination of the substantial cost of oil used in gelled oil stimulations.
Design and Deployment of a New Fracturing Port Technology to Increase Stage Number Capability of Openhole Multistage Systems
Authors: Roe Tully , Seale Rocky , Snyder Daniel
Published: December 2011

The Lower Huron Shale is of Upper Devonian age and produces in Ohio, Tennessee, Kentucky and West Virginia. This formation is a good candidate for hydraulic fracturing due to naturally occurring fractures and faults. Since the early 1900s, wells in the Lower Huron have typically been drilled and completed open hole with a variety of fracture treatment plans. However, to maximize production in the area, horizontal drilling using open hole multistage system (OHMS) completions began in the mid 2000s.

Studies in the Lower Huron led to operators require longer laterals with increased stage numbers in order to maximize production; however, the limitations of OHMS restricted the potential of many wells. In order to deal with these limitations, the repeatable fracturing port (RFP) was developed. The RFP utilizes the same size ball to activate more than one fracture port – essentially multiplying the number of isolated stages.

A field study in the Lower Huron demonstrated the benefits of using RFP technology, as the system functioned effectively and increased the number of potential stages. The success of RFP technology in the Lower Huron has been echoed throughout the U.S. and Canada, as increased knowledge continues to improve the technology and well performance.
Shale Engineering Application: The MAL-145 Project in West Virginia
Authors: Vassilellis George D. , Li Charles , Bust Vivian K. , Moos Daniel , Cade Randal
Published: December 2011

The "Shale Engineering" approach and modeling addresses production forecasting in shale and tight formations. This new reservoir simulation methodology relies on modeling the propagation of the stimulated rock volume from the near-well vicinity to deep into the formation. Simulation models are built for individual fracturing stages and validated by matching treatment pressures and rates while conforming to geomechanical and microseismic observations. Stage models are then combined into a larger well model where individual stage contribution and early production performance are matched. This approach was applied on a project that was developed by EQT in an Upper Devonian shale formation in West Virginia. Data available for this project included fit-for-purpose formation evaluation description, production logs and downhole microseismic data with advanced processing and interpretation. The results provided a good match to early well performance, despite the complexity of having to match a combination of shales and partially depleted tight sandstones that had been stimulated by foam fracturing with proppant. This approach can be used not only to predict production, but also as a practical platform for field development design and optimization. Furthermore, the matched results validated the shear stimulation model developed by the authors for this type of application. The approach makes it possible to exploit microseismic observations in a more realistic way in order to describe the stimulated rock volume (SRV), and it explains early-life production logs that indicate uneven fracturing stage contribution. The model also can relate stimulation effectiveness to pre-existing formation rock and fluid properties, and thus can be used as a guide to identify optimal formation targets. The "Shale Engineering" approach hinges on the premise that when unconventional "tight rocks" containing hydrocarbons are modified by hydraulic fracture stimulation, the process converts them into "reservoir rocks". In addition, interpretation of the newly created "artificial reservoirs" is accomplished through multi-displinary expertise that is focused on providing a rate performance and predictive model to aid in reservoir development. Because unconventional resource/reservoir formations are unique and subject to a wide range of conditions, they require a production predictive method more suitable for this task than the commonly used "Type Curves". The advantage of the "Shale Engineering" approach is that it allows validation with parameters that can be available at an early stage of the well life, which in turn are useful to constrain model solutions. It also offers the means to include geomechanics in a practical workflow that allows systematic workflow allows for step-by-step validation of the model. The suggested simulation process uses commerical software and it can be applied to either simple or complex cases.
Comparison of Downhole Control System Technologies for Intelligent Completions
Authors: Shaw Joel
Published: December 2011

Reliability and acceptance of intelligent completions has increased dramatically over the last decade. With this, there has been a demand to push the limits of intelligent completion technology to allow access to more zones at higher pressures and temperatures while minimizing cost and maximizing reliability. Meeting this demand not only requires flow control components such as packers or Interval Control Valves (ICV) but it also requires a system and methodology to control those components. Different control methodologies have been designed and tested over the years using hydraulic power, electric power, or combinations of the two. These hydraulic and electric requirements have been supplied by small diameter metal hydraulic control lines and metal-encased electrical conductors. Control and power requirements to the downhole components have increased as operators have desired control of more zones. Downhole control system requirements have become increasingly demanding to meet these requirements.

This paper discusses the history and future of control systems for intelligent completions. It describes how these systems have evolved from simple hydraulic systems to more complex multiplexing systems and presents the advantages and disadvantages of each.
Global Unconventional Gas Resource Assessment
Authors: Dong Z. , Holditch S. A. , McVay D. A. , Ayers W. B.
Published: December 2011

Most estimates of the resource endowment (original gas in place) reported for world unconventional gas start with Rogner’s 1997 "top-down" study. That global estimate is most likely quite conservative, since the oil and gas industry has discovered enormous volumes of shale gas around the world since the 1990’s. The data from these new reservoirs add substantially to our understanding of the unconventional resource base. Furthermore, the uncertainty of Rogner’s assessment was not quantified. Thus, a new assessment of original unconventional gas in place worldwide with considering the uncertainty is needed.

The objective of this project was to estimate the probabilistic distributions of original volumes of gas trapped in coalbed, tight sand and shale reservoirs, worldwide. To accomplish this objective, we reviewed published assessments of coal, conventional and unconventional resources and established the quantitative relationship between unconventional gas (coalbed methane, tight sands gas, and shale gas) and the conventional hydrocarbon (coal, conventional gas and oil) resource endowments for North America. Then, we used this relationship to extrapolate original unconventional gas in place, worldwide. Our assessment of the world resource endowment established an unconventional OGIP of 83,400 Tcf (P90)-184,200 Tcf (P10), which is 2.6-5.7 times greater than Rogner’s estimate of 32,600 Tcf.

Our regional assessments of unconventional OGIP should help industry better target its efforts to rapidly accelerate the development of unconventional gas resources worldwide. The methodology used to assess the distribution of each type of unconventional OGIP may be used to estimate unconventional gas resources at the country or basin level, knowing the coal in place and technically recoverable resources of conventional hydrocarbons.
Optimisation, Uncertainty, and Risk Analysis for Asset Development with Limited Data and Multiple Geographical Environments: A Heavy-Oil Field Case
Authors: Tillero E. , Perez E. , Gonzalez J. , Ungredda A. , Ferreira D. , Griborio G. E. , Mogollon J. L.
Published: December 2011

The studied reservoir has one of the greatest heavy-oil reserves (OOIP about 12.2 MMMSTB) in the Maracaibo Lake basin. It has been largely developed except for one coastline area (385 km2), which includes both zones’ land and shallow water. Limited access of conventional drilling rigs in the area, coupled with low definition of the structural, stratigraphic, and petrophysical model have reduced drilling activities.

Plans have been made to increase production by 20% through drilling of wells in the coastline area. This plan requires the consideration of multiple variables, such as new surface facilities, drilling rigs for both geographical environments, rock heterogeneity, compartmentalized structure (6 blocks), low number of drilled wells (8 wells), and limited reservoir data, which will generate a large number of development scenarios.

This paper presents a probabilistic production forecasting of the coastline reserves through an innovative approach based on a systematic evaluation of risk and uncertainty of reservoir variables, and a maximization of net present value (NPV). The optimization of a large number of decision variables, such as the type of drilling rigs, type of wells completion, and seismic acquisition zone, was obtained. The optimal stochastic scenario showed a NPV with a 340% increase compared with the best deterministic scenario.

This approach triggered warnings about the current plans for seismic data acquisition, which proved to be uneconomical despite expected improvements in the geological and stratigraphic framework. Therefore, the drilling of stratigraphic wells becomes an alternative to partially substitute seismic survey.

Finally, the different operational scenarios showed that development should be done in stages and by geographical areas, starting with stratigraphic deviated wells into shallow water zone using conventional rigs, then vertical and slanted wells in shallow water zone using swamp rigs, and verticals and slanted wells in the ground region using land rigs.
The Role of Crude Oil Shrinkage in Heavy Mix Light Crude in Main Oil Pipeline: Case Study Oman
Authors: Nengkoda Ardian
Published: December 2011

With the increasing trend of heavy oil production in Sultanate of Oman, it will be very interesting to see the impact on crude oil volumetric quality in the main oil pipeline. Pipeline oil management mass balance and custody transfer accuracy will be the focus. The volumetric measurement equipment show some time a discrepancies. Temperature, pressure and meter factor corrections were not enough to explain these discrepancies. The shrinkage factor of crude oil can be seen from upstream to main oil pipeline where the mixing already stabilize, such from separator conditions varies, dependant upon the pressure and temperature of the separator and the individual fluid properties. The more volatile the separator liquid phase, the more impact separator conditions and shrinkage will be. Shrinkage value will be very dependant upon the separator pressure and temperature and will change as these values vary. However, good shrinkage measurement is best approached by collecting the primary separator liquid and performing a separator test on it. A calculation based on API MPMS 12.3 (1996) have some limitationof mixing only at absolute P (100-700 KPa, 15-115 lb/in2) and T (15oC or 60oF). The study explaining a step by step of crude oil shrinkage by well testing approach, separator testing approach and equation-of-state (EOS) tuned in to measuring accurate shrinkage and as a result, the data shows less than 4% error band.
Stimulation’s Influence on Production in the Haynesville Shale: A Playwide Examination of Fracture-Treatment Variables that Show Effect on Production
Authors: Modeland Neil , Buller Dan , Chong King Kwee
Published: December 2011

In most developing shale plays, there is a learning curve for determining which factors best affect well production and yet still leave them economical. Advancing up this curve can take years to achieve as operators adopt a baseline treatment and th en adjust certain specific variables to find the best economic solution. However, by evaluating the reservoir on a playwide basis, the ability to find the optimal treatment method can be expedited, benefiting the operators by allowing them to achieve better wells earlier in the play’s development. Though many factors can hold a major influence (e.g., wellbore placement, rock properties, and flowback procedures), this study will review the production impact of specific variables of the fracture treatments, including well location. Using public production data with a database of stimulation treatments for several hundred wells in the Haynesville shale, variables such as pumping rate, volumes, proppant (type and volume), frac stage designs, base fluid, and surfactant usage can be analyzed to find which ones produce a positive effect on a well’s production. In addition to a well’s overall production magnitude, in the majority of the shale plays, regulating the decline of the production curve sometimes has been a crucial element in achieving the estimated ultimate recovery needed to make the play development economical. The stimulation-variables database will also be investigated to determine which factors can have an influence on ensuring a production curve’s decline will level off at a higher percentage of its initial production. By selectively identifying and grouping wells inside and outside the core area of the play, this study distinguishes which variables are positively affecting production while reducing the masking effect caused by geographic location. Conventional fracturing theory is applied to offer explanations of what might be occurring inside the reservoir or fracture system to make these findings hold true (or, at least, plausible).
Fracturing in the Oil-Sands Reservoirs
Authors: Yuan Yanguang , Yang Baohong , Xu Bin
Published: December 2011

Based on its deformation properties, Alberta oilsands reservoir material is classified as an interlocked sands. It possesses relatively high initial friction strength and exhibits a significant dilation tendency once it is shear-mobilized. How does such a medium behave under high injection pressures? Using analytical derivations and numerical simulations, this paper illustrates the evolving shear-induced failure and tensile-dominated fracturing behavior in the oilsands. It concludes that the fracturing process is a combination of shear dilation and tensile parting at micro scales. Laboratory and field data exist to support the theoretical observations. Finally, a discussion will be given about impact of such fracturing behavior on the reservoir engineering processes. It will shed light on proactive utilization of the dilation for the in-situ oilsands development.
Analyzing Variable Rate/Pressure Data in Transient Linear Flow in Unconventional Gas Reservoirs
Authors: Liang P. , Mattar L. , Moghadam S.
Published: December 2011

Unconventional gas wells often show linear flow during their transient period, and this transient behavior can last for several years. Currently industry uses typecurve matching technique to analyze this linear flow. The typecurves in common use are based on the assumption that wells produce at constant rate. However, most of the time, the production rate is variable, and in fact is closer to constant pressure operation. The constant pressure typecurve is useful but not suitable when both rate and pressure vary. It is necessary to have an easy-to-use method for analyzing variable rate/pressure data in linear flow.

There are two objectives for this paper. First, it serves to review the formulation, typecurve, specialized plots and superposition time that are used to analyze transient linear flow. It helps readers gain a deeper understanding of the theory. Second, it serves to illustrate a practical and effective way for analyzing variable gas production data.

In this development, we studied the effect of skin on the typecurve and on the specialized plot. We converted the constant pressure solution to its constant rate equivalent by using material balance time and found it to be acceptable for all practical purposes. We converted real time to corrected pseudo-time to account for variable gas properties, and found the effect to be small in the analysis of actual production data. We investigated the effect of outliers on superposition time. In the end, we proposed an approach to analyze variable rate/pressure data during transient linear flow and confirmed the validity of our methodology using synthetic data that generated in numerical models.
Benefits and Technical Challenges of Downhole Steam Generation for Enhanced Oil Recovery
Authors: Castrogiovanni Anthony , Fitzpatrick Nick , Ware Charles H.
Published: December 2011

Steam generated at the surface is currently the most common technology for in-situ thermal stimulation of heavy oil, however it has significant limitations due to heat loss that make it uneconomic for some 2 trillion barrels of deeper heavy oil resources. Downhole steam generators (DHSGs) have the ability to unlock these deeper deposits and allow steam to be used where it was previously not economical. A brief review of recent advances in DHSG technology and a description of potential applications using thermal oil recovery modeling and simulation are presented here. The DHSG technology described can be particularly suitable for recovering a number of known heavy oil deposits around the world that have experienced low recovery efficiencies through primary and secondary (water flood) production methods. These deeper resources typically require thermal stimulation to reduce viscosity in-situ for improved production volumes. Cost estimates and economic projections were developed based on a full green field project using production estimates obtained from STARS, a widely accepted heavy oil simulation program. Simulations and associated economic studies for the fields modeled, assuming the deployment of DHSGs, showed viable economics for all cases at both USD $75/bbl and USD $100/bbl 2009 WTI oil prices. The technological constraints of deep heavy oil production may be removed by further development of DHSG technology including direct-fired, umbilical-supported downhole natural gas fired systems that can be operated without maintenance for long periods of time. DHSG technology development activities are presented and specific issues relating to previous unsuccessful efforts are discussed. Finally, a new generation of DHSG technology is introduced and key design and operating problems with proposed solutions are presented. The uniqueness of the downhole environment is discussed along with the special requirements imposed on a downhole combustion system as a result. Technical challenges include tool positioning and inaccessibility, installation and operational safety, pressure management, and flame stability & control. Advances from the aerospace industry are also discussed as they pertain to robust combustion system development and downhole tool design which help enable a broad range of operating pressures and flow rate turndown. The demonstrated potential for DHSG technology to create optimum steam and EOR gas mixes that are tailored for a given reservoir may provide the basis for a new generation of thermal in-situ EOR technology to unlock deep heavy oil resources as well as those in environmentally challenged locales such as offshore or under arctic or permafrost environments.
Applicability and Assessment of Micro-Wave Assisted Gravity Drainage (MWAGD) Applications in Mehsana Heavy Oil Field, India
Authors: Jha Ashutosh Kumar , Joshi Nitin , Singh Aaditya
Published: December 2011

Exploitation of extra heavy oil resource will be the main R & D challenge in the future. In India Mehsana oil field is the one of the extra heavy oil belts. In such type of fields advanced EOR is of primary concern to increase the recovery. Apart from conventional thermal methods this paper discusses about the commercialization and broad application of (MWAGD) as alternative thermal method in the Mehsana oil field. In this study, applicability of microwave heating for heavy oil from Mehsana heavy oil field was experimented and analyzed quantitatively. In this paper a core sample of Mehsana field is taken and heated with the microwave energy provided by a microwave source consisting of magnetron tubes to generate the microwave power. Micro-Wave radiation is non-ionizing so requires high frequency current (3000 MHz) which causes friction by vibration of molecules which results in dielectric heating of the sample. In this experiment heat transfer between microwave source and core is described quantitatively. Temperature and viscosity profile of the gravity drained oil are observed graphically and analytically. Effects of initial oil and water saturations, wettability, porosity, permeability are discussed with respect to the drained oil. Economic evaluation is also done by comparing the costs in USD/barrel between the above proposed method and the method which is being run presently i.e. Steam Assisted Gravity Drainage (SAGD). In this paper authors have also shown the work-how of applicability of MWAGD in the Mehsana field in present scenario. MWAGD is cost effective than the conventional EOR methods. It is also more efficient and less time consuming as there is speedy heat transfer by dielectric heating. MWAGD does not cause any consequential damage and provides greater oil displacement efficiencies. Also, the heavy deposit of residual coke or carbon is rooted out.
Evaluation of Electric Heating on Recovery Factors in Extra Heavy Oil Reservoirs
Authors: Gasbarri S. , Diaz A. , Guzman M.
Published: December 2011

Most of the world hydrocarbon reserves represent extra-heavy oils. Exploitation of most of these reservoirs has not been carried out mainly due to the difficulty to produce the high-viscosity of extra heavy oils. Cold production can be achieved in the Orinoco Oil Belt through advanced horizontal wells. However, in many cases the drawdown exerted creates gas or sand production problems or excessive water production when an aquifer exists. Primary recovery factor under these conditions rarely go beyond 6%; and 3% in the presence of an active aquifer.

On the last decade several thermal mechanisms have been studied to increase the recovery of these types of reservoirs. This study analyzes the effect of bottom-hole electric heating on the production and recovery factors of extra-heavy oil reservoirs. The study was carried out by numerical simulation, analyzing the most influential parameters through an experimental matrix of 24 cases run in a horizontal well of 2000 feet. Four types of oils were studied, 8.1, 10, 12 and 15°API gravity. Reservoir thicknesses used were 300 feet and 80 feet. Two different heating rates were used (1.6e07 and 5e07 BTU/Day). The boundary conditions used in the model correspond to the installation of a typical downhole pump in Orinoco Belt. Several parameters were analyzed such as pressures, temperatures, viscosities, production rate, gas-oil ratio, in order to determine the effect of the heating.

Based on this study, electric heating represents a good option for good sand quality reservoirs with low API gravity oils where a small change of temperature generates great change in viscosity. Special grid refinement must be performed within the wellbore in order to allow the simulator to accurately estimate the properties and conditions in this area where significant changes occur. Electric heating reduces the viscosity near wellbore and increases the bottom-hole pressure avoiding excessive gas liberation near the well. This creates favourable conditions for production delaying an oil relative permeability drop. Based on the simulations studied, this method increases the recovery factor up to 60% the one obtained in cold production for a typical extra heavy oil.