bluuebunny/crossref_metadata_2025 huggingface dataset:
Distinctive properties of rock-forming blue quartz: inferences from a multi-analytical study of submicron mineral inclusions
Authors: Seifert W. , Rhede D. , Thomas R. , Förster H.-J. , Lucassen F. , Dulski P. , Wirth R.
Published: June 2012

The study discusses the mineralogical, geochemical and thermometric properties of rock-forming blue quartz from eight worldwide occurrences. Compared to non-blue quartz, blue quartz contains significant amounts of submicron-sized (1 μm—100 nm) and nanometre-sized (<100 nm) inclusions. Mica, ilmenite and rutile constitute the most abundant submicron-sized inclusions, and are formed probably by syngenetic precipitation in the boundary layer between quartz and melt (entrapment model). Nanometre-sized rutile possibly originated by epigenetic exsolution of Ti from the quartz structure (exsolution model). Rayleigh scattering of light by nano-particulate inclusions best explains the origin of the blue colour. Blue quartz is generally Ti-rich (∼100—300 ppm) and formed at high temperatures (∼700°C—900°C). The large number, and high spatial density, of tiny xenocrystic inclusions of Ti-bearing minerals make calculations of crystallization temperatures using the Ti-in-quartz thermometer unreliable. The geological significance of blue quartz remains obscure.
Hidden genetic diversity in the green alga Spirogyra (Zygnematophyceae, Streptophyta)
Authors: Chen Charlotte , Barfuss Michael HJ , Pröschold Thomas , Schagerl Michael
Published: June 2012

Background

The unbranched filamentous green algaSpirogyra(Streptophyta, Zygnemataceae) is easily recognizable based on its vegetative morphology, which shows one to several spiral chloroplasts. This simple structure falsely points to a low genetic diversity:Spirogyrais commonly excluded from phylogenetic analyses because the genus is known as a long-branch taxon caused by a high evolutionary rate.

Results

We focused on this genetic diversity and sequenced 130Spirogyrasmall subunit nuclear ribosomal DNA (SSU rDNA) strands of different origin. The resulting SSU rDNA sequences were used for phylogenetic analyses using complex evolutionary models (posterior probability, maximum likelihood, neighbor joining, and maximum parsimony methods). The sequences were between 1672 and 1779 nucleotides long. Sequence comparisons revealed 53 individual clones, but our results still support monophyly of the genus. Our data set did not contain a single slow-evolving taxon that would have been placed on a shorter branch compared to the remaining sequences. Out of 130 accessions analyzed, 72 showed a secondary loss of the 1506 group I intron, which formed a long-branched group within the genus. The phylogenetic relationship to the genusSpirotaeniawas not resolved satisfactorily. The genetic distance within the genusSpirogyraexceeded the distances measured within any other genus of the remaining Zygnemataceae included in this study.

Conclusion

Overall, we define eight distinct clades ofSpirogyra, one of them including the genusSirogonium. A large number of non-homoplasious synapomorphies (NHS; 114 NHS in total) was found forSpirogyra(41 NHS) and for each clade (totaling 73 NHS). This emphasizes the high genetic diversity of this genus and the distance to the remaining Zygnematophyceae.
Development of a dense SNP-based linkage map of an apple rootstock progeny using the Malus Infinium whole genome genotyping array
Authors: Antanaviciute Laima , Fernández-Fernández Felicidad , Jansen Johannes , Banchi Elisa , Evans Katherine M , Viola Roberto , Velasco Riccardo , Dunwell Jim M , Troggio Michela , Sargent Daniel J
Published: June 2012

Background

A whole-genome genotyping array has previously been developed for Malus using SNP data from 28 Malus genotypes. This array offers the prospect of high throughput genotyping and linkage map development for any given Malus progeny. To test the applicability of the array for mapping in diverse Malus genotypes, we applied the array to the construction of a SNP-based linkage map of an apple rootstock progeny.

Results

Of the 7,867 Malus SNP markers on the array, 1,823 (23.2%) were heterozygous in one of the two parents of the progeny, 1,007 (12.8%) were heterozygous in both parental genotypes, whilst just 2.8% of the 921 Pyrus SNPs were heterozygous. A linkage map spanning 1,282.2 cM was produced comprising 2,272 SNP markers, 306 SSR markers and the S- locus. The length of the M432 linkage map was increased by 52.7 cM with the addition of the SNP markers, whilst marker density increased from 3.8 cM/marker to 0.5 cM/marker. Just three regions in excess of 10 cM remain where no markers were mapped. We compared the positions of the mapped SNP markers on the M432 map with their predicted positions on the ‘Golden Delicious’ genome sequence. A total of 311 markers (13.7% of all mapped markers) mapped to positions that conflicted with their predicted positions on the ‘Golden Delicious’ pseudo-chromosomes, indicating the presence of paralogous genomic regions or mis-assignments of genome sequence contigs during the assembly and anchoring of the genome sequence.

Conclusions

We incorporated data for the 2,272 SNP markers onto the map of the M432 progeny and have presented the most complete and saturated map of the full 17 linkage groups of M. pumila to date. The data were generated rapidly in a high-throughput semi-automated pipeline, permitting significant savings in time and cost over linkage map construction using microsatellites. The application of the array will permit linkage maps to be developed for QTL analyses in a cost-effective manner, and the identification of SNPs that have been assigned erroneous positions on the ‘Golden Delicious’ reference sequence will assist in the continued improvement of the genome sequence assembly for that variety.
Insights into the evolution of mammalian telomerase: Platypus TERT shares similarities with genes of birds and other reptiles and localizes on sex chromosomes
Authors: Hrdličková Radmila , Nehyba Jiří , Lim Shu Ly , Grützner Frank , Bose Henry R
Published: June 2012

Background

The TERT gene encodes the catalytic subunit of the telomerase complex and is responsible for maintaining telomere length. Vertebrate telomerase has been studied in eutherian mammals, fish, and the chicken, but less attention has been paid to other vertebrates. The platypus occupies an important evolutionary position, providing unique insight into the evolution of mammalian genes. We report the cloning of a platypus TERT (OanTERT) ortholog, and provide a comparison with genes of other vertebrates.

Results

The OanTERT encodes a protein with a high sequence similarity to marsupial TERT and avian TERT. Like the TERT of sauropsids and marsupials, as well as that of sharks and echinoderms, OanTERT contains extended variable linkers in the N-terminal region suggesting that they were present already in basal vertebrates and lost independently in ray-finned fish and eutherian mammals. Several alternatively spliced OanTERT variants structurally similar to avian TERT variants were identified. Telomerase activity is expressed in all platypus tissues like that of cold-blooded animals and murine rodents. OanTERT was localized on pseudoautosomal regions of sex chromosomes X3/Y2, expanding the homology between human chromosome 5 and platypus sex chromosomes. Synteny analysis suggests that TERT co-localized with sex-linked genes in the last common mammalian ancestor. Interestingly, female platypuses express higher levels of telomerase in heart and liver tissues than do males.

Conclusions

OanTERT shares many features with TERT of the reptilian outgroup, suggesting that OanTERT represents the ancestral mammalian TERT. Features specific to TERT of eutherian mammals have, therefore, evolved more recently after the divergence of monotremes.
Use of human amelogenin in molecular encapsulation for the design of pH responsive microparticles
Authors: Bonde Johan Svensson , Bülow Leif
Published: June 2012

Background

Proteins can be used in drug delivery systems to improve pharmacological properties of an active substance. Differences in pH between tissues can be utilized in order to achieve a targeted drug release at a specific location or tissue, such as a tumor. The enamel matrix protein amelogenin has a pH dependent solubility profile and self-assemble to form aggregates at neutral pH. This could make amelogenin useful in the design of pH responsive drug delivery systems.

Results

In this study amelogenin was evaluated as a pH responsive component in drug delivery applications. This was achieved by testing the ability of amelogenin to entrap/release other proteins upon changes in pH, and by testing if amelogenin could confer pH responsiveness to an existing and versatile drug delivery system, such as gelatin microparticles. Amelogenin was able to encapsulate bovine serum albumin and insulin, whichwere used as model target proteins. The composite aggregates of amelogenin and target protein were formed at neutral pH and could be reversibly solubilized at weakly acidic pH. Gelatin microparticles prepared in the presence of amelogenin, showed a modulated structure in response to pH change, when studied by scanning electron microscopy, compared to particles without amelogenin. At neutral pH amelogenin induced formation of pores in the particle surface, which were not present at acidic pH, or in particles lacking amelogenin.

Conclusions

The results from this study demonstrate that amelogenin can be a useful component in drug delivery systems in order to achieve a pH dependent response.
NanoTIO2 (UV-Titan) does not induce ESTR mutations in the germline of prenatally exposed female mice
Authors: Boisen Anne Mette Zenner , Shipley Thomas , Jackson Petra , Hougaard Karin Sørig , Wallin Håkan , Yauk Carole L , Vogel Ulla
Published: June 2012

Background

Particulate air pollution has been linked to an increased risk of cardiovascular disease and cancer. Animal studies have shown that inhalation of air particulates induces mutations in the male germline. Expanded simple tandem repeat (ESTR) loci in mice are sensitive markers of mutagenic effects on male germ cells resulting from environmental exposures; however, female germ cells have received little attention. Oocytes may be vulnerable during stages of active cell division (e.g., during fetal development). Accordingly, an increase in germline ESTR mutations in female mice prenatally exposed to radiation has previously been reported. Here we investigate the effects of nanoparticles on the female germline. Since pulmonary exposure to nanosized titanium dioxide (nanoTiO2) produces a long-lasting inflammatory response in mice, it was chosen for the present study.

Findings

Pregnant C57BL/6 mice were exposed by whole-body inhalation to the nanoTiO2 UV-Titan L181 (~42.4 mg UV-Titan/m3) or filtered clean air on gestation days (GD) 8–18. Female C57BL/6 F1 offspring were raised to maturity and mated with unexposed CBA males. The F2 descendents were collected and ESTR germline mutation rates in this generation were estimated from full pedigrees (mother, father, offspring) of F1 female mice (192 UV-Titan-exposed F2 offspring and 164 F2 controls). ESTR mutation rates of 0.029 (maternal allele) and 0.047 (paternal allele) in UV-Titan-exposed F2 offspring were not statistically different from those of F2 controls: 0.037 (maternal allele) and 0.061 (paternal allele).

Conclusions

We found no evidence for increased ESTR mutation rates in F1 females exposed in utero to UV-Titan nanoparticles from GD8-18 relative to control females.
Re-orienting crop improvement for the changing climatic conditions of the 21st century
Authors: Mba Chikelu , Guimaraes Elcio P , Ghosh Kakoli
Published: June 2012

A 70% increase in food production is required over the next four decades to feed an ever-increasing population. The inherent difficulties in achieving this unprecedented increase are exacerbated by the yield-depressing consequences of climate change and variations and by the pressures on food supply by other competing demographic and socioeconomic demands. With the dwindling or stagnant agricultural land and water resources, the sought-after increases will therefore be attained mainly through the enhancement of crop productivity under eco-efficient crop production systems. ‘Smart’ crop varieties that yield more with fewer inputs will be pivotal to success. Plant breeding must be re-oriented in order to generate these ‘smart’ crop varieties. This paper highlights some of the scientific and technological tools that ought to be the staple of all breeding programs. We also make the case that plant breeding must be enabled by adequate policies, including those that spur innovation and investments. To arrest and reverse the worrisome trend of declining capacities for crop improvement, a new generation of plant breeders must also be trained. Equally important, winning partnerships, including public-private sector synergies, are needed for 21st century plant breeding to bear fruits. We also urge the adoption of the continuum approach to the management of plant genetic resources for food and agriculture as means to improved cohesion of the components of its value chain. Compellingly also, the National Agricultural Research and Extension System of developing countries require comprehensive overhauling and strengthening as crop improvement and other interventions require a sustained platform to be effective. The development of a suite of actionable policy interventions to be packaged for assisting countries in developing result-oriented breeding programs is also called for.
Bidialectalism or Dialect Death? Explaining Generational Change in the Shetland Islands, Scotland
Authors: Smith Jennifer , Durham Mercedes
Published: June 2012

This article investigates the use of traditional dialect forms in a community in Shetland, northern Scotland. Specifically, we seek to establish whether the younger generations' patterns of language use signal rapid dialect obsolescence or bidialectalism. It compares recordings in which audience design is manipulated—the addressee is either an insider or an outsider—across a range of lexical, phonological, and morphosyntactic variables. Results show that only some of the younger speakers are bidialectal: the remaining speakers use virtually no dialect forms. These findings may signal dialect shift and a move from local to standard in the coming generations. The article further explores the linguistic details of the bidialectal speakers' language use through a qualitative and quantitative comparison of forms across the different recordings. It finds that the use of the two varieties operates on a continuum, where rates of use differ but constraints remain the same across the two speech styles. It discusses these findings against the backdrop of bidialectalism and the process of dialect obsolescence in the British Isles and elsewhere.
The Mechanisms for Terrorizing Minorities: The Capital Tax and Work Battalions in Turkey During the Second World War
Authors: Çetinoğlu Sait
Published: June 2012

In this essay policies against non-Muslim minorities implemented during World War II by the Turkish government are analyzed: specifically, the mobilization of minority young men aged eighteen to forty-five years into work battalions from May 1941 to September 1942, as a repetition of the Amele Taburlari during World War I, and the capital tax implemented as a means of economic destruction of the non-Muslim minorities from November 1942 to March 1944. The motivations, conditions, and implementation of both antiminority measures are analyzed and their consequences are presented.
Games, Risks, and Analytics: Several Illustrative Cases Involving National Security and Management Situations
Authors: Paté-Cornell M. Elisabeth
Published: June 2012

This paper presents and compares four models of games and risk analyses designed to support strategic and policy decisions, three focusing on national security issues and one on project management. They share a common core of probability, linked decisions among the parties involved, and risks to a principal decision maker. Their structure is based on systems and decision analysis. Their level of complexity depends on the strategies, the environment, and assumptions of variation over time of probabilities, preferences, and options. They are part of the field of analytics and some of its real-life applications. The first model is based on a one-move game, in which the United States faces risks of terrorist attacks by several possible groups using various types of weapons. The result is a probabilistic ranking, at a given time, of the threat posed by these weapons. The second model is a dynamic simulation of counterterrorism scenarios in an alternate game between a government and a terrorist group. The objective is to compare the stabilizing effects of different short- and long-term government strategies. The third model is a dynamic evaluation of nuclear counterproliferation strategies involving an analysis of the weapon development program of a particular country with evolving intent and capabilities and of the effectiveness of different U.S. strategies to prevent or delay its success. The fourth model is a principal–agent representation of the development of an engineered system, in which an agent in charge of part of the project may consider meeting a deadline by cutting corners if he falls behind schedule, generally increasing the system failure probability. The goal is to support the decisions of the manager in setting constraints and incentives. This paper shows how a set of similar game and risk analysis models at different levels of complexity can provide valuable insights to decision makers, both in national security and management situations, and help them avoid mistakes such as excessive focus on the short term and underestimation of dependencies. It compares their capabilities, including the number of moves, dynamics of the underlying situation, possible changes of context, actors' preferences and strategic options, and risk characterization.
Jazz and race in colonial India
Authors: Dorin Stephane
Published: June 2012

Musical forms such as ragtime and jazz were played in Calcutta’s hotels and clubs, important institutions in elites’ social life in colonial India. The musicians could be European or American, when a foreign band was hired for a season. Some of these formations tended to include Anglo-Indian members. Anglo-Indian musicians acted as go-betweens, passing down the theoretical knowledge of western harmony as well as the practice of western instruments to the generations of post-Independence India. Moreover, they were the first Indian musicians to perform jazz and blues standards in Calcutta or Bombay, around World War II. Thus, they played a major role in the diffusion of jazz and blues music in India.
Jazz in Kuala Lumpur
Authors: Jähnichen Gisa
Published: June 2012

This article will focus on the development from ‘doing’ to ‘making’ jazz in Malaysia’s main urban centre Kuala Lumpur. ‘Doing jazz’ is here understood as ‘doing what the others do’, a practice of creating musical equality with existing practices that are considered ‘up-to-date’ in a small world of self-taught jazz musicians of which some were trained abroad. ‘Making jazz’ goes far beyond this understanding. It aims at creating difference and uniqueness in a conscious way, using individual resources related to local culture and history. However, the polarity between imitative and original has many facets resulting from ethnic, religious and social contradictions within the cultural construction of Malaysia. From this perspective, the role of different racial backgrounds and knowledge bases of various audiences and of jazz personalities, together with their self-perception, needs to be examined. Based on a brief outline of the social background and a concise historical overview, questions of shifting identity as well as of musicianship in the specific urban culture of Kuala Lumpur will be raised and discussed. Does the new generation, facing hegemonic representation, develop racially indifferent attitudes towards jazz or does it aspire to contribute a self-determined individuality, accepting the blurring of borders between global jazz and Southeast Asian popular music?
‘Down with bebop—viva swing!’
Authors: Reimann Heli
Published: June 2012

The study focuses on one particular year in Estonian jazz history—1948. This year marked the start of the pivotal period in Estonian cultural history—the beginning of the most intense ideological pressure in the sequence of the ‘tightening the screws’, as it was referred to metaphorically. This year began a period of the lowest political tolerance jazz has ever experienced in its entire Soviet Estonian history. This study addresses the following questions with particular reference to the Estonian jazz group Swing Club: How was the socio-political turmoil reflected in Estonian jazz life? How did the musicians attune their musical weltanschauung to the creative space provided by this subversive historical moment? How did Estonian jazz musicians realize their creative potential in the conditions of this limited creative freedom?
Effects of Pore Structure to Conventional Well Log Evaluation in Low Permeability Sandstones
Authors: Zhang F. , Liu Xiao-peng , Hu Xiao-xin
Published: June 2012

The conventional well log evaluation is a challenge for geologists and well log analysts in low permeability sandstones at present due to the effect of the complicated pore structure. In this paper, based on the analysis of the laboratory NMR measurements, core experimental mercury injection capillary pressure data, the casting thin-section and the drill stem testing data, the effects of the pore structure to low permeability sandstones can be conclude to form three different types of low contrast hydrocarbon bearing formations, they are low resistivity contrast of gas bearing formations with water saturated layers, the low porosity and permeanility contrast for effective formation with dry layer and the low porosity and resistivity contrast of formations with high productivity layer and low productivity zone. To evaluate low permeability reservoirs responsibly, the information of pore structure should be first obtained.
Risk Minimization when Perforating with Automatic Gun Release Systems
Authors: Baumann Carlos , Dutertre Antoine , Khaira Kuljit , Williams Harvey , Mohamed Hassan N.
Published: June 2012

Each month thousands of perforating jobs are executed without problems; however, certain wells are susceptible to gunshock damage if they are perforated with inappropriate gun systems. This paper presents the application of a simulation program that predicts perforating gunshock loads reliably. This simulation program enables us to evaluate gunshock loads for any perforating job, including gunshock loads sensitivities to changes in gun type, charge type, shot density, tubing or cable size and length, rathole length, use of shock absorbers, and placement of packers, among others.

This simulation program helps engineers to identify perforating jobs that have a risk of gunshock related damage, such as bent tubing, unintentional weak-point pull outs, failures in gun release systems, and unset packers. When predicted gunshock loads are large, changes to the perforating equipment or job execution parameters are sought to reduce gunshock loads and the associated risks. For example, in this paper we present a typical case where a simple change to the guns charge loading transforms a high-risk perforating operation into a very safe one.

A large number of comparisons between predicted wellbore pressure and field fast-gauge pressure data are available in related SPE articles. These comparisons show that predicted wellbore pressure transients are very good, and in most cases where shock absorbers were used, residual deformation of crushable elements correlate well with the peak loads predicted by this simulation program. Additionally, this program is able to simulate perforating job designs in a short time, allowing engineers to optimize perforating jobs in a timely manner.

The ability to predict gunshock-induced damage in deepwater perforating operations is very important because of the high cost of typical wells and rig time. With the gunshock simulation capabilities presented in this paper, engineers can optimize perforating jobs by reducing gunshock loads, thereby the risk of gunshock-related damage and non-productive time.
Application of Bacterial Mat for Optimized Gas Hydrate Recovery at the Sea Surface
Authors: Dubey A. , Saxena A.
Published: June 2012

With increasing energy demand, the oil and gas industry requires new technological developments in the field of unconventional resources along with sustainable development. In this paper we put forward the concept of Bacterial Mat for optimised recovery from marine gas hydrates. Along the India’s 7,500 km of coast line we have vast reserves of gas hydrates which can meet our needs for several centuries. Gas hydrate is a solid compound in which methane is trapped within a crystal lattice of water under high pressure and low temperature condition. The carbon content present in the form of gas hydrates is twice the carbon present in all known fossil fuels of the earth. One litre of gas hydrate contains on an average 168 litres of methane gas at STP.

The primary condition for the stability of gas hydrate is high pressure and low temperature i.e. a minimum depth of 300m and a temperature lesser than 2°C. Several technologies have been experimented for the extraction but the main problem faced was uncontrolled liberation of methane which is a powerful green house gas.

Our suggestion is to use Bacterial Mat for the optimised recovery of gas hydrates. This bacterial mat contains Archae bacteria. These bacteria can survive in extreme environment and can produce methane from CO2 & H2O. This process is exothermic and can raise the temperature to 140°C leading to escape of methane from gas hydrates. These bacteria will breed on an artificial animal intestine mat from which they will get nutrients for growth. The bacterial mat will be sent to the seabed and fixed to the bed with its arms on the edges where gas hydrates are deposited. After achieving the desired saturation of gas, it is produced from the sea surface installation.

The above suggested methodology is an optimised and economical way to recover gas hydrates. Firstly it will help to change the focus of extracting resources from conventional to unconventional resources. Secondly, it will lead to sustainable development and reduce the hazard of global warming to a large extent. Thirdly, this technology has huge potential in the petroleum industry.
Modeling the Effect of Pipe Rotation on Pressure Loss through Tool Joint
Authors: Bui B.
Published: June 2012

Drilling engineers frequently make expensive misjudgment due to improper prediction and control of pressure along the wellbore. The flow of fluid in the wellbore is complicated not only by contraction and expansion through tool joints, but also by the effect of pipe rotation.

Field data has proved the excessive pressure drop through tool joint. Extensive experimental and theoretical studies have been conducted to study the effects of tool joint and pipe rotation on pressure loss along the drillstring. However, there is a discrepancy between published studies about the effect of pipe rotation on pressure drop in pipe and annular flow. For Newtonian fluids, it is well known that pipe rotation does not affect the pressure drop. Nevertheless, for non-Newtonian drilling fluids, several experimental works reported the reduction of pressure loss; while other works reported the increase in pressure loss.

In this study, the flow of drilling fluid through contraction and divergence across the tool joint is investigated using Computational Fluid Dynamics (CFD) software package. Different pipe rotation speeds are used to simulate the flow of an incompressible Yield Power Law fluid in both pipe and concentric and eccentric annuli. The velocity and pressure profiles are analyzed and compared to emphasize the effect of tool joint and pipe rotation on pressure loss. The results show that pressure drop through tool joints is significant. Pipe rotation has small effect on pressure drop at low velocity, and different effects on pressure drop at higher velocity. Positive and negative effects depend strongly on flow geometry and flow velocity.

The results of this study provide valuable information about the flow of drilling fluids through tool joints and along the wellbore. These give useful insight into the effect of pipe rotation and tool joint on pressure drop. Accurate calculation of pressure drop along the wellbore with pipe rotation is highly important in hydraulic program, optimization and well control, especially for deepwater wells.
Influence of Resin/Asphaltene Ration on Paraffin Wax Deposition in Crude Oils from Barrackpore Oilfield in Trinidad
Authors: Garcia-James C. , Pino F. , Marín T. , Maharaj U.
Published: June 2012

The precipitation and deposition of paraffin wax during production, transportation and storage of crude oil are common problems encountered by the majority of oil producers around the world. During the last decade, the Barrackpore oilfield in Trinidad has reported wax deposition on nineteen (19) of its wells. This condition has been exacerbated due to the reduction of temperature, pressures and losses of gas which have allowed wax to separate from the crude oil, precipitate and deposit in the walls of tubings, thereby reducing their diameter and restricting the flow of oil through the system. The situation represented a serious problem for Petroleum Company of Trinidad & Tobago (Petrotrin), because it caused a reduction in the production levels and significant economic losses. This study was based on the necessity to find feasible solutions to minimize this problem. The research was focused to determine if there was influence of the resin/asphaltene ratio on wax deposition under laboratory conditions, to start an understanding process of the causative factors of these depositions. In addition, the influence of two (2) different wax inhibitors were studied for comparison, since it is understood they may behave as resins peptizing the asphaltene particles and keeping them in solution. To ensure the validity of this investigation, extensive bibliographical reviews were undertaken, followed by numerous laboratory tests such as SARA analysis, Cloud Point Tests and Wax Content Tests as methods to evaluate the crude oil and its behaviour under various conditions. The results showed that wax and asphaltene content are the controlling factors in the precipitation and depositions processes respectively.
How Advances in Technology Can Help Safely Abandon Offshore Exploratory Wells in and Around the Caribbean Sea Region
Authors: Segura Richard , Haq Mohammed A. , Durrant Steve
Published: June 2012

All oil and gas wells inevitably shifts from asset to liability, whether the result of reaching its economic limit or sustaining irreparable damage. At the end of its life cycle, a subsea well and its supporting infrastructure must be carefully dismantled to ensure they pose no safety or environmental threats and to salvage useable components. In addition to creating significant safety and environmental hazards, failure to properly abandon a subsea well can lead to a noncompliant status with regulatory agencies and undermine an operator’s image. Despite its multiple liabilities, abandonment offers no real return on investment, underscoring the importance of minimizing cost. The challenge is to retrieve the wellhead without damage so it can be used again, minimizing or eliminating damage not only to the wellhead but also to personnel and environment.

This paper will describe the technological tool system available to retrieve subsea wellheads in a single trip. This technology serves as an alternative to equipment that poses environmental and safety hazards, such as mobile offshore drilling units and explosive severance devices. By latching on to the external profile there is no damage to the internal seals. Also the external latch procedure allows more clearance to allow the cuttings to flow out of the ports and away from the working mechanism. The wellheads retrieved have a much greater chance of being re-used with minimal damage. The external latch design allow for more strength and less chance of tool failure. This paper will also discuss some global case histories.
Frac-packing Shallow Unconsolidated Reservoirs – Onshore Trinidad
Authors: Batohie G. , Maharaj G.
Published: June 2012

This paper presents the results from frac-packing of wells in shallow, unconsolidated reservoirs onshore Trinidad. The objectives of this type of treatment were to improve the initial production rate and consequently the net present value of the wells, as well as mitigate the productivity impairment associated with conventionally gravel packed wells.

Most of Trinidad’s onshore crude oil production is considered to be mature in that the oil reserves are still being produced by primary means with tertiary recovery methods accounting for roughly one third of total production. With declining oil production, there exists the need for higher production rates; frac packing is considered to be one suitable intervention to achieve this goal. In addition, lower skin from frac pack completions in comparison to gravel packs and the ability of the frac pack to maintain this low skin during the life of the well accrues recoverable reserves.

Treatment results show an increase in the average production rate of 200% compared to the pre-fracture rates. There is also a projected increase in recoverable reserves of 8-35% per well due an extended producing life prior to the eventual abandonment rate. The data presented in this paper provides encouraging results for future frac packing on land.
Simulation Study for Optimizing Injected Surfactant Volume in a Miscible Carbon Dioxide Flood
Authors: Afonja Gbolahan , Hughes Richard G. , Nagineni Venu , Jin Lu
Published: June 2012

The viability of any Enhanced Oil Recovery (EOR) method lies with its ability to increase oil recovery in an economically efficient manner. The practicality of carrying out a CO2/surfactant enhanced oil recovery operation is affected by the high cost and large volume of surfactant needed in the field.

This paper presents the results of a numerical simulation study that was carried out to analyze and establish critical parameters that can be used to obtain the minimum but most effective volume of surfactant needed for generation of foam in a porous medium which will in turn yield optimum oil production. The results obtained from laboratory experiments, which were based on the comparison of a low and high injected surfactant concentration, serve as inputs to a reservoir simulator for modeling and estimating surfactant requirements.

Numerical models were designed to simulate the co-injection of carbon dioxide and surfactant solution into a Berea sandstone core that was saturated with brine and oil after a waterflood process. Some of the values of parameters used include surfactant concentrations of 0.1 wt % and 0.5 wt %, average back pressure of 2350 psi and total flowrate of 0.4 cm3/min, with CO2 injected at 0.3 cm3/min and surfactant solution at 0.1 cm3/min, which gives a volumetric flow ratio of 3:1 and foam quality of 75%.

Results indicate that injecting a solution with a larger surfactant concentration increased foam strength with a corresponding increase in pressure drop. A decrease in CO2 relative permeability is also observed as more gas is trapped within the rock due to foam blocking. Carbon dioxide is thereby able to contact more of the oil contained within the reservoir.
Operational Challenges and Lessons Learned From Drilling an Ultradeepwater Wildcat Well in a Logistically Challenging Frontier Environment Offshore French Guiana
Authors: Peters A. , Priestley J.
Published: June 2012

Exploration for hydrocarbons continues to expand into frontier environments. The project management, logistical and supply chain challenges of drilling in these areas is increased due to their remoteness. This paper presents the operational challenges and lessons learned from drilling a successful ultradeepwater wild cat exploration well in a logistically challenging frontier environment offshore French Guiana.
The Role of the Oil and Gas Industry in the Transition Toward a Sustainable World
Authors: Strauss Nicolás
Published: June 2012

Throughout the decades to come world’s population is expected to rise as well as the energetic, food and water demand. All that, together with the everyday more rigid international environmental regulations alongside with the ongoing vertiginous technological advancement, will induce to a restructuration of global economy on the inter-governmental and institutional level in order to reinforce the fundamental pillars of sustainability: the environmental, social and economical. New energy systems will be implemented and scarcity of resources will be more severe, leading the economy not only to shift but to adapt to unconventional energy carriers and commodities. This combined with the targeted impact of these policies, concerning living standard improvements, social inclusion and carbon mitigation among others, will raise new and demanding challenges to face.

This paper intends to present an overview of the energetic playing field throughout the transition towards a more sustainable world and the role of the Oil & Gas industry within this period. This article will identify and explain the challenges and constraints to be faced as well as the opportunities of undertaking ventures in this shifting environment. Also, the paper will broaden the concept of Green Economy, main theme of the 2012 UN’s Conference on Sustainable Development, and present strategies to develop an energy system to function and sustainably endure in time within the mentioned framework and explain why the O&G industry is a fundamental participant and a major "game changer" in this process.

Petroleum holds a key role in this transition as being the most widespread energy carrier and the most competitive element of the current energy system. Therefore, the O&G industry has the opportunity to become the main "driver of change" and to impulse a more prosper and sustainable energy network for the world.

It’s imperative that the O&G sector keeps a long-term perspective in order to remain in force and profitable. This paper proposes some guidelines to do so and intends to raise awareness on the fact that sustainability is not only changing the way we analyze a project but moreover the way we do business in the O&G industry.
A New Generation of Well Surveillance for Early Detection of Gains and Losses When Drilling Very High Profile Ultradeepwater Wells, Improving Safety, and Optimizing Operating Procedures
Authors: Le Blay F. , Villard E. , Hilliard S. , Grønås T.
Published: June 2012

As the industry continues to expand into ultradeepwater plays, an increasing number of tight tolerance wells warrant the use of an efficient system for determining early influxes or losses during drilling, tripping, and cementing operations. The narrow mud weight window for the majority of these wells requires an advanced solution in order to operate in all such conditions without compromising on safety. This paper describes a new early detection flow monitoring system and setup for floating rigs, and presents its application via a case study of a very high-profile ultra deepwater well.

Good well surveillance for floating rigs requires precise measurements combined with an efficient smart process adapted to deepwater conditions in order to raise a reliable alarm in any condition, while minimizing the risk of false alarms. Careful sensor selection and sizing, together with particular attention to installation is required in order to achieve this degree of accuracy for all the drilling phases. The solution described in this case study provides drilling surveillance for all hole sizes, with flow up to 2000 gpm for accurate and early detection, and significantly increased safety during drilling, tripping, and cementing operations.

This case study describes how kicks can be detected with a high degree of reliability much earlier than with the standard pit volume and flow paddle monitoring. In addition to this, it has shown its value by characterizing, in real time, the consequences following a packoff event and also by differentiating between a wash out and pump failure.

Crew confidence in this detection system rapidly led to modifications of the operational procedures. For instance, flow checks were previously done for every pipe connection, taking up expensive rig time. Due to results obtained in the previous hole sections, the drilling procedures were updated in order to significantly reduce time spent flow-checking, while still maintaining maximum safety during the operations.
Understanding Trinidad Gas Reservoir Performance: Mango, Mahogany, and Immortelle Field Water Drive Reservoir Anomalies
Authors: Roopa I. , Khan Z. , Baksh K.
Published: June 2012

The Mango, Mahogany and Immortelle Field gas and condensate fields are located in the Columbus basin, 35-40 miles off the southeast coast of Trinidad in water depths of between 200 to 300 feet. All reservoirs are comprised of highly faulted stacked sandstone reservoir units of varying ages between Quaternary to Pleistocene. Most reservoir units are less than 0.5 tcf and are usually produced by one or two wells.

The permeability of these reservoirs varies from 10 – 2000 mD and due to the presence of both edge and bottom aquifer, water drive and subsequent water breakthrough prediction is key to understanding reservoir performance and reserves estimation. Some of the reservoirs in the Mango, Mahogany and Immortelle Field gas fields have tendencies toward pressure maintenance by natural water drive. The resultant effect of this phenomenon is not often readily apparent in the early stages of gas production.

This paper examines methods used in recognizing and evaluating this type of reservoir. The methodology here is to apply simple classical techniques before complex reservoir characterization and time consuming reservoir simulation models are built since it is not often necessary. The results of the comparison indicate the presence or absence of water drive. Results are illustrated using actual field data. It shows the "text book" Mango Field case compared to water drive anomalies from the Mahogany and Immortelle Fields; where the drive mechanism have historically been misunderstood. The earliest possible detection of water drive allows strategies to be formulated to achieve optimum conservation and economic benefits.
A General Model of Estimating Permeability from Mercury Injection Capillary Pressure (MICP) in Low Permeability Sandstones
Authors: Zhang Feng , Liu Xiao-peng , Hu Xiao-xin
Published: June 2012

Permeability is a very important input parameter for reservoir evaluation and productivity prediction. It’s a great challenge for permeability prediction due to the heterogeneity at present, especially in low permeability sandstones. Flow unit method can be used to classify core samples into six types to establish permeability estimation formulae, but how to calculate flow zone indicator (FZI) is a difficulty. In this paper, based on the analysis of the mercury injection capillary pressure (MICP) data, which are drilled from three different of basins, the linear function between the Swanson parameter and the pore structure index ((K/ϕ)) is found to be ubiquitous, and a general linear model is established to estimate air permeability. This model is usable not only in low permeability reservoirs, but also in any conventional formations. We also compare the relationship between the Swanson parameter with the air permeability directly, and the conclusion is that with the pore structure index brought in, the accuracy of permeability estimation is great improved.
Evaluation of Nondarcy Skin Correlations for Gas Wells in the Trinidad East Coast Marine Area
Authors: Martínez D. , Guerrero A. , Azuaje E. , Persad S. , Ramkissoon C.
Published: June 2012

Rate dependent skin is a key factor influencing the deliverability of gas producing wells because of the phenomena of high velocity flow behavior around a limited, near wellbore cross-sectional area. Forchheimer (1901) [1] proposed an additional factor in Darcy’s original equation to account for the pressure drop due to high velocity flux in the porous media, known as "Inertial Resistance Factor (β)", which is now a determinant parameter in the flow modeling of gas wells. Several authors have developed different correlations that account for the inertial forces acting under these producing conditions.

Multi-rate and Pressure Transient Analysis (PTA) evaluation was performed on nine (9) gas well tests in the Dolphin Field. The Non-Darcy Flow Coefficient (NDFC) obtained was compared with predicted NDFC’s using 18 Beta (β) correlations, where each correlation has its own assumptions and determinant parameters.

Existing correlations do not match the actual NDFC in the field, as a consequence, a new Inertial Resistance Factor Correlation (IRFC) is proposed for assessing the unknown NDFC in the ECMA fields with a minimum percentage error of 17%.

The following study will detail the results of a probabilistic approach which uses correlations to provide a better estimate of NDFC in the Dolphin field, with the final objective of reducing uncertainty in forecasting production on recompletions and new wells in East Coast Marine Area fields.
Good Practices: Energy Costs Management in Refineries
Authors: Cabrera J. D , Saray R.
Published: June 2012

The adoption of good practices to effectively manage energy costs in refining operations is highly recommended when downstream investments are being planned; this applies not only for new operations but when technology upgrades are being considered for existing plants.

Nowadays, 40% of the total operating costs in a refinery are coming from energy consumption; this causes a huge impact in the business´ P&L. In addition to the financials, the environment is heavily impacted by the emission of pollutant gases directly related to combustion as these emissions are 38% of the total emissions released by a refinery operation.

For any investment in the refining business, it is necessary to have a set of good practices that not only support the operation but also support the strategic planning in an integrated fashion. The proposed set of good practices to optimize the energy costs includes infrastructure monitoring and surveillance routines that are fully integrated with the maintenance, quality and production management processes. The most innovative contribution of this approach is the interaction and integration with the refinery´s business plan in the short, medium and long term; this holistic approach will allow the management team to measure and plan the investments in an structured way while controlling effectively the energy costs of their operation.

The intensive use of a comprehensive framework for energy management including information technology solutions and human resources training have achieved savings for up to 15% in annual energy costs. This is not only an outstanding financial result but also an impressive achievement for the HSE performance as the greenhouse effect gases emission was dramatically reduced.

A description of these good practices is detailed in the paper along with the most relevant operational, financial and HSE KPIs required to efficiently managing the energy costs in a refinery.