bluuebunny/crossref_metadata_2025 huggingface dataset:
Airway Expression of the Epithelial Sodium Channel α-Subunit Correlates With Cortisol in Term Newborns
Authors: Janér Cecilia , Pitkänen Olli M. , Helve Otto , Andersson Sture
Published: July 2011

BACKGROUND:

Glucocorticoids have profound effects on lung maturation and function. In in vitro and animal models, they induce epithelial sodium channels (ENaCs) in the airway epithelium, a process that is important to perinatal lung fluid clearance.

OBJECTIVE:

The objective of this study was to determine whether, in newborn infants, airway ENaC expression is associated with cortisol concentrations.

METHODS:

Cord blood, saliva, and cells from nasal epithelium were obtained from 69 infants delivered at term. Epithelial and saliva sampling was repeated 3 times: <3, 22 to 29, and 40 to 54 hours postnatally. Cortisol, thyrotropin, and free triiodothyronine concentrations were measured with immunoassays, and expression of α-ENaC and β-ENaC was quantified with real-time reverse-transcriptase polymerase chain reaction.

RESULTS:

Expression of α-ENaC <30 minutes postnatally correlated with cord plasma cortisol in infants delivered by elective cesarean delivery. In addition, in the total study population <2 hours postnatally, α-ENaC expression correlated with salivary cortisol concentrations. β-ENaC expression, in contrast, showed no association with cortisol concentrations. A significant decrease in β-ENaC expression during the first postnatal day was revealed, whereas timing of the peak in α-ENaC expression seemed to depend on mode of delivery.

CONCLUSIONS:

These results support a role in humans for endogenous glucocorticoids in the regulation of airway ion transport. This finding may be a physiologic mechanism mediating pulmonary adaptation in the newborn infant.
Use of a Nuclear Marker to Assess Population Structure in Hessian Fly (Diptera: Cecidomyiidae)
Authors: Johnson Alisha J , Morton Philip K , Schemerhorn Brandon J , Shukle Richard H
Published: July 2011

Mayetiola destructor (Say) (Diptera: Cecidomyiidae), the Hessian fly, is distributed across most of the wheat (Triticum aestivum L.)-growing areas of the world and can cause significant yield losses in wheat production. Native to the Old World, Hessian fly reportedly came to the United States in a single introduction during the Revolutionary War and has since spread across North America. Using a nuclear marker, the population structure of North American Hessian fly was examined with regard to collections from the Old World. White intron 1 (wint1) showed insignificant recombination within collections and a large number of informative characters, allowing its use as a phylogenetic marker. Thirty-three alleles of wint1 were identified. Population structure analyses divided the collections into four populations: Middle East, Old World I, Old World II, and New World. More variation was found within populations than between populations, indicating that gene flow exists between local areas. However, shared ancestral characteristics resulted in mixing of Hessian fly collections into more than one population as revealed by the population structure reconstruction. North American and Spanish collections were a mixture of the Old and New World populations. With the sharing of ancestral characters as well as wint1 alleles, this study indicates that the North American lineage may actually be associated to an unsampled location, perhaps northern Europe. If the single introduction hypothesis were correct, then both lineages would have to have been present at the time of introduction.
Distributions of Competing Container Mosquitoes Depend on Detritus Types, Nutrient Ratios, and Food Availability
Authors: Murrell Ebony G , Damal Kavitha , Lounibos L P , Juliano Steven A
Published: July 2011

Coexistence of competitors may result if resources are sufficiently abundant to render competition unimportant, or if species differ in resource requirements. Detritus type has been shown to affect interspecific competitive outcomes between Aedes albopictus (Skuse) and Aedes aegypti (L.) larvae under controlled conditions. We assessed the relationships among spatial distributions of detritus types, nutrients, and aquatic larvae of these species in nature. We collected mosquitoes, water, and detritus from artificial containers across 24 Florida cemeteries that varied in relative abundances of Ae. aegypti and Ae. albopictus. We measured nutrient content of fine particulate organic matter in water samples as total N, P, and C and ratios of these nutrients. We quantified food availability via a bioassay, raising individual Aedes larvae in the laboratory in standard volumes of field-collected, particulate-containing water from each cemetery. Quantities of detritus types collected in standard containers were significant predictors of nutrients and nutrient ratios. Nutrient abundances were significant predictors of relative abundance of Ae. aegypti, and of larval survival and development by both species in the bioassay. Survival and development of larvae reared in particulate-containing water from sites decreased with decreasing relative abundance of Ae. aegypti. These data suggest that N, P, and C availabilities are determined by detritus inputs to containers and that these nutrients in turn determine the feeding environment encountered by larvae, the intensity of interspecific competition among larvae, and subsequent relative abundances of species at sites. Detritus inputs, nutrients, and food availability thus seem to contribute to distributions of Ae. aegypti and Ae. albopictus in cemetery containers throughout Florida.
Reproductive Isolation between Two Populations ofSpodoptera frugiperda(Lepidoptera: Noctuidae) Collected in Corn and Rice Fields from Central Colombia
Authors: Velásquez-Vélez M I , Saldamando-Benjumea C I , Ríos-Diez J D
Published: July 2011

Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a Neotropical moth that has diverged into corn, Zea mays L., and rice, Oryza sativa L., host strains because these plants are their most frequently used hosts. The corn strain also has been found in cotton, Gossypium hirsutum L., and sorghum, Sorghum bicolor (L.) Moench, and the rice strain in small grasses and pasture grasses. Studies of the reproductive isolation between these two strains have provided ambiguous results from populations in the United States. In Colombia, we tested pre- and postzygotic isolation in these strains. Both strains showed postzygotic isolation for several life-history traits, including number of egg masses, number of larvae, number of females, pupal developmental time, female and male longevity, and female and male pupal weight. We observed a reduction of the number of hybrid females and a reduction in fertility in hybrids in S. frugiperda. These results suggest the possibility of Haldane's rule. Heterosis in the F1(2) and F2(1) generations was observed for number of larvae and adult longevity. This line presented a high standard deviation, suggesting instability in this cross. A possible effect of the X chromosome may explain the reduction in viability and sterility in F1 hybrids of host strains of S. frugiperda. No temporal isolation was observed between the corn and rice strains. Differences in longevity between corn and rice strains might be another form of temporal isolation between these strains, because differences in adulthood time might reduce the encounters between them and thus hybridization.
The Complete Mitochondrial Genome of Grapholita molesta (Lepidoptera: Tortricidae)
Authors: Son Yerim , Kim Yonggyun
Published: July 2011

The complete mitochondrial DNA (mtDNA) sequence of the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), has been identified. The mtDNA (15,717 bp) of G. molesta encodes 13 putative proteins, two rRNAs, and 22 tRNAs. Analysis of nucleotide composition of the genome indicates high A+T composition (80.74%), which results in biased codon use and richness in specific amino acids of mitochondrial proteins. All protein-coding genes are initiated by ATN codons except for COI, which is initiated presumably by CGA codon. Except tRNASer (AGN), the remaining 21 tRNAs form a typical cloverleaf structure. An intergenic space between tRNASer (AGN) and ND1 contains a lepidopteran-characteristic sequence (ATACTAA). The control region, rich in A+T, harbors several sequence characteristics shared by lepidopteran species, such as the motif ATAGA followed by 5′ poly T stretch and 3′ poly A stretch at just upstream of tRNAMet. The phylogenetic analysis, using whole mtDNAs, showed that G. molesta is clustered with other tortricid species, in which lepidopterans form a monophylogeny on the basis of Papilionoidea.
Host Associations of Thysanoptera with Paspalum distichum and Paspalum notatum (Poales: Poaceae)
Authors: Sharma Jyotsna , Paini Dean , Funderburk Joe , Mound Laurence
Published: July 2011

The western flower thrips, Frankliniella occidentalis (Pergande); flower thrips, Frankliniella tritici (Fitch); and tobacco thrips, Frankliniella fusca (Hinds), are abundant, polyphagous species in the southern United States. Paspalum notatum Flugge and Paspalum distichum L. (Poales: Poaceae) are low-maintenance, warm-climate, tolerant grasses that are used for pasture and residential lawns and along roadsides. The potential of P. notatum and P. distichum to serve as sources of the common polyphagous Frankliniella thrips in the southeastern United States was evaluated. The abilities of F. fusca, F. occidentalis, and F. tritici to survive and reproduce on vegetative-stage P. distichum, P. notatum ‘Argentine’, P. notatum ‘Pensacola’, and P. notatum ‘Tifton 9’ were compared in laboratory no-choice tests. Survival of the adults of each thrips species was ≈20% after 12 d on each of the Paspalum treatments. No progeny were produced by F. occidentalis on the U.S. native P. distichum, and the other thrips species produced very few progeny on this host. The number of progeny of each thrips was very low on all P. notatum cultivars. A field survey of the Thysanoptera associated with P. notatum Argentine also was conducted to determine whether the Frankliniella thrips were feeding or reproducing under field conditions. A few male and female adults of F. tritici and F. fusca were noted in the racemes, but larval populations were not observed. Reproducing populations of Caprithrips insularis Beshear and Haplothrips graminis Hood were present in the stems and leaves, and the racemes, respectively. Collectively, the laboratory and field studies revealed that the tested P. notatum cultivars and P. distichum accession are poor hosts for reproduction of the Frankliniella thrips in the southern United States and that the large plantings of these grasses are not serving as sources of pest Frankliniella thrips.
Life History and Laboratory Rearing of Mecidea minor (Hemiptera: Heteroptera: Pentatomidae), with Descriptions of Immature Stages
Authors: Scott Bundy C , McPherson J E
Published: July 2011

The life history of the stink bug Mecidea minor Ruckes (Hemiptera: Heteroptera: Pentatomidae) was studied in the southern half of New Mexico from January 2005 to December 2007, and the egg and nymphal instars are described. This species was active year-round, occurring on various species of grasses but primarily on Lehmann lovegrass, Eragrostis lehmanniana Nees; grama grasses (Bouteloua spp.); Bermuda grass, Cynodon dactylon (L.); and tobosagrass, Pleuraphis mutica Buckley. Adults and late instars (fourth and fifth) were present during winter. The appearance and abundance of the eggs, nymphs, and adults during the year suggest this species is bivoltine with the possibility of a partial third generation. Instars can be distinguished by differences in morphological features, including body size and presence and relative development of wing pads.
Effects of Nutrition on Lifelong Sleep and Activity Patterns in Drosophila melanogaster (Diptera: Drosophilidae)
Authors: Haselton Aaron T , Halpern Richard , Vinson Ryan , Klein Regina
Published: July 2011

Drosophila melanogaster (Meigen) (Diptera: Drosophilidae) exhibits several welldefined sleep parameters and a sleep:wake rhythm strength cycle that fragments and deteriorates with age. Because many aspects of functional senescence may be linked to the effects of accumulated oxidative damage, and as several lines of experimental evidence indicate that sleep parameters and sleep:wake rhythm strength may be modulated by oxidative stress in D. melanogaster, it has been postulated that sleep fragmentation is driven, at least in part, by accumulated oxidative damage in this fly. We investigated the contrasting effects of an enriched dietary regime that is likely to exacerbate processes associated with aging and oxidative damage accumulation, and a dietary restriction regime that has been demonstrated to delay the detectable effects of aging-related damage on lifelong sleep and activity patterns in male and female D. melanogaster. We found that female flies on a nutrient-rich dietary regime exhibited stronger sleep:wake cycles than females on a dietary restriction regime and that dietary restriction did not seem to alter the initiation of sleep fragmentation in female or male D. melanogaster.
Fine Structure and Distribution of Antennal Sensilla of Longicorn BeetlesLeptura arcuataandLeptura aethiops(Coleoptera: Cerambycidae)
Authors: Zhang Jian , Guan Lin , Ren Bingzhong
Published: July 2011

The longicorn beetles Leptura arcuata Panzer and Leptura aethiops Poda (Coleoptera: Cerambycidae) are predominant pollination beetles in Eurasia and North America. To further elucidate the mechanism of mate and host location, the type, number, and distribution of antennal sensilla of both species of the longicorn beetles were studied using scanning electron microscopy. The filiform antennae of both sexes of the both species consist of the scape, pedicel, and nine flagellomeres. Based on their morphology, three types of sensilla chaetica, one type of sensilla trichodea, four types of sensilla basiconica, and Böhm bristles were distinguished on the antennae in both sexes. No significant sexual differences in the types, numbers, and distribution of the antennal sensilla were found on the antennae, except for the number of sensilla basiconica type 2. The average number of sensilla basiconica type 2 on the antennae of the males was significant greater than that on the antennae of the females. Based on the ultrastructure we postulated that this type of sensillum on the male beetle's antennae should be responsible for the reception of the sex pheromone produced by the female beetle. The putative functions of other sensillar types also are discussed with reference to their morphology, distribution, and ultrastructure.
Feeding and Life History of Alabama argillacea (Lepidoptera: Noctuidae) on Cotton Cultivars Producing Colored Fibers
Authors: Nascimento ARB , Ramalho F S , Azeredo T L , Fernandes F S , Júnior J L Nascimento , Silva CAD , Malaquias J B
Published: July 2011

Quantitative analysis of the consumption and use by herbivore pest's of the host plant is a common tool used for studying the interaction between insects and plants. Our goals were to quantify cotton leafworm, Alabama argillacea (Hübner) (Lepidoptera: Noctuidae), larval consumption rate in three cotton, Gossypium hirsutum L., cultivars that produce colored cotton fibers, and the effects of the consumption rate on A. argillacea pupal weight in greenhouse conditions. Larvae consumed a maximum of 0.69–1.03 g of leaf tissue over a 24-h period in all cultivars tested. Total consumption by A. argillacea larvae was highest when fed with ‘BRS 200’ leaves (2.89 g) and the lowest when fed with leaves from ‘BRS Safira’ (2.26 g). The regression analysis showed significant relationships between the quantity of leaf tissue consumed and pupal weights for each cotton cultivar. A. argillacea larvae fed on BRS 200 demonstrated a longer developmental period (14.84 d) than larvae fed on ‘BRS Rubi’ leaves (11.62 d) or BRS Safira (11.14 d). We concluded that BRS Safira presents the best quality food source for A. argillacea, BRS 200 is the worst, and BRS Rubí is intermediate. The longer developmental times of A. argillacea on BRS 200 may allow longer windows of opportunity for the use of biological control agents to reduce the damage caused by this pest and also would complete less generations per phenological cycle of the cotton crop.
Life History, Development, and Rearing ofEucryptorrhynchus brandti(Coleoptera: Curculionidae) in Quarantine
Authors: Herrick N J , Salom S M , Kok L T , McAvoy T J
Published: July 2011

Eucryptorrhynchus brandti (Harold) (Coleoptera: Curculionidae) was identified in China and studied in quarantine in the United States as a potential biological control agent for the invasive weed, tree of heaven, Ailanthus altissima (Mill.) Swingle (Sapindales: Simaroubaceae). Studies on its general biology and development, and the most efficacious rearing method were conducted. E. brandti is univoltine. The metathoracic sternite and first abdominal segment are convex in females and concave or flat in males. Females are larger than males. Female and male sagittal measurements averaged 11.50 ± 0.14 (± SEM) and 10.35 ± 0.09 mm, respectively. Transversal measurements averaged 4.22 ± 0.06 and 3.73 ± 0.05 mm for females and males, respectively. Mean weight of females and males were 0.10 ± 0.003 and 0.07 ± 0.002 g, respectively. Females lived longer than males, averaging 66.3 ± 6.8 d and 46.5 ± 7.3 d, respectively. The egg stage averaged 5.0 ± 0.9 d, and the larval stage had six stadia and developed in 110 ± 15.0 d; the pupal stage was 16 ± 7.0 d at 25°C. A method for rearing E. brandti on cut A. altissima billets under quarantine conditions was developed. The most efficient egg-to-adult rearing method involved caging 12 males and 12 females or 24 males and 24 females for 7 d on 23-92-cm-long billets. Duration up to 3 wk after cutting did not affect adult emergence. This information will facilitate laboratory rearing and conducting host specificity tests to determine agent impact on nontarget species.
Redefinition of the Genus Dolichocybe (Acari: Dolichocybidae), with Description of Two New Species Associated with Insects
Authors: Rahiminejad Vahid , Hajiqanbar Hamidreza , Fathipour Yaghoub
Published: July 2011

The genus DolichocybeKrantz, 1957 (Acari: Heterostigmatina: Dolichocybidae) is redefined and two new species associated with beetles (Insecta: Coleoptera) are described from Iran: Dolichocybe silvani Rahiminejad & Hajiqanbar n. sp. associated with Silvanus sp. (Coleoptera: Silvanidae) and Dolichocybe varkana Rahiminejad & Hajiqanbar n. sp. associated with Corticeus unicolor Piller & Mitterpacher, 1783 (Coleoptera: Tenebrionidae). It is first record of the association between beetles of the family Silvanidae and Tenebrionidae and mites of the family Dolichocybidae. Also, it is first record of phoresy in the genus Dolichocybe. Chaetotaxy of tarsus I of the genus is discussed, host associations of the dolichocybids with insects are reviewed, and keys to the genera of the family and species of the genus Dolichocybe are presented.
Botanophila—EpichloëInteraction in a Wild Grass,Puccinellia distans, Lacks Dependence on the Fly Vector
Authors: Górzyńska Karolina , Lembicz Marlena , Olszanowski Ziemowit , Leuchtmann Adrian
Published: July 2011

In grass-infecting Epichloë (Ascomycetes: Clavicipitaceae) fungi, the transfer of spermatia for fungal fertilization depends on an insect vector: flies of the genus Botanophila (Diptera: Anthomyiidae). The flies use the fungal stroma, a spore-producing fungal structure surrounding the grass inflorescence, for laying eggs and as a food source for both adults and larvae. This fly—fungus interaction is generally regarded as obligatory and mutualistic. Two Botanophila taxa were noted among four populations of the nonagricultural grass Puccinellia distans (L.) Pari, that were infected with the fungus Epichloë typhina (Pers.) Tul. However, during the 7 yr of field observations, Botanophila flies were present every year in only one population of P. distans. The number of eggs per stroma ranged from zero to four and differed with year and site. Overall, eggs (or larvae) were observed on only 132 (19.2%) of the 687 stromata examined during the survey, with one (13.8%), two (4.5%), or more than two (0.9%) per stroma. However, 90.8% of the examined stromata were fertilized and produced perithecia, suggesting that other mechanisms or vectors of spermatia were responsible for fertilization.
Temporal Changes in Genetic Variation of Boll Weevil (Coleoptera: Curculionidae) Populations, and Implications for Population Assignment in Eradication Zones
Authors: Choi Sung Kyoung , Kim Kyung Seok , Lee Hang , Adamczyk John J , Greenberg Shoil M , Westbrook John K , Sappington Thomas W
Published: July 2011

An existing microsatellite genotype database has been used for several years in population genetic assignment analyses of boll weevils, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), captured in eradication zones. It is important to update it in case of changes in genotype frequency at any of the locations over time. Such changes at neutral loci could be caused by drift, immigration, or population bottlenecks. We examined allele frequency distribution for 10 microsatellite loci to determine genetic differentiation among 10 boll weevil populations sampled from Texas and Mexico in 2009. In addition, temporal changes in genetic composition were examined in the eight populations for which samples were available from previous years. Substantial levels of spatial genetic structure were observed, with the 10 populations clustering as four major groups. Pairwise FST estimates in 2009 samples ranged from 0.001 (College Station-Cameron) to 0.492 (College Station-Ojinaga). There was little change in genetic profiles over time at four of the eight locations. Thus, for those four locations, genotype and allele frequency data can be pooled over the two sample dates, which will provide greater statistical power in future population assignment tests. However, genetic profiles changed substantially at Ojinaga, and to a lesser extent at Uvalde, Cameron, and Rosales, so the 2009 genotype data should be substituted in future analyses. Finally, populations from two new locations, Brownsville and Lockhart, TX, were sampled, genotyped, and added to the database. The addition of Lockhart is particularly important given its surprisingly high differentiation from the relatively nearby populations of Cameron and Uvalde.
Revision of Family Helotidae (Coleoptera: Cucujoidea): VI. Candezei Group of the Genus Neohelota
Authors: Lee Chi-Feng , Votruba Petr
Published: July 2011

The candezei species group of Neohelota Ohta is revised. Six species are recognized, including one described herein, Neohelota jakli sp. nov., from Indonesia (Sumatra). Helota claudiae Nguyen-Phung, 1985 is placed as junior synonym of Neohelota candezei (Ritsema, 1899), and Helota jocelynae Nguyen-Phung, 1985 as a junior synonym of Neohelota montana (Ohta, 1929). Lectotypes are designated for Helota krugeriRitsema, 1900; Helota margarethaeRitsema, 1900; and Helota mariae Ritsema, 1899. A key for the candezei species group is provided. Figures of protibiae, genitalia, internal sacs, eighth abdominal tergites, and fifth abdominal ventrites are given for all species.
Short-Term, Efficient Sampling Strategies for Estimating Forest Moth Diversity using Light Traps
Authors: Ozaki Kenichi , Sayama Katsuhiko , Ueda Akira , Ito Masato , Tabuchi Ken , Hironaga Teruhiko
Published: July 2011

Evaluation of species diversity for highly diverse taxa is extremely time-consuming and costly; thus, there is a need to develop efficient sampling strategies. We established a short-term, efficient sampling scheme to produce samples that represent a full-season sampling of moth assemblages with a high degree of seasonality. We sampled adult moths monthly for the duration of the moth flying season by using light traps in five forest stands in a cool-temperate region in central Hokkaido, northern Japan. From this sample, we generated various subsamples that reduced the sampling period and the number of traps per stand, and tested whether these subsamples provide estimates of species richness, abundance, and species turnover representative of those revealed by the whole season sample. Comparisons between the whole season sample and each subsample indicated that setting one light trap on a night in July and August, which shortened the sampling period to 25% and reduced sample size to 38%, was the most efficient sampling scheme to estimate abundance, species richness, and similarity in the whole season sample. The comparisons also suggest that it is efficient to use rarified species richness as a species richness estimator, and the Bray—Curtis index or Morisita's Cλ for estimating species turnover between sites in moth assemblages.
Mechanistic Study of Improved Heavy Oil Recovery by CO2-Foam Injection
Authors: Emadi Alireza , Sohrabi Mehran , Jamiolahmady Mahmoud , Ireland Shaun , Robertson Graeme
Published: July 2011

CO2 injection is a relatively well-established oil recovery method but it has been mainly applied to conventional (light) oil reservoirs where the displacement of the oil by CO2 is likely to be miscible. Application of CO2 injection in heavy oil reservoirs has received much less attention and hence the performance of CO2 injection in these reservoirs has not been evaluated. Due to a much larger viscosity difference between CO2 and heavy oil, reservoir sweep efficiency is expected to be lower than that in conventional reservoirs. Moreover, CO2 is not expected to develop miscibility with heavy oil and hence displacement efficiency is also expected to be lower in heavy oil reservoirs. However, one major advantage of injection of CO2 in heavy oil reservoirs is the well-documented substantial drop in the viscosity of heavy oil when mixed with CO2 which is much larger than that in light oil.

To alleviate the problem of adverse mobility ratio, CO2 injection in heavy oil reservoirs needs to be augmented by other recovery techniques. The use of foam to improve sweep efficiency during CO2 injection seems a logical way to displace the CO2-diluted oil out of the porous medium. Foam has the potential to improve the sweep efficiency of the injected gas by reducing the effects of low gas viscosity and reservoir heterogeneity. Application of foam injection for increased heavy oil recovery has not been widely reported before and hence the ability of foam formation in the presence of heavy oil and its potential to increase heavy oil recovery is by and large untested.

In this paper, we present the results of a series of visualization experiments carried out in high-pressure transparent micromodels to investigate the performance of subcritical CO2 and CO2-foam injection in heavy oil. Pore-scale interactions of CO2-foam/surfactant/heavy oil and mechanisms of displacement, flow and oil recovery are presented through vivid micromodel images. The results show that in addition to increasing sweep efficiency, there are also microscopic mechanisms taking place during the displacement of oil by CO2-foam that can significantly impact the performance of foam injection in heavy oil reservoirs. Furthermore, we reveal that the displacement efficiency strongly depends on the stability of the foam and if strong foam is not formed, it will drop drastically. The results of these direct visualization experiments improve our understanding of the process of heavy oil recovery by CO2-foam injection under various injection strategies. Extended CO2 injection in heavy oil reservoirs can offer a viable method for increasing heavy oil recovery. It can also be used as a method for combining EOR and CO2 storage by capturing CO2 from nearby industrial sources (e.g., steam generator for nearby steam-based heavy oil recovery method).
Investigation Of The Effect Of Some Parameters In Miscible WAG Process Using Black-Oil And Compositional Simulators
Authors: Namani M.. , Kleppe J..
Published: July 2011

Miscible gas injection in oil fields in general results in a better microscopic displacement efficiency compared to water injection; however, higher mobility ratio and lower macroscopic sweep of gas is a major disadvantage compared to water injection. Considering this situation, water alternating gas (WAG) was proposed and implemented as a method to improve macroscopic sweep efficiency of gas using cyclic water injection to reduce its high mobility ratio.

In this simulation study, a systematic parameter study was carried out to investigate the effect of different parameters in a miscible WAG process using a horizontal sector model and both black-oil and compositional simulators. The base model was first built using a black-oil simulator but a compositional model was later implemented in order to investigate the differences in results for the two models.

This study shows that WAG injection is advantageous compared to both water and gas injection in term of oil recovery factor. Changes of cycle time did not affect the recovery factor significantly while in this particular model recovery is sensitive to the changes of gas half cycle time. It is not possible to find a simple dependency between half cycle time and oil recovery factor but it is obvious that recovery factor is a function of both gas slug size and half cycle time and that an optimum value exists for each case. The effect on recovery by changes in water half cycle time is on the other hand not significant.

Injection of water through all layers improved the advance of stable front and improved final oil recovery for all cases. However, the gas injection interval needs to be optimized for each case based on the ratio of vertical and horizontal permeabilities of the reservoir, and thus the injection perforation strategy for gas must take this into consideration.

In the model used, which has no aquifer or gas cap, increased dynamic forces by simultaneous increase of field production and injection rates resulted in increased oil recovery.

There is good consistency between black-oil and compositional base models with only ±4% OIIP differences in term of field oil recovery.
EOR vs. Infill Well Drilling: How to Make the Choice?
Authors: Alusta Gamal , Mackay Eric , Fennema Julian , Collins Ian
Published: July 2011

It is a common observation that operating companies are reluctant to use EOR techniques when they have the option of infill well drilling instead. Reasons for this include the advances in technology that allow accurate prediction of where unswept reserves are located. Other factors include the quicker recovery of the investment, and the fact that oil companies are well experienced in judging the risk and possible returns associated with drilling wells, whereas quantification of the risk and possible returns from EOR projects is difficult to calculate in advance and to evaluate once in place. However, are the oil companies missing opportunities for maximising return on their investment, and are there limitations in the way in which risk is evaluated which inherently favour infill well drilling?

This study involved setting up a range of EOR scenarios, performing reservoir calculations to evaluate additional recovery and then making a comparison with infill drilling to maximise recovery from mature assets. This paper develops an understanding of how the economic comparison should be performed, since the timescales for investment and return on investment and the associated risks and uncertainties are different for EOR projects and infill well drilling. One driver is whether the oil price is relatively high or low. The method involves studying a range of scenarios, selecting appropriate EOR techniques and modelling the impact these techniques have on recovery, and then running calculations of the impact of various options. An economic assessment is made of the costs and risks of the various options together with expected return under a range of economic scenarios.

For illustration, a synthetic reservoir simulation model is developed to study the impact of polymer flooding vs. waterflooding. Various uncertainties are tested, and the results are fed into an economic model for an evaluation of sensitivity to various parameters.

This was done for polymer flooding, but the approach could be used for other EOR techniques also.
Recovery Processes of Extra Heavy Oil - Mechanistic Modelling and Simulation Approach
Authors: Foo Y. Y. , Chee S. C. , Zain Z. M. , Mamora D. D.
Published: July 2011

Heavy/ extra heavy oil has captured the global attention as an unconventional hydrocarbon resource which may satisfy the ever-increasing energy demand in the future. Heavy/ extra heavy oil is often characterized as viscous and immobile fluid with high content of impurities and heavy metals, such as Nickel and Vanadium. These inherited characteristics impose great challenges not only to oil recovery optimization, but also various costs pertaining to downstream processing. Due to this fact, reservoir modelling and simulation are commonly conducted to evaluate the performances of enhanced recovery processes at early project stage. In this paper, the conceptual models for Oilfield Alpha are developed using CMG STARS reservoir simulator. They are grouped into 3 categories, i.e. (I) Horizontal wells, (II) 5-spot pattern vertical wells and (III) Horizontal well pairs, based on the nature and well configuration of the recovery techniques. These techniques are Horizontal Well (HORZ), Steam Flooding (SF), Cyclic Steam Stimulation (CSS), Steam Assisted Gravity Drainage (SAGD), Vapour Extraction (VAPEX) and some of their variations. Performance indicators, typically the Recovery Factor (RF) and Cumulative Steam-Oil-Ratio (CSOR), for each model are evaluated and compared within the category. The simulation results generally show that, after 20 years of production, the thermal methods have prevalently higher oil recovery factor, i.e. 7 – 37 % of OOIP, compared to that of cold methods, i.e. 8 – 13 % of OOIP. Further sensitivity analysis on Expanding Solvent-SAGD (ES-SAGD) and VAPEX are also conducted in order to investigate the effects of injected fluid composition imposed on the process performance. From the results, 95 % of steam and 5 % binary components of C3 and C6 presents as the optimum injected fluid composition for ES-SAGD method. On the other hand, injected fluid comprising 60 % of C1 and 40 % of C3 delivers the best oil recovery factor for VAPEX method.
Application of Radioactive and Chemical Tracers for Offshore WAG Pilot Project
Authors: Abdullah Zaidi Zainal , Zain Zahidah M. , Anua Nor Aidil , Singhal Ashok
Published: July 2011

Malaysia’s oil predominantly comes from offshore fields. Malay Basin located to the East of Peninsular Malaysia contains most of the country's oil reserves. In the maturing oil fields of Malaysia, EOR options are being field-tested for enhancing and prolonging production. A Water Alternating Gas (WAG) pilot was implemented in the Dulang Field S3 Block during 2002–6. The S3 Block contained six wells (three producers and three injection wells) in two reservoirs namely E12/13 and E14.

This pilot project was the first EOR pilot in Malaysia. The main objectives of the pilot project were to design and develop the EOR scheme, and to evaluate the feasibility of WAG injection to maximize the oil recovery from this and other similar oil fields. A comprehensive monitoring was undertaken to assist in evaluation of pilot performance. Identification of optimal operating conditions, Dulang field-specific screening criteria and success indicators were perceived to be germane for future WAG implementation.

Oil bearing sands of the Dulang field were deposited under fluvial or near shore environments as parts of sand-shale sequences. These strata were subsequently folded and faulted, resulting in discrete compartments’ with uncertain flow continuity across various faults. Due to existence of numerous major as well as, minor faults and thinness of shale layers at certain places, the critical considerations for EOR were a) confinement of the injected fluids within individual compartments, and b) flow continuity between different injector and producer wells. It was therefore decided to use different water and gas phase tracers at each of the three injection wells within the S3 block. The data gathered were used for assessing internal communication, flow parameters and inter-well reservoir heterogeneity such as high permeability streaks. This paper discusses details of the tracer program and significant responses observed during the pilot implementation.
Evaluation of Oil Recovery by Water Alternating Gas (WAG) Injection – Oil-Wet and Water-Wet Systems
Authors: Zekri Abdulrazag Y. , Nasr Mohamed S. , AlShobakyh Abdullah S.
Published: July 2011

Water alternating gas injection (WAG) is normally employed to improve the volumetric sweep efficiency of miscible flooding processes. Literature search indicated a number of numerical studies investigated the effect of flooding rate, gravity forces, slug size, and heterogeneity on WAG processes performance. However there are very few numerical and experimental studies conducted on the effect of wettability on the efficiency of WAG processes. This work examines how to optimize WAG processes for carbon dioxide (CO2) floods above the minimum miscibility pressure (MMP) in both oil-wet and water-wet reservoirs. Stream tube simulation was used to assess the effects of WAG ratio, system wettability, flood pattern, solvent injection rate, project timing, and reservoir heterogeneity on the sweep efficiency and overall all recovery efficiency for oil-wet and water wet reservoirs. A series of secondary miscible carbon dioxide WAG displacement runs were performed employing WAG ratio’s of 1:1, 2:1, 1:2, 3:1, 1:3 and straight carbon dioxide.

The main conclusions of this research show that system wettability has a significant impact on the optimization of WAG ratio, solvent injection rate, project timing, and flooding pattern selection.
Study of Asphaltene Precipitation and Deposition Phenomenon during WAG Application
Authors: Khanifar Ahmad , Alian Sima S. , Demiral Birol , Darman Nasir
Published: July 2011

Precipitation and deposition of heavy organic materials such as asphaltene inside reservoirs, processing and transportation facilities is a major concern in the oil industry. Asphaltene precipitation is one the most common problem in many reservoirs and unfortunately may lead to many safety operational issues that in end affect’s oil recovery which assumes to be a major economical loss. The precipitation and deposition of asphaltene in porous media and their interactions with rock and fluids is a complex phenomenon which begs to be investigated under reservoir conditions. As yet, there have been many studies conducted on asphaltene precipitation but majority of them focused on determining precipitation onset point. It is believed, the first step in attempting to find an engineering solution to this deposition problem is to identify the conditions at which asphaltene precipitation takes place initially and conditions after that influences deposition.

This paper presents an assessment of aspects that influences asphaltene precipitation and deposition. This research, attempts to understand the mechanism of asphaltene precipitation and deposition, parameters affecting the precipitation and deposition process, the effect of asphaltene precipitation and deposition on oil reservoir characteristics and performance. In addition, the research involves examining the existing thermodynamic models of asphaltene precipitation and deposition in porous media, reversibility of asphaltene precipitation and deposition, asphaltene deposition removal methods, and modelling and simulation of asphaltene by conventional simulators. Since this study is a comprehensive summary of the mentioned topics and contains all the essential information of asphaltene and its precipitation process, it therefore can be used as a reference for further exploration of this specialized field.The probability of asphaltene precipitation and deposition occurring during any EOR techniques and its effects on reservoir performance should be anticipated at earlier stages of any development project. Also it is believed that through a more comprehensive understanding of the mechanisms that lead to deposition in the first place; asphaltenes deposition if cannot be prevented fully may at least be controlled and managed.
Research on a New Profile Control Agent: Dispersed Particle Gel
Authors: You Qing , Tang Yongchun , Dai Caili , Shuler Patrick , Lu Zayne , Zhao Fulin
Published: July 2011

In order to achieve in-depth control of injection water and improve oil recovery, a new profile control agent called dispersed particle gel (DPG) is developed, which is significantly different from colloidal dispersion gel both in its preparation and its characteristics. The DPG is prepared by the tube shearing cross-linking method with polymer and cross-linker. Atomic force microscope (AFM) studies show that DPG is made of small pseudo-spherical particles and the sizes can be controlled from nm to mm by adjusting shearing rate in the tube. The particles have a ratio of major and minor axis length of near 1, and the larger the shear rate, the closer the ratio is to 1. Salinity has a minor effect on the micro-morphology and there is an aging aggregation phenomenon. The results on dynamic light scattering also support the conclusions above. The rotary viscometer measurements show that DPG has a low viscosity, and salinity has a minor effect on viscosity, and that the DPG has good shearing stability. Physical simulation experiments in this study demonstrate that DPG has good injectivity, the ability to control injection profile, and improve oil recovery. It can be concluded from this study that this new profile control agent has the potential for wide application.
Immiscible Foam for Enhancing Oil Recovery: Bulk and Porous Media Experiments
Authors: Andrianov Alexey , Farajzadeh Rouhi , Nick Mahmood Mahmoodi , Talanana Mohand , Zitha Pacelli L.
Published: July 2011

This paper reports a laboratory study of foam for improving immiscible gas flooding. The study is relevant for both continuous and Water Alternating Gas (WAG) injection schemes. The effect of oil on the longevity of nitrogen and air foams was studied in bulk for a selected set of surfactants. Foam heights were measured in a glass column as a function of time, in the absence and presence of mineral and crude oils. From the column experiments it was found that foam longevity increases as the carbon chain length in the oil molecule increases, i.e. foam is more stable for higher viscosity oils. A surfactant formulation that gave the most stable foam in the presence of oil was used in the core-floods. Oil recovery with CO2 and with N2 foams from natural sandstone cores was studied with the aid of X-ray Computed Tomography, varying the injection rates, foam quality and surfactant concentration. The core-floods revealed that foam increases the oil recovery by as much as 20% of the oil initially in place (OIIP) over water flooding while injection of gas increased oil recovery by 10% only. Thus, foam adds up to 10% additional recovery on top of gas injection. This confirms that foam is potentially an efficient Enhanced Oil Recovery (EOR) method.
Evaluation of the Impact of Relative Permeability Hysteresis and Three Phase Modeling on the Performance of Water Alternative Gas EOR Processes
Authors: Karkooti Hooman , Masoudi Rahim , Arif Anndy M. , Darman Nasir H. , Othman Mohamad B.
Published: July 2011

The complex physics of the displacement processes involved in three-phase flow in porous media in the tertiary oil recovery processes is yet to be understood. Three phase relative permeability are usually calculated from two phase experimental data due to the complexity of three phase measurements and its duration, hence introducing uncertainty in the adopted models. Pore-scale laboratory studies have shown strong irreversibility in the relative permeability among the successive drainage and imbibitions cycles and its path dependency, which is called hysteresis. Understanding this phenomenon and its effect play a major role in evaluation and success of any tertiary recovery processes such as WAG EOR. Several models have been proposed to predict this mechanism, three phase zone and predict the true residual oil saturation. To better evaluate and mitigate the risks involved, the impact of many parameters used in the current predictive tools and hysteresis models should be fully understood and investigated.

In this work relative permeability hysteresis, three phase region and various involved parameters affecting the hydrocarbon recovery have been investigated. A heterogeneous sector model supported with actual SCAL data were used for the purpose of this study. The results of the study and the adopted methodology have been later compared and verified with the actual real field performance data under the same processes.

Generally the results show significant difference in term of residual oil saturation whether or not a relative permeability hysteresis modeling is employed. The study also demonstrates the necessity of fine-tuning the hysteresis model parameters to the actual SCAL data to obtain more realistic parameters to be used in prediction phase. Reservoir heterogeneity play a major role in balancing the viscous and gravity forces as well as the three phase region size to achieve higher hydrocarbon recovery.
Flexibility Research of Hot-Water Flooding followed Steam Injection in Heavy Oil Reservoirs
Authors: Dong Xiaohu , Liu Huiqing , Zhang Hongling , Pang Zhanxi
Published: July 2011

With the accelerating of exploitation, a great number of heavy oil reservoirs or blocks have reached the intermediary and later stage of steam injection development. It is faced with changing the thermal development mode.

Aimed at the residual oil of thermal production, this paper studies the alternative development mode after steam injection. Using the physical simulation method, we study the development effect of converting into Hot-water flooding under different temperature and different moment, and investigate the oil displacement efficiency of Water-Alternating-Steam Process (WASP). Then the result of Nitrogen hot-water foam flooding is discussed. Furthermore, it also argues the optimal reservoir rhythm which is suitable to converting into Hot-water flooding, and optimizes the confinement of reservoir thickness and heterogeneity by the method of numerical simulation.

The obtained results indicate that Hot-water flooding with 120 °C will obtain a great recovery performance. The best converting moment of Hot-water flooding is when the heavy crude oil recovery was about 22%. In comparison with the Hot-water flooding, the capacity to enhance the sweep efficiency of WASP is more remarkable. Nitrogen hot-water foam flooding could reduce the water cut by 20% above, and enhance the oil recovery by 25% above. Due to the action of gravitational differentiation, a Reverse rhythm reservoir convert into Hot-water flooding will acquire a good result. That reservoir where the thickness is less than 5m, and the permeability coefficient of variation is less than 0.4 could yield a higher oil recovery.

These results could play an important guiding significance to switch the thermal development mode. In addition, they can also be used as a tool for the successful design of Hot-water flooding after steam injection to enhance crude oil recovery in heavy oil reservoirs.