bluuebunny/crossref_metadata_2025 huggingface dataset:
Conservation Genetics of Lake Superior Brook Trout: Issues, Questions, and Directions
Authors: Wilson Chris C. , Stott Wendylee , Miller Loren , D'Amelio Silvia , Jennings Martin J. , Cooper Anne M.
Published: August 2008

Parallel efforts by several genetic research groups have tackled common themes relating to management concerns about and recent rehabilitation opportunities for coaster brook trout Salvelinus fontinalis in Lake Superior. The questions that have been addressed include the evolutionary and genetic status of coaster brook trout, the degree of relatedness among coaster populations and their relationship to riverine tributary brook trout populations, and the role and effectiveness of stocking in maintaining and restoring coasters to Lake Superior. Congruent genetic results indicate that coasters are an ecotype (life history variant) rather than an evolutionarily significant unit or genetically distinct strain. Regional structure exists among brook trout stocks, coasters being produced from local populations. Introgression of hatchery genes into wild populations appears to vary regionally and may relate to local population size, habitat integrity, and anthropogenic pressures. Tracking the genetic diversity and integrity associated with captive breeding programs is helping to ensure that the fish used for stocking are representative of their source populations and appropriate for rehabilitation efforts. Comparative analysis of shared samples among collaborating laboratories is enabling standardization of genotype scoring and interpretation as well as the development of a common toolkit for assessing genetic structure and diversity. Incorporation of genetic data into rehabilitation projects will facilitate monitoring efforts and subsequent adaptive management. Together, these multifaceted efforts provide comprehensive insights into the biology of coaster brook trout and enhance restoration options.
Ecology and Life History of Coaster Brook Trout and Potential Bottlenecks in Their Rehabilitation
Authors: Huckins Casey J. , Baker Edward A. , Fausch Kurt D. , Leonard Jill B. K.
Published: August 2008

Lake Superior once supported abundant lake-dwelling brook trout Salvelinus fontinalis called coasters; however, only scattered remnant populations remained by the early 20th century. Owing to their early decline, there is little information about their ecology and life history, yet such information is vital for the ecologically based rehabilitation and management of coasters. This study reviews the ecology of coaster brook trout from a life history perspective and presents quantitative data on the biology and status of the few populations that have been studied. Within the Lake Superior basin, some brook trout are stream residents while others are lacustrine or adfluvial. Although the variation in migratory behavior may be related to individual energetics, the role of evolution and the proximate factors triggering specific life histories remain uncertain. Comparisons of recent biological data from populations in the Lake Superior basin show that the northern populations have longer lengths at age and length frequency distributions skewed toward longer individuals. The degrees to which this difference is driven by variation in individual growth rates and size-selective mortality are unknown. All known populations around the Lake Superior basin appear to have a small number of individuals and are thus of conservation concern. We believe that biotic interactions such as competition with introduced salmonines (in particular coho salmon Oncorhynchus kisutch) have a strong negative influence on the individual and population performance of coasters. Coupled with high past and recent mortality from fisheries, these factors may create bottlenecks limiting the growth and rehabilitation of the remnant populations. Lake Superior coaster brook trout are persisting, albeit uncertainly, under conditions different from those in which they once thrived. Management focused on native ecosystem rehabilitation may foster the return of these fish as abundant members of Great Lakes food webs, and recent basinwide restrictions on length and catch limits are a positive step toward enhancing their rehabilitation and evolution.
Tracking Coaster Brook Trout to Their Sources: Combining Telemetry and Genetic Profiles to Determine Source Populations
Authors: D'Amelio Silvia , Mucha Jamie , Mackereth Rob , Wilson Chris C.
Published: August 2008

Radiotelemetry and genetic analysis are potent tools for informing fisheries management. Although they are usually applied independently, combining them can provide insights on fish origins, movement, and reproduction that could not otherwise be achieved. We applied these two techniques in two separate studies to resolve the origins and habitat use of coaster brook trout Salvelinus fontinalis in Nipigon Bay, Lake Superior. Telemetry of adult fish was used to determine the habitat use of coaster brook trout and microsatellite DNA genotyping to determine the relatedness of coasters to river-resident brook trout. Both studies indicated that coaster brook trout utilize multiple tributaries within Nipigon Bay for spawning. In terms of philopatric homing, however, the tracking data suggested that coasters show site fidelity between years, whereas the genetic data indicated substantial gene flow among tributaries. For individual tracked fish, the genetic data supported the homing hypothesis for 10 of 11 fish but also conclusively showed straying for 1 individual. The complementary insights from these combined data sets significantly clarify the behavior and habitat use of coaster brook trout and provide an example of the power of these combined methodologies for fisheries management.
Development and Evaluation of Condition Indices for the Lake Whitefish
Authors: Rennie Michael D. , Verdon Richard
Published: August 2008

Despite frequent use of length-based condition indices by fisheries managers and scientists to describe the overall well-being of fish, these indices are rarely evaluated to determine how well they correlate with more direct measures of physiological or ecological condition. We evaluated common condition indices (Fulton's condition factor KF, Le Cren's condition index KLC, and two methods of estimating relative weight Wr) against more direct measures of physiological condition (energy density, percent lipid content, and percent dry mass) and ecological condition (prey availability) for lake whitefish Coregonus clupeaformis in Lake Huron. We developed four standard weight (Ws) equations using the regression length percentile (RLP) method: one for the species as a whole, and three separate equations describing immature, mature male, and mature female lake whitefish from 385 populations in North America. Species RLP-Ws showed less length-related bias and more closely matched empirical quartiles of lake-specific mean weight than did maturity- or sex-specific RLP-Ws equations. Significant length-related bias was detected in EmP-Wr. No biologically significant length-related bias was detected in KLC, but this index was specific to a single population of fish. Species RLP-Wr showed no significant length-related bias, and KF was significantly size dependent. All length-based condition indices were significantly correlated with energy density, percent lipid content, and percent dry mass. The index most strongly correlated with all three measures of physiological condition was KF, likely because both the physiological measures and KF exhibited positive relationships with body size. Across two Lake Huron sites, RLP-Wr was significantly correlated with density of prey (amphipods Diporeia spp.). Of the two condition indices developed in this study, RLP-Wr was consistently more strongly correlated with physiological condition indices than was EmP-Wr.
Effects of Reservoir Operations on Hatchery Coastal Rainbow Trout in Lake Roosevelt, Washington
Authors: McLellan Holly J. , Hayes Stephen G. , Scholz Allan T.
Published: August 2008

It is suspected that reservoir operations limit the mitigation fishery for coastal rainbow trout Oncorhynchus mykiss irideus in Lake Roosevelt, Washington. Entrainment through Grand Coulee Dam has been suggested as the primary impact of reservoir operations. However, the causal mechanisms and effects of entrainment have been difficult to quantify. A logistic regression model was used to examine the effect of reservoir operations on the coastal rainbow trout tag return probability. Eight independent variables were studied: release location, presence–absence of a tag reward, minimum reservoir elevation (m above mean sea level (msl)) during a sample year, reservoir elevation on the fish release date, mean daily water retention time (d) 2 weeks postrelease, mean daily retention time 4 weeks postrelease, mean annual water retention time, and water year type (associated with shallow, average, or deep drawdown events). Models were selected on the basis of likelihood ratio tests, odds ratio confidence intervals (CIs), and predictive ability. Analyses indicated that the significant independent variables were release location, water year, release elevation, and mean water retention time at 4 weeks postrelease. Angler return of tagged fish was 1.86 times more likely after a shallow drawdown event than after a deep drawdown event (95% profile likelihood CI = 1.15–3.03). The effect of mean water retention time was dependent on reservoir elevation at the time of release. When release elevation was low (366–381 m above msl), increasing mean water retention time increased the probability of tag return. However, when release elevation was high (381–393 m above msl), increasing mean water retention time did not increase the probability of tag return. The logistic regression model can be used by fisheries managers to predict the impacts of hydropower operations on the coastal rainbow trout fishery in Lake Roosevelt, thereby allowing for annual adjustments to release strategies that would maximize harvest potential.
A Modified Drop Net for Sampling Fish Communities in Complex Habitats: A Description and Comparison with Other Techniques
Authors: Beesley L. S. , Gilmour J. P.
Published: August 2008

A modified drop net (area = 19.3 m2) was constructed to enhance the collection of fish from within complex freshwater habitats. The net was evaluated in three pools located within the Pilbara region of north Western Australia. The net's efficiency was determined by comparison with gillnetting and beach seining; accuracy of the net was investigated using the toxicant rotenone. In terms of efficiency, the modified drop net and beach seine generated similar descriptions of the fish community (relative abundance, species richness, ordination of a species–abundance matrix); panel gill nets collected a diminished subset of the community. Efficiency of the drop net remained relatively constant among pools, whereas the seine became increasingly easy to use as habitat complexity decreased. In terms of accuracy, the drop net produced estimates of total fish abundance similar to those obtained by use of rotenone and adequately depicted site-related differences in fish community structure (multivariate ordination in space). The drop net and rotenone collected similar numbers of species, but the drop net missed some species that were present in very low abundance. The drop net also underestimated the abundance of one benthic species. We recommend use of the drop net when studying ephemeral pools where habitat complexity changes through time or when precise estimates of density are required. Beach seining, which has minimal gear requirements, is recommended for situations in which only a general description of the community (species–abundance matrix) or species richness information is required. When the drop net is used, gill nets should also be used to collect large size-classes that are in low abundance.
Redd Site Microhabitat Utilization and Quantitative Models for Wild Large Brown Trout in Three Contrasting Boreal Rivers
Authors: Wollebæk Jens , Thue Roy , Heggenes Jan
Published: August 2008

Riverine spawning areas are important but restricted source habitats for large brown trout Salmo trutta (≥40 cm total length). In hydrophysically different reaches within three contrasting boreal rivers, redds larger than 100 cm in length were located by direct underwater observation in 1998 and 2001 (n = 157 redds; range = 10–60 redds per reach and year) and were characterized based on 29 habitat variables. The microhabitat of utilized redd sites (total redd length: mean ± SD = 206 ± 83 cm, range = 100–615 cm) was typified by a mean total water depth of 103 ± 39 cm with a wide optimum (range = 23–215 cm) and a mean water velocity of 47 ± 32 cm/s (range = 2–124 cm/s). Mean velocity measured at 5 cm above the substrate was 29 ± 20 cm/s (range = 0–82 cm/s). Mean substrate particle size was 7 ± 6 cm and demonstrated a narrower optimum (range = 2–37 cm) than the other variables. Substantial differences among the three rivers, particularly in water depth and velocity measures, largely reflected size and gradient differences and indicated some flexibility in spawning microhabitat utilization. The use of substrate particle size was less variable. Multivariable analysis indicated that water velocity (except velocity measured just above the substrate) and water depth explained most of the variation. Depths and substrates utilized were larger than previously reported, probably reflecting the in situ habitat availability in the relatively large study rivers.
Novel Tools for Analyzing Proportional Size Distribution Index Data
Authors: Brenden Travis O. , Wagner Tyler , Murphy Brian R.
Published: August 2008

Proportional size distribution (PSD) indices are convenient measures for numerically summarizing size structure of fish populations. Several novel methods for analyzing PSD index data were examined as a means for potentially improving inferences of size structure: generalized linear mixed modeling, calculation of location quotients, and simultaneous construction of 100(1 − α)% confidence intervals for PSD indices through multinomial modeling. The methods are demonstrated using simulated and previously published PSD index data. Generalized linear mixed modeling was used to (1) conduct a model selection analysis of PSD index data relative to a change in harvest regulation for walleyes Sander vitreus, (2) partition the variance of PSD index data among spatial, temporal, and environmental attributes, and (3) nonlinearly relate PSD data to adult density for largemouth bass Micropterus salmoides. The location quotient, which is an index for describing relative concentration of proportional data, was used to describe spatial and temporal localization of largemouth bass and walleye PSD index data. Finally, a modified method of constructing simultaneous 100(1 − α)% confidence intervals for multinomial proportions was used to produce 95% confidence intervals for traditional and incremental PSD indices based on length frequency data from muskellunge Esox masquinongy. The approaches described herein can assist fishery biologists in size structure assessments of fish populations and ultimately aid in cost-effective fisheries management.
Effect of Artificial Sunlight on the Retention of External Calcein Marks on Lake Trout
Authors: Honeyfield Dale C. , Kehler Tom , Fletcher John W. , Mohler Jerre W.
Published: August 2008

When choosing a fish marking technique to address fishery related questions, it is important to consider factors that affect mark retention. Calcein, a chemical marking agent, is under investigation for potential use on fish. Two laboratory trials were conducted with calcein-marked lake trout Salvelinus namaycush to determine the effect of artificial sunlight on calcein mark intensity. In trial 1, fish exposed to 18,000 lx for 7 d lost 90% or more of the calcein mark intensity (relative to the colorimetric key, mg/L) on the head, body, ventral region, and pectoral fins relative to mark intensity in fish that were maintained in darkness. In trial 2, light intensity was reduced 2.5–3.0-fold. After 7 d of light exposure, calcein mark intensity on the head was reduced by 40–45% relative to mark intensity in fish that were held in darkness; by day 14, calcein mark intensity on the head was reduced by 55–60% relative to that of dark-treated fish. No further decline was observed in light-exposed fish, and head mark intensity values did not differ among days 14, 21, and 28 for this treatment group. Of the four areas evaluated, the head and pectoral fin were more easily read using a colorimetric key than the lateral or ventral regions of the fish. The concentration of calcein spotted on filter paper to devise the colorimetric key ranged from 1 to 100 mg/L. A difference of approximately 7 mg/L in apparent calcein mark intensity means for the head region could be detected using the colorimetric key. These trials showed that calcein mark intensity on lake trout declined when fish were exposed to artificial sunlight, and the use of a colorimetric key improved the objectivity of calcein mark intensity assessment.
Genetic Identification of Hatchery-Released Red Drum in Texas Bays and Estuaries
Authors: Karlsson S. , Saillant E. , Bumguardner B. W. , Vega R. R. , Gold J. R.
Published: August 2008

The stock enhancement program for red drum Sciaenops ocellatus in Texas annually releases from 25 to 30 million fingerlings into Texas bays and estuaries and represents one of the largest such programs for marine fishes worldwide. We used 16 nuclear-encoded microsatellites and a 370-base-pair fragment of the mitochondrial DNA (mtDNA) D-loop to assign red drum sampled from two bays along the Texas coast to either hatchery or wild origin. A total of 30 hatchery-released fish were identified among 321 red drum belonging to three year-classes sampled from Galveston Bay, while a total of 11 hatchery-released fish were identified among 970 red drum belonging to four year-classes sampled from Aransas Bay. Allelic richness (microsatellites) was significantly lower among hatchery-released fish than among hatchery broodfish and wild fish. Similarly, the expected number of mtDNA haplotypes in hatchery-released fish (based on simulation analysis) was significantly lower than that expected in a random sample of both brood and wild fish. The contribution of brood dams, sires, and dam × sire combinations to the hatchery-released fish was nonrandom, as was the distribution of hatchery-released and wild fish with respect to sampling stations (localities) within each bay. The possibility of a Ryman–Laikre effect is discussed.
Genetic Effective Size in Populations of Hatchery‐Raised Red Drum Released for Stock Enhancement
Authors: Gold John R. , Ma Liang , Saillant Eric , Silva Paul S. , Vega R. R.
Published: August 2008

Genetic analysis of progeny from 13 spawning events occurring over a 2‐week period in a Texas Parks and Wildlife Department (TPWD) hatchery for red drum Sciaenops ocellatus during the spring of 2002 and hatchery spawning and release records over the 2003 spawning season were used to estimate the average genetic effective size of an average spawn and an average hatchery‐released population. The purpose of this study was to assess the potential for a Ryman‐Laikre effect in the TPWD red drum stock enhancement program. Genetic analysis revealed that 16 of 27 dams (59.2%) and 16 of 18 sires (88.9%) spawned at least once. The average effective size (Ne) for a single spawn was 2.59, approximately 43% less than the maximum Ne (4.55) predicted if all possible mating (dam × sire) combinations had occurred and family size per mating combination had been equivalent. The reduction in Ne stemming from the actual number of mating combinations was approximately 34% and appeared to be due primarily to nonspawning dams; the reduction in Ne generated by the actual variation in family size was approximately 9%. Spawning and release records at the TPWD hatchery indicate that in 2003 the number of released populations per bay or estuary ranged from 7 to 27. Using the average effective size (Ne) estimate for a single spawn (2.59), the estimated average effective size of all released fish per bay or estuary (NeR) in 2003 ranged from about 28.5 to about 46.6. These values of NeR are less than the averages estimates of about 272 and 263 for the long‐term (NeI) and contemporaneous (NeV) effective size, respectively, of red drum in bays and estuaries in the northern Gulf of Mexico and indicate a reasonable potential for a Ryman‐Laikre effect. Approaches that might be employed to increase the NeR of TPWD‐released fish and decrease the probability of a Ryman‐Laikre effect are discussed.
Potential Role of Leukotriene Modifiers in the Treatment of Chronic Obstructive Pulmonary Disease
Authors: Usery Justin B. , Self Timothy H. , Muthiah Muthiah P. , Finch Christopher K.
Published: August 2008

Chronic obstructive pulmonary disease (COPD) is characterized by progressive, irreversible airflow limitation coupled with an abnormal inflammatory process. It is associated with high morbidity and mortality. Leukotriene modifiers, approved by the United States Food and Drug Administration as treatment for asthma and allergic rhinitis, may also alleviate the abnormal inflammatory response seen in patients with COPD. To explore the outcomes of research in this area, we conducted a literature search from 1950–2007, using the PubMed database. We found no published studies that provided conclusive evidence that the available leukotriene modifiers benefit patients with COPD. However, data do suggest that leukotriene modifiers may offer benefits to patients with COPD, including effects that pertain to airflow limitation, neutrophil and lymphocyte chemotaxis, and neutrophil longevity. Added to conventional treatment, these agents appear to reduce symptoms, improve objective measures of disease, and control inflammation. Further studies are needed to determine the precise role of leukotriene modifiers in the treatment of COPD.
Achieving sustainability in the construction supply chain
Authors: Adetunji I. , Price A. D. F. , Fleming P.
Published: August 2008

Sustainable construction and supply chain management (SCM) have, in recent years, become two of the most important performance-related issues within the construction industry. To achieve corporate sustainability within any organisation, it is essential that sustainability issues are addressed throughout the organisation's whole supply chain, a process referred to as sustainable supply chain management (SSCM). The implementation of SCM and sustainability is, however, an extremely complex undertaking. Through an extensive literature review and detailed interviews, this research has identified the conditions and strategies for achieving SSCM within construction organisations. The research also investigated the meaning, barriers and enablers, issues, tools and techniques for achieving successful SCM and SSCM. The study was based on the perspectives of senior managers of exemplar organisations with a proven track record in sustainability and SCM. It has been possible to identify best practice from which other organisations can learn, thus supporting the industry in the move towards more sustainable construction practices.
Paleoecology meets genetics: deciphering past vegetational dynamics
Authors: Hu Feng Sheng , Hampe Arndt , Petit Rémy J
Published: August 2008

Genetic analysis adds a novel dimension to paleoecology that is becoming increasingly important for elucidating vegetational dynamics in relation to climate change. Because past vegetational changes have often left distinct genetic imprints on current plant populations, genetic analysis can add detail to fossil‐based reconstructions. Recent surveys of DNA polymorphisms yield new insights into past vegetational changes and address long‐standing paleoecological questions. These studies reveal that small tree populations survived in mid‐ to high‐latitude refugia throughout the Quaternary glacial episodes. They further reveal migration pathways and demographic processes during postglacial range expansion. These results challenge previous notions regarding tree species responses to climate change and help to identify genetic conservation targets. Here, we review these recent advances and outline research prospects at the interface between paleoecology and genetics.
Tree die‐off in response to global change‐type drought: mortality insights from a decade of plant water potential measurements
Authors: Breshears David D , Myers Orrin B , Meyer Clifton W , Barnes Fairley J , Zou Chris B , Allen Craig D , McDowell Nathan G , Pockman William T
Published: August 2008

Global climate change is projected to produce warmer, longer, and more frequent droughts, referred to here as “global change‐type droughts”, which have the potential to trigger widespread tree die‐off. However, drought‐induced tree mortality cannot be predicted with confidence, because long‐term field observations of plant water stress prior to, and culminating in, mortality are rare, precluding the development and testing of mechanisms. Here, we document plant water stress in two widely distributed, co‐occurring species, piñon pine (Pinus edulis) and juniper (Juniperus monosperma), over more than a decade, leading up to regional‐scale die‐off of piñon pine trees in response to global change‐related drought. Piñon leaf water potentials remained substantially below their zero carbon assimilation point for at least 10 months prior to dying, in contrast to those of juniper, which rarely dropped below their zero‐assimilation point. These data suggest that piñon mortality was driven by protracted water stress, leading to carbon starvation and associated increases in susceptibility to other disturbances (eg bark beetles), a finding that should help to improve predictions of mortality during drought.
Maximizing arthropod‐mediated ecosystem services in agricultural landscapes: the role of native plants
Authors: Isaacs Rufus , Tuell Julianna , Fiedler Anna , Gardiner Mary , Landis Doug
Published: August 2008

Beneficial arthropods, including native bees, predators, and parasitoids, provide valuable ecosystem services worth $8 billion to US agriculture each year. These arthropod‐mediated ecosystem services (AMES) include crop pollination and pest control, which help to maintain agricultural productivity and reduce the need for pesticide inputs. Maximizing survival and reproduction of beneficial arthropods requires provision of pollen and nectar resources that are often scarce in modern agricultural landscapes. Increasingly, native plants are being evaluated for this purpose. Native plants can outperform recommended non‐natives and also provide local adaptation, habitat permanency, and support of native biodiversity. We predict that the success of insect conservation programs using flowering plants to increase AMES on farmland will depend on landscape context, with the greatest success in landscapes of moderate complexity. Reintegration of native plants into agricultural landscapes has the potential to support multiple conservation goals, and will require the collaboration of researchers, conservation educators, and native plant experts.
Fuel treatment effects on tree‐based forest carbon storage and emissions under modeled wildfire scenarios
Authors: Hurteau Matthew , North Malcolm
Published: August 2008

Forests are viewed as a potential sink for carbon (C) that might otherwise contribute to climate change. It is unclear, however, how to manage forests with frequent fire regimes to maximize C storage while reducing C emissions from prescribed burns or wildfire. We modeled the effects of eight different fuel treatments on tree‐based C storage and release over a century, with and without wildfire. Model runs show that, after a century of growth without wildfire, the control stored the most C. However, when wildfire was included in the model, the control had the largest total C emission and largest reduction in live‐tree‐based C stocks. In model runs including wildfire, the final amount of tree‐based C sequestered was most affected by the stand structure initially produced by the different fuel treatments. In wildfire‐prone forests, tree‐based C stocks were best protected by fuel treatments that produced a low‐density stand structure dominated by large, fire‐resistant pines.
Drill Collar with Auto Release Sleeve—A New Approach for Preventing Stuck Pipe Problems
Authors: Agarwal Navin Ashok
Published: August 2008

Drilling Industry is exploring various ways of reducing costs through multitude of initiatives. One of the major area where there is potential for cost reduction is downtime due to drill string failures. Losing a bottom hole assembly (BHA) is one of the most costly unplanned drilling events that can occur for an operator. Time spent on fishing for the lost assembly, the rig time wasted waiting on the mobilization of equipment and people, as well as the additional costs of whip stocks, cement, and directional tools significantly increase the cost of a well and often results in exceeding the approval for expenditure. Even though this is an old problem, with new drilling technology, especially related to the use of drill collars (larger OD), which is one of the main component of the drill string which in 60% of cases get stuck, therefore there is a need to redesign the drill collar which can be able to drill ahead even in case of stuck pipe situations. In this paper, a new solution to prevent stuck pipe problems and to retrieve stuck BHA is proposed. A drill collar is designed in such a way that during stuck situations, it can be released and we can continue drilling ahead and/or retrieve drill string easily. This is achieved by use of expandable techniques on drill collar. This proposed technique will allow us for continuous and easier drilling, thus saving rig time and ultimately economics of the entire operation at a fraction of increased cost in new drill collar.

This paper explains the causes and solution for stuck pipe problems and then presents a new designed drill collar with its design and operating concept. Finally conclude that use of this drill collar can be a viable tool for Drilling industry.
Parametric Analysis of Stress Reduction in the Cap Rock above Compacting Reservoirs
Authors: Morita Nobuo , Fuh Giin-Fa
Published: August 2008

It is well known that the fracture gradient is significantly reduced when drilling through depleted reservoirs, hence, mud density must be adjusted or a casing must be set before drilling through depleted reservoirs. However, the magnitude and extent of fracture gradient reduction in the cap rock above depleted reservoirs has not been well characterized. Several casing shoe tests performed in the cap rocks showed that fracture gradients in the cap rock above depleted reservoirs also significantly declined with reservoir depletion. This gives rise to the problem of determining a safe casing shoe set position without inducing lost circulation problems.

To answer the above questions, parametric analysis of stress reduction in the cap rock above compacting reservoirs were performed using a finite element structural model with fluid flow from cap rocks. It was found that two factors dominate the in-situ stress change in cap rocks. One factor is pore pressure change due to dehydration from shale to reservoir sections as reservoir pressure is depleted and the other factor is the horizontal stress reduction due to the roof effect of cap rocks. Although cap rock permeability is generally very low, shale pore fluid can drain over time into reservoir sections due to large pressure differences after reservoir pressure depletion. The loss of pore fluid causes a fracture gradient reduction in shale sections. By contrast, if the shear modulus in the shale section is high compared to the shear modulus of reservoir formation, the horizontal stress in the cap rock reduces due to the roof effect. Using the correlations of shale elastic modulus and permeability with respect to shale porosity, a practical method to estimate the extent and magnitudes of stress reduction in the cap rock above depleted reservoirs is proposed in this paper.
Breakthrough in 22" Hole Drilling in Kuwait Deep Wells
Authors: Al-Saeedi M. J. , Mahesh V. S. , Al-Ajmi H. S. , Al-Enezi D. , McKinnell D. C.
Published: August 2008

Exploration activities in Kuwait involve drilling of HPHT wells to search for high quality oil from the Jurassic formations. The wells drilled are very challenging with deep horizons (~16,500 ft), over-pressured formations and zones with narrow pore/fracture pressure windows which require the setting of multiple casing strings.

It is imperative that surface/intermediate casing strings are run to the maximum depths possible in order to reach well TD in a workable hole size. This presents the challenge of drilling long sections of large diameter hole in an acceptable time frame while maintaining borehole quality such that the big diameter tubular strings can be successfully run.

This paper will discuss the challenges of drilling 22" hole in such wells from 6,000 to 9,500 ft and the potential to replace established methods with new technology solutions to improve drilling performance.

The conceptual project consisted of an attempt to replace multiple 22" insert bits, rotary driven, with a single PDC bit design run on downhole motor. A partnership approach was initiated with the bit manufacturer and motor provider. Bit designs, downhole motor and rig equipment specs were developed and improved on over the project.

Bit and motor combinations were tested over a number of wells using several drilling rigs. The performance improvements were benchmarked with the original method. Over the trial, the goal was to try and drill the entire section with one bit from shoe to shoe, thus cutting interval costs and drilling times.

This paper will detail key factors in drill bit design, analysis of downhole motor performance, plus the critical role of ‘state of the art’ rig equipment. It will present a case history of this ‘design and development’ process with conclusions which provide the basis for future optimization of the technology.
Optimization of Multiple Bit Runs Based on ROP Models and Cost Equation: A New Methodology Applied for One of the Persian Gulf Carbonate Fields
Authors: Rastegar M. , Hareland G. , Nygaard R. , Bashari A.
Published: August 2008

Improving the rate of penetration (ROP) is one of the key methods to reduce drilling costs. Several ROP models have been developed and modified based on the concept where unconfined compressive strength (UCS) is inversionally proportional with the rate of penetration. These models can predict the rate of penetration of different bit types in an oil or gas field with a reasonable degree of accuracy. The ROP model studied herein relates the rate of penetration to operating conditions and bit parameters in addition to the rock strength. Also, the effects of bit hydraulics and bit wear on rate of penetration are included in the model.

In this paper, the drilling performance was optimized, using the ROP models, for upcoming wells in one of the Persian Gulf carbonate fields. Based on previous drilled wells a rock strength log along the wellbore is created and modified to mach the the new well survey. The rock strength is back calculated from the ROP model which includes bit design and reported field wear in conjunction with meter by meter operating parameters, formation lithologies and pore pressure. By conducting a number of simulations a learning curve was constructed to obtain the optimum bit hydraulics, best combination of operational parameters and the most effective bit design.

Based on the proposed ROP model, a simple and useful simulator was developed. This methodology can be used in pre-planning and post analysis to reduce drilling cost where previously drilled wells exist.
Theory and Application of a New Generalized Model for Torque and Drag
Authors: Aadnoy Bernt S. , Djurhuus Joannes
Published: August 2008

Well friction, or torque and drag play an important role in many well operations. Modelling is performed either with a numerical simulator, or by analytical mathematical models. Although the latter provide better physical insight, they are often cumbersome to use.

A mathematical study was undertaken, analyzing published friction models. Identifying a lot of symmetry in the solutions, we managed to reduce the complexity significantly. The result is a generalized friction model consisting of only two equations, one for rotating friction (torque) and one for pulling friction (drag) that is valid for all well geometries.

The derivation of the generalized friction model will be presented. It covers vertical sections, build-up bends, drop-off bends and straight sections. For all these geometries the new model is valid for tubular both in tension and in compression. The different solutions are obtained by selecting the signs of the coefficient of friction and the well inclination. The new model includes previously unpublished results such as pipe in compression in drop-off bends. Any deviated well geometry can now be analyzed using a spreadsheet with the new model, simply by adding forces starting from bottom of the well.

A field case is presented. An S-shaped well is modelled using the two equations. In addition to provide a worked example, physical effects like friction in bends are shown and discussed.
A General Dynamic Model for Single and Multi-phase Flow Operations during Drilling, Completion, Well Control and Intervention
Authors: Petersen Johnny , Rommetveit Rolv , Bjørkevoll Knut S. , Frøyen Johnny
Published: August 2008

A general dynamic model for any flow-related operation during well construction and interventions has been developed. The model is a basis for a new generation support tools and technologies needed in today's environment with advanced well designs, challenging drilling conditions and need for fast and reliable real-time decision support.

The solution method uses a "divide and conquer" scheme, which computes the flow in each well segment separately, and then solves for the appropriate flow in the junctions.

This simplifies greatly simulating complex flow networks, such as multilateral wells and jet subs. The flexibility allows incorporating additional pumps in the flow loop, as in Dual Gradient Systems.

The model includes dynamic 2-D temperature calculations, covering the radial area affecting the well and assuming radial symmetry in the vicinity of the well.

Other features: Flexible boundary conditions (which includes drilling, tripping)Non-Newtonian frictional pressure lossTransient well-reservoir interaction Slip between phasesAdvanced PVT relationship

The reason for this new approach was to respond constructively to today's challenges (complex and difficult drilling conditions, need for reliable real time decision support). Our approach has been more flexibility, improved accuracy, reduced numerical diffusion and increased computational speed.

The paper will present the basic model assumptions; the model architecture, and solution methods.

Integration of the model into a real time system with links to real time databases and advanced visualization tools is currently ongoing. Thus the model may follow the whole work process through planning, training, execution, and post analysis.

Examples of applications of the model so far will be presented, as well as visions for future applications.
Building a Geomechanical Model for Kotabatak Field with Applications to Sanding Onset and Wellbore Stability Predictions
Authors: Yi X. , Goodman H. E. , Williams R. S. , Hilarides W. K.
Published: August 2008

Kotabatak field, Sumatra, Indonesia is a heavily-faulted field undergoing an aggressive drilling and development campaign. Nine horizontal wells had been drilled with four more planned in 2008. One of the horizontal wells recently experienced well collapse (and sudden productivity decline) after some time on production, with cavings being flushed out during coil tubing workover operations. In addition to horizontal well drilling, feasibility of open horizontal well completions, hydraulic fracturing design and sanding onset prediction also warranted rock mechanics analyses. To make sound decisions on those issues, building a well-calibrated geomechanical model was critical.

In this study, we reviewed the drilling, completion, logging and production information from several wells across the field. We found that (1) The Kotabatak field has a general maximum horizontal stress orientation of NE- SW. However, there could be localized stress orientation variations depending on structure complexity near a specific well. (2) There was no consistent evidence indicating a significant contrast between the maximum and minimum horizontal stresses. Using a maximum/minimum horizontal stress ratio of 1.05 yielded a consistent calibration result for the wells studied. (3) Sand minimum horizontal stress for the Kotabatak field was calibrated against available closure stresses from hydraulic fracturing and mini-frac data. (4) Rock mechanical properties were calculated with openhole logs based on a Rock Mechanics Algorithm that is closely linked to Chevron's worldwide rock mechanical property database. Consequently, even though there were no core test data available from the Kotabatak field to calibrate rock mechanical properties directly, the log data set provided the means to estimate reliable formation mechanical property values that are consistent with Chevron's worldwide database. Furthermore the entire geomechanical model was calibrated against offset drilling performance measures resulting in a high degree of confidence in the predicted values.

Using the calibrated geomechanical model, horizontal well stability predictions were performed and indicated that horizontal sections can be drilled with low mud weight allowing the well to have some yield/failure. Open horizontal well sanding onset prediction indicated that the depth and width of a breakout (or plastic zone if reservoir sand behaves plastically) increase with increasing pressure drawdown. Since water flooding is used in the field to maintain reservoir pressure, sand control may not be needed if an appropriate Bottomhole Flowing Pressure (BHFP) is applied.
Lessons Learned from Highly Deviated Openhole Completions in Two HP/HT Retrograde Gas-Condensate Fields Using Expandable Liner Hangers, External-Sleeve Inflatable Packer Collars, and Swellable Packers for Zonal Isolation
Authors: Lee Seung Kook , Kim Yong Seok , Ou Kwang Kwon , Murugappan Basker , Williford James , Jackson Tance , Nizam Irwan , Lim Derek
Published: August 2008

The Korean National Oil Company (KNOC) has developed seven retrograde gas-producing wells located in offshore Vietnam. The scenarios presented by these wells taught the developers valuable lessons, and the intent of this paper is to share these lessons by presenting the concepts considered for well design, the selection process for the completion equipment and techniques, the preplanning for the installations, and the experiences encountered during the actual installations.

Several completion challenges had to be addressed, including isolation of water production below the casing shoe and control of condensate banking, sand production, and commingling of multiple production zones in the long openhole sections.

A different type of completion that involved an expandable liner hanger (ELH) with an external-sleeve inflatable packer collar (ESIPC) was chosen, and installation and cementing were accomplished in a single trip. The ESIPC was deployed just below the water-producing zone, and cement was pumped up the annulus from the ESIPC to where the expandable liner hanger (ELH) was set above it. It was felt that this design would prevent water from entering the wellbore while enabling optimum production. To prove the concept, a stack-up test was performed at surface before actual deployment on location to ensure that the cement wiper plugs would pass through the expandable-liner-hanger ball seat and that the concept would perform as intended.

Swellable packers were selected from the various proven openhole isolation devices available to the industry to provide the zonal isolation required in the multi-zone intervals.

This was the first openhole completion in Southeast Asia in a high-temperature, commingled gas environment in which isolation would be contained solely by swellable packers.
Evaluation of Water Swelling Elastomers
Authors: Al-Yami A. S. , Nasr-El-Din H. A. , Al-Humaidi A. S.
Published: August 2008

A conventional method of zonal isolation utilizes setting casing in the wellbore using cement. Then, the casing is perforated and a screen is installed. Finally, gravel is placed to control solids production. The shortcoming of this method is that it reduces the inner diameter of the completion, which limits the productivity of the treated well. The best current isolation method is to use either expandable casing or swelling packers. Swelling packers undergo dynamic swelling when in contact with water or oil. The swelling rubbers are bounded to any size of pipe where the thickness of the rubber controls the pressure difference developed across the pipe.1

In this study, water swelling packers from three different vendors were examined at 190ºF using different brines and 15 wt% HCl acid. The effects of 15 wt% HCl acid on the swelled elastomers and exposure to low salinity aquifer water after the acid were examined in detail.

Water swelling packers were able to hold differential pressures of more than 2,000 psi. Coupons obtained from vendors I&II showed acceptable results for 5 and 20 wt% NaCl. Packers soaked in fluids of high pH values (potassium formate with pH 9.5) or low pH values (15 wt% HCl acid with pH nearly 0) did not swell. Water swelling packers obtained from one vendor failed to seal in 20 wt% NaCl. Hydrochloric acid resulted in a significant reduction in the volume of the swelled coupons even after soaking for 15 minutes only. Immersing the coupons after acid exposure in field injection water did not regain their volume prior to soaking in HCl acid solutions.

Based on the above results, it is strongly recommended to perform quality testing for the elastomers before field application. Every effort should be made not to expose water swelled packers with concentrated HCl acids during matrix acidizing.