bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical application of nanoparticles, and their possible health risk
Authors: Pándics Tamás
Published: September 2008

A rohamosan fejlődő nanotechnológiai eljárások során előállított anyagokat egyre szélesebb körben alkalmazzák számos egyéb terület mellett a klinikai gyakorlatban is. Tekintettel kedvező tulajdonságaikra, alkalmazzák őket implantátumok bevonataként, csontpótlásra, gyógyszerek farmakokinetikai jellemzőinek optimalizálására. A hatóanyagok nanoméretű szemcsés, liposzómás bevonataként jelentős előrelépést jelenthetnek a hatékony terápia szempontjából. Előnyös tulajdonságaik mellett azonban a méretből adódó eltérő kémiai tulajdonságok számos veszélyforrást is magukban hordozhatnak, így felelősségteljes alkalmazásukhoz az egészségre gyakorolt esetleges kedvezőtlen hatásaik ismerete elengedhetetlen. A nanorészecskék nagyobb méretű anyagformákétól eltérő hatásai elsősorban a szemcsemérettel magyarázhatóak. Az eddigi vizsgálatok alapján a túlnyomóan lokális hatás mellett szisztémás, szabad gyökök termelésére, thrombocytaaggregációra gyakorolt hatással kell számolni, amely növeli a cardiovascularis rizikót. Tekintettel az eddig rendelkezésre álló igen hiányos ismeretekre, a nanoanyagok egészségre gyakorolt hatásaival kapcsolatos pontos kockázatbecslés elvégzésére egyelőre nincs lehetőség, így a nanoszemcsék alkalmazása a betegellátásban különösen nagy körültekintést igényel.
Movement of Reservoir‐Stocked Riverine Fish between Tailwaters and Rivers
Authors: Spoelstra Jeffrey A. , Stein Roy A. , Royle J. Andrew , Marschall Elizabeth A.
Published: September 2008

The movement of fish from onstream impoundments into connected streams and rivers has traditionally been overlooked in fish stocking decisions but is critical to the ultimate impact of stocking riverine species into reservoirs. Hybrid saugeyes (female walleye Sander vitreus × male sauger S. canadensis) stocked into Deer Creek Reservoir, Ohio, readily move from the reservoir to the tailwater below. Downstream movement of these saugeyes from the tailwater may have consequences for native prey species and parental stocks downstream. We used fixed‐station radiotelemetry to quantify the temporal movement patterns of 203 reservoir‐stocked saugeyes from the tailwater of the reservoir, the stream flowing from the tailwater, and the river into which the stream flowed. From October 1998 through July 2000, most (75%) saugeyes never left the tailwater, and those that left returned 75% of the time. Overall, saugeyes spent 90% of their time in the tailwater, 7‐8% of their time downstream in small streams, and 2‐3% of their time farther downstream in the Scioto River (45 km downstream). No radio‐tagged saugeyes moved to the Ohio River (155 km downstream). The probability of downstream movement generally increased with increasing flow and when dissolved oxygen dropped to lethal levels in summer. The probability of movement was highest in winter and spring, when it was probably related to spawning, and low in summer (except when dissolved oxygen was low) and fall. The patterns of movement seemed to reflect the relative suitability of tailwater over stream habitat. The predominant use of and return to tailwater habitat after downstream movement limited overall stream and river residence time. Although the daily movement probability for an individual was low, when we apply these rates to all of the stocked saugeyes in the Ohio River drainage, we cannot safely conclude that only small numbers move from reservoir tailwaters to downstream river systems. We recommend that managers refrain from stocking systems for which there are concerns about native species in connected drainages.
Breeding Success of Wild and First‐Generation Hatchery Female Spring Chinook Salmon Spawning in an Artificial Stream
Authors: Schroder Steven L. , Knudsen Curtis M. , Pearsons Todd N. , Kassler Todd W. , Young Sewall F. , Busack Craig A. , Fast David E.
Published: September 2008

First‐generation hatchery and wild spring Chinook salmon Oncorhynchus tshawytscha from the upper Yakima River, Washington, were placed into an artificial stream and allowed to spawn. Seven independent test groups were placed into the stream from 2001 through 2005. No differences were detected in the egg deposition rates of wild and hatchery females. Pedigree assignments based on microsatellite DNA, however, showed that the eggs deposited by wild females survived to the fry stage at a 5.6% higher rate than those spawned by hatchery females. Subtle differences between hatchery and wild females in redd abandonment, egg burial, and redd location choice may have been responsible for the difference observed. Body size did not affect the ability of females to spawn or the survival of their deposited eggs. How long a female lived was positively related to her breeding success, but female origin did not affect longevity. The density of females spawning in portions of the stream affected both egg deposition and egg‐to‐fry survival. No difference, however, was found in the overall distribution patterns of the two types of females. Other studies that have examined the effects of a single generation of hatchery culture on upper Yakima River Chinook salmon have disclosed similar low‐level effects on adult and juvenile traits. The cumulative effect of such differences will need to be considered when hatcheries are used to restore depressed populations of Chinook salmon.
Field Estimation of a Lethal Oxythermal Niche Boundary for Adult Ciscoes in Minnesota Lakes
Authors: Jacobson Peter C. , Jones Thomas S. , Rivers Pat , Pereira Donald L.
Published: September 2008

Ciscoes Coregonus artedi are coldwater stenotherms that are sensitive indicators of ecological stressors, such as eutrophication and climate warming, that reduce coldwater habitat. Temperature and oxygen profile data were collected during cisco mortality events at 17 lakes during an unusually warm summer in Minnesota in 2006. Combinations of temperature and oxygen from the profiles were mapped onto a two‐dimensional niche space to directly quantify an oxythermal lethal niche boundary for ciscoes. Quantile regression was used to estimate the niche boundary that described lethal combinations of oxygen and temperature for cisco. The fitted lethal oxythermal niche boundary exhibited a curvilinear interaction between lethal temperatures and lethal oxygen concentrations. The lethal temperature under normoxia (about 8 mg/L) was estimated to be 24°C. Lethal temperatures were progressively less at lower lethal oxygen concentrations (e.g., the lethal temperature was 23.0°C at 5.0 mg/L, 22.0°C at 3.0 mg/L, and 19.5°C at 1.0 mg/L). The lethal oxythermal niche boundary provides a basis for quantifying coldwater cisco habitat under current and future climate warming and water quality conditions.
Distribution and Use of Shallow‐Water Habitats by Pacific Sand Lances in Southeastern Alaska
Authors: Johnson Scott W. , Thedinga John F. , Munk Kristen M.
Published: September 2008

The Pacific sand lance Ammodytes hexapterus is an important prey species, but little is known about its distribution and habitat use, especially among early life stages in southeastern Alaska. To address this information need, we examined the distribution and habitat use of Pacific sand lances by sampling a variety of shallow‐water habitats (depth < 6 m) with a beach seine seasonally throughout southeastern Alaska from 1998 to 2006. An estimated 81,939 Pacific sand lances were captured at 31 of 49 locations and in 109 of 610 seine hauls. Total catch and percent frequency of occurrence (FO; [number of seine hauls with Pacific sand lances/total number of hauls] × 100) was greatest in summer (73,033 fish, FO = 21%), followed by spring (8,857 fish, 18%) and winter (49 fish, 1%). Pacific sand lances were captured in all habitat types; total catch in spring ranged from 16 fish in understory kelp (e.g., Laminariales) to 8,525 fish in bedrock outcrops, whereas total catch in summer ranged from 5,858 fish in sand to 54,851 fish in eelgrass Zostera marina. The FO was relatively consistent among the above habitat types and ranged from 15% to 20% in spring and from 15% to 35% in summer. Pacific sand lances use a variety of shallow‐water habitats for at least 4 months in spring and summer; habitat is not limited to sandy substrates for burrowing but also includes bedrock, eelgrass, and kelp as likely foraging areas. Age‐1 and younger Pacific sand lances dominated our catches; size range of captured fish was 39‐168 mm fork length. The importance of Pacific sand lances in the diets of other fishes, seabirds, and marine mammals justifies the need to better understand, protect, and manage habitats that are essential to Pacific sand lances.
Chromium in cement: development of an analytical method and investigation of contamination sources
Authors: Khmiri A. , Samet B.
Published: September 2008

A rapid method for determining chromium in cement has been developed. Chromium was analysed by atomic absorption spectrometry after dissolution of the sample in an acid medium. Precision, repeatability, reproducibility, accuracy and conformity prove that chloronitric attack followed by atomic absorption is a reliable method to determine total chromium and hexavalent chromium. The follow-up of the evolution of the chromium content along the cement chain of production showed that clay was the raw material, most contaminated by chromium and that the correction additions, mainly brick scrap, contributed significantly to the concentration of chromium in the kiln feed. It was also shown that the abrasion of the crushing bodies contributes slightly to the increase in the chromium content and that the clinkerisation process increases the chromium content in the clinker considerably, due to its presence in the fuel (petroleum coke).
Motivational Interviewing as a Pregroup Intervention for Partner-Violent Men
Authors: Musser Peter H. , Semiatin Joshua N. , Taft Casey T. , Murphy Christopher M.
Published: September 2008

This study investigated the effects of a pregroup motivational intervention for domestic abuse perpetrators. Men presenting for treatment at a community domestic violence agency (N = 108) were assigned to receive either a two-session intake using the techniques of motivational interviewing (MI) or a structured intake (SI) control. All participants were then referred to a cognitive behavioral treatment (CBT) program in groups homogeneous with respect to intake condition. The motivational intake led to more constructive insession behavior during the early phase of group CBT, greater compliance with group CBT homework assignments, higher late session therapist ratings of the working alliance, and more help seeking outside of the domestic violence program. No significant effects of intake condition were found on session attendance, self-reports of readiness to change abusive behavior, or client reports of the working alliance. Partner reports of abusive behavior outcomes during the 6 months after group CBT revealed a marginal effect favoring the MI condition on physical assault. The findings suggest that motivational interviewing can increase receptivity to partner violence interventions.
Motivational Interviewing as a Mechanism for Change in Men Who Batter: A Randomized Controlled Trial
Authors: Kistenmacher Barbara R. , Weiss Robert L.
Published: September 2008

The present study reports on the potential effectiveness of motivational interviewing (MI) in changing the way batterers think about their violent behavior. Thirty-three domestic violence offenders who were court-mandated to treatment were randomly assigned to MI or a control condition before attending their first mandated treatment group. Consistent with predictions, the MI group demonstrated generally more improvement on stages of change subscales than the control group. Further, the MI group demonstrated a significantly greater decrease in the extent to which they blamed their violence on external factors. Current data indicate that MI has the potential to increase batterers’ motivation to change, although validation trials with larger sample sizes and more refined measures are required.
Exploring Bystander Presence and Intervention in Nonfatal Violent Victimization: When Does Helping Really Help?
Authors: Hart Timothy C. , Miethe Terance D.
Published: September 2008

The current research explores two important issues related to the study of bystander intervention during nonfatal violent victimization. First, using data from the National Crime Victimization Survey (NCVS), conjunctive analysis of case configurations is conducted to identify the most dominant situational contexts in which a bystander is present during violent crime. Second, the prevalence of responses in which a bystander helps or hurts during these events is determined. Results and the analytical approach used in this investigation are discussed in terms of their implications for future research on the normative and deviant reactions to crime by third parties and its victims.
Contaminated suspended sediments toxic to an Antarctic filter feeder: Aqueous- and particulate-phase effects
Authors: Hill Nicole A. , King Catherine K. , Perrett Lisa A. , Johnston Emma L.
Published: September 2008

Disturbances such as dredging, storms, and bioturbation result in the resuspension of sediments. This may affect sessile organisms that live on hard substrates directly above the sediment. Localized sediment contamination exists around many Antarctic research stations, often resulting in elevated contamination loads in marine sediments. To our knowledge, the potential impact of resuspended contaminated sediments on sessile fauna has not been considered, so in the present study, we assessed the sensitivity of Antarctic spirorbid polychaetes to aqueous metals and to metal-contaminated sediments that had been experimentally resuspended. Worms were first exposed to aqueous metals, both singly and in combination, over 10 d. Spirorbid mortality was tolerant to copper (median lethal concentration [LC50], 570 μg/L), zinc (LC50, >4,910 μg/L), and lead (LC50, >2,905 μg/L); however, spirorbid behavior responded to copper concentrations as low as 20μg/L. When in combination, zinc significantly reduced mortality caused by copper. A novel technique was used to resuspend sediments spiked with four concentrations of three metals (up to 450 μg/g dry wt of copper, 525 μg/g dry wt of lead, and 2,035 μg/g dry wt of zinc). The response of spirorbids to unfiltered suspended sediment solutions and filtered solutions (aqueous metal exposure) was measured. Suspended sediments were toxic to filter-feeding spirorbids at concentrations approximating those found in contaminated Antarctica areas. Toxicity resulted both from aqueous metals and from metals associated with the suspended sediments, although suspended clean sediments had no impact. To our knowledge, the present study is the first to show that resuspension of contaminated sediments can be an important pathway for toxicity to Antarctic hard substrate organisms. Based on the present results, current sediment-quality guidelines used in the evaluation of Australian sediments may be applicable to Antarctic ecosystems.
Design and Implementation of Retention/Filtration Media for Sand Control
Authors: Underdown David R. , Hopkins Sam
Published: September 2008

The factors that control the performance of sand-control screens that use woven metal mesh as the filter media (i.e., commonly called premium screens), are not, generally, well understood by the end user. The end user is told that premium sand-control screens use filter media such as Dutch, Dutch Twill, or a Reverse Dutch Twill woven metal mesh, and in some cases the manufacturer will promote the benefit of multiple layers of woven-metal-mesh filter in the screen to control the sand. All this information is interesting, but the end user really does not understand the significance of the information.

This paper presents the results of a study to evaluate the effect of different metal-mesh weaves on the performance (e.g., dirt holding capacity, and plugging tendency) of media commonly used in sand-control screens. The work also introduces a new approach to designing sand-control screens that use woven-metal-mesh material. The performance criteria used in the evaluation of different designs for the filter media include the control of solids and the impact of particle size distribution on the formation of plugging on the surface and in the filtration media. Laboratory testing demonstrates that use of a different type of construction of the retention/filtration media allows for greater performance than media currently used in premium sand-control screens.

The significance of the approach discussed in this paper is the ability to design and engineer a premium sand-control screen with a retention/filtration medium for a given particle size distribution of the formation that allows for maximum oil production and minimum solids production. Critical to the success of this approach to designing sand-control screens is the thorough evaluation/testing of multiple media types to create the "formation specific" design.
Remote Real-Time Well Monitoring and Model Updating Help Optimize Drilling Performance and Reduce Casing Strings
Authors: Goobie Roger B. , Tollefsen Ed , Noeth Sheila , Sayers Colin , den Boer Lennert , Hooyman Pat , Akinniranye Goke , Cooke Jay , Thomas Ron , Carter Edgar
Published: September 2008

Remote real-time pore pressure monitoring using a combination of Logging-While-Drilling (LWD) services coupled with a predrill pore-pressure model reduces risk and cost by providing significant insight into wellbore stability and allowing for casing seat optimization. This paper presents the results of a shelf job in the Gulf of Mexico (GoM) that allowed an operator to drill successfully in a very tight hydraulic envelope and even eliminate a string of casing.

The uncertainty in the pore-pressure prediction ahead of the bit can be significantly reduced by model updating. The LWD measurements allow the predrill velocity-to-pore-pressure transforms to be updated while drilling using the velocities from the sonic tool and pressures from the LWD formation pressure tool. This calibrated transform is then applied to revise the predrill pore-pressure model while drilling, and thus provide an estimate ahead of the bit. In this case study, the predrill model used interval velocities extracted from a 3D mechanical earth model of the northern GoM based on velocities derived from checkshots and sonic logs. These velocity data were kriged to give a 3D velocity model over the entire northern GoM with uncertainty estimates.

Using state of the art LWD technologies, a new methodology was used to optimize drilling performance on a well in Vermillion Block 338. Continuously updated LWD annular pressure measurements effectively gauge wellbore pressures and help the driller rapidly intervene in pressure and/or geomechanical wellbore stability issues. A complete understanding of the hydraulic forces acting on a borehole can increase the rate of penetration, provide greater safety, minimize casing strings, reduce or eliminate kicks and formation fracturing, and allow faster and less expensive completions.

The techniques described in this paper using real-time measurements allowed the operator to extend both the 9 5/8-in. intermediate casing and 7 in. liner to TD. As a result, a critical casing string was pushed 1,287 ft deeper than planned and a pre-planned 5 in. liner eliminated. This saved casing expense, as well as slimhole drilling and completion costs.
Transport of Small Cuttings in Extended-Reach Drilling
Authors: Duan Mingqin , Miska Stefan , Yu Mengjiao , Takach Nicholas , Ahmed Ramadan , Zettner Claudia
Published: September 2008

Field experience has shown that inefficient transport of small cuttings is a main factor for excessive drag and torque during extended-reach drilling; however, very little is known about the transport behavior of small cuttings. In this study, extensive experiments with three sizes of cuttings (0.45 to 3.3 mm) were conducted in a field-scale flow loop (8 in.×4.5 in., 100-ft long) to identify the main factors affecting small cuttings transport. The effects of cuttings size, drillpipe rotation, fluid rheology, flow rate, and hole inclination were investigated.

The results show significant differences in cuttings transport based on cuttings size. Smaller cuttings result in a higher cuttings concentration than larger cuttings in a horizontal annulus when tested with water. However, a lower concentration was achieved for smaller cuttings when 0.25-ppb polyanionic cellulose (PAC) solutions were used. Unlike the transport of large cuttings, which is mainly dominated by fluid flow rate, the key factors controlling small cuttings transport were found to be pipe rotation and fluid rheology. Improvement by pipe rotation in the transport efficiency of small cuttings is up to twice as large as the improvement in large cuttings transport. Compared with water, PAC solutions significantly improve smaller cuttings transport, while the transport of larger cuttings is only slightly enhanced.

Mathematical modeling was performed to develop correlations for cuttings concentration and bed height in an annulus for field applications. Predictions from a three-layer model previously developed for larger cuttings were also compared with experimental results. Differences (up to 80%) indicate the need for improving the frequently used three-layer model by including correlations specifically developed for small cuttings to get a better design of extended-reach drilling. This study is also useful for horizontal or high-angle well drilling and completion through sand reservoirs.
Design of Well Barriers To Combat Circulation Losses
Authors: Aadnoy Bernt S. , Belayneh Mesfin , Arriado Miguel , Flateboe Roar
Published: September 2008

The paper summarizes a 10-year research program at the University of Stavanger in borehole fracturing and mud design. Novel fracturing cells and mud cells were built to better understand the mechanisms that lead to circulation losses. Numerous experiments were conducted using both oil- and water-based drilling fluids.

The paper presents a new mechanistic model for fracturing called "the elastoplastic-barrier model." It is different from other recent models, and it is verified with laboratory experiments. In simple terms, it defines optimal barrier filtrate loss to place particles in the loss zone, and the mechanical strength of the particles required to resist losses. Selected laboratory experiments are presented demonstrating that borehole fracturing resistance can be improved significantly by changing the mud composition.

While testing commercial lost-circulation-material (LCM) products, it was found that some worked well, some were poor, and some worked only in synergy with others. On the basis of these findings, the compostion of an optimal LCM pill will be presented. Nonpetroleum products also have been tested to search for improvements in mud design. One result is that calcium carbonate can be replaced with more-efficient materials. We also have shown that adding small amounts of carbon fiber has a positive effect.

This research has been conducted in close cooperation with major mud companies and operators. A field case is presented from a shallow field. The mud was designed and tested during operation at the laboratory of the University of Stavanger. The result was a clear increase in fracture pressure, resulting in a successful operation.
An ICA Approach to Purify Components of Spatial Components of Seismic Recordings
Authors: Haghighi Arash Moaddel , Haghighi Iman Moaddel
Published: September 2008

Decomposing linear mixtures or superpositions into their components is a problem occurring in many different branches of science, such as telecommunications, Seismology, and biomedical signal analysis. Blind source separation (BSS) in particular, deals with the case where neither the sources, nor the mixing matrix or process of mixing are known, the only available data are the mixed signals. The standard approach to BSS is Independent Component Analysis (ICA).

In fact ICA is a statistical technique that represents a multidimensional random vector as a linear combination of nongaussian random variables - ‘independent components’-that are as independent as possible.

In 3D seismic surveys involved in exploration operations, recorded time series in each dimension are taken to be independent in nature and behavior, which is a direct result of physical response of materials into which seismic waves penetrate. But as an observation one dimension is sometimes contaminated up to one fifth by information from another dimension, resulting an increase in SNR.

Here we have applied FAST-ica algorithm to a 3D seismic record sample to extract least dependent recordings for all three spatial dimensions. In order to test the reliability of the decomposition we used mutual information (MI) transfer between signals to confirm the result of outputs from FAST-ica algorithm as, least dependent components, leading to more accurate interpretations of petrophysical parameters.
The Art of Mentoring As Told by Both Sides of the 3-Decade-Old Struggle in the Petroleum Industry
Authors: Edwards J. T. , Woo G. T.
Published: September 2008

Along with the dramatic price changes in the petroleum industry including gas and oil, there is one resource that has been seriously overlooked and undervalued: experienced personnel in the field, including engineers and other technical specialties. The real challenge is how this lack of experience is overcome in the short term, rather than just waiting for the passage of time. The petroleum industry can make significant gains quickly by investing in true, on the job mentoring. It could mean the difference between success and failure. Companies could be focusing less on headcount, and more on effective and well organized mentoring programs.

The shifts in supply and demand over the past three decades have at times left many within the technical side of the industry barely holding onto their jobs or looking at other vocations in order to maintain employment. Hoping to ride out the waves of boom and bust, those with valuable experience are not passing on their knowledge at a rate that can sustain our industry. These trends have led many colleges and universities to back away from true Petroleum degrees. Now that a demand is increasing again, how can the voids be filled quickly in the field with qualified and well-trained personnel, while the slow process of ramping up academic programs begins?

The only way to fill the void is through hiring from other engineering fields along with the inclusion of like-minded individuals with technical backgrounds. But now that they have been hired and are on the job, how can we maximize their success? The answer is mentoring. This paper will present the case with a personal perspective as told by mentors in the petroleum industry on both sides of the struggle, spanning three decades.
Improving Well Safety and Maximizing Reserves Using an Innovative Surface Controlled Subsurface Safety Valve (SC-SSSV)
Authors: MILLET François , PETIT Hervé , WALLEZ Gery , LALANNE Philippe , DUCASSE Alain , BARZU Emile
Published: September 2008

A common cause of failure with surface-controlled, subsurface safety valves (SC-SSSV) is a defect in the down-hole hydraulic line, which controls the valve from the surface. Such a failure generates production losses and requires the intervention of a costly workover rig - usually not immediately available. In order to alleviate this type of situation, a system has been developed where the physical control line has been replaced by a communication system based on electromagnetic waves. The surface emitter continuously sends a signal to the SC-SSSV. Both items are designed to be fail-safe. The normally-closed valve remains open while receiving the signal and closes as soon as the signal is lost. This innovative, control-line free, wireline-retrievable SC-SSSV can be set in any landing nipple profile or anywhere in the tubing using monobore lock technology without a workover or well head modification.

The primary application is to secure wells with a damaged or blocked control line, damaged landing nipple, or wells completed without an SC-SSSV. It provides an immediate cost-effective solution - allowing production to resume with a surface-controllable safety barrier while avoiding or postponing a costly workover. With the arrival of this technology, sub-standard and temporary solutions, such as the normally-open velocity and ambient valves, no longer need to be considered. Another application is to free up a hydraulic SC-SSSV landing nipple in order to install a device like a capillary string for chemical or gas injection at the bottom of the well safely.

A prototype has been built and successfully tested for six months in a flowing gas well with 15% H2S – the case history is presented. The tool has proven to be easy to install and reliable. Deployment will start in 2008. Thousands of wells are concerned around the world.

This breakthrough slickline product offers new possibilities for safely and efficiently managing the countless failures of hydraulic SC-SCSSVs. Its versatility brings a reduction in production losses and provides the user with a cost-effective and reliable solution.
Dynamic Buckling and Snaking Motion of Rotating Drilling Pipe in a Horizontal Well
Authors: Gao Guohua , Miska Stefan
Published: September 2008

This paper is focused theoretical and experimental study on the dynamic buckling and the snaking motion of rotating pipe in a horizontal well. Firstly, a comprehensive dynamic buckling model, a group of fourth order non-linear partial differential equations were derived and discussed. Then, a perturbation solution of the model was obtained, which represents the snaking motion of the rotating pipe. Based the perturbation solution, critical dynamic buckling load and dynamic behavior of rotating pipe were analyzed. It has been found that there are two different kinds of snaking motion. One type is that the pipe moves up and down around its static buckling configuration. The other is that the pipe moves from one to another side of wellbore.

The authors also conducted experimental study with a small scale experimental facility. Depending upon axial compressive load and rotating speed, different motion patterns of drilling pipe were observed. Measurements of axial load at both ends and axial displacement at the loaded-end are recorded. Theses observations and measurements provide us with very important information about the dynamic behavior of rotating pipe in a horizontal well. Observations also show that the pipe may take two different patterns of snaking motions. Both critical static buckling load and dynamic buckling load were measured with this facility. Both theoretical and experimental results showed that the pipe rotation does not affect the critical load of sinusoidal static buckling and snaking dynamic buckling. Experiment also showed that there exist two different snaking motions, which support the analytical solution of the dynamic model presented in this paper. The results are useful for practical design applications related to calculating buckling loads, selection of BHA elements and pipe rotational speeds.
Hydraulic Fracture Feasibility, Design, On-Site Supervision and Post Job Evaluation in Southeast Pakistan Gas Fields
Authors: Lolon E. P. , Quirk D. J. , Enzendorfer C. K. , Bregar U. B. , Shah S. Q. , Mayerhofer M. J. , Cipolla C. L.
Published: September 2008

This paper presents the results of a fracture feasibility and design study, treatment execution and post treatment evaluation for a hydraulic fracture campaign in the Sawan and Miano Gas fields, located in the Sindh Province, Pakistan. This first successful fracture campaign (in four wells) was conducted from December 2005 to July 2006. One well is located in the Miano and three wells in the Sawan gas field targeting the Lower Goru B and Lower Goru C sands at depths of about 3,300 m. Several injection tests and minifracs prior to the main treatment were performed to quantify closure stress, fluid leakoff, perforation friction, near-wellbore tortuosity, and fracture complexity. Issues such as formation water sensitivity and fines migration are discussed. High reservoir temperature, proppant flowback issues and risk of fracing into a water transition zone are some of the challenges faced during the fracture campaign. A variety of fracture design sensitivities were performed to evaluate the effects of pad size, treatment size, fluid and proppant types on fracture geometry, conductivity and gas production.

In the Sawan, fracturing was found to be simple as opposed to more complex fracturing in the Miano area. Permeability ranges from low 0.06 mD to moderate 8 mD in the four fractured wells. Treatment designs were adjusted accordingly to minimize screen-out risk and maximize fracture stimulation efficiency. To help reduce proppant flowback into the wellbore, partially cured, resin-coated proppant was pumped at the end of the treatments. A low-polymer loading, high-temperature, CMHPG fracturing fluid was used due to a high-temperature reservoir. This type of fluid provided high fluid viscosity for proppant transport while also minimizing polymer damage to the proppant pack. The fracture campaign has successfully increased the gas production by two to four folds.
Revised Big Bore Well Design Recovers Original Bayu-Undan Production Targets
Authors: Ledlow L. B. , Gilbert W. W. , Omsberg N. P. , Mencer G. J. , Jamieson D. P.
Published: September 2008

The Bayu-Undan gas recycling project is located north of Australia, in the East Timor Sea and is designed to produce 1,100 MMscf/D of wet gas, strip out 110,000 B/D of condensate/LPG, initially reinject 950 MMscf/D of lean gas, and later export up to 700 MMscf/D of lean gas to a LNG plant in Darwin. The initial development called for 16 North Sea-style, 7 in. monobore wells (11 producers and 5 gas injectors).

By May of 2003, it became apparent that the original well design would not achieve the 1.1 Bcf/D production target because of well construction problems. Three wells on the remotely located wellhead platform were abandoned because of wellbore instability. Without the production contribution from these wells, the first year's production target would not be met. To meet the production targets, a complete well redesign was undertaken. First, the tubing was upsized from 7 in. to 9-5/8 in. Then semi-openhole completions with pre-drilled liners and openhole packers were selected instead of the conventional cased and perforated design to reduce installation time. Finally, oil based drill-in fluid was selected to provide lubricity, temperature stability, and low liftoff pressure of the filter cake for rapid cleanup.

Utilizing the Big Bore design, the production capacity of +1.1 Bcf/D and injection capacity of 1.1 Bcf/D was achieved in June of 2004, ahead of schedule. The well count was also reduced from 16 to 12 wells (8 producers and 4 gas injectors.) Two producers had capacities in excess of 300 MMscf/D, and three gas injectors had injection capacities in excess of 350 MMscf/D. The increased production resulted in 19 MMstb of condensate/LPGs produced in the first year, some 7-8 MMstb more than would otherwise have been the case.
History Match and Reserve Evaluation of Hydraulically Fractured Wells: Low Permeability Field Case History
Authors: Colombo I. , Fanello G. , Valzania S. , Isella D. , Tealdi L.
Published: September 2008

Due to the production decline of mature fields, the possibility to drain low permeability formations became recently of great interest in the Congo basin. Some of these reservoirs can produce at economic rates only if massive hydraulic fracturing jobs are performed. In the Congo off-shore environment, the capital expenditure associated to such kind of interventions can be critical. It follows the need to accurately identify the candidates, and then properly design and model such hydraulic fractures in order to have sound production profiles for economic evaluations.

Accurately modeling hydraulic fractures and mid-long term production profiles of slanted fractured wells can be extremely challenging.

Analytical methods can be misleading in estimating production profiles of hydraulically fractured wells due to multiphase flow and the reservoir heterogeneity.

The paper describes the successful history match process for highly deviated wells with pre and post frac production history in Kitina 3A oil field.

The static and dynamic 3D model is calibrated with dynamic data with a step by step approach, starting with the data gathered in the prefrac production history. Different criteria to establish cuf off are tested in order to properly describe the reservoir net pay.

The post frac data give insight into fracture properties. A huge effort has been made in order to properly modeling both hydraulic fractures geometry and conductivity in a consistent way with the data obtained with the treatment interpretation. The hydraulic fractures are described in a full field 3D model using refined grids around the wells and tuning the grid dimensions in order to have both production accuracy and acceptable run time. History match process gives indications that fracture conductivity may differs significantly compared with the value of the frac job interpretation. In addition post frac history match is improved greatly by the knowledge of formation permeability through for example well test interpretation. On the base of the experience gathered on the simulation of such wells, some general guidelines are drawn for a wider application.
Casing Ultradeep, Ultralong Salt Sections in Deep Water: A Case Study for Failure Diagnosis and Risk Mitigation in Record-Depth Well
Authors: Zhang Jincai , Standifird William , Lenamond Chris
Published: September 2008

The deepest well drilled to date in the Gulf of Mexico, the Well #1 discovery well in Green Canyon, required setting casing in a 15,000 ft thick section of tectonically active salt. After casing collapsed in the initial wellbore, a comprehensive model was developed to characterize wellbore stability, salt creep mechanism and implications for well design, and mitigation options for future well construction.

To facilitate the construction of models characterizing the interaction of casing and salt, the regional pore pressure and in-situ stress setting was analyzed. This analysis revealed that pore pressure in this area shows a significant regression in the subsalt formations. This pore pressure regression, if not accurately predicted, can lead to significant problems with the wellbore including wellbore breakouts and drilling fluid losses. The combined challenges of open-hole wellbore instability, salt creep, and casing damage made well design and construction very difficult.

In this paper, models are utilized to replicate wellbore instability, salt creep and the interaction of halokinesis, wellbore geometry, casing stress, and drilling fluid hydrodynamics. The modeling reveals that casing failure was caused primarily by non-uniform contact of salt on casing thereby generating stresses that exceeded the yield strength of the lightweight casing. The same model showed that heavier casing could withstand identical, non-uniform stresses if loading was diametric and not axial. The model was used to prepare an optimized drilling program that mitigates the risk of non-uniform application of stresses by salt and non-uniform application of slip loading. Recommendations included under-reaming in the slip zone, the use of drilling fluid of appropriate composition, and cementing practices that improve the stress distribution on the casing. Further, after setting casing through the salt, relatively high mud weights were required to avoid a large differential between internal and external loading on the casing. High mud weight had implications for wellbore stability in open-hole while drilling the subsalt sections to reach the reservoir. Modeling predicted accurate in-situ stresses and pore pressures that were utilized to drill a bypass well that successfully reached an unprecedented depth of 34,189 ft.

Both analytical and 3-D elasto-plastic finite element methods (FEM) were applied to analyze casing failure mechanisms, coupling the effects of in-situ stresses and mud pressures with the overburden. The methods were also applied to analyze mineralogic parameters that influence salt creep. The modeling process is applicable to essentially all Gulf of Mexico extended-reach wells to be drilled through salt sections.
Identification of Bypassed Pays in Low-Resistivity, Thinly-Bedded, Sand-Shale Sequences in the Ghdames Basin of North Africa Through Use of the Wireline Formation Tester
Authors: Chu Wei-Chun , Welch Paul M.
Published: September 2008

This paper presents a discussion on the use of the Wireline Formation Tester (WFT) to identify oil-bearing intervals in a reservoir section that contains thinly-laminated, low-resistivity pay sections in the Ghadames Basin of southern Tunisia. Pay zones previously bypassed by conventional log analysis have been conclusively determined as oilbearing through use of the tool.

Three field examples are discussed on the use of the Downhole Fluid Analyzer (DFA) to determine hydrocarbon type and in-situ GOR for three different hydrocarbon phase environments.

The paper also discusses, again through use of field examples, how analysis of the post-DFA pressure response could be used to determine zonal producibility. This zonal producibility from the WFT is then compared to conventional well-test productivity. A close agreement exists between the WFT and conventional well-test productivity estimates. Thus, it eliminates the need for zones to be conventionally tested to determine productivity.

Finally, the paper provides a method to significantly reduce the time necessary to collect representative fluid samples through proper monitoring of the DFA data stream.
Scatter Search for Optimizing the Formation-Rate Analysis (FRA) Model
Authors: Li Baoyan , Georgi Dan , Wu Jianghui
Published: September 2008

The Formation Rate Analysis (FRA) method applies the multivariate linear regression method to invert pressure test data to estimate formation parameters. This method is simple and works well if the measured pressure transient noise is small. However, if the noise is large, errors in the estimated formation parameters are unacceptably large.

To solve this problem, we present a multi-scale scatter search optimization method. The basic idea of this optimization method is to iteratively generate sampling points using Hammersley random sequences in regions of various sizes in the parameter space. A reference data set is generated from the candidate optimal solutions and then used to filter the generated sampling points. The uncertainty of the calibrated formation parameters is quantified based on the searched valid optimal solutions.

We test this algorithm with formation test data from low permeability, high permeability, and tight formations. Its accuracy, efficiency, and reliability are validated. We also compare it with the original FRA method. The test results show that:

compared with the linear regression method, this algorithm more accurately estimates the formation parameters, particularly for the tight formation; compared with the direct Monte Carlo method, this new algorithm more efficiently provides calibrated formation parameters and quantifies more accurately the associated uncertainties; for high permeability formations, the estimated uncertainty of the calibrated formation pressure is very small; for tight formations, flow-line fluid compressibility can be effectively calibrated. However, the short length of the measured pressure transient results in a large uncertainty in the estimated formation pressure and mobility. Also, the mean value of the formation pressure is underestimated if the pressure transient is far from being stabilized.
Potential Microbial Enhanced Oil Recovery Processes: A Critical Analysis
Authors: Gray Murray R , Yeung Anthony , Foght Julia M , Yarranton Harvey W
Published: September 2008

This paper summarizes a critical review of possible microbially enhanced oil recovery (MEOR) methods and mechanisms to identify the most plausible utilization of microbial technology to enhance oil recovery. This paper is intended to stimulate discussion about broad applications of MEOR to field-wide improvement of oil displacement and recovery.

The potential benefits of different MEOR mechanisms were examined for a representative North Sea reservoir of sandstone containing a light crude oil. In each case, the material input requirements for nutrients and inoculum were calculated in relation to the projected incremental oil production, assuming that the key components (bacteria, nutrients, or bacterial products) were uniformly distributed in the swept zone of the reservoir.

The capillary number for the reservoir suggested that incremental oil recovery by biosurfactant production in situ would be modest under ideal conditions. The achievable yields would be lower because the Microbiol. in the reservoir would not be controllable to achieve sustained surfactant production. Losses of biosurfactants by adsorption to reservoir rocks and in situ biodegradation would further limit performance. The stimulation of surface active bacteria in the reservoir may affect the flow of fluids by producing emulsion droplets of oil coated with bacteria. The formation of a biofilm at the oil water interface changes the rheology of the interface, and may provide a useful mechanism to control mobility and areal sweep in reservoirs. Any mechanisms that required changes to large volumes of reservoir material, to produce gases, solvents, acids, or to significantly alter permeability, were not considered to be feasible. The limiting case of plugging fractures with bacteria and their polymeric byproducts does have considerable potential, but only for reservoirs which offer significant improvements in production with minimal injected volumes. The biological deposits must retain longer term resistance in situ to ensure that the anticipated production increase is achieved.

This study provides a methodology for the systematic assessment of MEOR proposals using well-established reservoir engineering principles.