bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel Modeling of Reference Values of Cardiovascular Risk Factors in Children Aged 7 to 20 Years
Authors: Mellerio Hélène , Alberti Corinne , Druet Céline , Capelier Florence , Mercat Isabelle , Josserand Emilie , Vol Sylviane , Tichet Jean , Lévy-Marchal Claire
Published: March 2012

BACKGROUND AND OBJECTIVE:

Most of the cardiovascular risk factors strongly associated with obesity and overweight vary with age and gender. However, few reference values are available for healthy European children. Our objective was to establish pediatric reference ranges for waist circumference, systolic and diastolic blood pressures, fasting lipid levels (total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides), glucose, and insulin.

METHODS:

A representative sample of 1976 healthy French individuals (1004 female participants and 972 male participants) aged 7 to 20 years was used to obtain age- and gender-specific normal ranges for each of the above-listed cardiovascular risk factors, based on the Royston and Wright method.

RESULTS:

Mean waist circumference increased with age in both genders and was slightly higher in males than in females. Whereas systolic blood pressure increased gradually with age, with the increase being steeper in males than in females, no gender effect was found for diastolic blood pressure, which was therefore modeled after pooling males and females. Total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglyceride values varied little with age and gender. Glucose and insulin levels revealed pubertal peaks, which were sharper in females than in males, reflecting the normal insulin resistance during puberty.

CONCLUSIONS:

These ranges can be used as references for European children to monitor cardiovascular risk factors and to plan interventions and education programs.
Motor Coordination and Psychosocial Correlates in a Normative Adolescent Sample
Authors: Rigoli Daniela , Piek Jan P. , Kane Robert
Published: March 2012

OBJECTIVES:

Previous research has revealed an important relationship between motor coordination difficulties and internalizing problems such as anxiety and depressive symptoms. However, further research is needed to understand the potential mediating factors in this relationship. The aim of the current study was to examine whether the association between motor coordination and emotional functioning is mediated by self-perceptions in a normative sample of adolescents.

METHODS:

Participants included 93 adolescents aged 12 to 16 years. The Movement Assessment Battery for Children–2 provided 2 indicators of motor coordination; the Mood and Feelings Questionnaire and Spence Children’s Anxiety Scale provided 2 indicators of emotional functioning; and the Self-Description Questionnaire–II provided 6 indicators for self-perceived competence.

RESULTS:

Structural equation modeling revealed that motor coordination affects emotional functioning via self-perceptions.

CONCLUSIONS:

These results suggest that the relationship between motor coordination and emotional functioning in adolescents from a normative sample may be understood in terms of a mechanism by which motor coordination has an indirect impact on emotional outcomes through various self-perception domains. These findings have important implications for increasing awareness and developing appropriate treatment programs for motor coordination and emotional difficulties.
Immune Status in Very Preterm Neonates
Authors: Azizia Mallika , Lloyd Jillian , Allen Meredith , Klein Nigel , Peebles Donald
Published: March 2012

OBJECTIVES:

Preterm neonates are at increased risk of sepsis compared with those born at term. We investigated immune status at birth and early neonatal life in very preterm neonates and its association with short-term outcomes.

METHODS:

Prospective observational study conducted at a university hospital recruiting 113 preterm neonates (23–32 weeks) and 78 controls. Monocyte major histocompatibility complex (MHC) class II expression, serum, and ex vivo lipopolysaccharide stimulated levels of six cytokines (tumor necrosis factor α, interleukin (IL)-1β, IL-6, IL-8, IL-10, and IL-12p70) were measured in umbilical cord blood and over the first 7 days. The presence of neonatal sepsis and histologic chorioamnionitis was recorded.

RESULTS:

Prematurity (preterm labor and preterm premature rupture of membranes cohorts), neonatal sepsis, and histologic chorioamnionitis were associated with significant reduction in monocyte MHC class II expression. Neonates who had evidence of subsequent protracted sepsis had low levels of MHC class II expression at birth. Serial monocyte MHC class II expression revealed a fall by day 2, in all preterm neonates, with the degree being influenced by both prematurity and sepsis, and incomplete recovery by day 7, suggesting immunoparalysis in preterm premature rupture of membranes and preterm labor cohorts. Whole blood lipopolysaccharide stimulation assay showed significantly lower tumor necrosis factor α, values in preterm neonates who subsequently developed sepsis indicating a degree of immunoparalysis.

CONCLUSIONS:

Our data support the concept that fetal exposure to inflammation before preterm delivery leads to subsequent endotoxin hyporesponsiveness (immunoparalysis), which increases the risk of subsequent sepsis and associated organ dysfunction.
The National Perinatal Hepatitis B Prevention Program, 1994–2008
Authors: Smith Emily A. , Jacques-Carroll Lisa , Walker Tanja Y. , Sirotkin Barry , Murphy Trudy V.
Published: March 2012

OBJECTIVE:

To determine the trends and outcomes of the national Perinatal Hepatitis B Prevention Program (PHBPP) for infants born from 1994 to 2008.

METHODS:

PHBPPs in state and city public health jurisdictions annually submitted program outcome reports to the Centers for Disease Control and Prevention. The annual number of births to hepatitis B surface antigen (HBsAg)-positive women was estimated and used to evaluate the percentage of PHBPP-identified HBsAg-positive pregnant women. PHBPP reports were used to assess program objectives achieved, and infant outcomes by 12 to 24 months of age.

RESULTS:

From 1994 to 2008, the estimated number of annual births to HBsAg-positive women increased from 19 208 to 25 600 (P < .001). The annual number of PHBPP-managed infants increased (P < .001), comprising 40.8% to 50.5% of the estimated number. On average, 94.4% of PHBPP-managed infants received hepatitis B immunoglobulin and hepatitis B vaccine within 1 day of birth. The percentage of infants who completed the vaccine series by age 12 months decreased from 86.0% to 77.7% (P = .004), but the percentage who received postvaccination testing increased from 25.1% to 56.0% (P < .001). Incidence of chronic hepatitis B virus infection among tested infants decreased from 2.1% in 1999 to 0.8% in 2008 (P = .001).

CONCLUSIONS:

The PHBPP achieved substantial progress in preventing perinatal hepatitis B virus infection in the United States, despite an increasing number of at-risk infants. Significant gaps remain in identifying HBsAg-positive pregnant women, and completing management and assessment of their infants to ensure prevention of perinatal hepatitis B virus transmission.
Accuracy and Usefulness of the HEDIS Childhood Immunization Measures
Authors: Bundy David G. , Solomon Barry S. , Kim Julia M. , Miller Marlene R.
Published: March 2012

OBJECTIVE:

With the use of Centers for Disease Control and Prevention (CDC) immunization recommendations as the gold standard, our objectives were to measure the accuracy (“is this child up-to-date on immunizations?”) and usefulness (“is this child due for catch-up immunizations?”) of the Healthcare Effectiveness Data and Information Set (HEDIS) childhood immunization measures.

METHODS:

For children aged 24 to 35 months from the 2009 National Immunization Survey, we assessed the accuracy and usefulness of the HEDIS childhood immunization measures for 6 individual immunizations and a composite.

RESULTS:

A total of 12 096 children met all inclusion criteria and composed the study sample. The HEDIS measures had >90% accuracy when compared with the CDC gold standard for each of the 6 immunizations (range, 94.3%–99.7%) and the composite (93.8%). The HEDIS measure was least accurate for hepatitis B and pneumococcal conjugate immunizations. The proportion of children for which the HEDIS measure yielded a nonuseful result (ie, an incorrect answer to the question, “is this child due for catch-up immunization?”) ranged from 0.33% (varicella) to 5.96% (pneumococcal conjugate). The most important predictor of HEDIS measure accuracy and usefulness was the CDC-recommended number of immunizations due at age 2 years; children with zero or all immunizations due were the most likely to be correctly classified.

CONCLUSIONS:

HEDIS childhood immunization measures are, on the whole, accurate and useful. Certain immunizations (eg, hepatitis B, pneumococcal conjugate) and children (eg, those with a single overdue immunization), however, are more prone to HEDIS misclassification.
The effect of early immunosuppressive therapy on the rate of resections performed in patients with Chron’s disease, in Veszprém county, Hungary, a population-based cohort study
Authors: Golovics Petra Anna , Lakatos Péter László , Dávid Gyula , Pandur Tünde , Erdélyi Zsuzsanna , Horváth Ágnes , Mester Gábor , Balogh Mihály , Szipocs István , Molnár Csaba , Komáromi Erzsébet , Lovász Barbara Dorottya , Szathmári Miklós , Kiss Lajos S. , Lakatos László
Published: March 2012

Medical therapy for Crohn’s disease has changed significantly over the past 20 years with the increasing use of immunosuppressants. In contrast, surgery rates are still high and evidence about the the changes in the outcome of Crohn’s disease over the past decades is scarce. Aims: The objective of this study was to analyze the evolution of the surgical rates and medical therapy in the population-based Veszprém county database. Methods: Data of 506 Crohn’s disease patients were analyzed (age at diagnosis: 31.5 years, SD: 13.8 years). Both hospital and outpatient records were collected and comprehensively reviewed. The study population was divided into three groups based on the year of diagnosis (cohort A: 1977–1989, cohort B: 1990–1998 and cohort C: 1999–2008). Results: Overall azathioprine, systemic steroid, and biological (only available after 1998) exposure was 45.8, 68.6, and 9.5%, respectively. The 1 and 5-year probabilities of azathioprine use were 3.2 and 6.2% in cohort A, 11.4 and 29.9% in cohort B, and 34.8 and 46.2% in cohort C. In multivariate analysis, decade of diagnosis (P<0.001), age at onset (P = 0.008), disease behavior at diagnosis (P<0.001), and need for systemic steroids (P<0.001) were significantly associated with the time to initiation of azathioprine therapy. Early azathioprine use was significantly associated with the time to intestinal surgery in Crohn’s disease patients; in a multivariate Cox analysis (HR: 0.43, 95% confidence interval (CI): 0.28–0.65) and after matching on propensity scores for azathioprine use (HR: 0.42,95% CI:0.26–0.67). Conclusions: This population-based inception cohort showed that reduction in surgical rates was independently associated with increased and earlier azathioprine use. Orv. Hetil., 2012, 153, 541–552.
Chronic stress and epigenetics. Relation between academic sciences and theology
Authors: Simon Kornél
Published: March 2012

The author gives a short account on the principles of Selye’s stress theory, and discusses similarities and dissimilarities of acute and chronic stress. Both the external, and the internal environment, as well as the psycho-mental status are involved in the notion of the environment. Basic principles of epigenetics are reviewed: interaction between environment and genes, neuroendocrine and enzymatic mechanisms involved in silencing and activation of genes, notions of phenotypic plasticity, and epigenetic reprogramming are discussed. Epigenetic mechanisms of interrelation between pathological clinical states (diseases) and the characteristic phenotypes, causative role of psycho-mental status in evoking pathological somatic alterations, and the potential therapeutic consequences are briefly discussed. The etiological role of chronic, civilization stress in producing the worldwide increment of cardiovascular morbidity is cited, argumentation and criticism of the current therapeutical practice is discussed. The author concludes that recent advances in epigenetic knowledge seem to solve the controversy between the academic and theological sciences. Orv. Hetil., 2012, 153, 525–530.
The Success of Through-Tubing Impact Hammers to Dislodge Fish or Scale from Wellbore
Authors: Mitchell Michael W. , Ingram Gary , Haq Mohammed A. , Rossing Michael
Published: March 2012

Wellbore obstructions are a common dilemma and typically must be removed as they can severely restrict a well’s production capability and have proven to be very costly. For instance, scale formation will eventually result in lower yields and well failure, while a fish left in a well can hamper future wellbore operations.

The thru-tubing well intervention impact hammer was designed to dislodge fish or scale from a wellbore, by delivering an upward or downward impact force. The tool is activated by flow, in combination with compressive or tensile force, depending on the required impact. In operations that require bi-directional forces, both the single-acting up (SAU) and single- acting down (SAD) can be used concurrently on the same bottom-hole assembly (BHA). This paper describes the performance of "fluid activated impact hammers" for fishing operations. Case histories of recent field results are also discussed which illustrate the efficient removal of wellbore obstructions in deviated wells. This enables the well to be put back on production quickly and saves cost.

The impact hammers are utilized in various applications, such as shifting sleeves, shearing pins, breaking disks, assisting with fishing operations and scale removal; in fact, any application where high frequency localized impacts are required. The tool’s impact force can be adjusted to accommodate the specific parameters of an operation. Its maximum capacity is up to 80,000 lb (36,000kg) per impact depending on tool size. The impact hammers enable operators to cost-effectively remove a wireline-retrievable packer (WRP), where conventional wireline techniques have failed and jars had proved impractical. The design allows adjustment of the impact force by manipulating the tension or compression weight on the tool. This maximizes operational efficiency, by enabling the impact hammer to function in numerous situations and the individual up and down hammer components enable the BHA design to accommodate specific jarring direction.
Coiled Tubing Sand Cleanout at Low-Bottomhole-Pressure, Large-Diameter-Casing, and Long-Horizontal-Well Applications in Deepwater West Seno Field
Authors: Putra Koesnihadi J. B. , Wijoseno D. A.
Published: March 2012

The most challenging clean out work in the world of coiled tubing (CT) is cleaning out inside a large diameter casing at a low bottom hole pressure. In West Seno field, this type of work is the basic requirement to be able to recover production, which is mostly from sanded up & depleted horizontal wells. Deep wells & limited capacity of the tension leg platform (TLP) prohibit the use of big size coil tubing and this fact added complexity to the job. However, with the integration of several methods such as the utilization of special rotating jetting system, real time fiber optic downhole telemetry system, gas lift injection technique & the use of a new clean out shear thinning oil based gel fluid which has superior suspension ability, the work that was almost impossible before is now viable.

This paper will discuss two sand cleanout jobs in West Seno field, where one was successful & the other a failure. Both wells involved extremely challenging sand cleanout jobs in low bottom hole pressure (BHP), large diameter casing and long horizontal section below 3-1/2" tubing. The astonishing high sand retention & carrying capability of the oil based gel fluid will also be discussed as one of the key success factor in this sand cleanout method.
Downhole Mixing Fracturing Method Using Coiled Tubing Efficiently: Executed in the Eagle Ford Shale
Authors: Lindsay S. , Ables C. , Flores D.
Published: March 2012

The increased demand for natural gas from shale plays in the US has forced the industry to be more efficient and develop innovative methods for fracture-stimulation optimization. Pinpoint-fracturing methods represent a divergence from the conventional methods with minimal optimization needed to help maximize reservoir volume. Multiple-interval completions can be performed efficiently so that all intervals receive the designed proppant volumes, one interval at a time. To accomplish this efficiency, coiled tubing (CT) is used to hydrajet perforate intervals for individual fracturing treatments at predesigned depths. Using various methods, CT depths can be corrected to actual depths, resulting in the precise placement of the perforations. Proppant plugs are used not only for isolating previously stimulated intervals, but also for maximizing the near- wellbore (NWB) conductivity necessary for long-term production performance. These fracturing methods do not require removing the CT from the well between treatments, and contingencies for early screenout can be remediated immediately with minimal impact to overall completion costs. Treating intervals individually substantially reduces the amount of hydraulic horsepower required onsite.

The latest pinpoint-fracturing technique provides maximum engineering flexibility in the executionof these treatments by allowing downhole control of the proppant schedule; this can be used to optimize the stimulated reservoir volume (SRV) on- the-fly, in real-time, and with downhole control. The process also incorporates large-OD CT. A recent 25-interval completion in the Eagle Ford shale demonstrated the process and is discussed in this paper.
Concentric Coiled Tubing Well Vacuuming Provides a Solution for Flowline Hydrate Removal Offshore Brazil
Authors: Duque L. H. , Guimaraes Z. , de Almeida V. A , Chagas J. V. , Barros R. W. , Fonseca P. R. , Siqueira N.
Published: March 2012

One of the problems oil operators face in offshore fields in the production phase is the formation of hydrates in the production flow line, as well as in the gas lift injection line, on subsea wells. This problem is a consequence of the very common conditions in flow lines of submarine wells on production for some time, with high pressures, low temperatures and certain water in produced fluids. Once the hydrate is formed on either line, well production is compromised. Although several products and procedures have been applied to avoid this type of scenario, the problem persists, and operators must remove the hydrate plugs from gas lift and flow lines.

As those hydrate plugs are formed under high pressure (1400 to 2800 psi) and low temperature (2 to 4 ºC), exposing them to lower pressures even at the same temperatures will dissociate them. Hence, an operator offshore Brazil has for many years removed such plugs by injecting nitrogen in the lines and releasing the pressure at certain point, thereby reaching the lower pressures required to dissociate the plugs.

This procedure, although effective, is inefficient, as a floating rig is required to access the subsea Christmas tree and control over the pressure applied on the plugs is limited. As a result, most of the time the removal of thoseplugs takes weeks, making it a high-cost solution.

To find a more efficient solution, the operator and a service company joined in a technological cooperation agreement to test on two wells a field-tested concentric coiled tubing technology with a jet pump, to improve the control over the low pressure applied on hydrates formed in flow and gas lift lines.

This paper presents the case histories on those pioneering operations, the challenges found in offshore scenarios and the successful results of the application.
Intervention Operations in a Gas Salt Dome Storage Well Using E-Line Conveyed Inflatable Packers
Authors: Osorio Alejandro , Brooks Robert T.
Published: March 2012

A Natural Gas Liquid fractionation plant located in Ontario, Canada receives NGL feedstock from local industries in order to produce propane, iso-butane, and condensate. These finished products are stored in horizontal tanks and storage wells/salt caverns located within the chemical plant. One of these gas storage wells required two bridge plugs in order to create a barrier to enable workover operations to be undertaken.

The objective was to load the well with brine in order to perform a logging run and replace the wellhead. There were two challenges involved in this operation: the lack of a workover rig and ‘wellbore fluid’ for setting an inflatable bridge plug. TAM International’s SlikPak™ Plus inflatable bridge plug setting system was the optimal solution because its ‘carry fluid’ configuration is capable of transporting the necessary inflation fluid to set a bridge plug without a workover rig on location.

An additional challenge had to be overcome as well; both bridge plugs had to pass through a 7.6" (193.4 mm) ID wellhead restriction and inflate inside 13-3/8" (339.7 mm) casing. Therefore, during the first run, the inflatable bridge plug setting system had to carry twenty gallons (75.70 L) of inflation fluid within twelve 3-½" (88.9 mm) OD fluid chambers located along the toolstring in order to inflate and set the retrievable bridge plug. The client provided 105 feet (32 m) of lubricator and two cranes in order to perform a safe rig up of the 94 feet (28.65 m) long toolstring. The first bridge plug was successfully set at a depth of 2,040 feet (621.8 m) by stroking the mechanical Pull Intensifier. After the plug was set, the top section of the well was bled off and loaded with brine to enable the usage of the ‘wellbore fluid’ setting configuration, which successfully set the second bridge plug 31 feet (9.44 m) above the first one.

After the wellhead changeout took place, both bridge plugs were successfully equalized, deflated, and retrieved in order to re-enable gas storage in this well. It is expected that there will be similar operations on a nearby well in the future.
Ultradeepwater Riserless Subsea Slickline Intervention From Vessel of Opportunity: BC-10 Brazil Case Study
Authors: Gordon S. , Larimore D. R. , Cervo G. , Boechat N. , Klein M. , Buchan M. , Morris C. J. , Davis Scott
Published: March 2012

As the number of subsea wells in deepwater environments increases, companies who operate in these regions continue to seek safer and more viable economic solutions for improving value realization through well intervention. Traditionally, subsea well interventions are conducted from heavy-weight, mobile offshore drilling units (MODUs) with riser packages. Unfortunately, these intervention operationsinvolve significant operating day rates with consequent NPV negative results.

This paper discusses a riserless intervention that was performed from a dynamically positioned multi-support vessel (MSV) that involved setting and recovery of a mechanical flow-control device in a well with a water depth of approximately 1900 m in the South Atlantic Ocean. The technologies and methods used in this intervention proved that these difficult subsea operations can be performed in a much more flexible and financially viable fashion than previously possible with conventional methods. The techniques developed for this operation also mitigated safety concerns for personnel and equipment, while executing the potential high-risk riserless intervention with success.

The paper will cover the record-breaking, light-weight intervention and the technologies used on this campaign that eliminated the need for a traditional MODU. Of particular interest is the unique vessel interface that allowed the operation to be performed safely and efficiently with slickline.

This successful intervention opens new opportunities for safer and more economical interventions in the deep and ultra deepwater arenas.
Through-Tubing Sand Control Repairs Damage to Openhole Gravel Pack in a Subhydrostatic Well
Authors: Long N. , Moloney C. , Srisa-ard S. , Son N. H.
Published: March 2012

Remedial Sand Control is a challenging operation that requires economic judgment especially in brownfields. The operation turns into a greater challenge when the well, that needs to have a damaged gravel pack screen repaired is a sub hydrostatic well. We carried out pioneering repair project that was simple and cost-effective with minimum logistics using thru-tubing sand control. This method adapts thru-tubing tool advantages of coiled tubing to convey and set a smaller sand screen in a damaged gravel pack bore. The operation started by cleaning out in the deviated wellbore, controlling the well from kicks and deploying a long sand screen string in open-well conditions.

To use this technique, two main challenges had to be solved. First, a long sand screen string had to be deployed into the wellbore on a production platform without the assistance of the derrick or platform crane. We used a two-stage self-skidding jacking frame with a 4-ton hydraulic winch to deploy the screen string into the well. Each un-deployed component of the screen string was lifted up from the storage rack with an elevator and connected with the string in the wellbore above the Christmas tree by a hydraulic tong. The installed string was held above the Christmas tree by a pneumatic slip and bowl mechanism. Second, the method must control the well from unexpected kicks while the sand screen is being deployed. We used hydraulic hydraulic well control method, which involves spotting "damaged free" lost-circulation material (LCM) fluid along target intervals and topping up with kill fluid, we also prepared a mechanical solution as a back up during job execution.
Case Study: Successful Application of Coiled Tubing With Real-Time Data Communication System for Selective Reservoir Treatments Using Straddle Packer Assemblies
Authors: Oberascher R. , Breimer G. , De Jonge R. M. , Gesterkamp S.
Published: March 2012

Two gas wells in Germany showed a decline in production and wellhead pressures and were selected for acid treatments for skin removal. PLT measurements showed that certain reservoir intervals were not contributing to the gas production. To optimise treatment of individual zones a coiled tubing intervention with a resettable straddle packer assembly was chosen. Due to the depth-critical nature of straddle packer interventions, the use of an accurate depth correlation system was required.

Straddle packer well interventions were performed with real-time data communication, using a mono-conductor cable inside the coiled tubing. The robust data communication system provides real-time information from a Casing Collar Locator (CCL), down-hole pressure and temperature gauges and is suitable for use during acid treatments due to a protective jacket around the cable. Information provided by the CCL tool ensures depth correlations, whereas differential pressure measurements from the down-hole pressure gauges provide positive information about the setting and sealing conditions of the inflatable packer system. The combination of the down-hole real-time temperature and pressure readings allow full control during the injection process to avoid re-fracturing during acidizing. Furthermore, down-hole temperature readings can be useful for optimizing the corrosion inhibitor loading in acid recipes.

In this paper the real-time data communication system and the benefits in combination with straddle packers are discussed. Case histories in Germany illustrate the preparations, the execution and the lessons learned from selective treatment interventions with coiled tubing and real-time data communication in two gas wells.

After the treatments the production of the wells was increased by more than 10% in each well. The real-time in situ pressures and temperatures were a valuable input to the reservoir engineering model and further action will be based on the results. With the use of the resettable straddle packer several zones were treated in one run resulting in reduced operating time and thus a minimum in lost production.
Full-Scale Fatigue Testing With 130K Yield Tubing
Authors: Faszold J. , Rosine R. , Spoering R.
Published: March 2012

Coiled tubing (CT) is widely used in the well-intervention business as a practical and cost-effective means of servicing wells. Since CT’s inception, the use of continuous steel tubular has been the primary means of conduit for the applications required. The performance of CT has vastly improved throughout the years because of advancements in the tubing material and manufacturing processes, as well as extrapolated models predicting low-cycle tubing fatigue life. Because of these developments, CT has expanded to meet the increased demands of deeper and more rigorous wells. Utilization of new higher- strength grades of tubing plays one of the most essential roles for performing in these critical well applications.

This paper presents results from full-scale fatigue tests performed at several pressures on newly developed 130,000-psi (130K) minimum yield strength tubing. CT made with this new 130K material was cycled to failure in a real-world full-scale fatigue test setup. The collected fatigue-life values will help modify and validate the existing fatigue model used for CT job designs as well as lead to the development of a potential new model with further refinement for critical applications. This full-scale testing also verifies the correlation between tubing life observed in controlled, short-stroke lab-scale fatigue tests and real-world applications.
Selective Stimulation of Multiple Sets of Perforations With Straddle Tools: Lessons Learned Lead to Equipment and Methodology Optimization
Authors: Chow J. H. , Skaardal B. , Murphy R. , Fagley S.
Published: March 2012

Many of the more recent wells in the Ekofisk Field in the Norwegian North Sea have been completed as monobores with lengthy horizontal or high angle sections and several distinct perforation clusters – as many as 20 separate zones can occur. The early methods of stimulating these chalk reservoirs involved high volume acid jobs, featuring bull heading, and the use of frac balls to divert flow to the less permeable sections. However after collection and evaluation of much data it became clear that many of the perforated intervals were unproductive. In order to address this situation it was decided to change to a selective stimulation method using newly designed coiled tubing (CT) deployed straddle pack-off tools.

Subsequent evaluation of this method indicated that it was a more productive approach; however the reliability of the method was less than desirable due to equipment and methodology failures. This realization lead to a detailed study of these CT operations carried out over a period of 9 months involving evaluation of the results of stimulating 9 separate wells with perforation sets ranging from 7 to 20. The study involved review of equipment design and function, material choice and methodology such as pumping techniques, use of glycol trains, accuracy of depth measurements, reliability of pressure measurement equipment etc. with the objective of optimizing them for future operations.

In this paper the authors will briefly review the history and results of the initial stimulation of these wells and the decision to go to straddle pack-off methods. They will then describe in detail the results of the study to evaluate and improve equipment and techniques, the lessons learned and the changes that resulted, leading to more reliable and effective stimulation techniques that are now being used.
Influence of a Straightener on Coiled Tubing Fatigue
Authors: Tipton Steven M. , Smalley Ed , VanArnam Don
Published: March 2012

When coiled tubing exits the injector on its way into the wellbore, it contains residual curvature as a result of prior bending events (i.e. being wrapped around the coiled tubing reel). Coiled tubing straighteners are being used increasingly during field operations to remove this residual curvature in order to help delay the onset of coiled tubing lockup and successfully perform work in extended reach wellbores containing long horizontal intervals.

To straighten the coiled tubing, rollers are used above the injector to apply bending in the reverse direction of the residual curvature. After the tubing exits the straightener assembly, the residual bend of the tubing will have been mitigated and the tubing will spring back into a predominantly straight line. However, the reverse bend applied during the straightening process increases the overall strain range experienced by the tubing and should adversely shorten its fatigue life. Accurate estimation of cumulative fatigue damage along the tubing is critical for making decisions about retiring strings prior to tubing failure, which can result in injury to personnel, equipment damage, unplanned release of fluids at surface, as well as costly fishing operations.

This paper presents a methodology to quantify the incremental fatigue damage imparted on the tubing as a result of coiled tubing straightener use. An analytical technique is presented to compute the reverse bending radius required for tubing straightening and to quantify its subsequent influence on incremental fatigue experienced by the tubing. The analysis shows that only the radius associated with the tubing reel affects the residual curvature of the tubing under normal field operating conditions. It is also shown that it is not necessary to release the straightener during POOH operations to avoid incremental fatigue damage from straightener use. A case study is presented and fatigue life reduction is estimated on the order of 30% for the example tubing size and grade and the geometry of the deployment hardware. A test program is discussed to explore the influence of these parameters.
The Effects of Fluid Hammer Tools and Lubricants on Plug Milling Efficiencies - A Comparative Study
Authors: Schneider Christopher , Castro Luis , Craig Steven , Maddy Timothy
Published: March 2012

Long-reach horizontal wells with "Plug and Perf" completions are commonly used to achieve economic production in today’s unconventional reservoirs. After the multistage fracture stimulation operations are completed, coiled tubing (CT) is often used to remove the plugs. However as the lateral reach of wells increase, plug removal using CT becomes less efficient as weight on bit (WOB) decreases. Over the last few years, various fluid hammer tools have been introduced to the industry and have improved plug milling times significantly.

This paper will review the results and operational improvements observed from milling operations using both fluid hammer tools and/or lubricants. Data from shale formations across the U.S. (Eagle Ford, Bakken, Haynesville, Barnett and the Marcellus) is included. Analysis from the use of three types of hammer tools and/or lubricants will compare results to those of base case operations completed without fluid hammer tools or lubricants.

The paper will detail improvements in milling efficiencies, number of stalls, and stuck pipe incidents. Results will focus on when to run hammer tools and when to introduce pipe lubricant to achieve optimum efficiencies.

Many operators rely on word of mouth to design and perform extended-reach CT milling jobs. This can result in poorly executed, ‘non-engineered’ plug milling operations. This paper will provide data to assist operators in improving their completion efficiencies
Improving Coiled Tubing Plug Drillout Operations in Shale Gas Completions
Authors: Rowden Vanessa , Carlile Joddie , Chavez Manuel
Published: March 2012

The tight margin nature of shale gas plays puts the pressure on operators to strike that optimal balance between cost and production gained. This effect is magnified by the ‘manufacturing mode' mentality that operators are striving for to get the most wells in the ground efficiently, cheaply, effectively, and safely as possible. This approach of course extends to every operation in shale gas completions, including coiled tubing plug drill-outs (CTDOs). This paper reviews one operator's quest to achieve this ‘balance' in CTDO operations as well as overcome technical challenges in two different shale gas plays - the Haynesville and Eagle Ford Shales.
Production Logging on Coil Tubing in a Marcellus Shale Horizontal Completion
Authors: Mccluskey A.
Published: March 2012

Production logging plays an important role in understanding the impact that well trajectory, completion practices and trials, and well placement have on EUR. The data can further help to characterize the reservoir in new plays. This is particularly true in the case when both water and gas production deviate dramatically from expectations. Logging helps to answer the questions: Are all zones and perforating clusters producing equally? Is the toe unloading? What is the flow regime? Is water production isolated to a particular interval? Can it be shut off?

In traditional vertical wells, electric line logging is most often used to acquire production data. In a horizontal well, both active and memory tools can be deployed on coil tubing to acquire production data. Using coil tubing for production logging has its own unique challenges, one of which is getting to TD without damaging the tools. The difficulty of this challenge can be compounded by long lateral lengths and high dog leg severity.

Well trajectory, well flow regime, water rate, and gas rate all have an effect on choice of logging tools and method for deployment. This paper will discuss two production logging attempts: 3 successful logs with active tools and 1 failure with memory tools. The one failed attempt involved a low gas rate, low pressure, high water rate well with severe dog legs near the heel where the coil could not reach the logging interval.

The sections in this paper will discuss the role of an effective cleanout and how to achieve its success as well as best practices for acquiring high quality production data. Each of the four logging jobs will be discussed in detail with results provided.
Optimizing Coil Tubing Extended-Reach Capabilities Through the Application of Downhole Friction Reduction Tools
Authors: Hilling S. , Ayling G. , Yeung J.
Published: March 2012

The demand for drilling and completing horizontal wells in both conventional and unconventional oil and gas plays has drastically increased in recent years. A growing economic and environmental appetite for ever increasing horizontal lengths continues to apply pressure on drilling and completion technologies. Although well engineering programs have improved and adapted to solve some of these issues, coil tubing reach capabilities can, at times, become the limiting design factor for horizontal wells. To tackle this issue, the industry has developed and adopted the use of downhole friction reduction tools to optimize and extend the range of coil tubing.

Using case history from Shell Canada’s Groundbirch shale gas development, this paper will compare and analyse the effectiveness of three different downhole friction reduction tools currently available to industry. While this paper will discuss the use of Tubing Force Analysis (TFA) modeling software to obtain representative values for comparison, the focus of the study is to compare the overall effectiveness of the three friction reduction tools using actual field data.
Reducing Operational Time, Fluid Usage, Hydraulic Horsepower, Risk, and Downtime: Targeted Fracs Using CT-Enabled Frac Sleeves
Authors: Castro Luis , Watkins Thomas , Bedore Brian , Holt Robert , Manuel Greg
Published: March 2012

Unconventional reservoirs are an increasingly important part of the hydrocarbon production pool in North America. Since reservoir conditions typically mandate the use of hydraulic fracturing for economical production results, a significant amount of resources are focused on making the fracturing process faster, more efficient and lower its environmental impact.

This operational review focuses on a novel technique to rapidly perform targeted annular hydraulic fractures by deploying an activation tool on coiled tubing (CT) to open frac sleeves in a horizontal well. The paper covers results from the first operation of its kind in the United States – where a total of 48 stages were fractured in approximately 100 hours of operational time.

The new technology does not involve dropping balls or setting composite plugs to isolate stages. Rather, the technique utilizes frac sleeves that are swiftly activated using a CT bottomhole assembly. The sleeves can be cemented in place if desired and have a full-bore internal diameter that does not require post-treatment composite plug millouts, further reducing overall completion time and efficiency.

The operator preferred this method due to its targeted nature, efficiency and potential fluid savings. As opposed to multi- cluster fracturing methods (such as ‘plug-and-perf"), a single entry point during the frac job promotes increased fluid velocity, allowing for a more aggressive sand ramp and reduced required hydraulic horsepower. Similarly, the single entry point ensures that a fracture is generated at each port, as opposed to the possibility that some clusters are not treated. In addition, since no composite plugs or diverting devices are required to be pumped down the wellbore, water usage is reduced considerably. The system, already used in thousands of fracturing stages in Canada, speeds up the completion process, uses less fluid, minimizes risks, and reduces overall downtime.
Milling of an Electric-Line Obstruction With Electric Line Conveyed Technology
Authors: Dulic A. , McIninch B. , Mullin M.
Published: March 2012

A new application of electric wireline tractors in combination with the well milling technology has been successfully proven in an offshore Equatorial Guinea well.

In July 2011 on a small, unmanned offshore platform in Equatorial Guinea, a downhole tractor and a milling tool were conveyed on electric line to remove an obstruction created by Lost in Hole (LIH) electric line cable and production logging tools (PLT).

By using customized core milling bits, 13 successful milling runs were made. During this unique operation, most of the milled wireline material was recovered, and the challenges of controlling torque and milling penetration were achieved. In between milling runs, slickline fishing attempts were made in order to recover the remaining LIH wireline. After the last milling run, a major breakthrough was made when the PLT string moved downhole to a position that uncovered the proposed new completion interval. Ultimately the well was perforated and returned to production at projected gas and condensate rates.

Milling of wireline and other well bore obstructions on electric line offers a cost efficient alternative technology to existing methods. Furthermore, it offers reduced Health, Environment and Safety (HES) risk benefits and logistical advantages.

This paper will describe the actual process from preparation to completion of this first-of-its-kind fishing operation.
High-Angle Gas Lift Valve Removal and Replacement in a Single Run
Authors: Chow Hayes , Herrmann Daniel , Condio John , Albright Jeremy , Burley Leighton , Greenlee James
Published: March 2012

An operator in Prudhoe Bay, Alaska required the ability to replace gas lift valves in their completion for improved oil production. Conventional methods had reached their limits due to extended well lengths and high-angle well deviations. Slickline was unable to overcome the higher deviations, while imprecise depth control during coiled tubing operations required multiple run-in-hole attempts to pull and replace the valve.

Based on previous, positive experiences with electric line - mechanical solutions, the customer chose a unique solution using a newly modified Kick-Over Tool (KOT). Two KOTs run in tandem and combined with a tractor and a hydraulic stroking tool (HST) were used to pull the existing gas lift valve (GLV) and replace it in a single run. The tractor conveyed the tool string to the correct depth where the HST and the first KOT provided the pulling force for removal. Then, the HST and second KOT were used to successfully install the new GLV into the mandrel.

The operator is now able to optimize their gas lift design without the limitations imposed by conventional means for installing GLVs such as slickline and coiled tubing. This allows them to place gas lift valves in the high angle sections when necessary for increased oil recovery from their reservoirs.

Few changes have been made to the Kick-Over Tool technology in the past 40 years but it has been recently improved to operate more reliably in deviated and horizontal wells and has been modified to accommodate the forces generated by the HST. This paper will describe the challenges with the planning and execution of this operation and the implications for future gas lift design.
Slickline-Conveyed Electromechanical Tool Utilization in Deepwater Gulf of Mexico
Authors: Gary B. , Schlechtweg J. , Clemens J. , Garrett J.
Published: March 2012

Traditional slickline work usually encompasses basic mechanical manipulation for downhole intervention work. In the recent past, a variety of battery-powered downhole tools have emerged in the market, providing additional deepwater solutions for the industry. These tools include the extended-reach downhole power unit and the smart release tool. The downhole electrical power unit is an electro-mechanical setting tool that uses a timer activation switch to begin the setting process for a variety of downhole tools. The smart release tool provides a timer-based mechanism to release the deployment wire from the downhole toolstring, eliminating the exposures associated with dropping a cutter in the event of a stuck tool. These tools can be conveyed on slickline for a variety of intervention solutions, including setting tubing plugs and packers, pulling subsea tree plugs, setting pressure gauges in tubing profiles, and providing a mechanical release in highly-deviated, extended-reach wellbores.

This paper discusses specific well-intervention case histories using the downhole electrical power unit and the smart release tool. In the first case history, the downhole electrical power unit was used to set a packer assembly during a safety- valve repair. The smart release tool was used to soft set memory pressure gauges in wells without functioning, permanent downhole gauges, eliminating the need for jar action that could damage the gauges. Adaptations were made to the existing tool designs to respond to the well-specific challenges.

These case histories demonstrate applications in which the electro-mechanical timer-activated tools have provided solutions for deepwater Gulf of Mexico well-intervention projects. The discussion includes lessons learned from previous project designs, development of operational best practices, and possible future applications to extend the role of slickline in deepwater operations. Applications may include the use of the downhole power unit to set packers and bridge plugs in conjunction with memory logging tools to correlate depth, as well as continued use of the smart release tool to minimize risks associated with downhole mechanical evaluation and memory data acquisition.