bluuebunny/crossref_metadata_2025 huggingface dataset:
Dating Violence, Childhood Maltreatment, and BMI From Adolescence to Young Adulthood
Authors: Clark Cari Jo , Spencer Rachael A. , Everson-Rose Susan A. , Brady Sonya S. , Mason Susan M. , Connett John E. , Henderson Kimberly M. , To Michelle , Suglia Shakira F.
Published: September 2014

BACKGROUND AND OBJECTIVES:

This study tested whether dating violence (DV) victimization is associated with increases in BMI across the transition from adolescence to young adulthood and whether gender and previous exposure to child maltreatment modify such increases.

METHODS:

Data were from participants (N = 9295; 49.9% female) in the National Longitudinal Study of Adolescent Health. BMI was calculated from measured height and weight at waves 2, 3, and 4 of the study. DV victimization was measured at waves 2, 3, and 4 by using items from the revised Conflict Tactics Scales. Linear regression by using generalized estimating equations with robust SEs was used to test the association. Models were stratified according to gender and history of child maltreatment.

RESULTS:

From baseline to wave 4, BMI increased on average 6.5 units (95% confidence interval [CI]: 6.2–6.7) and 6.8 units (95% CI: 6.5–7.1) among men and women, respectively, and nearly one-half (45.5% of men; 43.9% of women) reported DV at some point. In stratified models, DV victimization (β: 0.3 [95% CI: 0.0–0.6]) independently predicted BMI increase over time in women. Exposure to childhood sexual abuse magnified the increase in BMI associated with DV victimization (β: 1.3 [95% CI: 0.3–2.3]). No other types of childhood maltreatment were significant modifiers of the DV–BMI association. Violence victimization was not associated with BMI among men.

CONCLUSIONS:

Screening and support for DV victims, especially women who have also experienced childhood maltreatment, may be warranted to reduce the likelihood of health consequences associated with victimization.
Electrosynthesized Polystyrene Sulphonate-Capped Zinc Oxide Nanoparticles as Electrode Modifiers for Sensing Devices
Authors: Sportelli Maria C. , Hötger Diana , Picca Rosaria A. , Manoli Kyriaki , Kranz Christine , Mizaikoff Boris , Torsi Luisa , Cioffi Nicola
Published: September 2014

ZnO nanoparticles were prepared by a green electrochemical synthesis method applying low current densities followed by a thermal treatment. Sodium polystyrene sulphonate (PSS) was used as stabilizer in the electrolytic aqueous medium due to its biocompatibility and stability. The as-prepared nanocolloids were then annealed to improve their stability, and then converted via hydroxide species into stoichiometric oxide. Different calcination temperatures were studied. ZnO@PSS nanomaterials were deposited onto SiO2/Si substrates, in part in combination with an organic semiconductor layer to evaluate their influence on organic field effect transistors (OFETs). All nanomaterials and composite layers were characterized by morphological and spectroscopic techniques. Promising results regarding the use of ZnO@PSS in OFETs could be demonstrated.
Dynamic investigation of defects induced by short, high current pulses of high energy lithium ions
Authors: Guo Hua , Persaud Arun , Lidia Steve , Minor Andrew M. , Hosemann P. , Seidl Peter A. , Schenkel Thomas
Published: September 2014

We employ intense and short pulses of energetic lithium (Li+) ions to investigate the relaxation dynamics of radiation induced defects in single crystal silicon samples. Ions both create damage and track damage evolution simultaneously at short time scales when we use the channeling effect as a diagnostic tool. Ion pulses, ∼20 to 600 ns long and with peak currents of up to ∼1 A are formed in an induction type linear accelerator, the Neutralized Drift Compression eXperiment at Lawrence Berkeley National Laboratory. By rotating silicon (<100>) membranes of different thicknesses and changing the incident ion energy, the fraction of channeled ions in the transmitted beam could be varied. In preliminary experiments we find that the Li ion intensity is not high enough to generate overlapping cascades (in time and space) that would be necessary to measure a change in the shape of the current waveform of the transmitted ion beam. We discuss the concept of pump-probe type experiments with short ion beam pulses to access defect dynamics in materials and outline a path to increasing damage rates with heavier ions and by the application of longitudinal and lateral pulse compression techniques.
Leer el mundo
Authors: Carrillo Pimentel Margoth
Published: September 2014

Reseña del libro Leer el mundo de Víctor Bravo.
Influence of mixture composition on the properties of SCC incorporating metakaolin
Authors: Hassan Assem A. A. , Mayo Justin R.
Published: September 2014

This paper studies and evaluates the properties of self-consolidating concrete (SCC) containing different percentages of metakaolin (MK) by varying the mixture components and mixture proportions. In total, 32 mixtures with varied percentages of MK and mixture compositions are investigated for the effects on compressive strength, flowability, passing ability and high-range water-reducer admixture (HRWRA) demand. The percentage of MK, coarse-to-fine aggregate (C/F) ratio, coarse aggregate size, binder content and percentage of air entrained in the mixture are varied to study the influence of these variables on the fresh properties of SCC containing MK. SCC mixtures containing silica fume and SCC containing slag are also tested for comparison. The results show that increasing the percentage of MK up to 20% in SCC increases the compressive strength, viscosity, passing ability and HRWRA demand, but decreases the flowability of the mixture. In addition, the flowability of SCC mixtures improves with larger aggregate size, higher binder content and higher percentage of entrained air. The passing ability of SCC mixtures also improves with lower C/F ratio, larger aggregate size, higher binder content and the inclusion of entrained air in the mixture. The results also indicate that increasing the binder content or increasing the percentage of the entrained air has the most significant effect on improving the fresh properties of SCC mixtures.
The Importance of Pre-Job Shock Modeling as a Risk Mitigation Tool in TCP Operations
Authors: Gilliat Jim , Bale Derek , Satti Rajani , Li Crystal , Howard Jesse
Published: September 2014

Large-diameter, long-interval tubing-conveyed perforation (TCP) operations are an important part of modern deepwater completion designs. Perforation jobs typically place a large dynamic load on the downhole equipment. Predicting the magnitude and transient behavior of such loads is a critical step in developing completion designs that avoid damage or destruction to tool strings and production equipment. Consequently, numerical modeling for accurate prediction of pre-job perforating designs is critical to mitigating risk for completing complex wells in a cost-effective manner.

The paper presents numerical simulations that are conducted using a dynamic perforation modeling tool. The modeling software is an engineering and scientific tool that simulates the dynamic response of a cased or uncased wellbore, its contents, and the porous rock formation to the energy released by gas-generating and stored pressure sources. In particular, the model can be applied to predict the shock loads generated during TCP operations. This paper presents successful predictions of pressure transients for deepwater well completions in West Africa and the Philippines. The results from both examples demonstrate how simulations are used to mitigate risk and design successful completion strings. In addition, some recent improvements to the modeling platform are presented, including a more efficient pressure solver, the implementation of a new tool-string friction model, and a new interface to the simulation output data. Finally, the paper ends with the next steps in the development of shock modeling capabilities of the software.
Drilling Optimization: Utilizing Lifetime Prediction to Improve Drilling Performance and Reduce Downtime
Authors: Carter-Journet K.. , Kale A.. , Falgout T.. , Heuermann-Kuehn L..
Published: September 2014

The capability to optimize drilling performance by predicting the life of drilling components is integral to preventing costly downhole tool failures and ensuring success of any drilling operation. Drilling tools are subject to various parameters such as vibration, temperature, revolutions per minute (RPM) and torque. These parameters can greatly fatigue even the most robust tool depending on the where and how the tool is operated. As a result, there is a need to predict time to failure of components operating in a downhole drilling environment. Analyzing operational data, inclusive of the parameters above, prior to or during maintenance actions and before starting drilling jobs, provides unique insight into how to improve the drilling performance of tools and to reduce downtime. Life prediction provides a cutting-edge way to identify precursors to costly failures in the field and enables proactive guidance during maintenance periods for parts which may otherwise have been disregarded strictly on maintenance procedures. Statistical models that relate operating environment to the component life and are derived from failure data of fielded components, introduce a new way to optimize the efficiency of drilling tools. Utilizing lifetime prediction to optimize drilling performance is a groundbreaking methodology developed to determine life of components operating in benign and harsh drilling environments by incorporating statistical aspects such as those caused because of variation in operating stress and maintenance upgrades. Since the algorithm utilizes field data, the need for costly laboratory experiments are also eliminated. Each model developed is unique to the specified part and can be calibrated for the best fit. In this methodology, a Bayesian-based model selection technique is developed that incorporates operating environment variables after each successful drilling run to dynamically select a model that gives the best survival probability for that component. Dynamic model selection ensures maximum utilization of a component, while avoiding failure to improve the overall reliability of the tool while in the field. The paper describes the methodology used to estimate the life of components in drilling systems by employing operational data, drilling dynamics and historical information.
Enhanced 1D Prediction of the Mud Weight Window for a Subsalt Well, Deepwater GOM
Authors: Shen Xinpu , Williams Ken , Standifird William
Published: September 2014

Because of the complex distribution of stress directions around a salt body, accurate prediction of the mud-weight window (MWW) for subsalt wells has presented a challenge within the industry for many years. This paper presents a method for the enhanced 1D prediction of the MWW for subsalt wells in the Viosca Knoll area in deepwater Gulf of Mexico (GOM). An initial stress solution is obtained using a 3D finite-element method (FEM). The stress solution is then used as input data to the 1D prediction tool. The field-scale model used in the calculation is a cubic block with a true vertical depth (TVD) of about 9000 m, a width of 7500 m, and a length of 7500 m. Along the wellbore trajectory, the salt body is 6000 m thick and 5500 m wide. Based on seismic sectional data, an anticlinal structure is constructed accordingly at its bottom surface. The 3D porous elastoplastic FEM calculation was performed first with the field-scale model. The effective stress ratio was provided for the 1D prediction of MWW along the given wellbore trajectory. The finite-element model simulates the geometry of the salt body in detail. Comparisons are made between the results obtained with the enhanced 1D method, the conventional 1D method, and a finite-element method. Solutions obtained with the conventional 1D method missed the abnormality of stress distribution at the salt base and have smaller MWW values, as compared to the other solutions. The solution for MWW obtained with the enhanced 1D method is near the value obtained with the finite-element method, but at only 10% of the time cost. The FEM enhanced 1D method proposed has proven to be the most cost efficient method for predicting MWW for subsalt wells. This work presents an example of a best practice.
Integration, Commissioning & Testing on MWCC's First Modular Capture Vessel - Expanded System Progress
Authors: Massey Marty
Published: September 2014

This presentation will provide an overview of the system integration test (SIT) conducted on one of Marine Well Containment Company's (MWCC) modular capture vessels (MCVs), the EAGLE TEXAS, during Summer 2014. The MCVs are an integral part of MWCC's containment system and the company's mission to remain continuously ready to respond to a deepwater well control incident. Conducting initial integration, commissioning and a SIT will help to ensure that the MCVs successfully perform as designed prior to ever being needed to respond to an incident and will also demonstrate MWCC's readiness to industry and regulators. Successful completion of the SIT will be a significant milestone in the delivery of MWCC's expanded system. Resulting outcomes and insights from the SIT will be shared during this presentation.

With a containment system in place, maintained in a state of readiness, MWCC is building on its current capabilities with the construction of an expanded system; enhancements include the ability to cap and flow a well in greater water depths and increased containment capacity. Additionally, the system includes use of specially converted Aframax tankers – MCVs – designed to improve response and containment efforts, including decreasing congestion at the incident site; providing increased liquid storage capacity; and the ability to process, store and offload the liquids to shuttle tankers.

MWCC selected Kiewit Offshore Services in Ingleside, TX as its shore base provider to house, maintain and test equipment that will outfit its MCVs. Kiewit is completing the initial integration and commissioning work on the MCVs, will support MWCC during the SIT, and would outfit the MCVs prior to deployment during a response. In September 2013, the EAGLE TEXAS arrived to Ingleside where it began module lift work and initial integration. The EAGLE LOUISIANA arrived at Ingleside in Spring 2014 for initial integration and commissioning work.

Completion of the initial integration, commissioning and SIT on the EAGLE TEXAS will signify an important step in MWCC's progress toward delivery of the expanded system in 2014. This achievement not only underscores industry's readiness, but it exemplifies MWCC's commitment to continue advancing technologies to keep pace with its members' evolving needs.
Time-Controlled Interventionless Barrier System for Effective Offshore Gas Lift Completion
Authors: Xu Zhiyue , Richard B. M. , Kritzler James H.
Published: September 2014

Multiple gas lift valves are usually installed in a well to ensure optimal production as the well's pressures, fluid type, and productivity change. In many gas lift systems, dummy valves are loaded in side-pocket mandrels (SPM) to isolate the annulus from tubing where pressurization is required to test the pressure integrity of tubing or annulus, or to set a hydraulic packer. If the well then requires gas lift to unload the completion fluid or to assist the well to flow, wireline intervention is necessary to change out the dummy valves with the live gas lift string. This process can be time-consuming and can pose risks to existing infrastructures. Production is also delayed while a new live valve unit is installed. In addition, slickline crews are a finite resource and sometimes cannot be scheduled on a gas lift valve change-out project for many weeks. This situation results in un-optimized platform production. Estimates state that one month waiting on a change out for 1 × 20 well platform can result in as much as 100,000 bbl in lost production. This paper presents a time-controlled interventionless barrier system with disintegrable nanostructured composite material technology. The barrier is installed in the well to function as a "smart" dummy valve during completion operations and then convert from a dummy valve to a live valve through in-situ disintegration of the nanostructured composite barrier in brine during cleanup process. This approach eliminates multiple slickline trips or well intervention to replace dummy valves with live valves and significantly increases completion operation efficiency of offshore wells. The nanostructured composite barrier is high strength, chemically resistant to drilling mud, slightly reactive with fresh water, and disintegrates within 12 to 50 hours in salt water. The nanostructured material, the barrier system design, the lab test data, and a successful case study will be presented.
First Dynamic Kill Drilling Application for Angola's Deep Water
Authors: Viera F.. , Liconga N.. , Santos C.. , Sarpy J.. , Dove R.. , Bonfim O.. , Navarro R.. , Jones R..
Published: September 2014

As deepwater exploration and development move toward deeper water depths and reservoirs, conventional riserless drilling techniques, such as seawater sweeps, no longer provide the required equivalent density from the formation integrity test (FIT) to set the surface casing at the required depth. During the planning phase of a 26-in. hole using 20-in. casing for a well in offshore Angola, expected shallow hazards such as faults, shallow gas, saltwater influxes, and shallow sands, were identified as the key concerns before reaching the section total depth (TD). To mitigate these shallow hazard risks, the dynamic kill drilling (DKD) technique was used.

DKD is widely used in the Gulf of Mexico and recently its use has expanded to other regions in China and Mexico. The most significant challenge for its first application in deepwater Angola was the DKD fluid volume availability, as well as the logistics involved. Drilling practices and parameters that posed a challenge with regards to control included rate of penetration (ROP), flow rates, rotation (rev/min), and reaming.

The DKD 16.3-lbm/gal fluid was mixed in the Luanda liquid mud plant (LMP) 2. Approximately 10,000 bbl were mixed and then taken to the rig for storage until req uired for the 26-in. hole section. The process continued until 30,000 bbl were created and sent offshore. The 26-in. interval was successfully drilled in 30 hours. Mud density was 10.7 lbm/gal, which was achieved by combining a total of 5, 544 bbl of 16.3-lbm/gal DKD fluid mixed with 14, 335 bbl of seawater. The mix-on-the-fly (MOTF) unit was rigged up on top of the pits. A line was attached from the pits holding the 16.3-lbm/gal DKD fluid and another line was attached to the pit with the seawater. The two liquid streams were blended to achieve the required mud weight. The 16.3-lbm/gal DKD fluid was reduced to form pad mud with a density of 11.5 lbm/gal, which was pumped and placed in the openhole section until the 20-in. casing was run and cemented.

A total of 19, 879 bbl of fluid was pumped downhole without any drilling or formation issues to conclude the first DKD application in Angola's deep water.
A Method for Buckling Analysis of a Riserless Drillstring
Authors: Li Ke , Collins Tony
Published: September 2014

The increasing demand for exploration of deepwater reservoirs poses significant challenges for operators, well planners, and drilling engineers. As a recently developed deepwater drilling technology, riserless drilling offers numerous advantages over traditional riser-based drilling. However, riserless drilling is accompanied by substantial operational challenges, one of which is buckling of drillstrings. Buckling failure occurs when the drillstring misses an existing wellhead or experiences excessive torque and drag inside the near–surface section of a well. Buckling could also take place when a pilot well is being drilled and the weight-on-bit (WOB) limit is exceeded. In the absence of constraint from a riser, this buckling can give rise to catastrophic failure. Deep water allows for enough of the bottomhole assembly (BHA) to be exposed to reach the critical load for buckling. Classical buckling models cannot be applied to this situation because the force varies along the length of the assembly. To determine the operational limits and eliminate the risk of buckling-induced failures, a method for buckling analysis of a riserless drillstring has been developed. It is based on the finite element method, and the drillstring is modeled with a number of beams. The method can be utilized to predict the bending moment distribution along the drillstring, which can then be used to determine the critical buckling conditions. A case study is considered on a field failure, where a threaded connection on a riserless drilling BHA failed due to excessive bending. The predicted location of failure agrees with the field observation. The results can readily be extended to other BHAs.
The Principle of Target Influx Selection and the Optimization Process of Variable-ICD Completion Design for Heterogeneous Reservoirs
Authors: Fu Xuan , Li Gensheng , Huang Zhongwei , Chi Huanpeng
Published: September 2014

ICD completion has been rapidly developed due to its effective mitigation of unwanted water breakthrough in horizontal wells. It prolongs the no-water production time by introducing an extra pressure drop in high inflow rate zones. With respect to the horizontal well, equally distributed influx is generally regarded as the ideal influx to achieve the longest no-water production period. Howeverin some cases, like producing with fixed bottom-hole pressure (BHP), this may not always correct. When designing the ICD completion, the target inflow profile should be carefully selected. The horizontal well needs to be selectively completed with variable ICDs to minimize the reduction of well productivity.

In this paper, a reservoir-wellbore coupling model will be given for influx computation, in which the ICD pressure drop is considered. Then we will propose the selection principle of the target inflow profile for ICD optimization on the constraints of BHP limits, required daily production and no-water production periods. The cumulative production at the time of water breakthrough is selected as the evaluation criteria. The flowchart of the ICD optimization process for the heterogeneous reservoir will be illustrated; and a synthetic case study will be carried out with a comparison of open-hole completion, constant ICD completion and optimal ICD completion. Results indicate that the effect of the water control of ICD completion can be maximized with a reasonable selection of the target inflow profile.
Maximizing the Production Potential of Multi-Stacked Heterogeneous Compartmentalized Oil Reservoirs by Cost Effective Intelligent Reservoir Management and Monitoring - A Case Study
Authors: Ahmed Sheraz , Shahrukh Muhammad , Hakim Bilal Abdul
Published: September 2014

Intelligent Reservoir Management and Monitoring has played a key role in the pursuit of improving the hydrocarbon recovery and reducing the development expenditure in the challenging multi-stacked compartmentalized fields which have proved to be perplexing in a number of ways which include preventing or delaying water breakthrough, extenuating wellbore instability, sand production etc.

Reservoir-management and monitoring options have been greatly improved in recent decade by smart completions comprising of downhole monitoring and control equipments like permanent down-hole gauges to have "eyes" into the reservoir and to monitor performance for each zone; dynamic active flow control valves, which aid in equalization of the reservoir inflow into the wellbore; and the SCADA system which enables the real time monitoring and control of the downhole and surface equipment remotely from the control room.

Proper application of this methodology can be one of the most lucrative ventures that an operator undertakes, by delaying water breakthrough problem to recover additional monthly cumulative production than a conventional production method in such reservoirs. This method also results in avoiding the heavy intervention expenses, extending economic life of the field, improving reservoir management, zonal isolation, allowing real time well testing, fewer wells and less operating expenditures.

This paper discusses real field design methodology and outcomes of different wells that resulted in restoring the production by greater than 1000 B/D, minimizing the OPEX by eliminating huge cost oriented interventions of $10 MM (per intervention), saving Millions of Dollar investments as CAPEX via IWC re-completion with multi-lateral technology and an augment of EUR of about 2 MMSTB per well. The paper also enlightens a comprehensive logic guideline towards the tool box of the technology, including the applied workflow, procedures and standards with the field examples and desired results.
Stability Analysis of Casings During Plastic Deformation
Authors: Morita Nobuo , Shiozawa Sogo
Published: September 2014

Multi-finger caliper logs obtained from the wells in the Gulf of Mexico and in the North Sea showed significant casing deformations, while they were still usable without losing integrity. The reason was that most of these casings were uniformly deformed without rupture or without kinks. The magnitude of elongation and compression of these casings were 3 to 5% while the strains at the yield strength were 0.3-0.5%. These observations indicate that casing design should include the steel properties beyond the yield strength while the API casing designcriterion is strictly based on the steel properties up to the yield strength.

Extension and compression casing tests were conducted from H-40 to V-150 casings up to failure by using a 5000 kN loading machine. For compression tests, some casings were cemented within a larger pipe to prevent the lateral buckling simulating the in-situ confinement condition. The tests gave the following results:

Under extension tests, the casings were uniformly deformed after exceeding the yield strength. The uniform deformation continued while the casing were stretched by 4 to 25% until non-uniform deformation was induced. The strain up to the peak strength was as large as 25% for H-40 casings while it was as small as 4% for P-110 and higher grade of casings. For compression tests, uniform compression continued exceeding the yield point. The uniform deformation continued up to the peak strength which varied from 3% to 12% from V-150 to H-40 casings. Both the cemented casings and short casings induced axisymmetric wrinkles (local buckling) after uniform deformation. The higher grade casings did not significantly increase the maximum strength after yielding while lower grade casings increased the strength while being stretched or compressed uniformly after yielding.

The analyses show that the casing failure observed in the fields can be explained from the casing failure tests beyond the yield points. The casings are uniformly deformed until the maximum load so that they are usable up to the maximum strength without significant distortion. In the past, casing failures were tried to be mitigated by increasing the casing grade, however, increasing the grade sometimes deteriorated the casing problems since a higher grade casing could not tolerate the significant stretch or compression once they exceeded the yield stress. Selecting a proper grade and thickness of casings is the key for mitigating casing failure where the data of casing deformation beyond the yield strength are essential information for casing designing using geomechanical models. This paper analyzed the casing deformation data of several North Sea chalk reservoirs and Gulf of Mexico sandstone reservoirs provided by oil companies and determined the usable limit of casing deformation based on the laboratory and field measurements.
Advanced Model for the Prediction of Tubular Shear Mechanics
Authors: Evangelatos Georgios I. , Pollock Tim , Payne Michael L.
Published: September 2014

Blow out preventer (BOP) manufacturers have conducted research and development for many years on how shear rams can shear drillpipe, casing and other tubulars passing through the BOP as a well is drilled. In this paper, a significant volume of data on the ability to successfully shear tubular goods is examined. Next, the commonly used and deterministically-based predictive equations for tubular shearing are re-examined and a probabilistic predictive model calibrated on a large test dataset is presented.
Challenges and Solutions for Qualifying Proppants for Deepwater Wells
Authors: Fuss Tihana , Shi Jingyu , Thompson Matthew J. , Wilcox Craig , Herndon Daniel C. , Stephens Walter T.
Published: September 2014

Gulf of Mexico Continental Shelf and Deepwater formations represent a harsh environment which causes difficulty predicting operational requirements for proppants using traditional methods. Common formation conditions are very high closure stresses approaching 20,000 psi and temperatures varying from 220°F and upwards, nearing 500°F, such as in the Lower Wilcox Formation on the continental shelf. Deepwater wells present economic investment for investors several orders of magnitude larger than onshore conventional and unconventional plays common in current land assets. Operators therefore place a great deal of focus on the design of the frac pack, completion tools, production and field development. Required qualification and understanding of proppant performance at these conditions far exceeds that needed for today's extensive shale market.

Understanding the proppant behavior that brings economic value to these applications is difficult as current API/ISO performance measurements do not apply under these extreme conditions. Measurement artifacts due to limitations in laboratory materials, highly integrated measurement environment, apparatus limitation or statistical variability in proppant performance are common. New proposed protocol individually examines loss mechanism as a function of mechanical, thermal and chemical forces at high-temperature and high-pressure conditions. Integration of these proposed protocols with conventional testing allows better understanding of root causes of proppant performance losses.

Laboratory measurements of proppants permit defining a boundary that separates stable, predictable performance from variable, unreliable performance. Closure stress, temperature, and several degradation mechanisms, such as cyclic stress and corrosion attack, influence the position of this boundary with respect to the mechanical strength of the proppant. Results show that commercially available high strength proppants exhibit a statistically proven variable performance when used under high-temperature, high-pressure conductions common to Deepwater conditions.

Employing materials operating within a predictable performance regime is both an engineering and economic design decision for any fracturing application. Through independent evaluation of the mechanical, thermal, and chemical forces acting upon materials in the application, optimized solutions are possible that permit extracting value and stable performance from the well.
Evaluation of Defoamer Chemistries for Deepwater Drilling and Cementing Applications
Authors: Bava Luciana , Wilson Robert
Published: September 2014

The search for high performance defoaming agents has been intensified in recent years due to, for example, the challenging deepwater conditions and new environmental regulations for offshore drilling. The major task is to find suitable additives that pose little to no risk to the environment without compromising the performance and system integrity.

The use of defoamers in drilling and cementing applications is of vital importance for controlling and preventing excessive foam that can lead to problems ranging from operational difficulties (e.g., pump cavitation) to quality control and performance interferences (e.g., miscalculation of slurry density as most field mixers determine the water/cement ratio by measuring the density of the slurry). The detrimental effect of foam in cementing and drilling operations becomes more serious in deepwater applications where not only new technical and logistic challenges are encountered (e.g., poorly consolidated formation, high potential for shallow-flow hazards, low temperatures, etc.), but also optimum drilling efficiency and reduced operational time are required to keep costs down.

In this study, traditional blender tests and a novel dynamic foam analyzer were used to benchmark defoamer performance during simulated slurry mixing operations. In-depth evaluation of the initial and persistent efficiency enables accurate dosage comparisons in the lab, resulting in effective and reliable field operations. This paper presents a comprehensive study of various defoamer chemistries. Testing on high-foaming media comprising fluid loss additives, dispersants and gas migration control agents indicates that non-silicone outperform silicone chemistries. In the case of foaming agents for drilling, studies show that only silicone defoamers were a feasible alternative.

The oilfield industry is presently facing several challenges both from increasing environmental restrictions and also from specific field application requirements. The focus on finding suitable replacement additives for cementing and drilling systems without compromising the properties of completion fluids is a priority for many oil service companies. The use of a systematic approach for material selection is instrumental in reducing or eliminating risks to ensure maximum operation efficacy and longevity of cementing and drilling jobs while accommodating the unique factors pertaining to each individual project.
Experimental Research on Structural Casing Soaking Time in Deepwater Drilling
Authors: Zhou Bo , Yang Jin , Xu Yunjin , liu Zhengli , Luo Junfeng , Ye Jihua , Liu Shu Jie , Zhou Jianliang , Wu Yi
Published: September 2014

Structural casing is defined as the first string of casing installed in the well construction process. It provides structure and support for all the casing strings, the subsea christmas tree, and BOP stact. In the deep water drilling process, the soaking time of structural casing has directly influence on the bearing capacity and drilling period, and that is crucial in deep water drilling design.

Jetting of structural casing has become the preferred method of installation in most deep-water drilling. In order to decrease the risk of deep water surface drilling work, and to shorten the drilling period, this paper gives a simulation experiment on soil-pile interaction to get the change rule between soaking time and bearing capacity.

Once the structural casing string has been jetted successfully to final depth, a period of soak time is employed to allow the skin friction to increase and improve the soil to casing adhesion. Based on field experiments and mechanical analyses, the paper builds up a calculate method on wellhead load in different situations.

Considering the structural casing safe driving depth and drilling efficiency, it gives a design method of soaking time window of deep-water structural casing in different formation. Soak period of two to three hours is prudent insurance against casing subsidence after running tool release in clay strata, and one to two hours in sand and mud interbed strata.

This method optimized the setting depth of structural casing, improved the drilling efficiency, and saved more than 12 h per well on average with the ensurance of deep water drilling safety. It turns out a great application results in South China Sea deep-water drilling practice.
Overcoming Losses in Tophole Sections in Deepwater Namibia
Authors: Awalt M.. , Bogaerts M.. , Bonsu-Gyimah M.. , Joneja G.. , Meyer A.. , Auman J.. , Paul J..
Published: September 2014

The continual increase in exploration drilling in southern Africa has translated into a number of remote deepwater campaigns, the most recent ones being in Namibia. One particular three-well campaign was exceptionally challenging as there was no near offset-well data available. The challenges were especially acute in the riserless tophole section.

The well designs called for top of cement (TOC) at seabed for the surface casing. This was of the utmost importance for adequate structural and axial support for the blowout preventers (BOP) and subsequent casing strings. The very low fracture gradient near the seabed was the main challenge as the formations would not support the hydrostatic pressure of the cement column. On the first well, total losses were encountered prior to and during the entire cementing operation. As a result, no cement returns were observed at seabed, contrary to what was expected from hydraulic simulations and volume calculations and required to meet the job objective.

To achieve objectives required for the success of the subsequent two wells, all aspects of drilling and cementing operations were reviewed based on the findings of the first well. Mud weight and casing setting depth were critically challenged, with other parameters adjusted. Cement formulation and density were optimized to reduce hydrostatic and hydrodynamic pressures and to increase the chance of success. The cement slurry was changed to a bimodal lightweight system with better fluid- and set-cement properties. Lost circulation fiber technology was also incorporated in the spacer preflush and in the cement slurry to mitigate any losses during placement.

Alignment of service company and operator objectives and optimization of drilling and cementing parameters were critical for the successful cementation of these challenging tophole sections. Continuous improvements resulted in the second well being effectively cemented to seabed, even though intermittent losses were observed. After further optimization, the third well was cemented to seabed with full returns. Reaching the target TOC eliminated the need for a top-up job, saving valuable rig-time.
Reducing Drilling Risk Using Look-Ahead VSP – A Success Case Study for Carbonate Exploration Well, Offshore Vietnam
Authors: Dac The Nguyen , Sanders Michael , Millot Pascal , Rehman Sadu-Ur , Al Badi Othman , Golding Christopher James , Aquilina Giovanni , Fichera Rosario
Published: September 2014

The accurate prediction of the depth of top carbonate while drilling carbonate reservoirs is important to avoid losses and well control problems. This can have a significant financial impact. This paper demonstrates the use of innovative look-ahead VSP technology in Vietnam to refine depth prediction of the top of carbonate ahead of the bit for accurate geo-stopping.

An offshore exploration well was being drilled in an area with drilling challenges. This was the first well in the field and lacked offset well velocity information, so there was a high degree of depth uncertainty to the top of the carbonate target from surface seismic interpretations, making drilling operations risky. An intermediate VSP was requested to look for reflections ahead of the intermediate TD using Schlumberger VSI1 tool. The VSP data was acquired in open and cased hole using an air gun cluster as the seismic source.

The drilling program required the casing to be set immediately above the top of the carbonate. By acquiring an intermediate VSP, the depth uncertainty was reduced and the target depth prediction was refined. This was achieved using the look-ahead VSP technique, from which the acoustic impedance and velocity ahead of the bit was estimated. This was combined with time-depth from the VSP data over the logged interval to help refine the predicted depth to the top of the carbonate. This was used to optimize the depth at which the casing was set. The error range for the top carbonate depth from the surface seismic interpretation was +/−50m. The final prediction depth from the VSP interpretation is 6m shallower than the actual carbonate reservoir.

Guided by the inverted acoustic impedance log and velocity ahead of the bit from look-ahead VSP, a further 100m was safely drilled before setting the casing. The casing point was set successfully without penetrating the carbonate. The intermediate VSP results helped to decide drilling ahead in a safe manner with confidence, after setting the casing before penetrating the carbonate target.
Comparison of Field Management Strategies for Preventing Iron Deficiency Chlorosis in Soybean
Authors: Kaiser Daniel E. , Lamb John A. , Bloom Paul R. , Hernandez Jose A.
Published: September 2014

Iron deficiency chlorosis (IDC) is a serious management issue for soybean [Glycine max (L.) Merr.] grown on calcareous soils. Strip trials were established on calcareous Mollisols to study the effects of Fe‐ethylene diamine‐N,N′‐bis (hydroxy phenyl) acetic acid (EDDHA) in‐furrow (IF‐Fe) and of an oat (Avena sativa L.) companion crop on two soybean varieties either tolerant or susceptible to IDC. The severity of IDC varied from low to severe within sites. The susceptible variety produced the highest yield in the absence of IDC. In‐furrow Fe increased the yield of a variety susceptible to IDC under moderate to severe IDC. The oat companion crop increased yield consistently for the susceptible variety under severe IDC and sometimes reduced yield when oat grew beyond 25 cm in height. The tolerant variety without IDC management produced yields similar to those of the susceptible variety with IF‐Fe or an oat companion crop. Oat reduced trifoliate nitrate N and Fe concentration regardless of IDC severity. Trifoliate Fe concentration lowered with IF‐Fe, but only when oat was not planted. Grain protein and oil concentration were affected by variety, but were not affected by IDC management. Soil test factors such as soil organic matter (SOM), pH, electrical conductivity (EC), or diethylene triamine phentaacetic acid Fe (Fe‐DTPA) were poor predictors of the severity of IDC. Variety selection is the most important strategy for lessening the severity of IDC. In‐furrow application of Fe‐EDDHA provides a solution for mitigating moderate to severe IDC and provides less risk than an oat companion crop.
Estimating Cultivar Effects on Water Usage and Greenhouse Gas Emissions in Rice Production
Authors: Nalley Lawton L. , Dixon Bruce L. , Brye Kris , Rogers Christopher W. , Myrteza Haxhire , Norman Richard J.
Published: September 2014

Previous research has demonstrated that rice (Oryza sativa L.) production poses two large, global environmental concerns: rice uses 25% of the global freshwater supply and generates considerable greenhouse gas (GHG) emissions. The shorter vegetative stage of hybrids compared with conventional (inbred) cultivars may provide two environmental improvements: reduced water consumption and decreased CH4 emissions. This study evaluated the effect of cultivar type on water‐use efficiency and net GHG emissions. Water usage and GHG emissions on a per‐hectare and per‐kilogram‐of‐grain basis were estimated for hybrid and conventional rice cultivars with a new methodology using seven consecutive years of cultivar‐trial data. Because GHG emissions have not been observed directly in cultivar trial experiments, a method of synthesizing GHG emission levels was designed. This method utilizes results from in‐field chamber experiments from flooding to after harvest plus emergence and 50% heading dates. Hybrid rice cultivars were estimated to be 23.22% more efficient than conventional cultivars in reducing GHG emissions and 33.47% more efficient in reducing water required per unit grain yield produced. Unlike other approaches to lowering GHG emissions and water usage, substituting hybrids for conventional cultivars appears to be a viable option with low producer transaction costs as opposed to such alternatives as alternate wet–dry flooding, building on‐farm reservoirs, etc.. The methodology used produced results that are consistent with the present knowledge of the physiological and cultural practice differences between conventional and hybrid rice production. The GHG synthesizing methodology could be directly applied to other states’ historic cultivar trial data.
Optimizing Sugarcane Cultivar Choice and Time of Harvest for Frost‐Prone Environments in South Africa
Authors: Ramburan Sanesh
Published: September 2014

Frost in low‐lying areas in the midlands region of South Africa limits sugarcane (Saccharum spp.) yields and information on breeding strategies, cultivar choice, and time of harvest in frost‐prone environments is lacking. This study aimed to (i) evaluate the yield and ratooning ability of test cultivars compared with commercial standards, (ii) identify an optimal time of harvest to maximize sugar yields, (iii) investigate cultivar differences in post‐frost yield deterioration, and (iv) gain insights into future multienvironment testing strategies for breeding purposes. Four cultivar trials established between 2004 and 2008 showed that test cultivars ‘N36’, ‘N41’, and ‘N48’ produced significantly (P < 0.05) higher tonnes estimated recoverable crystal yields (TERC) than commercial controls (‘N16’ and ‘N21’) across multiple ratoons. Pre‐ and post‐frost TERC estimates identified the mid‐May to mid‐June period as an optimal harvest time to maximize TERC, irrespective of frost onset or severity. Genotype + genotype × environment (GGE) biplot analysis showed that frost sites on humic and sandy soils are necessary when developing a breeding strategy. Cultivars N36, N41, and N48 may be suitable check cultivars for use in breeding trials. Cultivar N36 exhibited faster rates of TERC deterioration following frosts and may need to be prioritized for harvesting as a result. The estimation of pre‐ and post‐frost sugar yields through sequential sampling and determination of key sugar yield components like stalk population are recommended for sugarcane frost studies. These methods are shown to produce more commercially relevant information than conventional estimates of post‐frost quality responses alone.
Fungicide Management Does Not Affect the Rate of Genetic Gain in Soybean
Authors: Weidenbenner Nicholas H. , Rowntree Scott C. , Wilson Eric W. , Suhre Justin J. , Conley Shawn P. , Casteel Shaun N. , Davis Vince M. , Diers Brian W. , Esker Paul D. , Specht James E. , Naeve Seth L.
Published: September 2014

On‐farm U.S. soybean [Glycine max (L.) Merr.] yields have increased at an annual rate of 23.3 kg ha−1 yr−1 since the 1920s. These gains have come from a variety of sources including genetic, agronomic, and environmental changes. Genetic gains arising from breeding efforts have likely contributed the most to the U.S. soybean yield increase; however, the relative contribution of each source of gain is difficult to estimate. The objectives of this study were to compare yield of soybean varieties with different year of release, understand the effects of fungicide applications on soybean seed yield, and evaluate the composition of soybean cultivars chosen to represent historically significant releases in maturity groups (MGs) II and III released during the last 85 yr. A set of 116 cultivars in these two MGs, released from 1923 to 2008, received a fungicide seed treatment followed by foliar applications at R1, R3, and R5 and were compared to non‐treated controls. Seed composition changed over time with protein concentration decreasing 2.1 g kg−1 for every g kg−1increase in oil concentration. The significant interaction between fungicide treatment and MG III cultivar release year for plant stand revealed that such treatments were more beneficial with respect to obsolete cultivars of MG III, though this plant stand interaction did not translate into a significant yield interaction. The rate of genetic yield improvement made by breeders was not influenced by fungicide management and matched the observed rate of on‐farm yield improvement that occurred during the same period.