bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Solid Particle Concentration on Drilling Fluid Rheological Behavior and its Impact on Pressure Losses
Authors: Cayeux Eric , Leulseged Amare
Published: February 2019

Solid particles in suspension in a fluid, like barite, lost circulation material (LCM), cuttings or cavings, influence the pressure losses that are experienced when pumping or moving a drill-string in a borehole. As the volume fractions of those different solid particles varies along the hydraulic circuit, it is desirable to estimate the impact of local solid concentrations on pressure drops.

The influence of solid particles on the rheological behavior of fluid has mostly been studied for Newtonian fluids, but very little experimental work has been published for non-Newtonian fluids like drilling muds. For that reason, a series of measurements, made with a scientific rheometer has been conducted on a typical KCl/Polymer water-based mud. The experimental investigation covers the effect of particle concentration on the rheological behavior of the mix, in conjunction with the particle size.

The change of rheological behavior is slow at low solid concentrations but increases exponentially with larger proportions of solid in suspension. Furthermore, the increase of effective viscosity is larger with fine particles than with coarser ones. Empirical formulas are proposed to describe how the original Herschel-Bulkley rheological behavior of a base fluid can be modified to incorporate the effects of the variation of solid concentrations in the fluid mix.

All these results are based on measurements made with a scientific rheometer. As computerized and high precision rheometers are usually not available at the rig site, we describe a methodology to utilize standard model 35 rheometer measurements to estimate the pressure loss gradient as a function of the volumetric solid content.
Modeling the Effect of Axial Oscillation Tools in Torque and Drag Computations
Authors: Mahjoub Mohamed , Dao Ngoc-Ha , Menand Stéphane
Published: February 2019

When drilling complex wells, such as those with long lateral sections, the friction forces become significantly high, which can impede advancement of the drill string and reduce drilling performance. In these situations, Axial Oscillation Tools (AOT) could be used to introduce an axial vibration to the drill string. By locally reducing the friction forces, better transmission of weight to the drill bit is possible and an increase in the rate of penetration occurs. However, to optimize the use of these tools, predictive modeling is necessary to assess their effect on drilling characteristics.

A new modeling approach is proposed to accurately model the effect of the AOT on drilling operations without the need to carry out resource-intensive and time-consuming dynamic computations. To estimate the influence length (i.e. the extent of the axial vibrations) and the maximum displacement at the AOT, a study was performed to determine the most important parameters. Based on this study and on the theory of wave propagation, new analytic expressions are proposed. Once the influence length and the maximum displacement are calculated, an effective friction coefficient is estimated as the mean value of the instantaneous friction coefficient and used in a stiff-string torque and drag model.

The model was applied to a real case study, and an agreement between the modeling results and field measurements regarding the influence of the AOT was obtained. Moreover, the effect of the excitation force and rate of penetration on the drill string tension profile was investigated. This work should enable drilling engineers to better optimize the position of AOT along the drill string and to maximize its efficiency.
Modelling the 3D Bit-Rock Interaction Helps Designing Better PDC Bits
Authors: Pelfrene Gilles , Stab Olivier , Tilleman Danny , Gallifet Thomas , Cuillier Bruno , Carlos Julien
Published: February 2019

The bit-rock interaction has long been studied to assess PDC drill bit performance, which is driven both by cutting and non-cutting parts of the drill bit. While the cutter-rock interaction has been studied by many authors in the literature, only a few studies have focused on the interaction between the rock and non-cutting parts of the drill bit.

In this paper, we introduce a new method designed to model the interaction between the whole drill bit and the rock formation within a full three-dimensional framework. This approach is based on a generic computational geometry algorithm which simulates the drilling process considering both the drill bit and the hole being drilled as a set of 3D meshed surfaces. The volume of rock removed by the PDC cutters as well as the area and the volume of contact between the rock and the non-cutting parts of the drill bit can be computed with a high accuracy based on the 3D CAD model of the drill bit.

The in-house drill bit simulator implementing this algorithm primarily allows the engineer to estimate how bit-rock interactions distribute between cutting and non-cutting parts of the drill bit and to balance the bit design in the 3D space accordingly over a given range of drilling parameters. This approach has been brought to the field in order to address cutter breakage based on rubbing contacts optimization. Field results associated to some case studies in US shale plays and Canada are described and clearly show that contact points predictions closely match field observations. Moreover, design modifications applied following this process have led to an overall increase in bit performance and bit durability while preventing core-out issues.

The bit design methodology presented in this paper is dedicated to design drill bits whose interaction with the rock formation is predicted with a higher accuracy by accounting for the exact 3D shape of the drill bit.
Building a Rig State Classifier Using Supervised Machine Learning to Support Invisible Lost Time Analysis
Authors: Coley Christopher
Published: February 2019

This paper covers the development of a key component of an internal system to report invisible lost time (ILT) metrics across drilling operations. Specifically this paper covers the development of a generalizable rig state engine based on the application of supervised machine learning. The same steps used in the creation of the production rig state engine are appled here to a smaller data set to demonstrate both the tractability of the problem and the methods used to create the rig state engine in the production system.

The project objective was to provide efficiency and engineering metrics in a central repository covering operated regions. The system is designed to require minimal user configuration and management and provides both historic and near real time analysis to deliver a rich resource for offset comparison and benchmarking.

Identifying rig-state is at the heart of every performance and engineering analysis system. This can be thought of as a machine learning classification problem. A large supervised learning set was constructed and used to train classification models which were compared for accuracy. A key success metric was the ability to generalise the selected model across different operations. Output from the rig-state classifier was then used to derive KPI data which was presented through a web based front end. A pilot system was then developed using agile principles allowing for rapid user engagement. Testing demonstrated that the system can support all real time operations within the company simultaneously and rapidly process historic well data for offset benchmarking. The cloud-based architecture allows rapid deployment of the system to new groups significantly reducing deployment costs. The system provides a foundation for onward data science and more advanced functionality.

Minimal configuration, cloud storage and processing, combining contextual data with real-time rig data, near-real-time and historic analysis capabilities, rapid deployment, low cost, high accuracy and consistent metrics are all key and proven value drivers for the system. The output data is aso a valuable resource for additional machine learning and data science projects.
An Integrated Geomechanical Approach to Accurately Predicting the Fracture Gradient for Mitigating Drilling Losses of Challenging Wellbores
Authors: Fang Zhi , Zamikhan Norshah , Tarang Ravie-Tajit , On Chee Khong , Huver Pieter Hendricus
Published: February 2019

Fracture gradient (FG) of wellbores is the function of not only stresses, formation pressure and rock mechanical properties but also well trajectories. An accurate FG prediction is critical for safe well drilling. However, the existing methods do not account for the trajectory effects. An integrated geomechanical approach has been developed to more accurately predict the FG of wellbores subject to various trajectories. The approach deploys the Kirsch equations and takes into account the effects of formation pressure variations on stresses. It further integrates the elaborated individual procedures for deriving the geomechanical input parameters from regional field data to form a FG model. After verifying the losses test and offset well drilling data with necessary modifications, the calibrated FG model is then able to more accurately predict the fracture initiation pressure (FIP) of wellbores to mitigate the drilling losses for not only vertical but also deviated wellbores by guiding the equivalent circulation density (ECD) management.

The integrated geomechanical approach has been applied to the planning and drilling of more than 30 new wells at Brunei Shell Petroleum (BSP). It has significantly mitigated the drilling losses for the challenging wells of a field redevelopment project in which about 50 deviated wells were expecting narrow drilling windows due to penetrating heavily depleted reservoirs. In another drilling campaign, it saved the sidetrack of a lost hole section by revising the trajectory as instructed by the FIP predictions. The integrated geomechanical approach is an algorithm that can effectively mitigate drilling losses by accurately predicting the FG for any arbitrary wellbores.
Well Control Incident in the North Sea as Interpreted with Advanced Gas Influx Modelling
Authors: Skogestad Jan Ole , Bjørkevoll Knut S. , Frøyen Johnny , Linga Harald , Lenning Eivind , Håvardstein Stein T.
Published: February 2019

Objectives/Scope

Handling well control incidents during drilling operations safely and efficiently is of crucial importance, due to the potential danger to crew, rig and environment, as well as the economic aspects. In this paper, we study an actual incident from a North Sea drilling operation, using recent advances in gas influx modelling, which allows for improved understanding of the underlying physical processes, hence enabling more accurate well control simulations.

Methods, Procedures, Process

Data has been gathered from a drilling operation where a well control incident occurred, and put into a hydraulic drilling model. This model is enhanced with compositional modelling of PVT properties of the gas/fluid system, allowing for better description of the gas absorption capability of the drilling fluid. Furthermore, effects of non-instantaneous gas loading are handled by a novel kinetic model. Multiple simulations with varying model parameters are run in order to understand how different physical processes can explain the behavior observed in the dataset.

Results, Observations, Conclusions

Simulations of the case have been compared to the operational data, showing how the different modeling parameters of gas influx impact the simulation prediction performance. A key to safe handling of well control incidents is early detection, but relying only on recordings for topside process conditions limits accuracy and reliability as compared to using the topside data in combination with real-time downhole data and/or advanced mathematical interpretation software. The results show how, by using a combination of downhole modelling and observations, it is possible to obtain a more complete picture of the well conditions throughout the operation. The results also give an indication on early signs that may allow for faster reaction and more confident handling of a gas influx.

Novel/Additive Information

This case-study of a gas influx scenario with sophisticated gas absorption modelling is the first of its kind, providing useful insights relevant for well control handling and illustrating the benefit of digitalization of drilling operations. By implementing the technology for real-time surveillance, safer and more efficient handling of well control incidents is allowed for, thus reducing the risk of dangerous situations on the rig.
Design and Comparison of Two Drill String Solutions that Break Barriers in Extended Reach Drilling
Authors: Awad Ahmed , Carrois Fabien , Lafuente Marta , Matveyev Andrey
Published: February 2019

To date, extended reach drilling (ERD) wells drilled on one of the main UAE offshore reservoirs have been delivered by using a tapered drill string design that combines two sizes of drill pipe. To reduce the number of days per well, a one-size only drill string concept has been considered, but such an option required some improvements in torque and geometry to meet specific well design requirements.

An initial analysis of the drilling requirements in terms of torque, dimensions, tensile capacity, and hydraulics showed that the process limiter was the drill pipe connection as no option was available in the market that could meet the redesigned requirements. Two new technical solutions were separately developed that took into account the need for a reduced tool joint outer diameter (OD) for equivalent circulating density (ECD) and fishability in an 8½-in. hole. Once developed, the solutions were then validated for manufacturing and field trials.

The first solution consisted of designing and developing an ultra-high torque thread profile, while the second solution suggested to upgrade the tool joint material grade of a new 4th generation double shouldered connection. Both newly designed drill pipe strings successfully passed the shop stress tests and were mobilized for operations. The drill pipes were used for drilling within the tight hydraulic window of such ERD wells, further validating the original drilling simulation parameters. The successful trial of these two single size string solutions enabled the saving of more than five days of rig operating time per well.

This paper presents a detailed comparative evaluation of two innovative drill pipe design solutions that enable operators to run a single size string in challenging ERD wells. It also provides an insight into the operational benefits obtained by shifting to the new single size string.
Micro-Sonde Well Logging System; a Novel Method for Along-Well Measurements
Authors: Saelevik Gunnstein , Skadsem Hans Joakim , Kragset Steinar , Gardner Dave , Randeberg Erlend , Hjelstuen Magnus
Published: February 2019

The micro-sonde well logging system is a concept for obtaining along-well measurements of temperature, changes in fluid velocity and pressure while drilling. The micro-sondes are encapsulated, self-contained measurement devices designed to follow the flow from the bottom hole assembly to surface. Once retrieved at surface, the measurements can provide information about well conditions such as the presence of cuttings beds, washed out zones and gain/loss zones. Post-processing of the data requires knowledge of the forces acting on the micro-sonde and the resulting trajectories from the release point at the bottom hole assembly and to surface. The main objectives of the studies presented in this work are to understand the micro-sonde motion in the mud flow and to design and construct a demonstration device.

We have performed a literature study, CFD-modelling and experiments to better understand the behavior of a micro-sonde in a typical annular flow domain. The trajectory of a single micro-sonde has been investigated as it passes tool-joints under the influence of inner string rotation. Further, the experiments investigated the likelihood of transporting the micro-sonde intact to surface for a drilling application. For the experimental studies, two annular flow loops, one vertical without rotation of the drill-string and one horizontal with a rotating drill-string, including tool-joints and a model bottom hole assembly have been constructed and utilized.
Frictional Heating of Casing Due to Drill String Rotation – Finite Element and CFD Simulations
Authors: Assaad Wissam , Tarr Brian , See Kwee Choong
Published: February 2019

A drill string in a wellbore always contacts a casing. However, in a curved section of casing the contact force between the drill string and the casing can be significant. Friction between the casing and a rotating drill string tool joint in contact with the casing generates a heat source at the interface between the two objects. The generated heat energy is a function of rotational speed of the drill string, side force and friction coefficient between the hard-banding layer covering the tool joint and the casing. Heat partition between hard banding layer and casing depends on the thermal properties of both. When there is no mud circulation, e.g. due to a pack-off in the annulus or lost circulation, and the contact region stays in the same section, the resulting temperature increase can lead to degradation of the mechanical strength of both the drill string tool joint and the casing. In addition, the casing strength reduction can facilitate casing wear, which may lead to leak and tool joint heating can lead to heat checking cracks or mechanical strength weakening which may result in a parted drill string due to brittle or ductile fracture.

When there is no mud circulation, rotation of the drill string leads to mud angular rotation inside and outside the drill string. Convection heat transfer occurs due to mud rotation and convection heat transfer coefficient depends on mud flow regime. CFD simulations were performed to compute the convection heat transfer coefficient. Two and three-dimensional steady state and transient finite element simulations were performed to compute the temperature distribution in the casing and the drill string tool joint when there is no mud circulation.

Results show that, when there is no mud circulation, conduction through the drill string and casing has the highest impact on the maximum temperature generated due to frictional heating. Two graphs are plotted, one shows the steady state temperature versus side load at different rotational speeds while the other shows casing yield and ultimate stresses degradation versus increase in temperature. Both graphs can be used by drilling engineers at the well design phase to select the appropriate rotational speed of drill string to avoid failure when there is no mud circulation.

Novelty of this paper is in thermal analysis of a tool joint hard banding layer rubbing against casing. In the analysis the convection heat transfer through mud rotation is involved.
Managing Shallow Water Flow During Tophole Drilling Operations in the Southern North Sea – A Case Study
Authors: Solarin Adebowale
Published: February 2019

With a shallow water flow-back in excess of 200 bbl/hr from the Top Chalk formation during the 17½" section, the deviated exploration / development well "Well #4" was planned and drilled successfully with a jackup rig. The well was planned from a platform in the Southern North Sea.

The primary goal for the 17½" section was to safely drill to section TD, set casing and cement same with zero incident in a minimum amount of time while encountering shallow water flow.

The key challenges for this well were: Flowing Top Chalk Formation: The Top chalk formation flowed at all three previously drilled offset wells with 12.0 ppg EMW and approximately 200 bbl/hr. Several attempts to shut in the well and stop the flowing Top Chalk on the offset well "Well #1" failed.Obtaining regulatory approval from authorities, and commitment and acceptance by all involved parties to drill the well under flowing conditions.Hole cleaning and hole stability considerations when drilling with seawaterPermanently shutting off the shallow water flow with a two-stage cementation.Rig uncertainty and general service market (in 2017): A new drilling contractor and drilling services not familiar with the peculiarities of operations in this areaSafety, communication and human factor considerations for a potentially hazardous non-routine operation.

A collaborative well-planning and preparation process involving the operator drilling team, the drilling contractor and key service providers was critical to the success of the overall operation.

The team worked together to ensure all requirements, risk mitigating measures, lessons learned from previous operations and offset wells, and human factor considerations were incorporated in the execution program.

The well was successfully drilled to TD, evaluated, completed and flowed. The notable highlights from the top-hole drilling operation include: Fastest 17-1/2" phase compared to offset wells: drilling and casing operations completed in 94.25 hrs with the well flowing.Zero NPT in the 17-1/2" drilling phase: drilled 654 m in 37.5 hrs with an average ROP of 17.5 m/hr without any complications.Continuous monitoring and fingerprinting of the shallow water flow

This paper describes the key planning considerations, preparations and creative solutions deployed to deliver the well. The lessons learnt will serve as a resource for planning future wells with similar challenges.
Well Safety and Performance Gains from MPD in Unconventional High Overpressure Reservoirs in Argentina
Authors: Lage Antonio Carlos Vieira Martins , Arduino Edgard Gurgel do Amaral , Loureiro Sebastião de Andrade , Vanni Guilherme Siqueira , Filho Hercilio Pereira da Silva
Published: February 2019

The present paper describes performance improvements and well safety achieved with the use of Managed Pressure Drilling (MPD) in the exploratory block of Parva Negra Este, in Neuquén Basin. Petrobras Argentina S.A (PESA), with the technical support from the Petrobras’ headquarters, in Brazil, drilled two exploratory wells applying MPD and targeting Vaca Muerta shale oil & gas play.

High-pressure zones characterized the drilling scenario, reaching, usually, pore pressures higher than 18 lbm/gal in unconventional reservoirs, composed of tight sand and shale. The use of MPD in both well constructions was quite efficient, including well control and plug and abandonment (P&A) operational applications. Those operations proved that MPD can effectively replace the Under-Balanced Drilling (UBD) system, which is standard practice in that area.

In the first well, PESA reported significant gains in drilling performance when compared to other wells previously drilled. Drilling with MPD did not record non-productive time (NPT), differing substantially from the previous wells constructed in the surroundings of Parva Negra Este with an average NPT of 20 days. A considerably larger recovery of coring samples was achieved, being also possible to eliminate one well section, by drilling two zones of interest in a singlesection. Additionally, lessons learned were implemented, resulting on higher rate of penetration (ROP) with the support of MPD.

In the second well, a high overpressurized pore zone was reached, leading to a very complex well control event followed by a permanent P&A operation. The formation pore pressure was much higher than the expected for the area. Instead of using an 18 lbm/gal drilling fluid, it was necessary to weight the fluid up to 21.3 lbm/gal, adding hematite as weighting material. In that scenario, the use of MPD made the operations of circulation and well cementing safer than with the conventional drilling approach utilized in that vicinity.

The application of Dynamic Formation Integrity Tests (DFIT) and Dynamic Pore Pressure Tests (DPPT) ensured a more precise operational window, helping to formulate risk matrices for safely pulling the drilling string out of the hole. In addition, the precise definition of the operational window was a valuable information to plan the best approach for P&A. Besides performing those tests, the MPD system was very useful to evaluate operational parameters and verify how effective was the settlement of the abandonment cement plugs.

In summary, MPD supported safer drilling and P&A jobs, better drilling performance and greater information achievement through more efficient well logging and sample coring.
A Laboratory Study of the Effect of Casing Pipe Roughness to Cement Plug Integrity
Authors: Corina Anisa Noor , Opedal Nils van , Vrålstad Torbjørn , Sangesland Sigbjørn
Published: February 2019

Cement holds the most critical role for providing long-term zonal isolation for permanent abandonment phase. The loss of cement integrity is undesirable as it may threaten the surrounding environment and safety on the surface. The quality of cured cement is commonly associated with the properties of cement material and cement placement in the wellbore. However, there are still limited investigations that link these factors specifically to the sealing ability of cement plug, especially with the lack of proper equipment in the past.

In the present work, a small-scale laboratory setup has been constructed to test the sealing performance of a cement plug. The cement plug is contained inside a test cell, connected to a pressurizing system and placed inside a heating cabinet. Consequently, the test can be simulated at downhole conditions in a controlled manner. By using this setup, it is possible to monitor the minimum pressure required for the plug to fail and the gas leak rate.

Two different cement systems, neat- and silica-cement, were prepared as plugging materials. Both cement systems are placed inside pipes with three different levels of surface roughness and then tested. Results show that the inner surface roughness of the pipes affects cement plug sealing significantly, and the effect is independent of the type of cement systems. Plugs placed inside a very-rough pipe significantly reduce the gas leak rate. Our results also show that an immediate gas leak occurs in all samples from leak paths formed at the cement/steel interface.
A Novel Microbially Induced Self-Healing Cement/Concrete for Underwater Concrete Offshore Structures
Authors: Noshi C. I. , Schubert J. J.
Published: February 2019

Techniques for offshore structure concrete remediation have received minimal consideration in the oil and gas industry in spite of its potential. Emerging "bio-concrete" to plug micro-cracks have shown concrete results in various lab experimentations. Recently, MICP technology has garnered world-wide attention and popularity for various multi-disciplinary applications where smart synthesis of calcium carbonate minerals generate at ambient conditions contributing to bio-cemented self-healing agents by mixing bacteria into the cement slurry. Concrete fails to self-heal and repair cracks greater than 0.2 micron.

The technique comprises of mixing the preparatory material with operative quantities of urease producing spores and a calcium ions under standard conditions of hydrolyzed urea. Scientists found that microbes extensively multiply when nutrients comprising of cheap carbon sources like molasses/glycerol is added to the mixture. Live microbes propagate via cracks channels and micro-voids and smartly cement the cracks by calcifying the matrix structure.

Bacteria can then act as a autogenous self- healing agent. The precipitating bacterial strains generate urease enzyme which metabolically precipitate calcium minerals in the neighboring environment as calcium carbonate. The degradation of urea via bacterial metabolism locally rises the surrounding pH allowing the carbonate microbial calcification. These precipitates can autogenously plug the cracks and improve concrete robustness. The calcifying bacteria can be secluded from cement matrix or various natural sources. The purified spores can cultivate for limited time periods and then supplemented to the concrete matrix for application. The spores remained viable after prolonged periods. After short curing times, the healing capability of micro-cracks, durability, and tensile strength showed significant improvement.

This novel approach of crack plugging is highlighted to save substantial costs associated with crack restoration and repair of underwater concrete offshore structures and platforms.
Advanced Real-Time Monitoring Provides Early Detection and Prevention of Costly Well Problems
Authors: Mayani Maryam Gholami , Rommetveit Rolv , Helgeland Stig , Oedegaard Sven Inge , Kjørstad Kristian Olaf
Published: February 2019

The objective of this paper is to demonstrate how advancedrealtime monitoring (ARM) utilizing advanced hydraulic and mechanical modelling of the drilling process provided early detection of anomalies by giving diagnostic messages during drilling operations. These achievements can minimize non-productive time and invisible lost time and maximize the benefits and value of operations; if they are utilized to its full potential by operations. Some well cases are used to illustrate the methodology and its results. Among problems diagnosed are losses, stuck pipe during drilling and casing running, downhole equipment leakage and improper hole cleaning. In some cases, action was taken based on the diagnostics; and the operational conditions were modified to mitigate the situation. In other cases, the warnings were not taken seriously, the situation worsened until the problem was irreversible and a stuck situation occurred. In one well presented in the current study a stuck pipe situation happened during drilling 8½" section which led to a downtime of more than 20 days. By utilizing the ARM, it couldhave been possible to detect some early signs of the stuck conditions in the wellbore and avoid it. Another stuck situation in awell during 14-inch Casing running, led to downtime of more than 10 days which involved breaking out the casing above the stuck point and performing P&A. The ARM provided early signs of stuck casing that was about to occur, and these signs first started appearing about 15 hours before the pipe got completely stuck. This paper will present the Advanced realtime Monitoring ARM System and the modelling behind this. Also, the plans for further implementation and integration of this in the work processes will be discussed, before results from the first year of utilization will be presented with examples.
An Analytical Model for Double-Shouldered Connection Strengths
Authors: Pettit Grant
Published: February 2019

The drilling industry has become enamored with the extra torsional capacity and clearance that are available when double-shouldered connections are used in the place of the single-shouldered connections that are in the public domain. These proprietary connections allow us to drill farther, faster, and with less damage to our drill string.

To this point, however, no analytical model has been introduced that can accurately calculate the tensile and torsional capacities of these useful connections. Typically, the connection designer and/or manufacturer creates an empirical formula that is calibrated through laboratory and field testing. This approach is perfectly acceptable, but it hinders those tool designers that need something different from what is offered on the public market. It is rarely cost-efficient to perform laboratory and field testing for a one-off connection design.

Single-shouldered connections, such as API drill stem connections, have a straightforward analytical equation that can be used to determine the capacities of any connection. This equation may not be perfect—it relies on linear assumptions that are probably not descriptive of the connection loading—but several decades of use have allowed the industry to be confident in its strengths and aware of its shortcomings.

Thus, what is needed is to simply extend the approach of the original single-shouldered equation to account for a second shoulder. Though the mathematical complexity increases a bit, the assumptions are the same, lending the same confidence to the extended equation that the industry has for the original.

This paper presents the derivation of just such an equation. The implicit assumptions present in the original equations are discussed, and then the same ideas are applied to a double-shouldered connection. The full set of new equations are developed and described, including tips on their practical use gained from tool-design experience.
Advanced Drilling Simulators for Well Control Training: Bringing Together People, Procedures and New Technology
Authors: Howell Robert , McKenzie Brian , Leslie Craig , Poletzky Isabel
Published: February 2019

As more complex and challenging wells are being drilled along with the use of new technologies, well control remains a critical operation that requires personnel not only with the right skills set but also to be able to communicate and manage the operation during these stressful situations.

This paper will focus on describing the steps taken before, during and after drilling crews have participated in the well control training; it will also highlight the integration of people skills in the schedule and what results, advantages have been observed/obtained by operators and drilling contractors.

The use of advanced drilling simulators provides a new environment where drilling crews can not only be trained in how to react and implement the well control procedures, but also allows the implementation of new technologies such as Managed Pressure Drilling (MPD) in highly sensitive environments such as deep water; it provides a safe environment where the drilling team/crew can evaluate these new technologies, and it also facilitates the familiarization with the tools, operational procedures, and communication protocols.

While the Drill the Well on Paper exercises provide an opportunity to get the drilling team together and get more familiar with the drilling plan, high end drilling simulators offer a more realistic platform to illustrate the main challenges that crews could face when drilling wells, providing a hands-on learning environment where skills and procedures can be assessed for normal operations as well as during well control scenarios.
Effect of Polypropylene Fiber Reinforcement in Cement Sheaths Exposed to Cyclic Fatigue Loading at Wellbore Conditions
Authors: Giesler Steven , Schubert Jerome
Published: February 2019

Cement slurry is pumped downhole to create cement sheaths that induce zonal isolation and maintain well integrity throughout the well’s lifetime. This task is difficult to achieve due to adverse wellbore conditions and rig operations. In particular, hydraulic fracturing stimulation generates cyclic stresses detrimental to the cement sheath. The primary research objective was to conduct cyclic fatigue tests on cement sheaths reinforced with polypropylene fibers, then compare results with cement sheaths that were not fiber reinforced. The secondary research objective was to observe crack initiation and propagation in computed tomography (CT) scans of the cement sheath before, during, and after cyclic fatigue testing.

An experiment was built to mimic wellbore conditions during hydraulic fracturing. Cement sheath samples were cured at wellbore conditions of 6,000 psi and 250°F, then exposed to pressure and temperature cycles to evaluate fatigue performance. Internal casing pressure was applied to a restraining cement sheath, then cycled from the wellbore confining pressure to a positive pressure differential and back to the confining pressure. Intermittent temperature cycles were also applied from wellbore temperature to room temperature. Samples endured the applied stresses initially, but failed after reaching their respective fatigue limits due to cyclic fatigue.

Two baseline slurries without fibers were tested: one contained Class H cement plus 35% silica flour by weight of cement (bwoc) while the other contained Class H cement plus 35% silica flour bwoc plus 8% bentonite bwoc. Polypropylene fibers were added at a concentration of 0.75% by volume of batch (bvob) with the intention to improve performance of the baseline slurries. Results showed that fiber reinforcement increased the fatigue life of cement sheaths tested with 0 psi confining pressure, however it lowered the fatigue life of cement sheaths at 6,000 psi confining pressure. Three types of failure were observed including radial cracks, disk cracks, and cement-casing debonding. Cross-sectional CT scans displayed mature radial and disk cracks, but not the gaps formed from debonding. In conclusion, further testing is needed to assess fiber reinforcement’s ability to improve cement sheath durability in oil and gas wells.
Targeted Interventions to Prevent Chronic Low Back Pain in High Risk Patients: Development and Delivery of a Pragmatic Training Course of Psychologically Informed Physical Therapy for the TARGET Trial
Authors: Beneciuk Jason , George Steven Z. , Greco Carol , Schneider Michael , Wegener Stephen T. , Saper Robert , Delitto Anthony
Published: February 2019

Background

Low back pain (LBP) is a public health concern because it is highly prevalent and the leading cause of disability worldwide. Psychologically Informed Physical Therapy (PIPT) is secondary prevention approach that first aims to identify individuals at high risk for transitioning to chronicity and then provides tailored treatment to reduce that risk. Training models that are feasible to implement with acceptable training quality are needed to improve scalability for widespread implementation of PIPT. This manuscript describes the PIPT training program that was developed for training physical therapists providing PIPT in the TARGET Trial.

Methods

The PIPT training program was developed, tested, and modified using an iterative process. Content development consisted of stakeholder engagement, beta testing, modification of training and confirmation of final course objectives. Methods of delivery consisted of a website that included brief educational modules followed by a live 8 hour workshop that included video based mock case scenarios and case-based role playing. Attitudes, beliefs and confidence in implementing PIPT principles were assessed before and immediately after training to measure training quality and impact.

Results

Early stakeholder engagement and beta testing indicated the need for increased emphasis on experiential learning opportunities and patient-centered communication training. Booster training varied extensively across TARGET sites with involvement of ‘clinician champions’ brief follow-up sessions identified as best practice. Favorable post training changes in physical therapist attitudes and beliefs toward biopsychosocial treatment orientation and increased confidence in implementing PIPT principles were observed.

Conclusions

PIPT training for provider participation in the TARGET Trial was feasible to deliver. Course content was acceptable to physical therapists and resulted in improved beliefs and confidence in applying PIPT skills during clinical practice. Ongoing consultation and site-based continuing education were methods by which specific TARGET sites maintained or augmented PIPT skill training, however implementing ongoing training was challenging in general. Consistent with a pragmatic trial whether this training directly impacted treatment fidelity was not measured, which was a limitation to our training approach.

Trial registration

ClinicalTrials.gov Identifier: NCT02647658
Different EPHX1 methylation levels in promoter area between carbamazepine-resistant epilepsy group and carbamazepine-sensitive epilepsy group in Chinese Population
Authors: Lv Yudan , Zheng Xiangyu , Shi Mingchao , Wang Zan , Cui Li
Published: February 2019

Background: Epigenetics underlying refractory epilepsy is poorly understood. DNA methylation may affect gene expression in epilepsy patients without affecting DNA sequences. Herein, we investigated the association between Carbamazepine-resistant (CBZ-resistant) epilepsy and EPHX1 methylation in a northern Han Chinese population, and conducted an analysis of clinical risk factors for CBZ-resistant epilepsy.
Methods: 75 northern Han Chinese patients participated in this research. 25 cases were CBZ-resistant epilepsy, 25 cases were CBZ-sensitive epilepsy and the remaining 25 cases were controls. Using a CpG searcher was to make a prediction of CpG islands; bisulfite sequencing PCR (BSP) was applied to test the methylation of EPHX1. We then did statistical analysis between clinical parameters and EPHX1 methylation.

Results: There was no difference between CBZ-resistant patients,CBZ-sensitive patients and healthy controls in matched age and gender. However, a significant difference of methylation levels located in NC_000001.11 (225806929.....225807108) of the EPHX1 promoter was found in CBZ-resistant patients, which was much higher than CBZ-sensitive and controls. Additionally, there was a significant positive correlation between seizure frequency, disease course and EPHX1 methylation in CBZ-resistant group.
Conclusion: Methylation levels in EPHX1 promoter associated with CBZ-resistant epilepsy significantly. EPHX1 methylation may be the potential marker for CBZ resistance prior to the CBZ therapy and potential target for treatments.
The Effect of Implementing an Aseptic Practice Bundle for Anaesthetists to Reduce Postoperative Infections. Protocol for a Stepped Wedge, Cluster Randomised, Multi-Site Trial. The Anaesthetists Be Cleaner (ABC) Study
Authors: Merry Alan , Gargiulo Derryn A. , Bissett Ian , Cumin David , English Kerry , Frampton Christopher , Hamblin Richard , Hannam Jacqueline , Moore Matthew , Reid Papaarangi , Roberts Sally , Taylor Elsa , Mitchell Simon J.
Published: February 2019

Background

Postoperative infection is a serious problem in New Zealand, and internationally with considerable human and financial costs. Also, in New Zealand, certain factors that contribute to postoperative infection are more common in Māori and Pacific populations. To date, most efforts to reduce postoperative infection have focused on surgical aspects of care and on antibiotic prophylaxis, but recent research shows that anaesthesia providers may also have an impact on infection transmission. These providers sometimes exhibit imperfect hand hygiene and frequently transfer the blood or saliva of their patients to their work environment. In addition, intravenous medications may become contaminated while being drawn up and administered to patients. Working with relevant practitioners and other experts, we have developed an evidence-informed bundle to improve key aseptic practices by anaesthetists with the aim of reducing postoperative infection. The key elements of the bundle are the filtering of compatible drugs, context-relevant hand hygiene practices, and enhanced maintenance of clean work surfaces.

Methods

We will seek support for implementation of the bundle from senior anaesthesia and hospital leadership and departmental “champions”. Anaesthetic teams and recovery room staff will be educated about the bundle and its potential benefits through presentations, written material, and exemplar videos. We will implement the bundle in operating rooms where hip or knee arthroplasty or cardiac surgery procedures are undertaken in a five-site, stepped wedge, cluster randomised, quality improvement design. We will compare outcomes between approximately 5,000 cases before and 5,000 cases after implementation of our bundle. Outcome data will be collected from existing national and hospital databases. Our primary outcome will be days alive and out of hospital to 90 days, which is expected to reflect all serious postoperative infections. Our secondary outcome will be the rate of surgical site infection. Aseptic practice will be observed in sampled cases in each cluster before and after implementation of the bundle.

Discussion

If effective, our bundle may offer a practical clinical intervention to reduce postoperative infection and its associated substantial human and financial costs.

Trial registration

Australian New Zealand Clinical Trials Network Registry: ACTRN12618000407291
Computation of the Response Similarity Index M4 in R under the Dichotomous and Nominal Item Response Models
Authors: ZOPLUOGLU Cengiz
Published: February 2019

Unusual response similarity
among test takers may occur in testing data and be an indicator of potential
test fraud (e.g., examinees copy responses from other examinees, send text
messages or pre-arranged signals among themselves for the correct response, item
pre-knowledge). One index to measure the degree of similarity between two
response vectors is M4 proposed by Maynes
(2014). M4 index is based on a generalized trinomial
distribution and it is computationally very demanding. There is currently no
accessible tool for practitioners who may want to use M4 in their research and
practice. The current paper introduces the M4 index and its computational
details for the dichotomous and nominal item response models, provides an R
function to compute the probability distribution for the generalized trinomial
distribution, and then demonstrates the computation of the M4 index under the
dichotomous and nominal item response models using R.
Youths’ Online Political Participation in Ethiopia; A Study of Students’ Facebook Usage in Some Selected Public Universities
Authors: Muluye Ketemaw
Published: February 2019

This study was conducted to examine youths’ online political participation in Ethiopia with a focus on students’ Facebook usage in six randomly selected universities. The research specifically aimed to study the extent of participation, the main online political activities, and factors that determine such involvements. For this purpose, the research utilized a quantitative method with survey design. The sample size was 400 and the samples were selected by using the simple random method. Descriptive statistics were used for analysis. Accordingly, the research found limited youth’s involvement in those activities that require more commitments and efforts while they found to be active in activities that require low efforts and commitments. Low political efficacy and fear of political measures were found to be the main factors that force youths to have limited involvement in activities that require more efforts and commitments.
Kinetics of photocatalytic removal of imidacloprid from water by advanced oxidation processes with respect to nanotechnology
Authors: Derbalah A. , Sunday M. , Chidya R. , Jadoon W. , Sakugawa H.
Published: February 2019

In this study, the kinetics of photocatalytic removal of imidacloprid, a systemic chloronicotinoid insecticide, from water using two advanced oxidation systems (ZnO(normal)/H2O2/artificial sunlight and ZnO(nano)/H2O2/artificial sunlight) were investigated. Moreover, the effects of pH, insecticide concentration, catalyst concentration, catalyst particle size, and water type on the photocatalytic removal of imidacloprid were evaluated. Furthermore, total mineralization of imidacloprid under these advanced oxidation systems was evaluated by monitoring the decreases in dissolved organic carbon (DOC) concentrations and formation rate of inorganic ions (Cl− and NO2−) with irradiation time using total organic carbon (TOC) analysis and ion chromatography to confirm the complete detoxification of imidacloprid in water. The degradation rate of imidacloprid was faster under the ZnO(nano)/H2O2/artificial sunlight system than the ZnO(normal)/artificial sunlight system in both pure and river water. The photocatalytic degradation of imidacloprid under both advanced oxidation systems was affected by pH, catalyst concentration, imidacloprid concentration, and water type. Almost complete mineralization of imidacloprid was only achieved in the ZnO(nano)/H2O2/artificial sunlight oxidation system. The photogeneration rate of hydroxyl radicals was higher under the ZnO(nano)/H2O2/artificial sunlight system than the ZnO(normal)/H2O2/artificial sunlight system. Advanced oxidation processes, particularly those using nanosized zinc oxide, can be regarded as an effective photocatalytic method for imidacloprid removal from water.

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